Solar to run a fridge.

SkippySkippy Posts: 276Solar Expert ✭✭
hello all.

I bought 3 - 110 watt solar panels, mounted them on top of a 20' hydro pole in lots of sunlight (no tracker), then I found out that both the solar panels and the small 300 watt grid intertie inverter that I bought - I cannot use. Since they are not CSA certified, or do not have ANY Canadian content, I am not allowed to hook them to the grid (or my house) here in Ontario Canada.
I did find out, that I can set up a stand alone power system with batteries to run off grid. I already have a 20 amp morningstar charge controller now I would like to get a battery bank, inverter and battery state of charge meter.
I hope that when all is said and done, I will be able to run my fridge off of this system. I purchase a brand new fridge - don't have the square footage with me here - and then wrapped it in 2 inches of white styrofaom - front - back - sides and top. Using a Kill-o-watt meter, without the foam, it used about 1.6 killowatts over 24 hours, with the foam it uses .65 of a killowatt hour a day - 650 watts day ? That is from 11 pm to 11 pm, according to the meter...
Using the meter, the fridge draws 700 watts for a few seconds at start up (start up surge), and I do have a 700 watt square wave inverter, but I am worried about heating up and frying the fridge motor using this type of inverter. . .
I would like to just start firing all the usual questions at you guys, but I think I will take some time to read the forums, as there is ALOT of info here.

Thats it so far.
3 -110W-12V panels - wired for 36V  -  24V Sunsaver MPPT CC - midnight bat. monitor.
1 KW pure sine inverter 24V  -  2.5 KW inverter 24V  -  24V ~ 105 AHR battery.
3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rads
Tempra 12 ODWH  combined with  Apricus - Solar water heater for summer - water heat / winter - house heat.
9 -220W solar - net meter - Enphase inverters and internet reporting system
420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
Current project is drawing up plans for a below grade Hobbit / underground home.
«1345

Comments

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Solar to run a fridge.

    Welcome to the forum.

    First some terminology; your refrigerator is using 650 Watt hours per day, not just Watts. That is about half normal. :D A caution about covering it with insulation; over time this could backfire as you may be covering the areas that radiate heat. You can check this by simply putting your hand on the surface when it's running and see if it gets warm.

    You are right that the 'frige will have quite a start-up surge. It is doubtful that a 700 Watt inverter will handle it, especially an MSW type. You are also right that the 'frige will not like MSW; although it would work it will not work well.

    You have three 110 Watt panels or 330 Watts total. Over the course of a day you could expect 686 Watt hours AC from them; just enough to run the refrigerator (based on good insolation and 4 hours of equivalent good sun). That's also just enough panel for a couple of 220 Amp hour 6 Volt batteries in series which would also just provide the power necessary to run the 'frige. The panels are probably about 6 Imp, so the MS 20 Amp controller should do.

    It is possible for this to work, but it's a bit on the edge. When you add the power consumption of the inverter necessary to run the refrigerator you may not have enough power.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.

    to add to your standalone system to make it operational it may cost as much as buying new pvs and throwing small gt inverters on them, all certified.

    i know you don't want to have what you already bought to be useless to you so you could use it for lights being they aren't as critical of the modsine inverter. the batteries will need to be sized for your loads no matter what loads you opt for. keep in mind that you don't want to draw off more than 50% of the battery capacity over 24hrs to preserve battery life. they aren't meant to be drained dead.
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.

    Further to Carriboocoot's note on totally insulating all sides of the fridge - - - where does your fridge get rid of the heat it extracts from within? Many have coils just under the outer metal skin that do that, others have separate "coils" mounted on the outside of the back. The former will not operate properly if it can't get rid of the extracted heat, the latter will work fine IF you put the insulation under those external coils, between the coils and the actual cabinet.
  • Volvo FarmerVolvo Farmer Posts: 209Solar Expert ✭✭✭✭✭
    Re: Solar to run a fridge.
    Further to Carriboocoot's note on totally insulating all sides of the fridge - - - where does your fridge get rid of the heat it extracts from within? Many have coils just under the outer metal skin that do that, others have separate "coils" mounted on the outside of the back. The former will not operate properly if it can't get rid of the extracted heat, the latter will work fine IF you put the insulation under those external coils, between the coils and the actual cabinet.

    Wrong. Freezers have the coils wrapped under the skin. Refrigerators do not.
  • waynefromnscanadawaynefromnscanada Posts: 3,009Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.
    Wrong. Freezers have the coils wrapped under the skin. Refrigerators do not.

    Not so fast. I had a Sanyo fridge with the coils under the skin, and a local organization I belong to, has a Maytag fridge with under-skin coils, I know because I moved it by myself to another room this past Saturday. And three feet from me at this very moment, I have a Sears upright freezer which I use as a fridge, and it has external coils. I also used to sell fridges that had neither. They used a fan cooled condenser down under, beside the compressor. So it depends on the design the manufacturers decide to use.
  • Volvo FarmerVolvo Farmer Posts: 209Solar Expert ✭✭✭✭✭
    Re: Solar to run a fridge.

    Sorry about my trite response, my original post did not go through. You are correct. However 95% of USA domestic refrigerator freezer combos have the coils underneath and are fan cooled. I would be curious to get a model number of that Maytag, because I have never seen one that was not static air cooled from the back or fan cooled from underneath. Almost every USA sold freezer built in the last 15 years, either upright or chest has the coils under the skin like you describe. My understanding was that the OP had a brand new refrigerator/freezer combo, and I have never seen that configuration with the coils wrapped under the skin. I have been repairing appliances for twenty years now and have seen a lot of refrigerators, but I'm always interested in learning something new.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Solar to run a fridge.

    I think I have the same Maytag in my kitchen. It has the freezer on the bottom. The model is MBB1954GEW. And yes the sides get warm when it is cycling in Summer.
  • WindsunWindsun Posts: 1,164Solar Expert admin
    Re: Solar to run a fridge.
    Wrong. Freezers have the coils wrapped under the skin. Refrigerators do not.
    My almost new Maytag refrigerator has the coils under the skin.
  • peakbaggerpeakbagger Posts: 325Solar Expert ✭✭✭
    Re: Solar to run a fridge.

    I have a kenmore 5.5 cubic foot chest freezer. It has a grill on its side and vents hot air through the grill. I am in the process of adding insulation. It was quite noticible that by laying a piece of 4" iso board foam on the top cover that when I removed the foam, the top cover was a lot colder. I have also done this with the sides and noticed the same effect so I guess it depends on the design.

    I think in the "old days" the manufactureres were cheap on the insulation so the cases would be cold enough to condense vapor int he air leading to puddling, by putting the coils in the outer layer of the case it kept it warm so water didnt condense. Generally old freezers were energy hogs.
  • Volvo FarmerVolvo Farmer Posts: 209Solar Expert ✭✭✭✭✭
    Re: Solar to run a fridge.
    I think I have the same Maytag in my kitchen. It has the freezer on the bottom. The model is MBB1954GEW. And yes the sides get warm when it is cycling in Summer.

    Okay, I looked up that model number. Your refrigerator has 90% of it's condenser coil folded underneath the unit, and it is fan cooled. The other 10% is what we refer to as a "yoder loop". It is a coil of the condenser coil tubing buried under the skin and foamed in, right behind the door gaskets on the body of the refrigerator. The purpose is to keep the doors warm enough to prevent sweating in humid environments.

    The OP stated he had added foam to the sides and top and back of the refrigerator. This does not affect the yoder loop so much because it gives up most of its heat around the door openings and 90% of the condenser cooling is done underneath the unit by means of the condenser fan. You might feel a little heat on the outside of the refrigerator, but it is inconsequential to the total amount of heat which is dissipated underneath, where the majority of the coil lives.

    http://www.searspartsdirect.com/partsdirect/part-model/Maytag-Parts/Refrigerator-Parts/Model-MBB1954GEWPMBB1954GW0/3048/0161000/M0403067/00005?blt=06&prst=&shdMod=

    That #19 is your condenser coil.



    If the administrator of this forum would give me his model number, I could look it up as well.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Solar to run a fridge.

    The point well-made is that you need to know where the coils are before you start covering everything with foam.

    It was easier in the old days because you could see them: that big white cylinder on top of the ice box! :D
  • SkippySkippy Posts: 276Solar Expert ✭✭
    Re: Solar to run a fridge.

    I did not include all relevant information again, sorry.

    My refridgerator has back of the set coils, I made up 4 metal brackets, and extended the "stand offs" that came with the fridge by another 2 inches. Then wrapped it everywhere but the bottom. . . Yes, I did try this with my small chest freezer, and it did work on the lid, but the sides of the unit did get warm when it was running, so I did not even try it on the sides. I agree with you guys on that one, - if the sides of the unit are warm - don't cover it up !

    Thanks for the info on the RE system. I would LIKE to run the fridge off of these panels, but there are a few other lower power items that I can connect. It would just be nice to have a system to get me started . . . which leads me to the next question, I have a -15 amp- grid powered - 12 V battery charger. Does it change anything having a bigger battery to charge or can I just hook up the charger to the battery posts to charge - or possibly run a seperate "+" and "-" wire outside the battery box ( connected to terminals) to avoid sparks in the battery box ? I am going to get a battery monitor of some kind, so on a low sun day, I would like to charge the battery up with the grid powered charger. . .hopefully not too often. . .

    I stopped by a local "solar installer" and was told that too run 30 feet (12 V) into the house, I would only need to use 10 gauge wire . . I did not want to argue with an "expert", so I accepted his decision. . . came home and ran it thru the on-line wire size calculator (again) and found a sizing of 6 gauge. . I already called him to see if I can return it or not. . .
    The other thing is, I am sure that the codes require steel conduit when entering the building envelope, but he sold me pvc conduit. . . which would not meet code if I am right. . :grr
    Oh, and the morningstar charge controller is not a mpp charger, a buddy is trying to tell me that I will loose something like 30 percent right off the top. . . is it worth getting a mpp charger ?

    I'll keep you guys updated as I go.
    3 -110W-12V panels - wired for 36V  -  24V Sunsaver MPPT CC - midnight bat. monitor.
    1 KW pure sine inverter 24V  -  2.5 KW inverter 24V  -  24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rads
    Tempra 12 ODWH  combined with  Apricus - Solar water heater for summer - water heat / winter - house heat.
    9 -220W solar - net meter - Enphase inverters and internet reporting system
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • inetdoginetdog Posts: 3,112Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.
    Skippy wrote: »
    Oh, and the morningstar charge controller is not a mpp charger, a buddy is trying to tell me that I will loose something like 30 percent right off the top. . . is it worth getting a mpp charger ?

    I'll keep you guys updated as I go.

    Just compare the cost of replacing your PWM charger with an MPPT charger, and then look at how many panels you would have to add to get the same amount of additional power (assuming you have the space) and what they would cost. Decide on that basis.

    How much you lose will depend on exactly what the Vmp value of your panels is. However, the MPPT controller will also give you a bit more extra power during the winter when the panels are colder. (An interesting calculation because in the winter you need the extra energy more, but 30% of a small amount is still a small amount!)
    SMA SB 3000, old BP panels.
  • PhotowhitPhotowhit Posts: 3,327Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.

    Since we have a repair guy here, would it help cool the coils if there was an aditional air space under the fridge? I've heard of retrofitting an aluminum shield between the bottom condenser and the fridge. I'm worried about my soon to be off grid fridge, and anything I can do to help it work better...

    I honestly thought it had coils under the sides but never felt them get warm, like my friends upright freezer. It would be fine to me to put 2" of blue board around it if it would help.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • Volvo FarmerVolvo Farmer Posts: 209Solar Expert ✭✭✭✭✭
    Re: Solar to run a fridge.
    Photowhit wrote: »
    Since we have a repair guy here, would it help cool the coils if there was an aditional air space under the fridge? I've heard of retrofitting an aluminum shield between the bottom condenser and the fridge. I'm worried about my soon to be off grid fridge, and anything I can do to help it work better...

    I honestly thought it had coils under the sides but never felt them get warm, like my friends upright freezer. It would be fine to me to put 2" of blue board around it if it would help.

    I'm a repair guy, not an engineer. Engineers are the guys I cuss when they make stuff hard to fix. :) However, I think 2" of foam on the outside would help immensely. Look at the OPs stated increase in efficiency when he did that. Obviously, if you could get all the hot parts out from under the box altogether it would help, but I don't think a piece of aluminum is going to make any difference and trying to create a larger airspace would be a challenge. Cheap $500 18CF top freezers have broken the 1KWhr/day barrier. Personally, I wouldn't try and chase 200-300 watt hours a day by fooling with one. It's far easier to just design a little more solar into the system. Here's a neat list if you are shopping!

    http://wattsthematter.com/refrigerator/2011/TopFreeze-AutoDefrost/bykwhpercuft.html
  • inetdoginetdog Posts: 3,112Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.
    ... trying to create a larger airspace would be a challenge.

    Depends on where you are trying to create it. If the design blows air out from under the front of the machine, or just relies on convection to get air past the condensor you may benefit at very little expense just by putting a couple of pieces of wood under the supports at the bottom of the fridge. That also makes it easier to do a quick clean of the coils, or at least see how they look.
    For a rear-mounted condensor, adding more space between the bottom of the unit and the floor can improve air flow, (provided you have enough open space at the top!)
    SMA SB 3000, old BP panels.
  • PhotowhitPhotowhit Posts: 3,327Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.

    Lots of space, and I can always find uses for blue board, I have a 12 year old fridge and lots of expenses next year before I want to try and replace it, but hope to go off grid this winter. Thanks for the thoughts and info!
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • westbranchwestbranch Posts: 4,184Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.

    Icarus has added a fan to the top of one of his fridges (Propane?), and i believe a shroud around the cooling fins, to get more air flow past the fins...
     
    CL 647 asleep  24V 900Ah C&D AGM
    CL29032 FW 2079/ 2073/ 2054 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,Omnicharge 3024,
    Linksys Wet54g WiFi Bridge, ASUS RTN10 router, Hughes1100 Sat Modem
     Eu3000i & 1000i Gens, 1680W & E-Panel/WBjr to come,
    West Chilcotin, BC, Canada



  • icarusicarus Posts: 5,070Super Moderators admin
    Re: Solar to run a fridge.

    Not particularly applicable to under cabinet coiled fridges, but Timothy my Propane fridges, ia have. T stat controlled computer fan (24 volt, runs on 12 so it is nearly silent) mounted above the condenser coils. The fridge is on the outside wall of the house. Behind the fridge are a couple of 3" vents drilled through the wall, allowing fresh air in low. The natural convection, helped by the fan draws air over the condenser very easily. That, and adding 1 1/2 " of foam board on the top and sides of the case have reduced run times dramatically. Mid summer, I have some openale vents above the fridge so the heqt events out side. In the winter' it just vent into the room ( not the burner, it is always vent outside!)

    I would seem if you could (easily) duct fresh outside cool air over conventional coils, and then vent the heat out side ( unless you wish to " heat the house" , you soho uld be able to reduce the run time a bit. I am guessing that a fridge workes ewt when there is a much larger Delta T, so drawing in cold air would pull heat off the coils faster than using room air, or priviously heated air.

    Tony
  • inetdoginetdog Posts: 3,112Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.
    icarus wrote: »
    I am guessing that a fridge works best when there is a much larger Delta T, so drawing in cold air would pull heat off the coils faster than using room air, or priviously heated air.
    Tony

    The better way to look at it is that a fridge or freezer works best when the temperature difference between the inside and outside is a low as possible. Both because there will be less heat leakage and because the refrigerant cycle will be more efficient.

    But if the condensor (hot coil) temperature gets too low there could be problems with low pressure in the system and other things outside the intended design conditions of the unit. A good rule of thumb is that you should not go much below a human-tolerable room temperature and definitely do not go below about 10F above the temperature you are trying to reach inside
    SMA SB 3000, old BP panels.
  • icarusicarus Posts: 5,070Super Moderators admin
    Re: Solar to run a fridge.

    Good point,,

    What I wrote was not exactly clear (what else is new?!) when I said large Delta I was referring to the temp of the condenser compare to the air cooling it. Keep the box in thcoolest prt of the house,, within reason.

    We run a LP fridge occasionally for over supply when we are waiting for safe ice in the fall, or bak up in the spring. This fridge is in an unheated building, and the ambient can be below freezing. The fridge has automatic controls, so it only fires as needed. I have never had a problem with it getting and staying cold, and in general the stuff in the box does not freeze unless we are consistently close to 0f. Overnight as thbuilding picks up a bit of heat from the sun and,, from the fridge.

    Tony
  • vtmapsvtmaps Posts: 3,642Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.
    inetdog wrote: »
    But if the condensor (hot coil) temperature gets too low there could be problems with low pressure in the system and other things outside the intended design conditions of the unit. A good rule of thumb is that you should not go much below a human-tolerable room temperature and definitely do not go below about 10F above the temperature you are trying to reach inside

    I had a couple of sears freezers that I kept in an unheated porch. They were rated to operate in 0° F temperatures. I know that on some old freezers the lubrication of the motor was the reason they were not rated for very cold temperatures. I have heard of folks placing a heat blanket over their freezer motors.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SkippySkippy Posts: 276Solar Expert ✭✭
    Re: Solar to run a fridge.

    Wow ! Didn't think I would get this much activity out of my fridge :) :) But then I guess refridgeration is a real power drain... so any way to reduce it would be good...
    I understand that I should buy an inverter that suits my needs, as well as "future" needs, but which one ? I am looking at this site "northern arizona wind and sun" , and I have never heard of Samlex Inverters before. . The outbacks are way out of my price range, so its down to the exelttech and the samlex. . . any advice ?
    Currently I am looking into ordering the Trimetric 2025 battery monitor, any opinions on that one as well ?
    Thanks for any help.
    3 -110W-12V panels - wired for 36V  -  24V Sunsaver MPPT CC - midnight bat. monitor.
    1 KW pure sine inverter 24V  -  2.5 KW inverter 24V  -  24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rads
    Tempra 12 ODWH  combined with  Apricus - Solar water heater for summer - water heat / winter - house heat.
    9 -220W solar - net meter - Enphase inverters and internet reporting system
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Solar to run a fridge.

    The Exeltech and Samlex inverters don't have built-in chargers. This must be taken into consideration, as it means you'd need a separate stand-alone battery charger for use with gen/utility if the sun fails to shine enough to recharge the batteries. There are also two different models of Samlex; the lighter duty ones are not really sufficient for refrigerator use as they have poor surge capacity. The hard-wired ones are better in that respect.

    But before you can make any inverter choice you need those hard power consumption numbers. If all you need to supply is 1kW +/- to start the 'frige and the rest will be running it (under 200 Watts) you can use something like the Exeltech XP1100 http://www.solar-electric.com/exxp12vol11w.html If you expect to have higher average loads you might prefer the 24 Volt version to the 12. Either is less money than the Samlex 2000 Watt hard-wired unit (which would start a 'frige; the stand-alone version probably would not).

    Nothing wrong with the Trimetric meter. You do have to program it correctly from the start. But do you really need it? For daily use systems it is quite an asset, and nearly a necessity for AGM batteries. For occasional back-up use you might save money and buy MidNite's battery meter http://www.solar-electric.com/mnbcm.html (not as precise as a battery monitor). Particularly if you get flooded cell batteries - and a hydrometer. I don't know what kind of budget you're looking at. Victron also makes a good battery monitor.
  • BB.BB. Posts: 25,058Super Moderators admin
    Re: Solar to run a fridge.

    Windsun, our Admin from NAWS--He has been recommending about a 1,500 Watt inverter minimum for running a normal Energy Star Fridge (you might get away with a 1,200 watt inverter that has good surge).

    Wayne from NS Canada has been able (by playing with starting capacitors/custom motor start relays and such) been able to run some of his fridge/freezers on a 300 watt TSW MorningStar unit--But that is beyond the ability of most folks here (and you to have the time/knowledge to even try such a project).

    Talk with your inverter retailer and find out what and who they recommend for your application. We tend to try and be conservative (1,500 watt inverter from just about anyone will start just about any Energy Star type fridge/freezer)... But if you are tight for money/power budget--Support by your retailer would be helpful.

    Specific setups (Woods chest freezer converted to a refrigerator may allow you to use a smaller inverter--No defrost coils, no auto ice maker, etc.) may allow a smaller setup--But unless we have somebody here who runs such a setup on XYZ Inverter--The could be some experimentation on your part (which you may not want to be the guinea pig for)...

    Here are the basics--Refer back to the thread for more discussion:
    I assume it has a "solid state" varistor type start control in series with the start winding, nearly all now do compared to the older mechanical relay types. If you are good around electrical, you can add a 150 MFD Start Capacitor in series with the varistor. You MAY have to play with the 150 MFD value a bit to get the perfect match, but this will HUGELY reduce the start surge of the compressor and also in some cases allow it to restart even under full back pressure that hasn't been given a chance to bleed down. I've done this with both my freezers and my converter fridge, as well as other older fridges and freezers. All with fantastic results.
    Some of the older freezers worked best with 200 MFD, but my newer upright converter freezer works best with 140 MFD. If you have lots of surge capacity you won't see much difference, but if things are cut close, finding the value that matches best definitely does make a difference. AND, it helps if you're friends with someone who owns or operates a motor repair shop, they'll let you try several values till you find the best. Also be aware that the value marked on the capacitor can be way off. I've run into that and had it verified with a capacitor value tester. With the added Cap Start, your freezer should definitely start no problems on your 600 watt PS inverter.
    In fact, with additional and rather complicated external circuitry, I run all three of mine on a single dedicated Morningstar SureSine 300. One at a time of course, and the additional circuitry also takes care of that. The "fridge" has priority, followed by the freezer in the basement, then if neither one of these are running, finally the freezer in the outside shop - - if indeed it needs to run. Been working fine this way for years.
    Haha No, the Fridge ALWAYS has priority. When it goes to start, the first thing happens is a relay switches power from the freezer and passes it to the "fridge" which only runs about 5 minutes out of every 65 minutes, then when the "fridge" shuts off, the relay reconnects the freezer. Freezers can wait.
    To get the compressors started on the PureSine 300, I have a small autotransformer, 115 volt with a 15 volt tap. When a compressor goes to start, a relay connects the autotransformer in such a way that only 100 volts is supplied, but as a result, more amps are available to get things up to speed. As soon as the starter kicks out, the autotransformer is removed from the circuit and the compressor connected directly to the inverter. From then on, it's business as usual. Keep in mind though that all the compressors have been changed to capacitor start. Took a lot of trial and error to find what worked best, and the varistor start controllers on the compressors were exchanged for timed relays. Timed too long and the excess load would kick out the inverter. Timed too short, and the starter would kick out before the motor got up to speed. A very fine line, but has worked for several years with no problems.
    It would probably be a good one to TRY, and I would STRONGLY recommend only trying it while you are monitoring power consumption with a Kill-A-Watt, so you will see if the Hard Start relay is taking the Start Capacitor out of the circuit once the compressor comes up to speed. Compare running watts without the Hard Start, with running watts after installing Hard Start. There should be no difference other than that caused by changing pressures the compressor is dealing with from time to time. Otherwise, if the Start Cap stays in the circuit after the comp is up and running, there will be way too much current in the start winding of your compressor and will shortly burn out that winding.
    It's a rather tricky thing to ensure it's going to work right for your freezer.
    BTW, the reason for finding the AC voltage across the Run Cap is for the supplier of the Hard Start to determine which relay to give you. That voltage will be quite low until the motor comes up to speed, at which time it raises dramatically, usually above the line supply voltage. It's this higher voltage that's used to activate the Hard Start relay that cuts the Start Cap out of the circuit.
    Oh, and NO, that voltage does NOT indicate the MFD of the capacitor that should be used. It would however indicate the MIN voltage rating of the capacitor.
    And BB, I'm using a START Capacitor, as it is only in circuit while the compressor is being started. It is however, when in action, connected by relay, across the existing (if any) Run Capacitor that was supplied with the freezer. The two capacitors are in parallel until the compressor is up to speed, then the Start Cap is disconnected and only the Run Cap remains in circuit.
    Additional info: My older freezer has no run capacitor. The other has I think (memory) roughly 14 MFD run cap, and the "fridge" I believe has a 12 MFD run cap. In all cases, where the compressor was designed for and came with a run cap, that capacitor stays in circuit at all times. Only the Start Cap is connected and disconnected as required for starting. (I'm not trying to beat a dead horse here, just trying to be perfectly clear, as best I can)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: Solar to run a fridge.

    it might depend on the inverter too as some inverters do well up to and even beyond their rated capacity while some you take a chance. my magnum mms1012 rated at 1000va does quite well with my 21cf non e star 1997 model roper refrig. you also have to watch as some inverters can't have the ground and neutral tied together like house circuits are.
  • SkippySkippy Posts: 276Solar Expert ✭✭
    Re: Solar to run a fridge.

    Thank for the reccommendations. Did not see the midnite meter. . . for monitoring the battery voltage, would a car volt meter do for a 12 volt system ? Whatever meter I pick up, I like the idea of seeing when it was last fully charged. . . and getting a bit of a "reminder" to get it done ! :D
    If I ever get around to getting more solar panels, it will be a higher voltage system. . this little set up is just a learning system for now. . . I think :) :p
    Here is a picture of my set up so far. .
    Keeping in mind, that I left the wires a bit longer than needed, untill I get the new parts for the system. .
    From the fuse protected combiner box outside (with a dc rated disconnect), the #4 wire is in the large conduit to the left, connects to the charge controller - the battery connector has a in line fuse, and the inverter is hooked to the load side with the 120 volt wiring going around the room in the smaller conduit - with the 120 V plug installed beside the outlet where the fridge plugs in. right now, I turn on and use the inverter only when I am home to run my desk top computer, or watch a movie on a laptop.... when I am not home, I unscrew the # 4 wire from the charge controller, pull the inline fuse, and turn off the inverter. . . so no power is connected... I am making sure, that the batteries are kept up to the float voltage of 13.1 V, since these are not deep cycle batteries - and yes, I know, they will not last long in this system (not deep cycle batteries), but its a starting point.... till I can upgrade. .. these batteries were free :D
    There are probably any number of things I have done wrong here, the main one being no battery box / protection (I have no kids to worry about- so no little fingers touching anything). ... but thats why I am here, feel free to let me know how to improve this system, on the list so far, is a new 400 amp hour battery bank in a vented battery box - a new inverter, and a new battery monitor... I have been wondering how you exit the conduit to get to the inverter. . .
    Thanks.


    One last thing, would there be a way to disconnect the defrost on my fridge ? Right now, it has automatic defrost, you can hear it clicking and poping as it runs, then the compressor comes on and cools it off again. . . I hope, I can connect a switch in there somewhere and only have it defrost when I have an excess of solar power. . .

    Manufacturer : Roper
    Model Number : RT14HDXK000
    Manufactured: 10/01
    Type: 14TFA

    Still looking into this one ;)
    3 -110W-12V panels - wired for 36V  -  24V Sunsaver MPPT CC - midnight bat. monitor.
    1 KW pure sine inverter 24V  -  2.5 KW inverter 24V  -  24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rads
    Tempra 12 ODWH  combined with  Apricus - Solar water heater for summer - water heat / winter - house heat.
    9 -220W solar - net meter - Enphase inverters and internet reporting system
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
  • BB.BB. Posts: 25,058Super Moderators admin
    Re: Solar to run a fridge.

    Here is:

    wind-sun_2235_8272202MidNite Solar MNBCM Battery Capacity Meter

    Regarding the battery bank--Put some plastic or a plywood cover over the top--A dropped tool, scrap of metal, will ruin your day.

    Regarding the auto defrost--In general, the evaporator coils will ice up in about 24 hours and reduce airflow (leading to longer compressor run-times)... It is not a good idea.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Solar to run a fridge.

    An ordinary Voltmeter isn't going to tell you much except what the Voltage is at the moment. MidNite's battery meter is an "intelligent" meter in that it relates Voltage to SOC (never perfectly accurate but better than nothing) and it keeps track of when the battery last received a full charge; it will warn you if this hasn't happened lately.

    You're batteries don't appear to be connected right. Looks like you have the (+) and (-) going to the middle one, effectively making them "laddered". Move one of those cables to the left battery, the other to the right.

    Your inverter appears to be wired with very light wire (700 Watt is it? Could draw 70 Amps so needs at least 4 AWG) and also seems to be attached to the LOAD terminals of the SunSaver? That is not where to connect an inverter. Wire it through an appropriate fuse to the battery bank. Inverters run off batteries, panels recharge batteries. Always think of it like that. LOAD terminals are for low power DC not exceeding the capacity of the charge controller.

    I hate to think what that second picture shows. It looks suspiciously like you've plug in to the inverter at one end, and then plugged in to a wall outlet at the other. If that is not a dedicated outlet that is in no way connected to the grid it will be a problem. One involving smoke and flames. Or is that second outlet dedicated output from the inverter so that you can switch the refrigerator over if needed? That would make sense.

    Can you turn off the defrost on your 'frige? Depends on the 'frige and how easy it is for you to open it up and clip the right wires. Without a schematic it is difficult to figure that out. I can well understand why you'd want to, though; 500 Watts on defrost is not unusual.

    I have to ask: have you actually managed to start and run a refrigerator off the CT 700 Watt inverter? It's almost unbelievable! I tested a bunch of their inverters four or five years ago and none of them lived up to their ratings. Maybe they were forced to improve things because of that. It's hard to imagine a 700 Watt inverter starting a typical 'frige anyway, as they usually demand over 1 kW to get going.
  • SkippySkippy Posts: 276Solar Expert ✭✭
    Re: Solar to run a fridge.

    Thanks for the suggestions. I will be changing the wiring to the batteries (yes they are laddered), and hooking in the inverter as well (to batteries). I have a fuse in line with the batteries, do I need a fuse between the batteries and the charge controller (as it is now) , or should I get another seperate fuse for the inverter run ?
    No, it is a completely seperate circut. the lower plug outlet in the wall is 120 V grid, and the surface mounted outlets are the solar. That way if the batteries have not been fully charged in a few days, just pull the plug out and let em recharge.
    I was kinda hopeing to be able to flick a switch when I needed to defrost, and all other times have it turned off to save juice. ..
    I will have to do a few test runs for ya. I think when I first picked up the inverter, I did run the fridge off of it. This time when I tried to do it, it blew a fuse, but that might have something to do with the defrost running at the same time. . which does happen. . . I will let you know after I run a few tests. .

    I have not grounded the system yet, so I am not leaving anything hooked up for long. . . How heavy of a grounding wire would you reccommend ? I have some of that # 4 left over, I was thinking of getting the bare copper heavy duty stuff to ground the panels (panels to ground - straight wire) and then in the house, grounding the charge controller with the #4 to the same spot as the house AC grounding - ideas ?

    Oh, and I have already covered the batteries with a piece of plywood, they just looked - too - dangererous ! ;)
    3 -110W-12V panels - wired for 36V  -  24V Sunsaver MPPT CC - midnight bat. monitor.
    1 KW pure sine inverter 24V  -  2.5 KW inverter 24V  -  24V ~ 105 AHR battery.
    3 ton GSHP.- 100 gallon warm water storage / house heat - radiant floor / rads
    Tempra 12 ODWH  combined with  Apricus - Solar water heater for summer - water heat / winter - house heat.
    9 -220W solar - net meter - Enphase inverters and internet reporting system
    420 Gallon rain water system for laundry.***  6" Rocket Mass Heater with 10' bed for workshop heat.
    Current project is drawing up plans for a below grade Hobbit / underground home.
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