Garage solar system size requirements?

bsolar · February 2011

Hi all, im new to all this and putting a system together as a winter project for my stand-alone garage and have 50 questions so bare with me. ive done alot of reading but i just dont have a feel for what i need exactly. I am trying to keep cost down but want performance and the ability to run a few things overnight is my goal ..
what i want to be able to run overnight
-fridge
-electric fry pan or microwave to make a meal
-computer or tv
-electric blanket
-i plan on using LED lighting

what ive aquired so far
-made (7) 144W panels from ebay cells (36 .5VX8A rated 6X6 cells)
-sunforce 2500W sine inverter
- ( 8 ) 215AH 6V batts - i was thinking wire them series/parallel to 12V

im at a point im still building frames for the panels so i havent hooked anything up yet.
-so is this enough system to sustain things without worrying about it, should i add more panels, larger inverter, a second inverter, or more batts?
-also when i wire the panels from the roof, i was thinking 12 gauge fine stranded wire from the panels and tying them all together at a common point and then running about 8 gauge main cables down to my system .. does this sound adequate?
.. im budget minded so im not going to go buy 1 grand pieces of equipment or anything, and prefer to just piece everything together diy style, but please give me any ideas or advice you can or let me know if im on the right track to a workable system

thanks,
Brad S.

Cariboocoot · February 2011

Re: Garage solar system size requirements?

Hello and welcome to the forum!

Shall we go right to the bad news?

The first four things on your list are murder for solar electric.

Refrigerator: high start-up surge and pretty healthy over-all power consumption, plus a need for pure sine wave inverter for optimum performance.

Electric fry pan or microwave - you're looking at 1000+ Watts here. Uses lots of power even in a short time.

Computer or TV - consumption all over the board. Little netbook consumes 12 Watts. 50" Plasma 200+.

Electric blanket - not the biggest user, but in general electricity is a poor way to heat things.

(This list sort of sounds like you're building a man cave/dog house for when the Mrs. kicks you out for snoring!

)

But here's the good news: you can get a Kill-A-Watt (or similar) meter for about $30 and get some real world figures on what those intended loads will really use in a day. This is an essential tool & process for planning any type of off-grid power set up.

Now for the standard warning about homemade solar panels. Be prepared to be disappointed, no matter how good job you did building them. They can never be sealed as well as commercial units and inevitably will fail. As a learning experience it can be interesting to build one. But for a dedicated system it is usually not even cost effective, much less practical. Besides, some jurisdictions and insurance companies really don't like homemade solar on your roof; they have been known to start fires.

Your equipment list is short one key item: charge controller.
Let's look at its power potential anyway. The four batteries would give you 430 Amp hours @ 12 Volts (nominal). That means a maximum power potential of 2580 Watt hours. That's a fair amount.
Seven 144 Watt panels is 1008 Watts total. The standard derating factor leaves you with 776 Watts. Over a typical 4 hours of "good equivalent sun" you'd harvest about 3.1 kW hours - a good balance against the battery capacity. It should also be able to peak 54 Amps @ 14.2 Volts charging, which is slightly better than the "target" 10% of Amp hours. In essence, those panels should be able to charge those batteries.

But you are going to need a big charge controller to keep things regulated. That means something like the Tristar 60 PWM http://www.solar-electric.com/tr60amp12244.html or the more expensive MPPT type http://www.solar-electric.com/motr60ampmps.html (just as examples - not recommendation or endorsement).

And you will also need fuses or circuit breakers. If all those solar panels are paralleled they will need one fuse each (I can't tell you what size because we don't know the Isc of the homemade panels). The charge controller should have a fuse around 70 Amps between it and the batteries. The inverter needs a fuse of about 250 Amps on its supply line (check manufacturer's recommendation).

Got more questions? We have more answers!

bsolar · February 2011

Re: Garage solar system size requirements?

mancave? the idea never crossed my mind

this is more of a hobby type project at the moment but want the ability to use it eventually as a backup to grid failure to tell the truth ..

hmm that is kindof disappointing to hear on the power consumption of my list. Im not real up on figuring what my system will do, so as an example what would my 'power level' look like starting from a full charge and running a 1500watt fry pan for 20 minutes? What is the main problem area running my list or would i need to beef everything?

i dont know if you made a typo or i didnt see your figuring there but i have 8 215AH 6V batts. My charge controller i got from a guy on ebay, its actually a voltage sense/relay thing for wind turbines that can either chop voltage off or redirect it to another load, its rated at 160A and was cheap.

the panels being homemade was purely financial heheh. I laminated two pieces of glass together and theyre sealed all the way around with aquarium sealant, may not last i dont know and the glass is thin, a hailstorm would take them out in a hurry but i have about 150$ in each panel .. theyre going on a sheetmetal roof so fire shouldnt be a problem ..

Cariboocoot · February 2011

Re: Garage solar system size requirements?

I missed the '8' and thought '4'. Probably confusing it with another post.

Well 8 will get you 4X 215, or 860 Amp hours. That's 430 Amp hours usable, or about 5160 kW hours.
But it brings you two new problems: 1). You no longer have enough panel to recharge the batteries and 2). You're going to have trouble wiring all those batteries up and keeping the current balanced; you need bus bars and some careful attention to wire lengths/sizes. I'd suggest you skip the double-sized battery bank and keep to four, as in my original calculations.

So how much does a 1500 Watt fryer use in 20 minutes? That's 1/3 of an hour so it's (roughly) 1500/3 or 500 Watt hours. A big chunk of power.

I'd be leery of that charge controller. Make sure it has the right functions for 3 stage charging and some method of adjusting the Voltage set points. Otherwise you may be buying replacement batteries sooner than you'd hoped.

Good to know you stayed away from combustible materials in your panels. Some people build them on plywood! :roll:

icarus · February 2011

Re: Garage solar system size requirements?

It's pretty simple. For example, 1500 watts for 20 minutes (.33 hours)= 500 watt/hours

For a well designed, well cited and well build off grid system here is my quick napkin calc. Take the name plate rating of the solar panels (PV) divide that number in half to account for all cumulative system loses, then multiply that by the average number of hours of good sun one might reasonably expect daily. In most cases 4 is a good number on average over the course of a year.

So in your case 144*4=576/2=284*4=1152 watt/hours or 1.1 kwh. Running your frying pan for 20 minutes would use almost 1/2 of your daily output. It does get worse however. It is very likely that you homemade panels will not perform as expected. (This is no slight to you, it is just the history of HM panels shows that they do under perform)

The short answer is, proceed with your project, as it is a very interesting learning curve, but incorporate into it as much electrical conservation as you can. (Read, no resistance electrical heat on small PV/battery systems). Alternatives exist for any and all electric heating appliances including toasters, frying pans, coffee makers, tea kettles, soldering irons and yes, hair dryers.

Get a Kill-a-watt meter and fully log your loads and I think you will have an eye opening experience. The reality is with beginners is that they over estimate the amount of solar harvest they can get, while at the same time underestimate their loads.

As an FYI, we live off grid with ~400 watts of PV, 450 ah of battery. We routinely draw ~5-800 watt hours per day total consumption. We are able to have three days of reserve, and on most days we can get that back. On a perfect day, we can generate upwards of ~1.5kwh, but on average we generate ~ 800,, just as my napkin calc suggests.

Good luck and keep in touch. There are some very smart, experienced folks here who have forgotten more about PV than most of us will know. Your project sounds like a good place to start.

Tony

bsolar · February 2011

Re: Garage solar system size requirements?

@Cariboocoot
.. the controller does have adjustable voltage points and seems like a serious controller to me . Here is the thing:
http://cgi.ebay.com/Coleman-Air-C160M-12v-24v-160A-Charge-controller-Meter-/180474531579?pt=LH_DefaultDomain_0&hash=item2a051ecefb
And im sitting on 8 golf cart batteries now

.. i got to use them. So how many more panels am i building?

@icarus
im going to have to write that formula down and have a watt meter on order now. Yes i dont have my hopes too high on my home-brew panels, but taking one out the other day in the evening low sun around 4pm i got a no load reading of 21V at 6-7A .. i know that doesnt mean much in the real world with a load on them though. So sounds like i need to tighten up on my energy use thinking if you are off grid with that.

thanks very much for the replys guys, im starting to get a better feel for where im at with this ...

icarus · February 2011

Re: Garage solar system size requirements?

Yo need to build enough panels to produce 5% of your battery AH capacity. 900 ah would require ~ 45-100 amps. Into 12 vdc that would 600-1200 watts.

Also, in that event your controller is not going to cut it.

As a side note, get those batteries on a good 4 stage charger now, or they will become toast if you let them sit partially charged. You will need a charge anyway, so get one now. I would suggest an Iota or Xantrex TC 40 amp charger.

Tony

PS Damn, 'coot you are fast.

BB. · February 2011

Re: Garage solar system size requirements?

Several ways of looking at the system... You pick your loads and design the system to support them (usually with a small backup genset for 3 months of winter backup). Or, you start with something (like the battery bank) and design around it.

You have 8x 215AH 6V batts so--We know a few things. You can wire this up as a 12 or 24 volt system... If you peak loads are over 1,200 to 2,000 watts, you need to look at making this a 24 volt (or even 48 volt) system. 1,200 watts is already looking at wiring/fuses/breakers that support ~175 amps (using NEC requirements).

Say you start with 12 volts... That is 2x batteries in series * 4 parallel strings (I would not go more parallel batteries, getting them to share current and some other issues usually limit you to around 2-3 parallel banks maximum--At least in my humble opinion).

12 volts * 1,630 AH battery * C/20 = 1,304 watts 20 hour discharge (nice rate)
12 volts * 1,630 AH * C/8 = 2,445 watts 8 hour discharge rate (don't recommend higher discharge for flooded cell bank)
12 volts * 1,630 AH * C/2.5 = 7,824 watts maximum surge

As you can see, this is already a lot of power, and a 24 or 48 volt battery bank will cut your battery wiring current by 1/2 or 1/4 (depending on voltage you choose.

Next, you will want somewhere between C/20 to C/8 charge rate (5% to 13%) from the solar panels:

14.5 volts charging * 1,630 AH battery * C/20 * 1/0.77 system derating = 1,535 Watts minimum
14.5 volts charging * 1,630 AH battery * C/10 * 1/0.77 system derating = 3,069 Watts nice sized system
14.5 volts charging * 1,630 AH battery * C/8 * 1/0.77 system derating = 3,837 Watts around maximum cost effective solar array

Could you go smaller--Yea... But you probably would want a good quality AC charger to run from your home utility power and/or a backup genset.

The problem is that over-sized battery banks actually drive a lot of the design issues (more solar panels, more charge controllers, more backup generator, more losses from trickle charging batteries, heavy current means lots of thick
copper wire/higher battery bank voltage/more fuses & breakers for wiring up parallel battery banks, more batteries to replace 5-15 years down the road, more distilled water required to keep batteries full, more battery cells to check, etc...

In general, you are much better off storing some fuel for cooking/space heating. Propane is great but needs a lot of gallons of storage as it is not very dense fuel, diesel is OK but smelly/messy, gasoline is terrible but it is cheap and you can siphon your vehicles. I use mutli-fuel camp stoves for my emergency heating.

Could you build a system to power your needs--Yes. But it would not be very cost effective.

An alternative would be to go with a Hybrid system. Basically Solar panels + batteries + Inverter that has a Grid Tied mode to sell power to the utility (if they allow net metering) and has an emergency off-grid power mode that works like a giant whole home UPS (uninterruptible power supply). Still not cheap, but at least you can use the power all of the time (grid tied mode) without cycling the batteries (which wears them out sooner).

But--For Grid Tied systems, usually your local inspectors / power company will want UL/NRTL Listed parts for your system (home made stuff is a no go) and a licensed electrician to install.

In the end, usually you design the smallest system you can use to power a few lights / radio / small TV... And use fuel to cook/heat, and possibly a genset (like a Honda or Yamaha 1-3kW size unit) to provide power during the day and recharge your battery bank in bad weather (the Inverter / Generator types like the Honda eu1000i/2000i/3000i series are very quiet and pretty fuel efficient... The smaller gensets you can do a pretty good job on 1-2 gallons of fuel per day (if you are not running air-conditioning).

In the end, realize that Solar PV off-grid power costs around 10+x that of utility power. It is usually not practical to figure that you will use the same amount of electricity off/grid (emergency situation) as you would normally.

Anyway, lots of options.

-Bill

Cariboocoot · February 2011

Re: Garage solar system size requirements?

The controller info doesn't saying anything about Bulk, Absorb, Float. It seems to be an adjustable, single Voltage point limiter. I'm still leery of it.

Don't build anything more until you get your loads determined. It is an essential step.
Note Icarus' super-low consumption. Mine is significantly higher, but I have to run more equipment (like an electric 'frige).

In general, you design a system by starting with the loads. They will give you the info you need to size the inverter (maximum Watts at any one time) and battery bank (total Watt hours per day). The battery bank size will tell you how much panel and what size controller you need. Trying to construct a system any other way will lead to disappointing compromises. Like the 'frige shutting off at 2:00 AM because there's no more power.

bsolar · February 2011

Re: Garage solar system size requirements?

@icarus
so the wheels are turning in my mind. Maybe i could make up some kind of switch system to charge half the batts at a time?
What i have on hand is a regular shop type 12-6V 60A charger with low medium and high settings. Also i bought a BLS battery desulfator that actually recommends not balancing the batteries .. im lost on that at this point. The batts are new i got them about a week ago but im going to check their charge level tomorrow for sure.

@BB.
lots of good info there. So if i understand things correctly and i wanted to charge all 8 batts on the same circuit i would need about 11-12 of my 144watt panels minimum?

@Cariboocoot
ok, so i will just try geting everything operational and figure out my loads before going futher with expanding the system.

icarus · February 2011

Re: Garage solar system size requirements?

First, battery desulfaters are mostly snake oil. I have no idea what they mean by "not balancing" your batteries.

Second, be very careful using your 50 amp automotive charger on these batteries as they don't regulate absorb and float voltage very well. They also do not have any temperature regulation.

Start here:

http://www.batteryfaq.org/

http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

Get a good (not a auto parts store) battery hydrometer, and at the very least keep these batteries topped up a few hours a week with your charger until you get a proper charger, but don't leave it plugged in for long periods of time or you will cook your batteries.

Cariboocoot · February 2011

Re: Garage solar system size requirements?

For switching between two battery banks you can't beat one of these: http://www.solar-electric.com/diblsea90bas.html

It is possible to have a "back-up 'B' bank" but it can be problematic to charge and maintain both banks with one PV array.

bsolar · February 2011

Re: Garage solar system size requirements?

@icarus
got it, hydrometer is on the list. Yes, i wasnt sure on the desulfator either but it does make some good promises ...

@Cariboocoot
that switch looks like just the ticket, im going to have to sleep on all this but a backup bank just sounds 'right' at the moment ..

last question for the night, and im sure its is one of those million times asked questions, but what voltage am i looking for as my cutoff voltage while under charge and what static voltage should i be looking for, considering the batts are wired to 12V?

thanks so much for all the help guys. im sure i'll be digging this thread up alot with more questions over the coming weeks

Cariboocoot · February 2011

Re: Garage solar system size requirements?

Basic "12 Volt" system charging levels:

Bulk charge @ up to 5-13% of bank's Amp hour rating until ...
Absorb Voltage of 14.2-14.4 is reached. This Voltage level is maintained through the Absorb cycle (current level will fall off as battery absorbs) which ends after a set time or current falls below a set point then Voltage drops to ...
Float level of approximately 13.8 Volts. Charge controller will try to maintain this level until loads demand too much and Voltage falls off or supply (PV array) can no longer supply sufficient power for the day.

There is some margin on the set points of course. Some batteries want/need/can take more, others less.

mike95490 · February 2011

Re: Garage solar system size requirements?

bsolar wrote: »

... My charge controller i got from a guy on ebay, its actually a voltage sense/relay thing for wind turbines that can either chop voltage off or redirect it to another load, its rated at 160A and was cheap.....

List it back on flea bay and sell it, put the $$ toward a high power MPPT controller.

You would want to wire the panels in series, to reduce the amps in the wires you run from the PV to the controller. If you wire a couple panels in series to get 110V, and then a couple in parallel, you can get by with 12Ga wires. The controller will downconvert that to your battery voltage (better plan on this being a 48V system)

Voltage loss in your PV wire harness, if you did this all at 20v in parallel, would be very lossy, 20% or so. Yucch ! Series to a higher DC voltage, and MPPT down convert will be much better.

instead of an electric frypan which heats a lot of air, look into an induction hotplate, which has very low losses to heating air, and you can dial in the power you want. example of what I use:
http://www.amazon.com/gp/product/B0037Z7HQK

Mike

SteveK · February 2011

Re: Garage solar system size requirements?

mike90045 wrote: »

instead of an electric frypan which heats a lot of air, look into an induction hotplate, which has very low losses to heating air, and you can dial in the power you want. example of what I use:
http://www.amazon.com/gp/product/B0037Z7HQK

Mike

This is great advice Mike. Thanks for the heads-up. We were gonna go gas in the new homestead. After researching this tech I scratch my head as to WHY?

Great stuff...

bsolar · February 2011

Quick question ...

Hello again everyone,
Still making slow progress on getting my system going and still building aluminum frames for my panels today, hence my 'bright idea' and i want to get your thoughts ..

So as im struggling working and grinding the aluminum for the frames and considering how much wire i need to purchase i got to thinking 'why cant i use this 1 1/2" angle aluminum for buss bars?' Its relatively cheap compared to like 4/0 cable and i can drill it easily to fit my bank configuration with no multiple complex screw points, just straight shots ... also i could do the same under the roof and drop in 2' pieces of 10 gauge wire and tie to some long buss runs up there for the panels and run it down close to my charger .. so my question -- Do i want to do this?
thanks
Brad S.

mike95490 · February 2011

Re: Garage solar system size requirements?

NO

Aluminum oxide

Aluminum electrical wire is a alloy, for improved thermal properties, and corrosion resistance. Even then, it's half as conductive as copper, and needs special goop and connectors to safely carry power.

for bussbars consider instead flattened and tinned water pipe. Not quite as good as copper wire (the pipe alloy is for strength, not conductivity), but way better than aluminum.

bsolar · February 2011

Re: Garage solar system size requirements?

alrighty .. dang .. i thought i was going to get away cheap there

bsolar · February 2011

Re: Garage solar system size requirements?

hello again,
i know this may be overkill in some peoples eyes, but im doing a modest system strictly off grid in the 1800 watt range on panels, and sorry im not too up on figuring numbers this is kindof a go for it deal for me but i do have electrical background .. until i feel what i got out i'll never know what its going to do i dont think, but i have water figured out and have a 12volt well system going, and the induction hotplate sounds good .. i have access to wood to burn and am planning to get a wood stove on top of the fireplace and electric blankets for heating needs .. i do have one question though ... what can i do about heating water that can be better than roasting a bucket of it over fire .. maybe something that will work with the solar? ideas?

icarus · February 2011

Re: Garage solar system size requirements?

Heating water with PV solar is way more expensive (and ergo less efficient) than just heating that water with direct solar. PV has energy conversion rates in the 15% range, while solar water heat can be better than triple that, at less expense. Simple flat plate collectors can be built using readily available parts and pieces.

http://www.azsolarcenter.org/tech-science/solar-for-consumers/solar-hot-water/solar-hot-water-a-primer.html

Tony

bsolar · February 2011

Re: Garage solar system size requirements?

thanks for that, so for example, if i got a 30gal metal drum, painted it black, enclosed it in a mirror lined (or aluminum foil lined) box with a glass front do you think it would heat up 30 gals of water on a sunny day or am i going to need alittle more 'design' there?

BB. · February 2011

Re: Garage solar system size requirements?

Solar thermal does lend itself to DIY type projects... However, it also helps to use some rules of thumb to keep out of trouble.

Roughly, 20 gallons of hot water per person per day... Around 1/2 to 1 sq.ft. of collector area per gallon of water storage.

Especially during summer, your system can generate scalding water. A tempering valve should be used to keep faucet temperatures safe.

The solar batch heater is a pretty common project... Watch out for freezing/bursting water pipes (much of the US can have hard freezes). And test your insulation to ensure that it will withstand > 212F (many will not). Also, if mounting on your roof--watch the extra weight (40 gallon batch heater may weigh ~400+ lbs or so when filled with water).

-Bill

icarus · February 2011

Re: Garage solar system size requirements?

There are a lot of "ifs" in your proposal.

First you have to figure our where you live and how much sun you get, how much water you need at what temp. A simple batch type heater (like you suggest) will heat water fairly well, but not as efficiently as other methods. On the other hand, if freezing in not an issue, then a batch heater is the simplest to build and plumb as it needs no pump.

As another simple example. I have built a couple of simple flat plate collectors, ~12'X3' covered with discarded patio door glass, with ~150' of 1/2 copper loop in it. On a good day in the Pacific NW it will produce 50+ gallons of 85 degree rise water, as a preheat tank for demand gas. In the midst of winter it might produce 50 gallons of 20 degree rise.

Define what it is that you are trying to accomplish and get back.

Tony

PS Solar hot water is far and away the most effective solar energy project one can invest in. Cheapest up front cost, greatest long term benefit. It astounds me that people who live in predominately sunny climes haven't universally retrofitted houses with solar water heaters!

The little systems that I have built produce ~ 75% of the hot water for a family of 2 on an annual basis. ~ 150% in the summer,, 30% in the winter, that in the grey NW. This for a system that cost under $500.

bsolar · February 2011

Re: Garage solar system size requirements?

thanks for the replys

,
hmm what it is im trying to accomplish is relatively simple. Im not a big expenditure kind of person and work a low pay job and do great but have to be thrifty about what i try to do. I dont mind if its alittle jerry rigged but i like nice things, and my thinking is if i have to live outside of 'big brothers' system and need to heat water how can i do it at the least cost without being cold in the tub.

.. i dont have a problem in other words sliding a hose through the window to dump some warm water in my tub. What I have is (2) 55 gallon blue water barrels that im not using now i upgraded to a 350 gallon water tank i will be able to fill with either a handcrank 'simple pump' brand well pump and i plan on buying their 12V electric pump upgrade that will bolt right on it soon as a save up for it.

.. so what i really need is some way to warm water off the grid. I have the two 55 gal blue barrels i could paint black and build a box for if that will work. i can afford a couple of pieces of glass for a front and the wood to build a box. So i have the BIG 350 gallon tank which will top fill and provide at least some water pressure to the house ... if the box/55gal tank think will work, how do i plumb it? Would i put a drop pipe to the bottom to fill and just a short one at the top to the house to take the warm water out with?

cold isnt too much of a problem im in north Florida which freezes maybe 5 days out of the year and not too hard, maybe in the teens occasionally, and plenty of sun.

icarus · February 2011

Re: Garage solar system size requirements?

Two things to note.

Water temp for domestic use is fairly critical,, ~ 110-120F is useable, below that is much less so.

Consider the smallest volume that will suit your needs. While the total BTU gain might be the same raising 10 gallons 100F or 100 gallons 1F the former is more useful net/net. (That is not the formula, but just an illustration!)

The most efficient solar gain is the smallest Delta T, that is the difference between ambient water temp, and the outlet temp of any collector. So you, for example, more efficient to raise the temp less, but with more passes through the collector than raising a lot with fewer passes,, if that makes sense.

So you want to design a system, such that at the end of the day you get reasonable water temps, not too hot, nor too cold, and adjust the sizing of the system then to suit your actual use.

The second thing to note, most glass shops will either sell you cheaply or give you used tempered patio door glass. When insulated patio doors get broken (one pane) they routinely replace both panes because they cannot ensure a perfect seal in the field. so they are left with lots of pieces of glass that often just gets tossed. Stock tempered glass sizes are 34x76" and 28X76" so if you design enclosures for any hot water system using these sizes you are ahead of the game in terms of cost.

Also, (I know I said two, but as I write I often think of more) using plastic barrels may not be a very good idea. First, they will degrade in the sun, they don't transfer heat very efficiently. See if you can find some surplus stainless drums of some sort, like beer kegs.

Just thinking out loud,

T

bsolar · February 2011

Re: Garage solar system size requirements?

i was thinking the same about the plastic barrels .. beer keg does sound like it would do better, and i know from experience that a 30 gallon water heater is about right for providing enough hot water to fill a tub. I'll see if i can come up with a keg and i think im going to try it ....

bsolar · February 2011

quick question on battery terminals

..im finally getting around to wiring my batteries, and was wondering if i should goop up the terminals with grease or somthing before i bolt the lugs on to keep them from corroding?

BB. · February 2011

Re: Garage solar system size requirements?

Lots of people use Silicon Grease (used for spark plug wires, get from autoparts store).

I prefer to use the stuff from the autoparts store that is designed for battery wiring. I find it less messy.

If you want my reasons for not recommending Silicone grease...

You can also look at Deoxit or conductive grease with anti-oxidants (used by phone companies).

Be careful about using silicon sprays and grease around contacts (switches, relays, etc.). Silicon does vaporize and contaminate switch contacts. When the switch operates, the arc will turn the vapor into silicon dioxide (an insulator).

From Omron (a switch manufacturer download pdf file and search for silicon dioxide):

If a switch is used in the atmosphere of silicon gas, arc energy may attract silicon dioxide (SiO2) to the contacts and contact failure may result. If there is silicon oil, silicon sealant, a wire covered with silicon, or any other silicon-based product near the switch, attach a contact protective circuit to suppress the arcing of the switch or eliminate the source of silicon gas generation. Even for a sealed switch, it may not be possible to prevent all of the gas from penetrating the seal rubber, and contact failure may result.

In this thread, one of the electricians here (DHW) recommended Led Plate or Noalox as a anti-seize/anti-corrosion:

Lead based oil+grease anti-seize compound (MSDS)
Vendor page.

-Bill

bsolar · February 2011

Re: Garage solar system size requirements?

thanks, i never knew that about silicone but good to know info .. not trying to be funny, but i have some valvoline bearing grease here .. good idea, should i use or not?

BB. · February 2011

Re: Garage solar system size requirements?

Heavy grease probably works better than nothing. (seriously). You do need to make sure the connections are made securely and the grease is squeezed out of the electrical connections (greases are typically insulators).

-Bill

Garage solar system size requirements?

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