Classic water heater diversion
Comments
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Re: Classic water heater diversionCould you tell more about induction problem?
I don't know too much about it, but believe it is caused by fluctuating current through the heating element, that can cause a back feed that may damage the Midnite controller, without a large diode in place for protection. There's a discussion about it in the field lines thread you linked (page 3, half way down). Recommendations are you don't do it. -
Re: Classic water heater diversion
I briefly looked at using high voltage DC power with a DC SSR. But gave up on it. Using AC from the inverter is a more elegant solution, and much simpler. Folks that have Magnum inverters are evidently having problems with flickering power due the Magnum's poor voltage regulation for varying loads like a SSR-driven heater element. This has not been a problem here with either our SW Plus or our new XW6048.
I would say the simplest solution for folks that have Magnum inverters is to use a separate, smaller, cheaper inverter to power the element. Or trade your Magnum inverter off on a more capable one. Assuming you have enough excess RE capacity you end up with way more than just luke warm water. Two 55 gallon heaters here, both heated from well temp to 165+ degrees at least once a week.
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Chris -
Re: Classic water heater diversion
Hi Chris,
What were the reasons for you to give up on DC power? I've read that you did it on PV power but did you try on battery power? Are you thinking that it would be the same regulation voltage problem?I briefly looked at using high voltage DC power with a DC SSR. But gave up on it.
Some guys here are thinking that it could be done using MSW inverter, what do you think about MSW to do it?I would say the simplest solution for folks that have Magnum inverters is to use a separate, smaller, cheaper inverter to power the element
Cheap 48V inverters are not common here in Canada
, and I don't understand why this cheap inverter would not have the same regulation issue 
Erik -
Re: Classic water heater diversion
Stealing DC between the array and Classic was not recommended by boB. Heating water requires minimum 1,500 watts on the job if you're going to make it work. Any less power than that for heating water is like peein' in the ocean. 1500 watts / 48V nominal = 31 amps. Heating water with battery bank voltage is an exercise in heating wires instead of heating water. You need to use at least 120V and 240V is better.
Heating water with MSW works perfectly. The "flickering" that people are experiencing with their Magnum inverters is because the load varies on the inverter from the SSR turning the element on and off. The Magnum evidently cannot cope with this so it makes every other load in the house pulse and lights flicker from it.
By using a separate inverter you are taking the load off the Magnum so the separate inverter can handle the pulsing load imposed by the SSR and heating element, which leaves the Magnum alone to run the other stuff that you don't want flickering. A friend of ours not far from us bought a PAE Magnum for their off-grid home and hates it. They can't even run the washing machine without turning the house into a disco.
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Chris -
Re: Classic water heater diversionSolarMusher wrote: »Hi Chris,
What were the reasons for you to give up on DC power? I've read that you did it on PV power but did you try on battery power? Are you thinking that it would be the same regulation voltage problem?
Some guys here are thinking that it could be done using MSW inverter, what do you think about MSW to do it?
Cheap 48V inverters are not common here in Canada, and I don't understand why this cheap inverter would not have the same regulation issue
Erik
It sounds like you would need to protect the charge controller from surges and back feeding if using battery power directly, particularly if the load is heavy relative to the source. Water heating elements don't have as much inductance as a open air heater, but there could be an issue with this. Also, the contacts of the water heater aren't designed to handle high voltage, high power, DC. If you use a lower voltage DC, then you would need heavy cable, and may not be feasible if the distance is great.
If you use a separate inverter, surging on the ac output won't affect your main power (fluctuations) and the inverter acts as a buffer for the battery source, preventing the back feeding issue.
I googled and found this cheap 48v inverter. Mind you it it 50 hz, so you wouldn't want to use it on anything other than a heating element, I would think!
http://www.amazon.ca/Modified-inverter-converter-battery-function/dp/B009ZC4JCE -
Re: Classic water heater diversion
Hi Chris,
How do you deal with your Surrette high charge rate (62V if I remember) and low over voltage capabilities of cheap MSW inverters, for example, Cotek TSW 48V 1500W are 61.2V max (voltage range 42/60V)?
Absorb is set 59.2V on my batteries but voltage could be higher when battery temp is under 15c°.
Erik -
Re: Classic water heater diversion
We don't use a separate inverter. Our Schneider Conext inverter handles just about anything you can throw at it. I was just saying that for people that have Magnum inverters, that using a smaller separate inverter might be the answer to prevent the fluctuating load on their Magnum. This only seems to be a problem with Magnum inverters.
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Chris -
Re: Classic water heater diversionIt sounds like you would need to protect the charge controller from surges and back feeding if using battery power directly, particularly if the load is heavy relative to the source. Water heating elements don't have as much inductance as a open air heater, but there could be an issue with this. Also, the contacts of the water heater aren't designed to handle high voltage, high power, DC. If you use a lower voltage DC, then you would need heavy cable, and may not be feasible if the distance is great.
If you use a separate inverter, surging on the ac output won't affect your main power (fluctuations) and the inverter acts as a buffer for the battery source, preventing the back feeding issue.
I googled and found this cheap 48v inverter. Mind you it it 50 hz, so you wouldn't want to use it on anything other than a heating element, I would think!
http://www.amazon.ca/Modified-invert.../dp/B009ZC4JCE
Hi North,
Thanks for the link.
Have you seen that: High-Voltage Protection: DC52V±1V (5) Low-Voltage Protection: DC46V±0.5V. These cheap inverters are always very funny
.
The more I think about DC, the more I don't understand where 30A @ 59.2/60V could be harmful on WH contacts and on the other hand, how a #6 30A wiring could heat on such a small distance (10 feet max)
Erik -
Re: Classic water heater diversion
Just a technical note here.
Above 15 Volts DC can form a sustainable arc. If contacts aren't capable of separating far enough quick enough they may not 'separate' at all.
The same is not true with AC which effectively shuts itself off on every cycle.
The equivalent power or lower Voltage/lower Amps is not actually a factor in the arc sustaining which can damage or destroy the contact points.
That's why switches/breakers not rated for DC should not be used for DC. The fact that people often get away with it at low Voltages does not mean it will always work.
End of safety lecture. -
Re: Classic water heater diversion
Ok I understand. You seems to be very happy with you XW6048ChrisOlson wrote: »We don't use a separate inverter. Our Schneider Conext inverter handles just about anything you can throw at it. I was just saying that for people that have Magnum inverters, that using a smaller separate inverter might be the answer to prevent the fluctuating load on their Magnum. This only seems to be a problem with Magnum inverters.
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Chris. If I'd have to change my Magnum AE now, I think that I will go back to Outback with their Radian 8kw, even if my first VFX3648 gave me a lot of headaches. The problem that you describe with Magnum would be really the first with my 4448AE, never have problem at this time with washing machine or any other stuff.
Erik -
Re: Classic water heater diversionSolarMusher wrote: »Hi North,
and on the other hand, how a #6 30A wiring could heat on such a small distance (10 feet max)
Erik
The thing is, 1,500 watts is going to be the minimum if you want to heat any amount of water. Electric water heating is almost 100% efficient. But it takes a LOT of power to heat any serious amount of water. We use 2,000 watts and it works really good and heats water in a reasonable time. But 2,000 watts @ 48V nominal is now over 40 amps. You can run that 2,000 watt heater element on 240VAC with only 8 amps.
When you're using excess RE capacity to heat water, it has to be efficient if you want it to work. If you pencil it out, a 240V inverter running at ~94% efficiency is a better way to go than trying to use low voltage DC and taking a hit in wiring losses - plus the heavy duty contactors, relays, special elements and thermostats it takes to handle it.
Using household AC power from your inverter is simple, legal (easy to make meet NEC), and effective. You're not taking any hit on battery charging losses because the power is basically going direct from your RE source to the inverter, and the only loss is what is lost in the inverter based on its efficiency. I have played with various methods of heating water with off-grid power over the past 7 years or so, and to-date have not found a more efficient way than using the Classic's Waste Not Hi mode with an AC SSR and inverter power to drive the element.
This is about making real, serious amounts of hot water, not just diverting power to get rid of it.
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Chris -
Re: Classic water heater diversionSolarMusher wrote: »Hi North,
Thanks for the link.
Have you seen that: High-Voltage Protection: DC52V±1V (5) Low-Voltage Protection: DC46V±0.5V. These cheap inverters are always very funny.
Erik
I didn't pick that up as DC 52V will not work.
Here is a better 48v MSW inverter, but a bit more $$. And it's 60 hz too.
http://www.aimscorp.net/5000-Watt-48-Volt-Power-Inverter/ -
Re: Classic water heater diversionSolarMusher wrote: »Ok I understand. You seems to be very happy with you XW6048. If I'd have to change my Magnum AE now, I think that I will go back to Outback with their Radian 8kw, even if my first VFX3648 gave me a lot of headaches. The problem that you describe with Magnum would be really the first with my 4448AE, never have problem at this time with washing machine or any other stuff.
Erik
I wanted a little bit more power available than what our 5548 had so I can use my welder in the shop without having to pre-start the generator. We looked at putting in a Radian and I was not satisfied that the Radian is a proven enough unit. So we selected the XW6048 and it is indeed One Mean Beast, and it easily powers my Lincoln 225 Spark Welder without even making a CFL flicker when I strike an arc with the welder.
There has been some problems noted by folks trying to use a Magnum MS-PAE with water heating using a AC SSR and the Classic. I'm not totally sure what the solution is. Ryan at MidNite said he had one and its poor voltage regulation about drove him nuts. Our neighbors got one and the flickering of their lights in their house with their washing machine going drives them nuts. Now you have the same problem with one with your lights flickering. So it is an issue with that particular inverter. That's good information for folks to know - if you a Magnum PAE this is probably not a good setup to mess with. Ryan is one person that I know that is using this method with Outback inverters, and he has no problems with it that I have heard of.
So my conclusion is that if you have a Magnum MS-PAE, and want to use AC SSR on a Classic with inverter power driving a heating element, you should probably look at using a different inverter for powering the heating element.
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Chris -
Re: Classic water heater diversion
Chris,The thing is, 1,500 watts is going to be the minimum if you want to heat any amount of water. Electric water heating is almost 100% efficient. But it takes a LOT of power to heat any serious amount of water. We use 2,000 watts and it works really good and heats water in a reasonable time. But 2,000 watts @ 48V nominal is now over 40 amps. You can run that 2,000 watt heater element on 240VAC with only 8 amps.
When you're using excess RE capacity to heat water, it has to be efficient if you want it to work. If you pencil it out, a 240V inverter running at ~94% efficiency is a better way to go than trying to use low voltage DC and taking a hit in wiring losses - plus the heavy duty contactors, relays, special elements and thermostats it takes to handle it.
Using household AC power from your inverter is simple, legal (easy to make meet NEC), and effective. You're not taking any hit on battery charging losses because the power is basically going direct from your RE source to the inverter, and the only loss is what is lost in the inverter based on its efficiency. I have played with various methods of heating water with off-grid power over the past 7 years or so, and to-date have not found a more efficient way than using the Classic's Waste Not Hi mode with an AC SSR and inverter power to drive the element.
This is about making real, serious amounts of hot water, not just diverting power to get rid of it.
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Chris
Thanks for sharing your water heating experience, you and Marc convince me that AC is really the way to go for diversion when talking about safety.
Marc, Thanks a lot for adding your comment. I think that I'm gonna play with my old VFX3648 to make it work safely.Just a technical note here.
Above 15 Volts DC can form a sustainable arc. If contacts aren't capable of separating far enough quick enough they may not 'separate' at all.
The same is not true with AC which effectively shuts itself off on every cycle.
The equivalent power or lower Voltage/lower Amps is not actually a factor in the arc sustaining which can damage or destroy the contact points.
That's why switches/breakers not rated for DC should not be used for DC. The fact that people often get away with it at low Voltages does not mean it will always work.
End of safety lecture.
I'll add a little air conditionner load on the Magnum and keep the Outback or a cheaper one for water heating.
Thanks all,
Erik -
Re: Classic water heater diversion
On the subject of using a separate MSW 240 VAC inverter to activate a water heater there's a coupe of other things to keep in mind:
1). The inverter itself will consume some power; don't forget to include that in your calculations.
2). The inverter may not like being fired up with a load already on the output and may fault immediately (depends on the particular inverter). This means you may have to have a two-stage start up where the inverter is turned on first, then the load connected. Sort of like some auto-gen start installs.
Otherwise it really is a good plan for all the reasons Chris mentioned.
*sigh* It must be nice to have so much PV power you have to find things to do with it.
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Re: Classic water heater diversionSolarMusher wrote: »Marc, Thanks a lot for adding your comment. I think that I'm gonna play with my old VFX3648 to make it work safely.
I'll add a little air conditionner load on the Magnum and keep the Outback or a cheaper one for water heating.
Thanks all,
Erik
You could leave the VFX connected all the time but in search mode, then have the controller connect the water heater load when power is available. The inverter would come out of search only then. And it would drop out automatically if the water tank reached temperature and the thermostats shut off the elements.
Simple install, smooth operation, but a cost of 6 Watts continuous to keep search active. -
Re: Classic water heater diversion
I am having the same issue with lights flickering with diversion using an Outback inverter. This wouldn't be an issue for you of course if you used your Outback as a dedicated diversion. I do believe that buffering with an auto transformer, prevents much of that. My set up is a little different as well, in that I'm currently using a space heater, rather than water. -
Re: Classic water heater diversionCariboocoot wrote: »On the subject of using a separate MSW 240 VAC inverter to activate a water heater there's a coupe of other things to keep in mind:
1). The inverter itself will consume some power; don't forget to include that in your calculations.
2). The inverter may not like being fired up with a load already on the output and may fault immediately (depends on the particular inverter). This means you may have to have a two-stage start up where the inverter is turned on first, then the load connected. Sort of like some auto-gen start installs.
Otherwise it really is a good plan for all the reasons Chris mentioned.
*sigh* It must be nice to have so much PV power you have to find things to do with it.
For my dedicated inverter, I plan to have it on a breaker which I could just turn off the inverter when no significant sun is expected.
As for the start up, it normally should be gradual, as the batteries get into absorb, they will start pulsing the SSR, turning on the load. I could see a case where, if you suddenly switched on the inverter with the absorb or float in full swing, that there could be an issue with the load on the output.
It's necessary to have so much PV power when you live in a northern climate. It's great if you can make use of the excess, when it's there.:D -
Re: Classic water heater diversion
I agree that it could be hard on a cheap MSW inverter, Eric.L dit it that way but I don't know which MSW inverter it was.On the subject of using a separate MSW 240 VAC inverter to activate a water heater there's a coupe of other things to keep in mind:
1). The inverter itself will consume some power; don't forget to include that in your calculations.
2). The inverter may not like being fired up with a load already on the output and may fault immediately (depends on the particular inverter). This means you may have to have a two-stage start up where the inverter is turned on first, then the load connected. Sort of like some auto-gen start installs.
Otherwise it really is a good plan for all the reasons Chris mentioned.
*sigh* It must be nice to have so much PV power you have to find things to do with it.
I was on float at 11am today, and was full at the end of the past days when cloudly :cool:. Air Con would a small unit for 2 hours only max, better than 35°C inside.
I would like to have 4kw on roof when more money avalaible, I saw that Chris did it with 4.5kw PV.
PV price drop help us to build better system!
Yeah, that's the way I was thinking about it, 144W/day is not so bad but obviously it won't work year round.You could leave the VFX connected all the time but in search mode, then have the controller connect the water heater load when power is available. The inverter would come out of search only then. And it would drop out automatically if the water tank reached temperature and the thermostats shut off the elements.
Simple install, smooth operation, but a cost of 6 Watts continuous to keep search active.
Ending Absorb might be a problem with EA value, would have to deal with time, not so accurate. We really need a MN batt monitor that could monitor charge amps and load amps...
Erik -
Re: Classic water heater diversionCariboocoot wrote: »2). The inverter may not like being fired up with a load already on the output and may fault immediately (depends on the particular inverter). This means you may have to have a two-stage start up where the inverter is turned on first, then the load connected
There are few inverters that like being started up under load.
But I think it would be really easy to use the AUX1 output on the Classic in Diversion mode to operate a switch or contactor to fire the inverter up when the bank gets to, say, 56 volts so the inverter is running and on standby as the bulk stage gets done and it enters absorb where it starts heating water. Many of those cheaper inverters have a remote switch available for them and I think they can be turned on and off with just a little ice cube relay if you can tap into the wires for the remote. Or even tap into the wires for the on/off switch in the inverter.
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Chris -
Re: Classic water heater diversionChrisOlson wrote: »There are few inverters that like being started up under load.
But I think it would be really easy to use the AUX1 output on the Classic in Diversion mode to operate a switch or contactor to fire the inverter up when the bank gets to, say, 56 volts so the inverter is running and on standby as the bulk stage gets done and it enters absorb where it starts heating water. Many of those cheaper inverters have a remote switch available for them and I think they can be turned on and off with just a little ice cube relay if you can tap into the wires for the remote. Or even tap into the wires for the on/off switch in the inverter.
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Chris
That's a great idea Chris. If the inverter can be turned on/off with a switch or relay from aux 1, you could then eliminate the need for a heavy breaker on the battery cable input, and just fuse it for safety. -
Re: Classic water heater diversion
North, I believe Marc is in BC, not in CaliforniaIt's necessary to have so much PV power when you live in a northern climate. It's great if you can make use of the excess, when it's there.;) -
Re: Classic water heater diversionSolarMusher wrote: »North, I believe Marc is in BC, not in California;)
Yup. Cariboo, British Columbia. 52 degrees North Latitude. Ground is still covered with snow. It usually melts by June or July. Although it can also comes back sometimes. In August. -
Re: Classic water heater diversion
Chris, that's the way my submersible starts during the night. It seems to work flawlessly (1/2 force). Magnum inverters are really toughThere are few inverters that like being started up under load.
But I think it would be really easy to use the AUX1 output on the Classic in Diversion mode to operate a switch or contactor to fire the inverter up when the bank gets to, say, 56 volts so the inverter is running and on standby as the bulk stage gets done and it enters absorb where it starts heating water. Many of those cheaper inverters have a remote switch available for them and I think they can be turned on and off with just a little ice cube relay if you can tap into the wires for the remote. Or even tap into the wires for the on/off switch in the inverter.
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Chris -
Re: Classic water heater diversion
Marc, did you have a lot of snow this winter?Cariboocoot wrote: »Yup. Cariboo, British Columbia. 52 degrees North Latitude. Ground is still covered with snow. It usually melts by June or July. Although it can also comes back sometimes. In August. -
Re: Classic water heater diversionSolarMusher wrote: »North, I believe Marc is in BC, not in California;)
I think that he's just wishing he was in California.:p -
Re: Classic water heater diversion
Water should be just a little coldernortherner wrote: »I think that he's just wishing he was in California.:p;);) -
Re: Classic water heater diversionSolarMusher wrote: »Marc, did you have a lot of snow this winter?
Pretty good. Probably a metre total. we've had some odd thawing this year too.northerner wrote:I think that he's just wishing he was in California.
Are you kidding? With all their rules, regulations, and high-priced electric? No thanks! -
Re: Classic water heater diversionSolarMusher wrote: »Chris, that's the way my submersible starts during the night. It seems to work flawlessly (1/2 force). Magnum inverters are really tough
Yes, they are indeed tough. But being tough and having tight enough voltage regulation so they don't make lights flicker with varying loads is a couple different things. It was discussed here before and Ryan (midnite solar) said:
Magnum has some REAL slow regulation. I complained early on in the AE series. Serial number 5 or something and they sped it up a touch but refuse to go any more. This can be an issue for a lot of people and drove me nuts living offgrid. I went from the SW's to the Magnum and was not very happy. I then went to a pair of outbacks and it is better but I sort of miss my SW's
http://www.fieldlines.com/index.php/topic,147132.81.html
Quite a few other folks have run into this problem with them. So folks should be aware of that if they're going to try use one with this AC SSR water heating method on a Classic. That's my message that I'm trying to say so folks don't try it then end up disappointed with it. It DOES work, and it works well. But it takes the right equipment.
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Chris -
Re: Classic water heater diversionThere are few inverters that like being started up under load.
But I think it would be really easy to use the AUX1 output on the Classic in Diversion mode to operate a switch or contactor to fire the inverter up when the bank gets to, say, 56 volts so the inverter is running and on standby as the bulk stage gets done and it enters absorb where it starts heating water
That's what I did. I put a 40 amp DC-DC solid state relay between the DC breaker and the dedicated inverter, and control it with the "Daylight" function on the AUX1 output of one of my Classics.I agree that it could be hard on a cheap MSW inverter, Eric.L dit it that way but I don't know which MSW inverter it was
My inverter is a PSW -- a second-hand Exceltech.
One observation on the Magnum/Xantrex comparison. For me, it was very important to have an inverter that had a properly functioning grid support function, since my whole system was designed around a smaller battery bank. There are a lot of threads here about people having trouble with grid support and the XW line of inverters, including some really annoying issues like people being unable to get it to go completely off-grid (the XWs always draw like 100 watts or something from the grid when it is available).
So for me, but presumably not for someone like Chris O. who I think is 100% off-grid, this was a deal-breaker. By contrast, the Magnum grid-integration worked flawlessly out of the box.
Someone needs to make an inverter with the XW's guts and the Magnum's control system.
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