Can You Run A 24v Panel Straight To A 24v Water Heater Electrode..?

[JRH]

In a 55 gallon metal drum would you need a thermostat or can 24v solar panels be wired straight to the 24v 600 watt electrode.. There would be a DC disconect switch and fuse in the pv wire…

I am thinking a CC isn’t needed for this device…but I may be wrong and it’s OK if I need one..

It would be for heating a small shed …to about 40 - 50F in winter.

.the element is a Dernord…can use 1 or 2 …..or as many as recommended …

The PV panels would be 400- 600 watts. Or whatever is recommended …

This is meant to be very simple and basic set up.

The shed only needs minimal heat in winter not to freeze.

The lack of good sun days could be supplemented with a small space heater when needed.

Thx in advance …….J.

 

[DIYrich]

The 24v 600 watt electrode is just a resistance heater. It shouldn't be sensitive to voltage. Don't exceed 24v by much, and it won't overheat.

But, you still need a thermostat. You don't want to heat the drum too high.

 

[JRH]

The 24v 600 watt electrode is just a resistance heater. It shouldn't be sensitive to voltage. Don't exceed 24v by much, and it won't overheat.

But, you still need a thermostat. You don't want to heat the drum too high.

Thank you…

The panels I have for it are an about 30 volts under load ….will have to experiment with how many watts are actually needed..

considering I only get a bout 3 - 4 hours max of decent sun in the winter per day im hoping one electrode will even heat it up good….it may take two..? I will get a thermostat to have on hand.

There’s probably a formula out there to calculate that question, but in my world I will just hook it up and see what happens …adjust- tweak- adjust - etc…

It costs me about 500 dollars a winter to run a small space heater in the shed …im thinking it would be a quick payback if this works like I think…a year or two maybe, .we will see.

Thanks for your info……

J…

 

[Mattb4]

400-600w of heating over 5 hours is unlikely enough to keep anything but a very small well insulated space warm. Putting it in a barrel of water does not change BTU needs for a space. One rough way you can check is finding the daily kWh used now to keep the shed at 40-50F on a Winters day.

 

[JRH]

400-600w of heating over 5 hours is unlikely enough to keep anything but a very small well insulated space warm. Putting it in a barrel of water does not change BTU needs for a space. One rough way you can check is finding the daily kWh used now to keep the shed at 40-50F on a Winters day.

Yep…time to get out the ole kilo- watt meter…and test how much it requires from the space heater when below freezing and how far below freezing….better insulation would be of great help too…nothing is ever easy it seems…ha…

thanks.
J.

 

[Supervstech]

Id want to verify the specs of the element, 24v what wattage?
A 4500W 240V element should produce 450W at 24v or so...
At 30V it would produce 562
48V would be 900...
My point is, the element will alter the wattage based on the volts feeding it.

 

[Steve777]

A thermostat is good insurance, just in case you forget to check on it for a while or something else happens. You probably don't want the drum boiling or boiling dry; unlikely I know but possible...

A 240v element, running at 120v will burn itself out in <10sec if turned on dry, don't ask how I know

 

[JRH]

Id want to verify the specs of the element, 24v what wattage?
A 4500W 240V element should produce 450W at 24v or so...
At 30V it would produce 562
48V would be 900...
My point is, the element will alter the wattage based on the volts feeding it.

It is a 600 watt element …it states on Amazon and on my package it’s a 24 volt element…
The panels I have are about 400 watts each with 31.3 volt Vmp and 13.3 Imp..

Originally I was wanting to use 2 400 watt panels and two electrodes and heat sand in a metal container in winter and in summer power a small window unit with the same panels hooked to different gear for three or 4 months…then switch back in winter…

(None of this is connected in anyway to my normal system outside in the solar trailer ..nor the grid… )

Somehow I got distracted over to heating water .
I’m not certain sand will work properly and haven’t researched it deeply…, but water presents a lot of problems that sand avoids…
I like the idea of sand in a heavy gauge metal container ..gotta look into that some more.

It may be common for all I know…dunno….

 

[JRH]

A thermostat is good insurance, just in case you forget to check on it for a while or something else happens. You probably don't want the drum boiling or boiling dry; unlikely I know but possible...

A 240v element, running at 120v will burn itself out in <10sec if turned on dry, don't ask how I know

Haaaa…those little coffee and soup heaters I used in the early days to put a load on different things while testing as I was building the DC stuff will glow red and burn up in about 2 seconds if you’re not carefull and they lift out of water …12 and 24 volt …12 dollars each…. Poof poof poof …a poof here and and a few more poofs there and soon you spent some good money making poofs….

Don’t ask me how I know either…

J. ….

 

[NIFE]

It is a 600 watt element …it states on Amazon and on my package it’s a 24 volt element…
The panels I have are about 400 watts each with 31.3 volt Vmp and 13.3 Imp..

Originally I was wanting to use 2 400 watt panels and two electrodes and heat sand in a metal container in winter and in summer power a small window unit with the same panels hooked to different gear for three or 4 months…then switch back in winter…

(None of this is connected in anyway to my normal system outside in the solar trailer ..nor the grid… )

Somehow I got distracted over to heating water .
I’m not certain sand will work properly and haven’t researched it deeply…, but water presents a lot of problems that sand avoids…
I like the idea of sand in a heavy gauge metal container ..gotta look into that some more.

It may be common for all I know…dunno….

It will work best if the panel power curve matches the element power curve as close as possible. In your case, the 2 panels in parallel feeding the 24V/600 watt element is pretty close. The 2 panels in parallel like a 1.17 ohm load resistance to achieve Vmp/Imp. The element you are considering comes out to .96 ohms if the specs are correct.

 

[JRH]

It will work best if the panel power curve matches the element power curve as close as possible. In your case, the 2 panels in parallel feeding the 24V/600 watt element is pretty close. The 2 panels in parallel like a 1.17 ohm load resistance to achieve Vmp/Imp. The element you are considering comes out to .96 ohms if the specs are correct.

Hmmmm… so use one electrode per 2 paralleled 400 watt panels for best efficiency ..
is that correct..?

 

[DIYrich]

A 24v element being fed 31v is 130% of nominal rating. Probably ok, but just don't be surprised if it burns out. Also, panels rarely produce rated wattage, so you will likely be way under the rated watts to avoid too many watts on a good day.

 

[Zwy]

In a 55 gallon metal drum would you need a thermostat or can 24v solar panels be wired straight to the 24v 600 watt electrode.. There would be a DC disconect switch and fuse in the pv wire…

I am thinking a CC isn’t needed for this device…but I may be wrong and it’s OK if I need one..

It would be for heating a small shed …to about 40 - 50F in winter.

.the element is a Dernord…can use 1 or 2 …..or as many as recommended …

The PV panels would be 400- 600 watts. Or whatever is recommended …

This is meant to be very simple and basic set up.

The shed only needs minimal heat in winter not to freeze.

The lack of good sun days could be supplemented with a small space heater when needed.

Thx in advance …….J.

4hours x 800W (two 400W panels)= 3200Wh

1Kw = 3412 btu's

3.2Kwh x 3412 = 10,912 btu's

Go to the table here https://windandsolar.com/how-to-siz...How many watts does it,one degree in one hour. and look up 50 gallons of water. You could heat 50 gallons of water with an 80°F temp rise with 11,000 btu's in one hour if you could put all 11,000 btu's in during that time frame. You won't get there with an uninsulated tank. At 50 gallons, the needed watts per hour is 617 watts just to raise water 5°F and your barrel will lose that amount easily.

The question is what is the heat loss of the building? Heating with electric takes many Kwh. That same 3.2Kwh would produce 33,000 btu's with a 3.0 COP heat pump.

 

[myles]

This is interesting I never thought of hearing sand to use as a heat battery

 

[time2roll]

In a 55 gallon metal drum would you need a thermostat or can 24v solar panels be wired straight to the 24v 600 watt electrode.. There would be a DC disconect switch and fuse in the pv wire…



The PV panels would be 400- 600 watts. Or whatever is recommended …

Match the wattage as close as possible. If the panel is under wattage the voltage will sag and power will drop accordingly along the panel power curve.

 

[JRH]

A 24v element being fed 31v is 130% of nominal rating. Probably ok, but just don't be surprised if it burns out. Also, panels rarely produce rated wattage, so you will likely be way under the rated watts to avoid too many watts on a good day.

I assure you where they will be positioned in winter the panels will not produce full power …Haa. It even close except on a rare day now and then……but they will in the summer very often , but I won’t be using them for a heat in the summer..
Thanks…
J.

 

[JRH]

4hours x 800W (two 400W panels)= 3200Wh

1Kw = 3412 btu's

3.2Kwh x 3412 = 10,912 btu's

Go to the table here https://windandsolar.com/how-to-size-a-dc-water-heating-element/#:~:text=How many watts does it,one degree in one hour. and look up 50 gallons of water. You could heat 50 gallons of water with an 80°F temp rise with 11,000 btu's in one hour if you could put all 11,000 btu's in during that time frame. You won't get there with an uninsulated tank. At 50 gallons, the needed watts per hour is 617 watts just to raise water 5°F and your barrel will lose that amount easily.

The question is what is the heat loss of the building? Heating with electric takes many Kwh. That same 3.2Kwh would produce 33,000 btu's with a 3.0 COP heat pump.

I am beginning to see your point from reading on line about this…it would be a huge effort to really insulate the shed properly …… things seems a lot easier in concept than when you do the math of the amount if energy required and study the modifications and prep work….thanks for the links …I have further thinking to do……..

 

[JRH]

Match the wattage as close as possible. If the panel is under wattage the voltage will sag and power will drop accordingly along the panel power curve.

All things I mentioned were just a starting point to build off of. I have already got a bunch of spare and new stuff laying around to work with and I now am figuring on at least 800 watts ( which I will never see in winter ) with the trees I have where these 2 panels would have to be…

I’m beginning to like the the little space heater I have used for years more and more ..when I have lost power I throw a Mr buddy in there and it cooks the place…

This is looking like much more work than I wanna do right now …….starting next month when the weather breaks up here I will be starting to build the new frames , digging trench’s ,cement ground anchors , adding hundreds of feet of wire , the new CC’s and blaa blaa blaa other stuff and quadruple my array for the main system…that will take till mid summer working by myself..

I’m getting tired thinking about it…..

Thank for the info…
J.