Solar Powered 48v DC water heating element for Hydronic Buffer tank

[ChronicHydronic]

I plan to install a 48vdc 1000watt water heating element in an old Rheem 20gal water tank to use as a pre-heat buffer tank for an infloor hydronic system I put in this past winter. The infloor system has it's own electric boiler so I am just trying to preheat the water to save on electric bills....not run the whole system.

I have 2-300watt panels that will be roof mounted. It was recommended to me that I could put the panels in parrallel and run straight to the element without ; controller, batteries, etc. While this would be the cheapest method, I would prefer gaining the maximum utility of the panels especially in the summer when the closed loop heating system is not required.

The other option would be to run the system off controller/ 48v of batteries and have an 48v inverter that could ideally power a dehumidifer in the crawlspace.

I wonder if anyone has done something similar and has a gear list or wiring diagram that they can share?

There also is lots of online discussion about wiring directly into the onboard AC thermostat of the water heater. Some have suggested a capacitor (A grunty 6 microfarad non-polarised capacitor) across the contacts will drain off any arcing that may occur. Other folks have suggested 600 watts of solar power likely won't get the tank hot enough to worry about needing a thermostat. Likely a DC thermostat is best.

I also wonder if the inverter and water heating element can be wired to the batteries at the same time or if a switching unit would be required?

Thanking you in advance for gear suggestions.

 

[timselectric]

You can use the on board thermostat to control a DC contactor.

 

[efficientPV]

You could use something like this

PWM MPPT Heater Boiler Charger Regulator Photovoltaic PV Solar Panels Hot Water | eBay

PWM regulator for heaters with an algorithm for finding the maximum MPPT power point from photovoltaic panels. The regulator enables powering standard electric DHW boilers from solar panels. It is fully automatic and starts working as soon as you plug it in.

www.ebay.com

I am not providing any endorsement for the product.

Direct connect would take twice as many panels. That is pretty north for much success for what it would cost. I do my domestic water heating with controllers I've designed. Do have someone in Lithuania who built one of my systems for hydronic heating. Also designed a microprocessor system for a 4,000W system in Canada.

 

[ChronicHydronic]

You could use something like this

PWM MPPT Heater Boiler Charger Regulator Photovoltaic PV Solar Panels Hot Water | eBay

PWM regulator for heaters with an algorithm for finding the maximum MPPT power point from photovoltaic panels. The regulator enables powering standard electric DHW boilers from solar panels. It is fully automatic and starts working as soon as you plug it in.

www.ebay.com

I am not providing any endorsement for the product.

Direct connect would take twice as many panels. That is pretty north for much success for what it would cost. I do my domestic water heating with controllers I've designed. Do have someone in Lithuania who built one of my systems for hydronic heating. Also designed a microprocessor system for a 4,000W system in Canada.

HI EPV Thank you for your information........I have been reading all kinds of info since your post and have not gotten back to you as I am new to this field.
I am convinced an MPT controller type system is required to get the most out of my panels in an unfortunate spot in the world. There is a new (improved?) version of the one you recommend. Actii AC7392

PWM Controller MPPT Heizwasser Heizstab Photovoltaik Solarmodule Sonnen PV 3KW 6931240073926 | eBay

Find many great new & used options and get the best deals for PWM Controller MPPT Heizwasser Heizstab Photovoltaik Solarmodule Sonnen PV 3KW at the best online prices at eBay! Free shipping for many products!

www.ebay.ca

I plan to seriously explore this further although this unit only helps me in the winter for water heating as it is not intended to be a battery charge controller.

So my newbie question. Does it make any sense to use a nice Victron controller between the panels and 2 batteries and hook a DC heating element directly to the batteries? A thermostat solution would still be required, but this solution is appealing if it makes sense. That way in the summer I can also use the controller and battery with an inverter to run some appliances.
I read with great interest your answer to another post (below) and the concept that other's xcel formulas may not be ideal:

"""That ideal resistance is good for less than 2 hours each day. It is better to design for a much lower current. If you often get haze or clouds, a 5500W 240V element would be 10.5 ohms and give better daily performance with two panels in series. Even the 2000W 120V element would work well with one panel. Save that extra money for another panel later.""""

I have 2- 300 watt panels and I purchased a 48vdc 1000watt heater. I am happy enough to buy another AC heater if a higher resistence makes more sense. Just wonder what my best configuration of panels and heating element would be from your experience?

If anyone has any usage comments on the Actii controllers, I think many of us would be happy to hear them.

Thanks In advance Glen

 

[Whats-n-Watts]

HI EPV Thank you for your information........I have been reading all kinds of info since your post and have not gotten back to you as I am new to this field.
I am convinced an MPT controller type system is required to get the most out of my panels in an unfortunate spot in the world. There is a new (improved?) version of the one you recommend. Actii AC7392

PWM Controller MPPT Heizwasser Heizstab Photovoltaik Solarmodule Sonnen PV 3KW 6931240073926 | eBay

Find many great new & used options and get the best deals for PWM Controller MPPT Heizwasser Heizstab Photovoltaik Solarmodule Sonnen PV 3KW at the best online prices at eBay! Free shipping for many products!

www.ebay.ca

I plan to seriously explore this further although this unit only helps me in the winter for water heating as it is not intended to be a battery charge controller.

So my newbie question. Does it make any sense to use a nice Victron controller between the panels and 2 batteries and hook a DC heating element directly to the batteries? A thermostat solution would still be required, but this solution is appealing if it makes sense. That way in the summer I can also use the controller and battery with an inverter to run some appliances.
I read with great interest your answer to another post (below) and the concept that other's xcel formulas may not be ideal:

"""That ideal resistance is good for less than 2 hours each day. It is better to design for a much lower current. If you often get haze or clouds, a 5500W 240V element would be 10.5 ohms and give better daily performance with two panels in series. Even the 2000W 120V element would work well with one panel. Save that extra money for another panel later.""""

I have 2- 300 watt panels and I purchased a 48vdc 1000watt heater. I am happy enough to buy another AC heater if a higher resistence makes more sense. Just wonder what my best configuration of panels and heating element would be from your experience?

If anyone has any usage comments on the Actii controllers, I think many of us would be happy to hear them.

Thanks In advance Glen

I'm working on the same. How did it all work out for you? Hope you have lots of tips!