Solar excess to electric heater

[12VoltInstalls]

I am going to put my ~2kW of panels online at some point. I know most sunny days in winter I have been fully charged by 9-10AM with only 800W split direction array.

With the cost of propane I have explored a couple of options to shave propane heat use this winter. A promising option mathematically (when calculated for BTUs) was to heat water and circulate it to 48” of hydronic baseboard. I could theoretically “save” $40/month for four months at current propane cost with full sun every day. Not only do I know THAT won’t happen, it would require about $300 of equipment. A good idea but no immediate savings this year.

I have an electric 120VAC fan/heater with a 300W setting, and this relay which could either be triggered by the accessory output on the Epever SCC or with a separate micro programmable charge controller board I have on hand.

The idea has merit as I can set it to engage once LiFePo’s hit 13.4V and disconnect if it starts drawing from the batteries. It’s not much heat, but I’m wildhat guessing on sunny days the excess production could potentially make 7k or as much as 10k-BTUs over the day (although literal math suggests 25k BTUs I’m not optimistic on that).

That’s not much but I have everything needed on hand and modestly I think that could save $15/month for 4-6 months, so without getting silly that’s like $50 or $60 over the winter.

It’s free and I don’t see any problems with this but that I’d throw it out here for whatever crosses other’s minds.

Please commence slinging mud!
Thanks

 

[DThames]

What is your PV voltage that you have available?

 

[12VoltInstalls]

What is your PV voltage that you have available?

I’m either going to have 2S for 90VOC or 3S for ~145VOC depending on what I decide to do with my charge controllers.

Though I’m not sure what relevance the panel voltage is. I’ll be running off the inverter.

 

[DThames]

I’m either going to have 2S for 90VOC or 3S for ~145VOC depending on what I decide to do with my charge controllers.

Though I’m not sure what relevance the panel voltage is. I’ll be running off the inverter.

Your subject says, "Dump Heater". You can have a DC heater. I have been using an oil filled 120v AC radiator type heater, turned on to max so the thermostat will not switch off and on. I run 6, 60cell panels in a 3p2s configuration. The heater runs about 70% of its rated power, based on the amps and voltage. I have also played with some cook top elements in a stack of concrete pavers.

 

[12VoltInstalls]

Your subject says, "Dump Heater". You can have a DC heater.

Oh, gotcha. Not a direct dump. That probably wasn’t an accurate term.
Same results, but I was going to run it under 120AC and not have to buy a robust DC relay.
Thanks, I misunderstood.

 

[DThames]

Not sure about the relay that you referenced but you should be able to get a relay with a 12v DC coil and 120v AC rated contacts. For example...would allow control directly from the Load output of a charger to control a typical AC space heater.

 

[12VoltInstalls]

Thanks.
Those have the function of the two relays I have on hand.

 

[12VoltInstalls]

So the thing I noticed yesterday (running 300W straight up without the voltage controller or relay) is that with my existing panels and light haze and partly cloudy is that while the ‘dump load’ of the 300W draw is constant but the solar input is quite a bit less than 300W.
I’m frying other fish at the moment so I haven’t configured the additional 2kW of panels.
However, it appears that on average- once I add 2.5 the current wattage- this should easily contribute $0.60 to $1.02 per sunny day based on the speculative price of propane, and it ‘may’ support the 800W setting on the heater on good sunny days. That’s a worthwhile effort based on the savings imho. Even if propane stays ‘low’ it’s worth something because I don’t need to buy anything and as little as $10/month is still making my solar pay more of its own way. Furthermore, in spring and fall where some but not much heat is required overnight it may be adequate for that- though admittedly not very much propane is required then, either.

I don’t see a downside and apparently no one else does either.

 

[PunchySunshine]

I'm trying to use an oil filled electric heater with the excess electric and hopefully lower the gas bill. I've only got one so far and it's just the start of winter but I'm impressed with it as a heat source!

 

[12VoltInstalls]

I'm trying to use an oil filled electric heater with the excess electric and hopefully lower the gas bill. I've only got one so far and it's just the start of winter but I'm impressed with it as a heat source!

I considered that as well.
I do have an electric oil field heater somewhere in storage, but I do not believe that it allows me to lower the wattage. If I recall the lowest setting is 400 W. At 90 bucks apiece I wouldn’t go out and buy one because you can produce the same amount of heat or more out of a $15 or $20 heater fan. Which makes more sense if saving money is the object because the upfront cost is 20% of an oil filled heater or less. Plus for me, I was looking to have a little air movement under the kitchen sink and into the other water line facilities and that does that for sure. Watts to watts: An oil filled electric radiator makes no more heat per watt than a heater fan does. So the lowest cost is of interest to me.
Never mind the stories about the oil filled electric heaters shorting out inside or the thermostat failing and it overheating and becoming smoky which sounds like the beginning of a fire to me.
I tend to avoid those kind of situations unless it’s for fun