I have free electricity! (for a heat pump)

[Matteo92065]

I just read the Heat pump / furnace thread, and had a couple more questions…
I recently installed a 5kW solar system on my house and am finding out that I'm getting more electricity than I can use. So I'm looking into changing over my split system AC and propane furnace to a dual fuel heat pump. It seems to me that I should be able to keep the air handler and propane heater in the attic and replace the AC pump with a heat pump(appropriately sized), and replace the thermostat controller with a new dual fuel controller.
I must have called 15 local HVAC repair/installation companies and only one ever heard of a dual fuel system. That one company just said to replace everything in order to get it to work. Electricity is expensive in Southern California and I don’t think anyone here uses, or knows about, heat pumps.
My questions are; Where can I find out more about converting an existing system? Is it even possible? Where would I find the individual components such as a dual fuel thermostat? What would it take to continue using my existing air handler with a new heat pump? Is this something that I can purchase and install everything to the point of leaving the last solder joints and charging the system to a pro?

 

[slowrev]

Most pros won't touch a system partially installed by the home owner. Keep looking and you should find someone that will do it. Dual fuel systems are fairly common in other parts of the country.

Ben

 

[slowrev]

You can pick up a lot of good info on hvac-talk.com. If you post a question the pros might know someone in your area that can do it for you. also lots of good info in the vast array of threads.
Ben

 

[techman]

While it may be possible to convert as you mentioned, there is a good chance that the indoor air handler as well as the outdoor condenser unit will need to be replaced. If you are lucky, the refrigerant lines can be retained, but that too is not certain.

The air handler for a heat pump may have a larger coil than an A/C one. Also a valve at the air handler would need to be changed, or components added. This is to allow the reversing function (A/C to heat) to work. The labor involved may justify a new unit instead. If your A/C is 8 to 10 years old, replacing it is a wise move anyway.

Given your "free" power, doing the changeover is a good move with a fast payback.

As for dual fuel, it is a common system. The heat pump coil is attached to the outlet side of the furnace. The dual fuel control can be either with what is called a "dual fuel kit", or by using an advanced digital thermostst, like the Honeywell VisionPro 8000, which can properly control the heat pump, furnace and the changeover between them.

As for the refrigerant lines, modern high SEER heat pumps may require a bigger diameter line than you currently have. This is to acheive the high efficiencies. You would need mfg's data on the heat pump to find out for sure.

BTW a dual fuel is also sometimes called a fossil fuel backup on heat pump systems.

paul

 

[kenmac]

I don't see any problems changing out the a coil & the outside unit to a heat pump & keeping your current furnace, provided there are no cracks in the combustion chamber.I have installed new a coil & a/c units & left in the original furnaces.I don't know why an hvac dealer wouldn't do this, but then again you also said, hvac dealers you have contacted have never heard of a dual fuel system. /forums/images/graemlins/confused.gif That's news to me. /forums/images/graemlins/wink.gif

 

[DannyD]

If I am not out of touch with things here, you can sell that extra to the power company. We can here in Indiana.......and I think they have to buy it.

 

[thcri]

</font><font color="blue" class="small">( If I am not out of touch with things here, you can sell that extra to the power company. We can here in Indiana.......and I think they have to buy it. )</font>

Danny,

That is true here also, but I also think it is a Federal Mandate that utility companies have to buy your extra power back. However, they only have to pay what they would pay for it. Here I beleive it is around .02 cents per kilowatt. Not much so if you can use it someplace else that is the better.

murph

 

[BobRip]

Not as efficient, but cheap and easy to install, could you just add a baseboard electric heater. If you could control it so it is only on when you have excess power it would be very cheap to operate. You payback would be very short.

Bob Ripley

 

[greatrandini]

You the man. I think that base board elec heaters would be the way to go. Just use the old system for back up.. They make some very nice oil filled baseboard heaters. Just put one in each room.

 

[mahlers]

In California, there's a net metering law that allows us to choose whether to sell the power back to the utility at the standard set retail rate, or install a time-of-use meter and sell it back at the prevailing retail rate at the time the power was pumped back into the grid. With the time-of-use method, you can get up to $0.30 per kwh if you're pumping electricity into the grid at peak hours - not a bad deal at all. Otherwise, if you just spin your standard meter backwards, you get the standard rate which is about $0.14 per kwh. The caveat to all of that is that you have to be connected to the utility - and you can't sell more power back to the utility than you've used. At the end of the year, they reconcile everything - and if you've pumped more electricity into the grid than you took out, you forfeit it.

Personally, I'd look into lots of different ways to use that extra power if net-metering isn't possible. Something as simple as using a 12v dump load to heat water in a separate electric water heater (set it up inline as a pre-heater to your usual gas heater) can save tons of money in the long run because you don't need to use as much gas or propane to heat the water. That solution won't cost much at all - you can find a used electric water heater really easily, and just swap out the 240v heating element with a 12v dump-load heating element and you're set.

 

[Matteo92065]

Hey, thanks for all the input.

It sounds like the job gets too involved (for me) once I'm replacing all the refrigerant lines! The system is less than one year old, so I guess I'll just keep it intact and inplace.

We have put small electric room heaters in each bedroom, and that has cut down on our propane use.

I like the idea of heating water! Never thought of that.

In San Diego, residential accounts don't have the option of Time Of Use meters. We only get Net Metering with no payment for excess generation.

Attached is a picture of my new system. It took me 3 months of on and off working weekends, and large number of trips to Home Depot.
Never mind the landscaping, its a new house.

 

[jinman]

</font><font color="blue" class="small">( Never mind the landscaping, its a new house. )</font>

So... I probably couldn't interest you in any landscaping rocks, huh? /forums/images/graemlins/laugh.gif

Nice looking place and one hekuva view. /forums/images/graemlins/cool.gif

 

[kenmac]

Kinda looks like a ducane brand a/c unit. That's a GREAT VIEW !

 

[techman]

The ideas of electric baseboard heaters is a nice, cheap solution, but the big point has been missed. By going to a heat pump, you will get 2 to 2.5 times the heat per KW than with electric resistance heat. Your original idea of a heat pump was a good one. Given your limited amount of free power, getting the higher efficiency is a smart move. It does require a higher investment, but I think a wise one.

If you really want to spend some money, put in a geothermal heat pump. This will give you the maximum amount of heat (and A/C) for the given KW input. If you really want to be creative you could get a water-to-water gothermal heat pump. This will generate hot water for domestic water or heating. You could use it to heat up 2 or more 50 gallon hot water heaters during the daylight (w/o having the elements connected, just as an insulated storage tank). You could then draw the water out of the tank and use radiant loops or a heat exchanger in the air handler to provide comfortable heat all night. Again a higher initial investment but maximum BTUs for your KW.

paul