Replacing a gas furnace with an electric one

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Old 10-29-20, 07:53 PM
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Replacing a gas furnace with an electric one

Hi all,

I've got a Carrier 58SX080-BC gas furnace. I guess it's from the 80's. I'm thinking about replacing it with an electric as I just got solar panels on my roof. How can I tell the size of my current furnace in order to find a similar sized electric? Is the size printed on it somewhere? Or is the size in the model number?

Does anyone have any recommendations for brand of electric furnace?

Will I have to replace my A/C condenser on the roof as well? Or should I just do it as a matter of course because it's probably of the same age as the furnace.

Incidentally, the furnace has some issues with the 3 wire pilot burner switch almost annually, so I'm starting to lose my patience with it. When it doesn't start reliably, I just replace that part myself and it works fine for the season. I'm about to do it again tomorrow. :/

Thanks in advance for your insight!
 
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Old 10-29-20, 08:37 PM
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How much solar do you have, and what are your electric rates? What is your gas rate per therm?
Its very likely you don’t have enough solar to operate an electric furnace, and your utility rates will increase.
If you decide to go electric, it would be best to do a heat pump with electric backup.
 
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Old 10-30-20, 12:31 AM
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The Carrier number is incomplete, no way of determining the heating capacity without a complete M/N.
 
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Old 10-30-20, 12:34 AM
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The 080 in the model is 80k btu.

I see several issues here.
Natural gas is usually the most cost effective to run. Propane not so much. Electric typically the most costly.
Your solar panels will not be enough to run the electric heat but they may entitle you to a good electric rate which may make an electric furnace attractive. I agree that a heat pump would be a good choice.

If your furnace is that old..... how old is the A/C equipment ?
If it's the same age you'll be wanting to replace that too.

You have solar panels and your A/C condenser on the roof ?

 
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Old 10-30-20, 12:44 AM
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I thought it was 80%, and that the next few numbers gave capacity. Regrettably, not the first time I was wrong. It'd still be good to have the full M/N though. Agree on heat pump: About a third the power requirement as compared to resistance heating.
 
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Old 10-30-20, 03:43 AM
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Carrier 58SX-080.......... specs...........



 
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Old 10-30-20, 09:12 AM
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Thanks, guys!
My solar system is 78Kw, designed to cover my current electric demand with a pool and two girls in the house who need to be comfortable and cool in the summer, lol. No, my solar would not cover an electric heating bill, but, if what PJmax says is correct about a better rate, maybe I'd spend less in the long run vs keeping the house warm in the winter with gas. Granted we are in So Cal so not a large demand but weighing my options is a great idea.

A/C equipment is old, yes. It would probably be reasonable to replace it as well. Yes, the condenser is on the roof. We also have a separate system (furnace) with condenser also on the roof for our upstairs.

I can look up my gas price/therm. It's probably tiered so I'm not sure how to answer that question right now. I'll look it up and let you know.

I know nothing about heat pumps. I'm intrigued and will have to look it up. Tell me more if you can.

Thanks so much for the info and please keep it coming if there are any other ideas. Now I at least know the size of my system so I can do some research.
 
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Old 10-30-20, 11:01 AM
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You probably don't need 90k of heat in california. Don't use what you have to size, most furnaces are oversized.

With solar, keep in mind, it doesn't sync with heating demand, so while on paper it may look like you're partially heating with solar, in reality you're just heating with electricity from fossil fuel/nuclear plants.
 
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Old 10-30-20, 11:22 AM
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If you have a grid tied solar system..... you don't use that power directly but based on your contract you receive a significantly reduced electric bill or one set price regardless of use. This should bear heavily on your choice.

As was previously mentioned..... based on your need and area.... a heat pump system would be a good choice. You might not even need any backup resistance heating.
 
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Old 10-30-20, 03:00 PM
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Yes, my system is grid tied. It's new so I don't have all a handle yet on how SCE will charge me. I'll look into that as well as my cost of gas.

user 10, got it. I'm just hoping I can "sell" enough back to the grid to make a solid dent on my bill.

PJmax Would you mind suggesting a specific heat pump brand/system as an example that I can price out and learn about? I don't mind over-sizing a bit. Do I understand correctly that it does heat and A/C as well?

Is there a condenser on the roof with a heat pump system? This is a new concept for me.
 
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Old 10-30-20, 05:03 PM
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I have a neighbor that has solar and pays something like $98 a month for his electric..... period.
I have another neighbor that gets a percentage back off his actual use.
It's pretty confusing.

You should have an HVAC company come in and do a heat loss calculation. They measure the rooms and based on that and construction.... arrive at a certain figure that the heating system needs to cover. In your case..... A/C will be as important and maybe even more important based on your location.

If you want to just look around..... pick a company you like and look at a 3 ton system. Lennox, Trane, Goodman are several companies. The more efficient the system..... the more you'll pay for equipment, the more you'll save on energy and the more it will cost to repair. You're in California. They are pushing for extremely high efficiency systems out there.
 
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Old 10-31-20, 01:56 AM
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Thanks PJ!

My son lived in San Diego for several years, his condo had a furnace he rarely used and no air conditioner. It might be good to know where 26 lives in CA and how big the home is.
 
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Old 10-31-20, 08:04 AM
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I have a 6kW solar system on my roof. When it came time to replace my 1st floor HVAC I asked all the quotes to include an option to have a heat pump option on a gas furnace/air conditioner system. On average it was about $500-700 option for most systems to convert the outside A/C unit to a heat pump system. At this point in time it is dirt cheap to run gas heat, but that may change in the future. I went with heat pump to give myself some options.

What is your long term prospect on gas? If this is the last gas appliance and your long term goal is to get rid of gas altogether (and the monthly meter charge), then heat pump may be the way to go. If you still have a household full of gas appliances (water heater, gas stove, other HVAC systems), then the solution may be a gas furnace as a back up to a heat pump system.
 
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Old 10-31-20, 10:40 PM
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caddymac Sounds like we're similar. I'm in Long Beach, CA. Mild climate, but we like our HVAC, lol. My downstairs is probably 1600 sq ft..

That's great to learn that you can run a heat pump and have a gas back up. Do I have that right? I have gas everything but an electric stove so gas is still needed.

To add to all this, the fix that I thought would work isn't working so my furnace is currently out of order. We have warm weather this coming week but we may be on the fast track to a new system sooner than I thought. I'll call Long Beach Heating and Air and get a quote with all of these suggestions. Is there anything else I need to know when getting a quote?

Is it a gas system with a heat pump backup? Or a heat pump system with a gas backup?

PJmax Since I just got solar, I think it would be great to go electric where I can. The heat pump sounds good. From what I understand, my system is designed to zero out my electric bill. IOW, I make extra during the day so what I use at night is covered. If I add an electric appliance, I may end up with a small bill. But if I'm not using as much gas....?

Here are screenshots of my two most extreme recent gas bills. https://photos.app.goo.gl/dzG3EkzgL6C5pdPV9
$25 in Sept to $153 in Jan. What do you guys think? Can I save some money with solar and a heat pump? I would say the biggest difference in my gas usage is the furnace in those months, and maybe some extra water heater usage, but mostly furnace.

Now I'm off to write a new thread to try to figure out if I can fix my furnace for the short term....

Thanks again for the info!
 
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Old 11-03-20, 03:05 PM
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26kick - I think the common name of my system is "dual fuel". It is primarily a heat pump system with a gas backup.

On the really really cold days (where highs are 0F or lower), I'll go to the thermostat and switch the system to Emergency Heat to force just the gas to run. Mostly because on those days the heat feels "better" when it is the hot gas heat.

For your situation, as it doesn't get all that cold, it would run on heat pump most of the time. I'm not sure if it is possible to do automatically, but at least manually you might be able to avoid peak electric rates (if applicable) by running gas from sundown until the off peak rate.

Looks like on your gas bill you have a Tier II usage when you go past a certain amount of therms. A heat pump would keep you out of that region. Of course that's done by shifting gas usage to electrical usage, so plan accordingly!
 
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