Convert from Propane to Dual Fuel?

[brentmc]

I searched and read through the results but cannot find my specific question addressed.

I need to replace my home AC/Furnace. The AC company is recommending I switch to a dual fuel set-up to save money and get better heating.

Any opinions on doing that?

Anything I should ensure I do if I go that route? Variable speed, etc?

Thanks!

 

[yeldogt]

Yes -- get a heat pump. It adds almost nothing to the cost vs straight AC.

What is your electric rate? .... in my area depending on propane costs and outside temps -- the heat pump is cheaper to run.

In may areas there is no longer a need for backup with heat pumps -- they work that well.

I'm doing a propane furnace in my new build along with HP -- only because it's initially going to be a weekend use and we also lose power often -- so I want the extra boost of the furnace and to use furnace and not heap pump should we be on generator

 

[Bretny]

Dual fuel? You mean a furnace with a hrat pump AC? Usualy a heat pump will add roughly $300 to a central air system. In your location i would think you could run the heat pump very efficiently most of your heating season.

If you lease/rent your propane tank the supplier may not be happy but thats if you dont use alot of propane.

I just replaced my central air and chose not to get a heat pump unit for one reason. My primary heat is wood, wood is cheaper than a heat pump. Secondary is oil heat.

 

[Sunosauno]

Yes -- get a heat pump. It adds almost nothing to the cost vs straight AC.

What is your electric rate? .... in my area depending on propane costs and outside temps -- the heat pump is cheaper to run.

In may areas there is no longer a need for backup with heat pumps -- they work that well.

I'm doing a propane furnace in my new build along with HP -- only because it's initially going to be a weekend use and we also lose power often -- so I want the extra boost of the furnace and to use furnace and not heap pump should we be on generator

+1

 

[mm08822]

I too am looking into replacing forced hot air furnace and ac with new equipment. Currently furnace is ng and I intend to stay with that fuel.
However, I may consider a heat pump instead of a basic ac compressor. I understand the "balance point" can be adjusted to change from operating with the heat pump to that of furnace fuel.

Does anyone have/know of an analysis tool to the determine optimum balance point temp and if even switching to hp has a pay-back or winds up costing more to operate.

This would be good input for the OP as well.

 

[fitter30]

Most heat pumps start dropping off below 47*. If your have a brand and model # coil and condenser should be able to find the performance chart on line.

 

[yeldogt]

I too am looking into replacing forced hot air furnace and ac with new equipment. Currently furnace is ng and I intend to stay with that fuel.
However, I may consider a heat pump instead of a basic ac compressor. I understand the "balance point" can be adjusted to change from operating with the heat pump to that of furnace fuel.

Does anyone have/know of an analysis tool to the determine optimum balance point temp and if even switching to hp has a pay-back or winds up costing more to operate.

This would be good input for the OP as well.

With the cost of electric an NJ .. and with you having NG .. my guess is you will never use the heat pump.

I own a house in NJ -- the house has hot water heat with a NG boiler. Panel Radiators/Radiant Slab/ Radiant wood floors. I got a heat pump when I recently redid the house (previously only AC) -- the reason: I use the heat pump when it's a little cold and I don't have the radiant running -- shoulder seasons. Just to warm up the house -- I also keep in on so it balances out the building. I could have added a furnace -- but that would have needed piping and flue -- 4k more and I will never use that much electric running the heat pump the way I do.

Being in NJ -- use the NJ Clean Energy program. It's an amazing deal .. it's not quite as good as it was when I did mine a few years ago .. but still worth using.

I qualified for the 5k rebate -- as well as the 10y 10k 0% loan. With the upgrades over stock I save the 83 bucks a month that the loan costs. It's like getting 15k for free.

 

[yeldogt]

Most heat pumps start dropping off below 47*. If your have a brand and model # coil and condenser should be able to find the performance chart on line.

Yeas ago this was true .... not today .. it's amazing how efficient they are at 5 degrees .. 2x to 3x the running of resistance/

Mine .. Carrier 5 speed ... is putting out hot air at single digit conditions.

The new heat pumps are making geo even ore unworkable for typical houses with < 5t needs.

 

[brentmc]

Dual fuel? You mean a furnace with a hrat pump AC? Usualy a heat pump will add roughly $300 to a central air system. In your location i would think you could run the heat pump very efficiently most of your heating season.

If you lease/rent your propane tank the supplier may not be happy but thats if you dont use alot of propane.

I just replaced my central air and chose not to get a heat pump unit for one reason. My primary heat is wood, wood is cheaper than a heat pump. Secondary is oil heat.

Yes--that is correct--it will use propane when the temp gets below 30 degrees, but use the electric heat pump above that.

I am paying 2.85 per gallon for propane and go through about $800 each month during the winter.

Besides thinking that Amerigas is ripping me off with their practices of "venting" the gas on fill up and filling the tank at the beginning of summer so that gas evaporates over the next few months, and refusing to fix a leaky valve, and leaving the valve open once and draining my tank, etc...(that is worth another post in itself), my unit is 22 years old.

The HVAC guys says he uses a dual fuel in his own house and it saves quite a bit of money for him.

I just don't want to take only his word for it when I can ask you GJ guys what you have experienced too.

So, it sounds like dual fuel is the way to go.

What about other upgrades? variable speed, humidifier, etc?

 

[yeldogt]

You should get a heat load done on the building -- energy audit. Use your current consumption and a guess as to efficiency for usage -- see what the building uses per foot and if you should do any upgrades to insulation -- air sealing.

Then you look at equipment. The better equipment with both VS speed fans and compressors can really improve comfort .. all the while saving some $$.

The 30 degree number is no longer valid -- my thermostat can actually input the fuel and electric rates and determine when to switch between fuels .. with propane .. that may be never.

I'm building a new house and it's surprising .... some HVAC people are stuck in the dark ages. Others get it --- do better systems .. and make more money as well.

 

[Bretny]

Holy **** $800 a month just for heat? Thats over half my mortgage payment. How many gallons are you useing? Also i would be looking for a different suppliers of propane.

Pellet stoves are prety easy to use and cheap if you dont feel like making the decision before winter.

 

[vavet]

We have a similar set up. It's an electric heat pump with a propane back up instead of electric resistance heat.
IDK how much it saves, but it's more comfortable. The air coming out of the vents on those really cold days is actually hot instead of "just not quite as cold as the air already in the house."
This was installed in the crawlspace of a new construction house. We had lots of issues and no heat the first winter. They finally figured out it was because the slope of the exhaust vent pipe was too shallow. They had to run a new vent pipe out to the side of the house instead of the back because it was a shorter run. I think a competent HVAC installer would get it right the first time. The fact that it took at least 4 tries to get it right tells you what I think of the HVAC company our builder used.
Now that the installation issues are sorted, I'm pretty happy with it. It was a slight upcharge vs the regular heat pump, but we didn't care about having the fireplace with gas logs, so the builder gave us a credit for that and then charged us the difference on the heat pump. I think we actually came out a little ahead.

 

[mm08822]

Most heat pumps start dropping off below 47*. If your have a brand and model # coil and condenser should be able to find the performance chart on line.

With the cost of electric an NJ .. and with you having NG .. my guess is you will never use the heat pump.

I own a house in NJ -- the house has hot water heat with a NG boiler. Panel Radiators/Radiant Slab/ Radiant wood floors. I got a heat pump when I recently redid the house (previously only AC) -- the reason: I use the heat pump when it's a little cold and I don't have the radiant running -- shoulder seasons. Just to warm up the house -- I also keep in on so it balances out the building. I could have added a furnace -- but that would have needed piping and flue -- 4k more and I will never use that much electric running the heat pump the way I do.

Being in NJ -- use the NJ Clean Energy program. It's an amazing deal .. it's not quite as good as it was when I did mine a few years ago .. but still worth using.

I qualified for the 5k rebate -- as well as the 10y 10k 0% loan. With the upgrades over stock I save the 83 bucks a month that the loan costs. It's like getting 15k for free.

Yes I realize they drop off as temps lower and that is where the question starts. I have read (on the internet!) that from roughly 40 - 70 F, the heat pump is a lower operating cost. Once you get below 40F, ng is the lower cost heating method. But by how much - pennies or $$.

Obviously a hp cost a few $ more than a straight ac unit. Supposedly there is ~4 yr payback to recover the added purchase price. I know my energy rates and was hoping to drop them into some model along with my location and see if it has any value.
Since two stage furnaces and variable flow are also available, I don't have any reference points to do a real comparison.

And then comes the additional system complexity and increased risk of component failure.

Yes, I'm familiar with NJ Clean energy offers. There at $4K right now and do have a $10K loan but with low interest.

 

[yeldogt]

Yes I realize they drop off as temps lower and that is where the question starts. I have read (on the internet!) that from roughly 40 - 70 F, the heat pump is a lower operating cost. Once you get below 40F, ng is the lower cost heating method. But by how much - pennies or $$.

Obviously a hp cost a few $ more than a straight ac unit. Supposedly there is ~4 yr payback to recover the added purchase price. I know my energy rates and was hoping to drop them into some model along with my location and see if it has any value.
Since two stage furnaces and variable flow are also available, I don't have any reference points to do a real comparison.

And then comes the additional system complexity and increased risk of component failure.

Yes, I'm familiar with NJ Clean energy offers. There at $4K right now and do have a $10K loan but with low interest.

MM --- with you having NG -- it a different calculation. The OP is propane and that's factors more than NG. My guess is you may never have a situation where running the heat pump is cheaper .... you have to do the math based on your electric rates and NG rates and efficiency rates of the equipment.

I did the Carrier 5 speed -- they make a special unit for NJ. It's the 36 btu unit in the 48's case So the condenser coil is larger -- comes out as a 37k BTU unit. That hit all the NJ rebate buttons as a HP ...

The 4 year payback may just be the better equipment for AC .. electric usage.


As I said in another post -- the multi speed units are as much about comfort as savings. They can ramp way down and run for a long time on low -- this makes them very quiet and they eliminate all humidity. In heat either with HP or furnace both can modulate ,,, they match what the house needs based on outside and inside temps.

 

[mm08822]

MM --- with you having NG -- it a different calculation. It’s the same calculation – just different costs for different fuels.

The OP is propane and that's factors more than NG. I realize that. LPG is roughly 2 -2.5x that of ng I believe.
My guess is you may never have a situation where running the heat pump is cheaper .... you have to do the math based on your electric rates and NG rates and efficiency rates of the equipment. That’s what I said earlier. Biggest problem is I don’t have any temp profile for my area or the time.

I found a calculator on line finally. It showed less than $60/yr savings for my situation. I’m surprised there was any savings and actually expected zero or negative savings. Not worth doing IMO.

I did the Carrier 5 speed -- they make a special unit for NJ. It's the 36 btu unit in the 48's case So the condenser coil is larger -- comes out as a 37k BTU unit. That hit all the NJ rebate buttons as a HP ... I’ll check this out – thanks.

The 4 year payback may just be the better equipment for AC .. electric usage. No, they were claiming as the benefit of hp vs ac. Same seer. They didn't provide any real details so it means nothing to me.


As I said in another post -- the multi speed units are as much about comfort as savings. They can ramp way down and run for a long time on low -- this makes them very quiet and they eliminate all humidity. In heat either with HP or furnace both can modulate ,,, they match what the house needs based on outside and inside temps. Yes I understood these points from some earlier research. I agree, these are worth the money purely based on occupant comfort.

OP, go to alpinehomeair dot com and there is a calculator where you can plug in your specific data. I used it purely for the differences between one system and another - not the absolute #'s. I can't vouch for the calculator, but it was good enough to me to confirm my hunch.

 

[yeldogt]

MM -- my use of the words "different calculation" was a reference to the low cost of NG and the fact that any heat pump -- even the most efficient one out there may not match the low cost of running a NG heater.

Although I have seen situations where people install high end HP's and use 80% furnaces for backup. The furnace has a VS blower ... the units don't condense ... so they have no freeze problems.

MM -- being in NJ ... you would be foolish not to use the program. Call two Co's that do a lot of the work in the program -- see what they say. In my case using standard equipment was MORE costly. Bumping all the way to the 5 speed in the Carrier line kept getting more of the rebate .. it did not cover all the costs .. but it make the decision easy. Going the last jump up to the Greenspeed was only going to get me slightly better operational efficiencies .. mostly in low temp HP operation ... that was not really important.

The NJ profile can use various set numbers. One guy originally used 2 and 102 -- with 72 set point. See how that comes out for sizing. Then you play around with the numbers. You would not want to go to a 4 ton just to capture the 72 on a 102 day.