Any HVAC experts or Contractors ?

John T

Well-known Member
I'm buying a well insulated home that has a fairly new Heat Pump with Central Air which works well and Duke Energy has decent much better then REMC rates, HOWEVER they, as typical in this area, use resistance electric heating when temp drops and heat pump efficiency drops drastically and the bearings in the electric meter smoke lol..........

But Natural Gas is available and "typically" in this area Natural Gas heating is more economical then Heat Pump with electric back up.

NOOOOOOOOOO I don't have exact gas and electric rates nor required BTU nor any energy audit nor exact R values etc etc to quote at this time, although I WILL before making any decisions.


QUESTIONS in the meantime to the HVAC gents before I get rates and energy audit and talk to HVAC Contractors


Do they make and is it possible to add on,,,,,,,,,,,, and/or modify,,,,,,,,,,,, or even an ALL NEW unit that would utilize the Heat Pump at say X temp and above BUT WHEN TEMP DROPS TO X DEGREES the Natural gas Furnace kicks in versus the old electric resistance heat at cold temps ???????????????????????????????????? Sure, turn off the electric strip heat and set the t stats so Natural Gas comes on at x degrees BUT THAT SOUNDS SQUIRELLY AND TOO SIMPLE LOL or dump Heat Pump heat all together but leave AC portion and heat ONLY with Gas ???????????? WHAT ARE MY OPTIONS ????????????

I'm NOT interested at this time regarding advantages or disadvantages of different heat methods be it wood or pellet or geothermal or solar or electric or heat pump etc etc etc.......... I'm ONLY wondering if they make or I can modify or add on or buy all new so I have NATURAL GAS HEAT (if cold below X degrees) BUT still utilize the Heat Pump (NO Electric resistance back up) when its not very cold ??????????????????????????????????????

Thanks yall

John T
 
Just use a separate thermostat for the gas furnace, and disable or disconnect the wiring for the resistance heat.
 
I know they make heat pumps that switch to LP gas rather than resistance heat. They're popular here in Michigan in rural areas without natural gas; my son has one. Cheaper to operate than either resistance heat or straight propane. Presumably they also make natural gas versions.
 
The electric heat strips are probably in an air handling unit. Remove the air handler and slip in a gas furnace. May need a new coil also to fit the furnace dimensions. You would need to hire a professional installer to make sure everything is sized properly and do the installation. The outdoor condensing unit can be reused.Duke energy will be complaining tho. You electric rate may go up. Good luck.
 

Probably the best answer.. If you have room, add a gas unit next to you existing unit.... and a separate thermostat as said. Will get you in cheapest for now.

John, I believe that you find the gas will always beat the heat pump, unless they have it priced out of site, so a heat thermostat set for the winter and a cooling thermostat set for summer will be cheapest till replacement time comes along. If you have to trench in the gas service, and build it into the house, that might make you wonder a bit about how long you'll be there. But you can plumb in the water heater, dryer and stove for additional long term savings.

Good luck on the task.
 
Yes, using a more sophisticated thermostat or outdoor reset on your current thermostat you can set the ambient temperature change over for the different heat sources. It all depends how much you want to spend and how involved you want the system to be. I believe the Carrier CoR and CoR 7 thermostats have this capability.
 
Long time since I was in that industry but yes. Set up is as a heat pump out door unit with a out door thermostat. Gas or oil furnace with a heat pump coil like you would have for AC. Takes care of AC in the summer, heat pump in the spring and fall when temps are mild, 30 35 degree's and above. Then shifts to your furnace as the main source of heat when the out door thermostat tells it to. It has been a while but I am sure this is still out there for use in the colder northern climates. If I recall right at that time testing showed us that at an outdoor temp of 27-28 degrees and an indoor temp of 70-72 a 3 ton heat pump had lost about 1/3 its heating capacity. 3 ton = 2 ton. Also a good idea to have a hot water hose bib put in right next to the out door unit if you have a lot of rainy, misty, foggy weather to de-ice the out door unit. Just what I recall doesn't make it so.
 
Bloomington, south central Indiana

PS Don't tell Gary FLOLDFORD, to him I'm still HOMELESS LOL

John T
 
John, what you are referring to is called a 'dual-fuel' set up and it is pretty common. All it requires is a thermostat that is capable of running it.

The heat pump is set up as heating stage 1 and then the gas furnace is the auxiliary heat source (instead of the electric heat strip package) and the 'emergency heat' source.

The thermostat disables the heat pump when you are below a certain outdoor temperature and runs the gas furnace (auxiliary heat) instead.

If you set the thermostat to 'emergency heat' mode it will run the gas furnace no matter what outdoor temperature you have.

Not a difficult thing to set up for any competent HVAC contractor.
 
Thanks all GREAT information, I appreciate it.

It looks like the BOTTOM LINE and CRITICAL DETERMINATION is at what outside temperature do you disable the Heat Pump (Of course, elec resistance heat portion is totally GONE) and turn on the Natural Gas Furnace ??????????????

And that depends on the cost of Electricity and Natural Gas. At this time a pure GUESS might be say 35 degrees ???????????? Time to talk to Duke Energy, Vectren Gas, and HVAC Contractors...........

THANKS AGAIN

John T
 
IF, natural gas heating is more economical and if you add ng backup, then why don't you you make it the primary heat and only use heat pump in cooling mode only. Also, one needs to factor in ng installation, connection fees and minimum use bill during the off heating season.
 
Just about anything is possible these day with enough electronic gadgets.

I have several friends using heat pumps with gas furnace back-up. They "say" that their gas furnace takes over when the temperature drops below a certain point. I have a rural home in Sullivan County Indiana that has an electric heat pump with electric resistance heat back-up. It uses a two stage thermostat. The first stage is wired to the heat pump and the second stage is wired to the resistance heat. The thermostat doesn't care whether the second stage is wired to electric heat or a gas furnace. There is nothing wired to an outdoor thermometer, so I assume that the second stage kicks in based on some algorithm that basically calls for the second stage when the first stage is unable to handle the load.

My city home in Indianapolis has a two stage geothermal heat pump with a third stage wired to electric resistance heat. It has somewhat fancier thermostats that require the various stages to be programed for either gas, heat pump, or electric resistance heating. I'm just guessing that this information is needed because each kind of heat has its own quirks. A heat pump needs its compressor to "rest" for about five minutes between compressor cycles. A gas furnace needs to have the blower fan run for a longer period after the burner shuts off.


Things get more complicated when you have set back thermostats and/or zone heating. With a heat pump there is little reason to turn the heating level back when you are gone for the day IF you have to use resistance heat to warm the house back up when you return. The situation may be different if you have gas heat back up.


Don't forget that installing gas service and a reasonably high efficiency gas furnace is fairly expensive----and you will be paying a minimum gas bill twelve months a year even though you might only need gas heat for several of those months.
 
You'll have to examine the technical information for your heat pump to see how many thousand btus of heat it will produce at the various outdoor temperatures vs energy consumption to run the compressor. This will vary from unit to unit based on the SEER rating. you are correct in realizing the cost of each 1000 btus will be higher and higher as the outdoor temperature gets colder.

Then you need to figure out what a 1000 btus of gas heat costs you in terms of fuel.

Basically you want to graph out both costs. where the lines intersect, that is the point where you want to switch from heat pump to gas.

I think you are probably in the ballpark figuring that point is 35 or 40 degrees.
 
John T I would really check Duke Energy's rates out close. I have family that was on the CGE, Cinn. Gas and Electric, for years. Duke bought them and their electric bills doubled.

As to your original question. Dual fuel heating systems are pretty common around me. The heat pump is great/cheaper until you get into the lower 30s. Most of the rural houses use propane and the in town homes use natural gas backups.

Also consider the heating needs of the house your buying. Meaning I would assume a smaller house that is well insulated. The cost of installing a dual fuel system may never pay back when compared to the cost of the electric backup on this "new" house. I am living in an 150 year old farm house. My heating/cooling cost are high. In your "new" house the costs should be next to nothing.
 
Just a bit more info. YES I'm well aware the cost (but a ton of variables and gas and elec costs would have to go into the equation) of installing a new natural gas furnace and duel fuel modifications is gonna be expensive and MIGHT NEVER PAYBACK PURELY AS AN INVESTMENT. Duke Energy is my ONLY electric utility option and regardless of its cost I do know for a fact its cheaper then REMC I was on where I sold my farm yayyyyyyyyyyyyyyyyyy

HOWEVER I'm thinking about when we get really oldddddddddd and/or I'm gone and the wife maybe chooses to live there I WANT HER OR ME TO STAY WARMMMMMMMMM AND HAVE AS LOW AS POSSIBLE ENERGY BILLS. I remember how OLD people like my old mom was and they needed need the temp HIGH in the winter lol

Soooooooo even if in the long run it may be cheaper to stick with what I have (spend like nothing, its already well insulated and has a good 4 yr old heat pump) as the cost of dual fuel and a new furnace may never pay for itself, its in my DNA to prob go ahead and upgrade to dual fuel for my own personal reasons and preferences and current and future budget reasons.

THANKS TO ALL I learned a lot from this thread and am better informed now when I talk to HVAC contractors

John T Still currently HOMELESS however lol
 
(quoted from post at 09:42:42 06/24/18) John, what you are referring to is called a 'dual-fuel' set up and it is pretty common. All it requires is a thermostat that is capable of running it.

The heat pump is set up as heating stage 1 and then the gas furnace is the auxiliary heat source (instead of the electric heat strip package) and the 'emergency heat' source.

The thermostat disables the heat pump when you are below a certain outdoor temperature and runs the gas furnace (auxiliary heat) instead.

If you set the thermostat to 'emergency heat' mode it will run the gas furnace no matter what outdoor temperature you have.

Not a difficult thing to set up for any competent HVAC contractor.

This is exactly how mine is set up. Been there 21 years with no trouble. My LP furnace is set to kick in below 35*. My electric coop puts heat pumps on their own meter and is about 30% less than standard rate. Makes for very economical AC in the summer.
 
Hello John T,

A well insulated house, and a fairly new unit? It may be all you need. Outside mean temp in the area? My vote is to wait and see. You mentioned wood, it might be the cheapest way around, especially if you have the wood available and will do the grunt work. It will certainly keep you in shape as well,

Guido.
 
They used to make furnaces that were heat pump with natural gas back-up. Look at your set up and see how it's built, is their room for a conventional furnace? Seems most heat pumps are mostly coils in an air handler, if your ducting allows for a furnace to be added you're okay. If it doesn't it might still not be a lost cause as you can install a gas fired residential boiler or hot water heater and slip a hot water heating coil into your duct work and you then have a fuel combustion back up, and depending on your sight you can set yourself up for solar or even thermal batteries to heat the water when it's cheaper and use the heat later or even use the boiler for heat AND a indirect hot water heater, floor radiant heat or radiators in the occupied space.
 
Talk about staying warm, with a heat pump it will always feel colder than say a gas furnace or even when the heat strips kick in you will notice the difference. The heat from the heat pump will be not much higher than your body temperature so it always feels cooler. Go with a gas furnace and the heat pump as an AC unit.
 
I thought about it but it gets expensive to dig up the yard and bury all the pipes and install the new unit so I decided against it. Leaning more towards leaving the good heat pump for AC and heat when its a bit warmer and back it up with the natural gas furnace.......

Thanks for your post and ideas

John T
 
Hello John T. Here in WI I did air to air heat pump, electric backup and wood heat when I built my house in 1979. My son had very bad Asthma when young and the smoke from the wood was a suspect. In the end it was not the culprit but I went to Natural Gas Heat and just AC. That was one of the best decision I ever made.

Now I cannot tell you about Indiana and your power company rates but you got to do the math. Even if the math is crude or estimates you will get a feel. If you cannot find a number see if you can guess one in the ball park and then test different variations around that. Again, you will get a feel. I think sometime people get frustrated because that don't have exact numbers.

Oh, I did the math and straight Natural Gas was hands down my best choice for heat. Nothing else was even close. That was in the mid 80"s.

Paul
 
Hi Guido - I agree that wood-heat is something to think about. That smooth and consistent ( and quiet ) source of heat does have advantages for those who are willing to do some work. And it will never leak or explode.
 
I don't have gas available in my neighborhood (SW Houston), so when my heat pump was working (the changeover valve sticks and needs to be replaced), the thermostat would first come on in heat pump mode first and try to "warm" the house, and if the fancy electronics realized it wasn't heating enough, then the system will turn on the coils. On my thermostat there is also the option of running Emergency Heat which bypasses the heat pump and goes straight to the coil. Make sure the house has the proper thermostat which is Heat Pump WITH backup Heat (they are more expensive than basic ones). Mine is a Honeywell.

When the heat pump is working, it really does do a good job of keeping the electric bills lower as compared to when I have been running on Emergency Heat (electric coil) only.

With a gas furnace instead of coil I imagine, the thermostat and control board would behave the same. Keep in mind the efficiency of a heat pump is not only related to temperature but also relative humility, so down here in Houston it probably run more efficient in the winter than say Arizona at a given low temperature.
 
For GSHP you can use vertical "wells"...for small lots or no desire to rip up yard. BIL has that on his lake lot. We have air source heat pump, LP furnace with elec plenum heater, so we can use either elec or LP, depending on price. I imagine switching system would be similar to what you need. I wish we had NG- always about the cheapest heat. Very few in rural areas get that- gotta be along the gas line going between towns.
 
I replaced a 20 year old heat pump this spring. I looked at alternatives for the backup heat source because electric strip (resistive) heaters are expensive to operate. I did a great deal of research to find a rating for the outside temperature where the heat pump was no longer effective. It was around 32(F) for the one we replaces and 17(F) for the new one. I looked at the cost adder for gas versus electric for the secondary heat source. The additional cost for gas over electric was about $4.5K more than the ~$14K base price with electric secondary heat. In the end we went with electric secondary heat. The efficiency of the heat pump at moderate sub-freezing temperatures was the deciding factor as we rarely experience outside temps below 20 and even more rarely for extended periods.

Good luck.
 
My first choice would be to ad a separate NG furnace piggybacked to the existing system.

If you want to go whole hog look into residential central heat and air system that is powered by NG.
 
(quoted from post at 09:05:21 06/24/18) IF, natural gas heating is more economical and if you add ng backup, then why don't you you make it the primary heat and only use heat pump in cooling mode only. Also, one needs to factor in ng installation, connection fees and minimum use bill during the off heating season.

Bingo........!!!?????

Unless your calling a water in ground system a heat pump?????
 
John T,

I have EXACTLY the set up you are asking about in my house near Winchester, VA. It works great. I have a gas furnace with a add-on heat pump coil attached. I use a heat pump thermostat inside and have an outside thermostat that switches from heat pump to gas at 32 degrees. The way it is wired, if the emergency heat is called for (2 degrees below the set point on my system) it also runs the gas furnace.

In the Summer, Spring, and Fall we use the heat pump to get economical heating and cooling. Works great. In the cold of winter we are using the extra hot air from the gas furnace. It really feels good on a cold winter morning.

The only cons that I have found are that it was a little more expensive to install than either a straight heat pump or straight gas furnace with AC. Also your typical heat pump life is somewhat shorter that a similar AC unit. We have a 2 zone system so have 2 of everything. One heat pump failed at 8 years (condenser turned into swiss cheese), but the other one and both gas furnaces are pumping along fine in year 13.

I think my email is open. Please feel free to contact me if you have questions. cliff at cantrellhome dot com.

Cliff(VA)
 

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