HVAC/Heat Pump repair price- reasonable or ripoff?

[Texas Proud]

I will say that a heat pump heating is much better than my sister who lives in Oregon and has a wood stove heat the house!!!


But, they do have 40 acres of trees so it does not cost them much...

 

[ERD50]

Also you are way better off heating with your gas furnace anytime it is below 60 degrees outside.

Not necessarily. It depends on the cost of gas vs the cost of electricity, which are both subject to price fluctuations.

+1.

Al in Ohio, where do you get your info from?

https://www.trane.com/residential/en/resources/hvac-basics/is-a-heat-pump-right-for-my-home.html

The heat pump is effective by itself down to temperatures around 25 to 30 degrees Fahrenheit. At that point, either a gas furnace or an air handler with supplemental electric heat will kick in and help heat your home.

And be careful of broad strokes. I saw some info that there are heat pumps optimized for even lower temps. But it sounds like ~ -4 F is the limit.

-ERD50

 

[Al in Ohio]

You would save on heating costs by using gas heat whenever the outside temperature is below 60 degrees. The heat pump is usually the better option from 60 to 70 degree outdoor temp when you have a choice between both. Having natural gas heat as your supplemental heat source for your heat pump system is much superior than having an electric coil. Often because of its cheaper rate at lower OA temps it is really most often your primary heat source. Every degree outside it gets colder and increase the delta T from your desired inside temp causes a heat pump system to become more and more inefficient and cost more to operate. Your high efficiency gas furnace is a cheap method of heating regardless. It’s efficiency is not effected by outside temp. A gas therm is also almost always cheaper than electric except in some areas of the country ONLY when that heat pump is operating in the high efficiency range when outside temperature is not too cold.

 

[Al in Ohio]

As far as comfort goes, I prefer gas heat when it's really cold. Seems to warm my bones better.

Yep. That’s because the discharge air temperature of gas heat is much warmer than that of a heat pump. Most people feel somewhat drafty and not as comfortable with heat pump systems for that reason too.

 

[Al in Ohio]

Not necessarily. It depends on the cost of gas vs the cost of electricity, which are both subject to price fluctuations.

See my other post relating to degrading of a heat pumps operating efficiency for every degree outside it gets colder. It is only cheaper at the higher outside air temp conditions. Both rate comparisons and operating efficiency losses of the heat pump have to be evaluated. A gas heat system coupled with a heat pump system will be much more favorable for a much greater portion of the heating season than will the electric coil option. Unfortunately for many, only all electric is available or the additional capital cost of gas heat wasn’t chosen for other reasons.

 

[ERD50]

+1.

Al in Ohio, where do you get your info from?

https://www.trane.com/residential/en/resources/hvac-basics/is-a-heat-pump-right-for-my-home.html



And be careful of broad strokes. I saw some info that there are heat pumps optimized for even lower temps. But it sounds like ~ -4 F is the limit.

-ERD50

You would save on heating costs by using gas heat whenever the outside temperature is below 60 degrees. The heat pump is usually the better option from 60 to 70 degree outdoor temp when you have a choice between both. ...

So you repeat it. Got a source?

I think I've asked you before - are you really an Engineer, as your sig suggests? You don't sound like one to me.

So little heat energy is required at 60F-70F outdoor temperatures, it wouldn't make sense to install the extra heat pump complexity for that small range of heating.

Got a source?

-ERD50

 

[samclem]

So little heat energy is required at 60F-70F outdoor temperatures, it wouldn't make sense to install the extra heat pump complexity for that small range of heating.

Got a source?

I'm not Al in Ohio, and I don't have a definitive source, nor did I sleep in a Holiday Inn Express last night, but I'll offer up two observations and some back-of-the-envelope calculations:


Observation: Just because Trane says that a heat pump can be >effective< down to 25 or 30 (Deg F), doesn't mean it is more >cost efficient< than other available options might be. There's no doubt that air-to-air heat pumps use more energy to supply heat as the outside temps go down. Clearly at some point, depending on the cost of alternatives (which >don't< have efficiencies that change with outdoor temps), the heat pumps aren't the most cost effective option

Observation: Builders do all kinds of things to reduce their costs that ultimately increase long term costs to home owners. If a central AC unit (or mini-splits) are needed anyway for cooling, the incremental costs of adding a heat pump are small, compared to plumbing a gas line, installing a gas flue (or vents in and out), giving up floor space for a separate furnace, etc. The same goes for other auxiliary sources of heat (oil, propane, etc).

Promised back of the envelope example: I couldn't find any ready-made, impartial "with numbers" examples of heat pump costs vs alternatives at low temps, so I did the hard way. A Fujiitsu mini-split model ASU/AUO12RLFW1 uses 5.9 amps at 220VAC = 1300 watts (outdoor unit only). It has a nominal heating output of 16K BTU/hr (outside temp not provided in specs), but only produces 12.7K BTU/hr at 17 deg F outside temp (and 10.2K BTU/hr at 5 deg F outside temp.) Since Golden Sunsets (post 45) is in New England, let's use their electric rates: 19.93 cents per KWH in Jul 2018. So, for this heat pump to make 10.2KBTU at 17 deg F, it takes 1.3 KWH of electricity, which costs 25.9 cents.

Natural gas (2017 avg, New England residential) costs $13.32 per 1000CF, which provides 1,037,000 BTU. So, to make this same 10.2K BTU of heat (with a 95% efficient furnace) requires us to burn 16 cents worth of gas.

Notes:
1) I didn't include the cost of electricity needed to run the fans on the internal mini-split units, but I also didn't include the fan for the furnace. It would probably be close to even.

2) This is at 17 deg F. It's a lot colder than that for much of the winter in New England, the efficiency of the heat pump would be even lower and the advantage of gas would be even higher.

3) Even at its "nominal" heat output of 16K BTU (outside temp not given, but you can be sure it's pretty warm), the heat pump still is not as cost efficient as gas, given these prices. The heat pump cost is 1.6 cents per KBTU, while the gas furnace requires 1.56 cents per KBTU.

There are lots of variables not included here. Some heat pumps do better/worse at low temps. The cost of fuel oil, wood, wood pellets, propane, or other alternate fuels will almost surely be higher than natural gas.

Even with a well designed (and expensive) heat pump, it takes a lot of energy to extract 100 deg+ temps from air that is 30 degrees. I don't find it hard to believe that it costs more to make heat this way than to simply burn natural gas.

 

[ERD50]

.... some back-of-the-envelope calculations:

....

Even with a well designed (and expensive) heat pump, it takes a lot of energy to extract 100 deg+ temps from air that is 30 degrees. I don't find it hard to believe that it costs more to make heat this way than to simply burn natural gas.

The short version of that is there are a lot of variables, which is why I asked Al in Ohio for sources. Is he talking about Ohio NG and kWh costs, or the OP's area?

But it does seem to me that if the break-even temperature for an area is 60F~70F outside temperature, that it would be unlikely to justify much added cost in a standard HVAC system. I'm not sure how much a full heat pump plus NG costs versus A/C plus NG, but I think it might be a larger delta than a mini-split, as those are more commonly used as heat pumps?

At 60~70F outside temps, the system just isn't running much at all, so weighted fuel costs will be low. I doubt we have the heat on at all with 60F~70F outside temps, the sun is enough to warm the house. In the spring/fall, it's the overnight dips that drive heating, but early AM when the heat comes on, it's still under 60F, so that would be NG anyhow.

-ERD50

 

[Al in Ohio]

Good backup detail Samclem. I was considering providing similar extended explanation, but just did not put forth the effort to go into that much detail (kudos to you). And yes those heat pumps will work and extract heat below 30 degees , even 20 degrees when specified for a lower temperature capable model, but they are not very good at those temps. Another factor worth mentioning is that while even at the higher outdoor temperature ranges where heat pumps work better, the lower discharge heating supply temp they produce also require them to run longer (more inside fan operation) than the higher discharge temp of a gas heat option. Think how long it takes to warm your house when a heat pump is pumping out 100 degree supply air versus the high efficiency gas furnace pumping out 140 degree heat? The gas heat will finish heating in less than half the time.

 

[JoeWras]

Another factor worth mentioning is that while even at the higher outdoor temperature ranges where heat pumps work better, the lower discharge heating supply temp they produce also require them to run longer (more inside fan operation) than the higher discharge temp of a gas heat option.

Absolutely, and also the most user UNfriendly aspect of heat pumps. Someone mentioned that gas "feels better." Darn right, because of this aspect of heat pumps.

I'm still glad I have a heat pump upstairs, installed in an attic retrofit. The retrofit was easier, and I don't have to worry about combustion in a hard to access place (no attic stairs... this may not even pass today's code).

I still am using the original Carrier electronic thermostat from 1999. Works well, and I have the installer manual. I can play with a lot of things on this unit in installer mode, including when the so called "heat strips" (auxiliary resistance heat) comes on. I have that temperature way down to 40, so I'm heat pump only all the way to 40 outside. It is OK since it is just bedroom space, not used much during the day. And the gas heat from downstairs rises up.

Even though I have the aux come on only when really cold, it may still come on by itself when the unit detects frost on the coils. This can happen at any temperature up to about 50. Nothing I can do to stop that. It is also one of the most inefficient modes that the unit runs. Basically, the outdoor condenser briefly goes to A/C mode (in the winter!) to melt the ice. Inside, the aux runs. You can watch your electric meter fly when this happens.

 

[samclem]

Basically, the outdoor condenser briefly goes to A/C mode (in the winter!) to melt the ice. Inside, the aux runs. You can watch your electric meter fly when this happens.

Ouch!

Think how long it takes to warm your house when a heat pump is pumping out 100 degree supply air versus the high efficiency gas furnace pumping out 140 degree heat? The gas heat will finish heating in less than half the time.

And, this also has an impact on the expected life of the equipment. In a moderate climate a unit might need to run, say, 20% avg duty cycle in a 5 month "summer" cooling season (720 hours), then run 60% avg duty cycle for a 5 month "winter" heating season (2160 hours). In much of the US, the heating loads (BTU/hr) are much higher than the cooling loads, and the rediuced heat pump efficiency at low outdoor temps makes things even worse. That expensive compressor is not going to last as many years if it is running 4 times as many hours per year (AC only vs AC+ heat).

The short version of that is there are a lot of variables . . .

True. In theory, it wouldn't be hard at all to build a calculator that used a home's expected heat loss/gain, local weather data (daily averages, not just heating degree days and cooling degree days), heat pump performance curves, the cost of electricity, and the cost of alternate fuel to provide useful estimates for estimated heating fuel costs. Then, plug in the cost of equipment and the expected life of the units to know what the overall most economical choice is. I didn't find calculators like this, but I'm pretty sure they must be out there. If not, >that< is the kind of thing that DoE should be doing--making good info available to consumers so the markets can work.

 

[Al in Ohio]

True. In theory, it wouldn't be hard at all to build a calculator that used a home's expected heat loss/gain, local weather data (daily averages, not just heating degree days and cooling degree days), heat pump performance curves, the cost of electricity, and the cost of alternate fuel to provide useful estimates for estimated heating fuel costs. Then, plug in the cost of equipment and the expected life of the units to know what the overall most economical choice is. I didn't find calculators like this, but I'm pretty sure they must be out there. If not, >that< is the kind of thing that DoE should be doing--making good info available to consumers so the markets can work.

There are. I used to run them for clients that requested comparative analysis on system selections in either heating or cooling seasons or both. It was an economic analysis program that compared any type of HVAC system running at any selected city location with any other type of system for any time of year (usually it was for the full year). You input the rate for whatever the fuel or electric source was, could tweak occupied vs. unoccupied set-points etc. it could compare overall system run times per year, annual cost comparison for heating or cooling between systems, overall energy usage, fan run time, you name it. Trane has one (System Analysis) and so does Carrier (HAP) as well as a few others that aren’t on the equipment selling side.

 

[W2R]

I don't have anything to add to all the wrangling about gas vs electric heating costs.

BUT - - I did have my entire HVAC unit replaced with a Trane system in September of 2016. It was six times hotter than Hades when the work was done and the workmen were my kind of heroes to work up there in the hot attic and get decent AC going again in my dream home.

Later in the year, when it was time to turn on the heat, it didn't work!!!

I called the company that did the original installation since of course, it was still under warranty. They came out and fixed it for free. I didn't have to pay one cent, not even their minimum for a visit. According to what they told me, there was a switch to allow it to start functioning, and their helpers had accidently forgotten to set it in the proper position during installation.

Don't know if this is any help but as you probably guessed, I know nearly nothing about this stuff. Anyway that's all I can contribute to this thread.

Carry on....

 

[ncbill]

... In much of the US, the heating loads (BTU/hr) are much higher than the cooling loads, and the reduced heat pump efficiency at low outdoor temps makes things even worse. That expensive compressor is not going to last as many years if it is running 4 times as many hours per year (AC only vs AC+ heat).

Yep, this is why I selected "emergency heat" on the thermostat so my HVAC uses only the gas furnace (not the heat pump compressor) for heat.