My geothermal compressor just died.

[davesl708]

I think a big problem is HVAC installers like to size based on cooling load. It isnt as hard to keep a home 20 degrees (F) cooler than ambient than it is to keep it 80 degrees warmer.

Doing a manual J load calculation, heating load is usually around double the BTUs than cooling load. (I am getting ready to do a geo when the weather breaks and did a manual J) my cooling load is ~26k BTU and heating load right at 48k BTU. This is based on outdoor temps of 0F for heating and 95F for cooling.

So if sized according to a HVAC guy, I would get a unit that runs almost all of the time when temps are 95+ trying to keep the house cool (which is what they want for humidification). But anytime the ambient temps drop much below 30F (which is alot), the system cannot keep up and needs a backup source like heat strips. Sure dont sound efficient to me. I'd rather have a larger unit that dont run as often but is able to keep my house warm in the winter.

I am likely going to be installing a 4-ton based on my 48k heat load.

I agree. When I had three HVAC contractors bid on my system all their estimates were it would cost more to cool than heat. We have more cooling days here than heat days. With the base cost of having gas hooked up ($348.00 per year) and heating water and air with gas made the cost of operating the heat pump/AC and gas heat around $270 per month.

My current Geo cost me on average $65 per month to cool and $120 per month to heat. Compared to my pre-Geo utility cost I am saving over 50% on my whole house energy cost without the gas.

 

[LD1]

I agree. When I had three HVAC contractors bid on my system all their estimates were it would cost more to cool than heat. We have more cooling days here than heat days. With the base cost of having gas hooked up ($348.00 per year) and heating water and air with gas made the cost of operating the heat pump/AC and gas heat around $270 per month.

My current Geo cost me on average $65 per month to cool and $120 per month to heat. Compared to my pre-Geo utility cost I am saving over 50% on my whole house energy cost without the gas.

Even though you have more cooling days, I am sure it still takes more BTU's to heat.

ITs all about temp differential.

If a home needs to be 20* cooler than outside.....or 20 * warmer than outside, there aint much difference in BTU required. (technically it would take a little more to cool to offset the appliances and solar heating through the windows that also make it easier to heat).

But if it gets down to 20f and you want it 70f, thats a 50 degree difference. If the hottest it gets is 100f, and you want it 70f, only a 30f difference.

Perhaps in florida or arizona, where it may get to 40 on the coldest of days, but is regularly 110+f where you would need to be 40 cooler than outside but only 30 warmer on the coldest days, then AC would take more BTU. But up here in the midwest, that aint the case

 

[Redneck in training]

Two to one ration between heat and AC load is about right. I am in similar climate as Ohio. Our house is about 2400 sqft heated to 68F by floor heating plus 1400 sqft garage heated to 50F (no AC). When it gets really cold and windy the heat pump will keep about 90F inlet to floor and run about 90% of the time. No matter how hot it gets in the summer it it keeps the house cool running about 50% of time max. The heat pump has 60 gal heat accumulator heated to 90 and cooled to 32F. The unit is 5 ton (6HP, 4.5 kW)
Having the accumulator proved certain advantage during current compressor failure because it has 9kW heater built in. We also have two propane fireplaces for the time it gets really cold.

 

[Redneck in training]

Even though you have more cooling days, I am sure it still takes more BTU's to heat.

ITs all about temp differential.

If a home needs to be 20* cooler than outside.....or 20 * warmer than outside, there aint much difference in BTU required. (technically it would take a little more to cool to offset the appliances and solar heating through the windows that also make it easier to heat).

But if it gets down to 20f and you want it 70f, thats a 50 degree difference. If the hottest it gets is 100f, and you want it 70f, only a 30f difference.

Perhaps in florida or arizona, where it may get to 40 on the coldest of days, but is regularly 110+f where you would need to be 40 cooler than outside but only 30 warmer on the coldest days, then AC would take more BTU. But up here in the midwest, that aint the case

Not all heat pumps are created equal. You need to buy unit optimized for your climate and application. There is definitive difference between unit keeping swimming pool warm in Florida and unit keeping house warm in Canada.

 

[LD1]

Agreed.

Point was most heatpumps and geo units are undersized for heating on purpose by the HVAC "pros".

Not many realize that and are disappointed in how much backup heat gets used.

The claims that it is more efficient, and having to have adequate dehumidification in the summer IMO is hogwash.

Heat is what is important to me. I want the most efficient way to do so. And having a $15000 unit that is undersized and relys on strips or propane is foolish IMO. Any savings in summer by creating drier air that " feels" cooler is quickly wasted in the winter when you need heat.

Summary:
HVAC pros want a unit running nearly 24/7 in the summer but grossly undersized in the winter forcing you to use propane or strips much below 30 degrees.

I like a unit sized to keep my house warm and only on the bitterest days below zero need backup. In turn it may only run a few hours a day in the summer and I have 70 degree and humid air instead of 70 and dry.

The difference is I need twice the tonnage. But will pay for itself with winter bills quicker than burning the strips in an undersized unit most of the time

 

[Redneck in training]

Agreed.

Point was most heatpumps and geo units are undersized for heating on purpose by the HVAC "pros".

Not many realize that and are disappointed in how much backup heat gets used.

The claims that it is more efficient, and having to have adequate dehumidification in the summer IMO is hogwash.

Heat is what is important to me. I want the most efficient way to do so. And having a $15000 unit that is undersized and relys on strips or propane is foolish IMO. Any savings in summer by creating drier air that " feels" cooler is quickly wasted in the winter when you need heat.

Summary:
HVAC pros want a unit running nearly 24/7 in the summer but grossly undersized in the winter forcing you to use propane or strips much below 30 degrees.

I like a unit sized to keep my house warm and only on the bitterest days below zero need backup. In turn it may only run a few hours a day in the summer and I have 70 degree and humid air instead of 70 and dry.

The difference is I need twice the tonnage. But will pay for itself with winter bills quicker than burning the strips in an undersized unit most of the time

That is the problem with forced air units because they lack a tank. Since we have floor heating we have separate "fan coil" in the attic that uses chilled glycol mix pumped from a tank for cooling. Once the HP chills the tank (heat sink when AC is running) it shuts down but the fan coil still can run independently based on room temperature. If the fan coil would cycle too much I could increase the tank temperature and vice versa.
Similarly in the winter the HP heats the tank only. The floor loops operate independently based on zone thermostats. I have the temperature set to 90F because when it gets extremely cold it can't make higher temperature despite the HP running almost constantly. 90F going to floor is enough to keep the house cozy even at extreme cold. Lower temperature makes it also marginally more efficient.

Aren't the new forced air units dual or variable speed? That would solve the heating/cooling power demand issue.

 

[LD1]

The two speeds do somewhat solve the problem. But still have the AC running ALOT in the summer but on low only. I still don't like it running that much. Get it cool and shut off. Not run all day just to maintain

 

[truckdiagnostics]

That is the problem with forced air units because they lack a tank. Since we have floor heating we have separate "fan coil" in the attic that uses chilled glycol mix pumped from a tank for cooling. Once the HP chills the tank (heat sink when AC is running) it shuts down but the fan coil still can run independently based on room temperature. If the fan coil would cycle too much I could increase the tank temperature and vice versa.
Similarly in the winter the HP heats the tank only. The floor loops operate independently based on zone thermostats. I have the temperature set to 90F because when it gets extremely cold it can't make higher temperature despite the HP running almost constantly. 90F going to floor is enough to keep the house cozy even at extreme cold. Lower temperature makes it also marginally more efficient.

Aren't the new forced air units dual or variable speed? That would solve the heating/cooling power demand issue.

You can get variable everything! loop pumps, compressor and fan.
Our house has the forced are unit, fan is variable works ok. We did our shop like you did your house, with the air handler running the office. When I redo things that is the way I will do it. However, I will use a gas furnace for the air handler which will give me back up. Then use a marathon water heater for the tank. They are plastic. I have never needed back up heat on the house unit. I went as far as to unpluging back up. IMO if you are needing to run back up heat when weather gets cold system is not designed correctly. Also, IMO issues you described with sizing is why water furnace has a tighter dealer network. Climate master has a tendency to sell to just any HVAC dealer and there in is the issue. Geo thermal is a different animal! There is nothing wrong with climate master in fact I am looking at them to replace my water furnace unit in the house.

 

[davesl708]

Not all heat pumps are created equal. You need to buy unit optimized for your climate and application. There is definitive difference between unit keeping swimming pool warm in Florida and unit keeping house warm in Canada.

With my Geo system it has a two stage compressor. First stage takes care of heating and cooling. Second stage kicks in if 1st cannot keep up.
On our coldest days (0 to -10) the second stage has never needed to kick in. Same for heat days (110) 2nd stage has never kicked in.
E heat if system fails during the winter. Hope that never kicks in (60K watts).

 

[buckeyefarmer]

For my upstairs unit My 2nd stage kicks in around mid t o upper 20's. 3rd stage elect backup around 10°.
Downstairs unit rarely kicks in 2nd stage. It is oversized, upstairs undersized. Im thinking of swapping rhe units. Sizing based on manual j.