How to i calculate Heat Pump supplemental heat for service size.

[StarCat]

Clarification on Heat Pump Theory

Clarification on Heat Pump Theory

Typical standard " old school " electric heat pumps operate as thus:

The condensing unit supplies heat down to what was once known as the balance point, below which the aux. heat is supposed to take over all heat demand based on outdoor air temperature lock out. This is due to efficiency loss of the condensing unit below the balance point for " air source " heat pumps.

If " EMERGENCY heat is selected on the Thermostat control. The Condensing unit is fully locked out.

The Condensing unit and the aux. heat BOTH run when the out door unit is defrosting.

I was certified as a Heat Pump Technician by RSES international in 1992 and have worked on many different types.
They can be useful in residential settings when installed well. Within commercial settings they almost always become a service liability wich totally overruns the perceived energy savings.

Sincerely

 

[suemarkp]

The only thing that doesn't make sense to me is to lockout the compressor below the balance point. The balance point is when the heat required to heat the building is more than what the heat pump can put out. As it gets colder, the heat pump puts out less and the heat required in the house increases. So the curves quickly cross to make the balance point. As long as the Coeifficent of Performance (COP) is still around 2 or more, I'd keep the heat pump running (so you get heat pump plus aux heat). A COP of 1 means the compressor is making the same amount of heat as a strip heater based on the power consumed (so you might as well use a strip heater and not wear out a compressor). At some outside temp where the heat pump COP falls below 2 is where I'd lock out the compressor. My heat pump came with a nice thermostat where you could lock out the compressor at a cetain temp (chose < 20F for me), and lock out the aux heat at a certain temp (chose > 38F for me). My balance point was 34F.

The COP of new heat pumps is staying decent to lower and lower temperatures now days. Even below zero F.

 

[kwired]

The only thing that doesn't make sense to me is to lockout the compressor below the balance point. The balance point is when the heat required to heat the building is more than what the heat pump can put out. As it gets colder, the heat pump puts out less and the heat required in the house increases. So the curves quickly cross to make the balance point. As long as the Coeifficent of Performance (COP) is still around 2 or more, I'd keep the heat pump running (so you get heat pump plus aux heat). A COP of 1 means the compressor is making the same amount of heat as a strip heater based on the power consumed (so you might as well use a strip heater and not wear out a compressor). At some outside temp where the heat pump COP falls below 2 is where I'd lock out the compressor. My heat pump came with a nice thermostat where you could lock out the compressor at a cetain temp (chose < 20F for me), and lock out the aux heat at a certain temp (chose > 38F for me). My balance point was 34F.

The COP of new heat pumps is staying decent to lower and lower temperatures now days. Even below zero F.

If the heat pump is putting out the same amount of heat as the heat strip will put out, then the idea of leaving the heat pump running is that it should use less energy input at that output level than the strip heater uses, so you run the heat pump. You are supposed to lock out the heat pump when it is no longer efficient, not just because the efficiency is lower.

 

[kwired]

Typical standard " old school " electric heat pumps operate as thus:

The condensing unit supplies heat down to what was once known as the balance point, below which the aux. heat is supposed to take over all heat demand based on outdoor air temperature lock out. This is due to efficiency loss of the condensing unit below the balance point for " air source " heat pumps.

If " EMERGENCY heat is selected on the Thermostat control. The Condensing unit is fully locked out.

The Condensing unit and the aux. heat BOTH run when the out door unit is defrosting.

I was certified as a Heat Pump Technician by RSES international in 1992 and have worked on many different types.
They can be useful in residential settings when installed well. Within commercial settings they almost always become a service liability wich totally overruns the perceived energy savings.

Sincerely

If you were certified as a heat pump technician, then you should know there is no fixed condensing unit. When in heating mode the condenser is the indoor coil and the outdoor coil is the evaporator, in cooling mode the reversing valve changes the direction of refrigerant flow and the indoor coil is then the evaporator and the outdoor coil is the condenser.

Why is service issues different with a commercial unit? Same size unit in a dwelling is going to put out same BTU's as the same unit in a commercial space.

If you are saying there is more demand in commercial - then you likely need a larger unit to keep up with the demand, an improperly sized unit in any install will be prone to certain problems depending on if it is too small or too large for the application.

 

[StarCat]

Commercial Heat Pumps

Commercial Heat Pumps

Kwired, I'm speaking from sheer experience of 30 years working commercial industrial HVACR.
I would not give a thin dime for a commercial heat pump based on every problem I have seen them give and the associated repair costs and down time for such properties involved. I am a cracker jack Tech in this field.
I have fixed systems that were hacked badly that no one else coulf fix and also dealt with others that have design flaws that are unresolvable, even with factory engineers involved.
The down time and repair time for major failures is especially significant. There are more things to go wrong than straight AC and more moving parts. This increase in complexity make repairs on larger tonnage system even more difficult. I have never seen them pay off on a commercial property, in fact quite the opposite as regards matters in Texas. Larger tonnage split system heat pumps can be the most self destructive units one has ever witnessed.

Its that simple. Other persons may have different opinions. If any business owner asks my opinion about the most reliable system to have, I will steer them away from the heat pump idea in accord with what I have stated above. A great deal of what goes on in this industry is a re-inventing of the wheel which in many cases involves moving away from engineering that is fully tried and true to much less stable configurations. Behind this are a lot of politics, fradulent science and game playing based on the hydrocarbon model.


IN the heating cycle, the condensing unit is performing refrigeration duty. The running amps and refrigerant mass flow will be significantly less than when running full load in cooling.

All the best.

 

[GoldDigger]

I have never seen them pay off on a commercial property, in fact quite the opposite as regards matters in Texas.

Which may also be related to the fact that electricity prices in Texas (except Austin) for demands associated with electric heating are anywhere from a factor of 1.5 to a factor of 5 lower than in other states.

 

[kwired]

Kwired, I'm speaking from sheer experience of 30 years working commercial industrial HVACR.
I would not give a thin dime for a commercial heat pump based on every problem I have seen them give and the associated repair costs and down time for such properties involved. I am a cracker jack Tech in this field.
I have fixed systems that were hacked badly that no one else coulf fix and also dealt with others that have design flaws that are unresolvable, even with factory engineers involved.
The down time and repair time for major failures is especially significant. There are more things to go wrong than straight AC and more moving parts. This increase in complexity make repairs on larger tonnage system even more difficult. I have never seen them pay off on a commercial property, in fact quite the opposite as regards matters in Texas. Larger tonnage split system heat pumps can be the most self destructive units one has ever witnessed.

Its that simple. Other persons may have different opinions. If any business owner asks my opinion about the most reliable system to have, I will steer them away from the heat pump idea in accord with what I have stated above. A great deal of what goes on in this industry is a re-inventing of the wheel which in many cases involves moving away from engineering that is fully tried and true to much less stable configurations. Behind this are a lot of politics, fradulent science and game playing based on the hydrocarbon model.


IN the heating cycle, the condensing unit is performing refrigeration duty. The running amps and refrigerant mass flow will be significantly less than when running full load in cooling.

All the best.

But why do you say they are a problem with commercial but not necessarily residential? Doesn't a residential install still have same main components, indoor coil, outdoor coil, compressor, and reversing valve? Both can have all the possible accessories and add on features.

I do agree that there is more parts and more potential for failure than for a unit designed for cooling only. Find me something mechanical that is "higher efficiency" than the old school versions that doesn't have this issue. There are many high efficiency items out there that definitely use less energy, but sadly often the cost of owning/operating is still offset (at least to some extent) by the need to have repairs done more frequently than maybe was needed with the "old school" product.

 

[mtnelect]

Heat Load Study

Heat Load Study

The first step is to determine the "Heat Load" of the structure, then you can start to determine the size of the "Emergency Heat" required.