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Old 02-21-2010, 09:09 PM   #1
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Heat Pump, is it performing within spec?


Hello!

I have a Goodman heat pump Model CPL T36 1B and air handler ARUF042-00A-1A. All of my ducts are within a conditioned wall/ ceiling space. The outside temperature is 38 degrees. The inside temperature at the return is 70 degrees. The output temperature is 85.5 degrees.

Is this what can be expected out of the unit? I purchased an existing home so should you assume that the equipment is properly sized? You know what they say about assuming...

I will be upgrading the air-handler to a hydronic unit later this year. At that time I am going to replace the unit with a two-stage heat pump. Will a two stage heat the same in first stage, but maybe output 95 degrees with the second stage running with no change in the ductwork?

This unit is a 3 ton, what would happen if I changed to a 4 ton unit? Currently the 3 ton unit is running on/off every 5-10 minutes to maintain temp of 72 degrees. I will be doing some insulation/caulking but the house doesn't seem to be that leaky. Poorly designed I'll admit. Second floor has cathedral ceiling (16-18ft at peak) and has an open foyer (lofts) to first floor in two places. Return duct is in the floor of the second floor above the unit that is located in a first floor closet. The closet is being used at a huge return duct as the duct in the floor/ceiling of closet if not connected to the unit.

Thanks,

--Chris


Last edited by ChrisDIY; 02-21-2010 at 09:14 PM.
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Old 02-21-2010, 10:13 PM   #2
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Heat Pump, is it performing within spec?


Assuming you are running 1200 cfm for a 3 ton unit, the BTU output is low. Temp rise x cfm x 1.o8= BTU. Should be closer to 33,000 btu at 38 degrees instead of the 20,000 you have.

A two stage heat pump produces full capacity on second stage and about 60% on first stage. It will not make the air coming out of the registers any hotter. The biggest advantage of a two stage is you can oversize for heating and first stage can take care of the cooling. Duct work has to be big enough to handle the whole load though.

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Old 02-22-2010, 03:48 AM   #3
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Heat Pump, is it performing within spec?


Could have a dirty indoor and or outdoor coil. Or could be a refrigerant under or over charge.
With a 4 ton 2 stage you would need to replace all of your duct work. As it would be too small for the 4 ton unit.

Doubt a 4 ton 2 stage would remove enough humidity in the milder times of summer. So you would also need to get a dehumidifier(probably a whole house). Since most 4 ton 2 stage would be 3.2 tons capacity in first stage. With the exception of the Trane/American Standard 20i(2.4 tons capacity in first stage), and Carrier/Bryants 16/17 SEER units with the Bristol TS compressor(as low as 2.2 tons capacity in first stage).

If your heat pump is cycling on and off like that and maintaining temp. Its not undersized for your home.
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Old 02-22-2010, 09:14 AM   #4
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Heat Pump, is it performing within spec?


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Originally Posted by beenthere View Post
Could have a dirty indoor and or outdoor coil. Or could be a refrigerant under or over charge.
With a 4 ton 2 stage you would need to replace all of your duct work. As it would be too small for the 4 ton unit.

Doubt a 4 ton 2 stage would remove enough humidity in the milder times of summer. So you would also need to get a dehumidifier(probably a whole house). Since most 4 ton 2 stage would be 3.2 tons capacity in first stage. With the exception of the Trane/American Standard 20i(2.4 tons capacity in first stage), and Carrier/Bryants 16/17 SEER units with the Bristol TS compressor(as low as 2.2 tons capacity in first stage).

If your heat pump is cycling on and off like that and maintaining temp. Its not undersized for your home.
I will de-energize the unit and take a look at the evaporator coil to see if its dirty.

Which side of the ductwork would need to be changed supply, return or both? This unit has no return ductwork...

I have the Aprilaire 8870 thermostats I have control over the temp that second stage will kick in. If I currently have a 3 ton unit a 2.4 ton first stage would be too much? I am being harassed about my hydronic air-handler saying two coils will impeded my airflow anyway???

I know I need to replace this second furnace I just need to plan on dual fuel, hydronic-heat pump or variable speed furnace-heat pump. The variable speed is far more difficult install as the closet where the unit is central to house and exhaust vent will be very long run. Shortest route would be down into crawlspace and then about 15' to outside wall then up to spec. height. Other option which wife said no was run through laundry room (exposed) into garage make left turn run 15' to exit on same side of house.

--Chris

Last edited by ChrisDIY; 02-22-2010 at 09:27 AM.
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Old 02-22-2010, 02:05 PM   #5
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Heat Pump, is it performing within spec?


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I will de-energize the unit and take a look at the evaporator coil to see if its dirty.

Check both sides of it.

Which side of the ductwork would need to be changed supply, return or both? This unit has no return ductwork...

Might need to increae return grille size. Plus the supply duct.

I have the Aprilaire 8870 thermostats I have control over the temp that second stage will kick in. If I currently have a 3 ton unit a 2.4 ton first stage would be too much?

Won't have good moisture removal at lower outdoor temps.

I am being harassed about my hydronic air-handler saying two coils will impeded my airflow anyway???

2 stage doesn't use 2 indoor coils.

I know I need to replace this second furnace I just need to plan on dual fuel, hydronic-heat pump or variable speed furnace-heat pump. The variable speed is far more difficult install as the closet where the unit is central to house and exhaust vent will be very long run. Shortest route would be down into crawlspace and then about 15' to outside wall then up to spec. height. Other option which wife said no was run through laundry room (exposed) into garage make left turn run 15' to exit on same side of house.

--Chris
Vent can't run down over and then up. Thats a code violation.
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Old 02-22-2010, 02:26 PM   #6
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Heat Pump, is it performing within spec?


There isn't a return duct. The closet the air-handler is in has a whole cut in the ceiling which has a grill in it that is in the floor of the second floor. Inside the closet there is just a plenum just tall enough to clear the top of the air-handler. The plenum and the grill above is not connected. When unit is running and you open the door to closet the negative pressure slams the door shut.
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Old 02-22-2010, 02:38 PM   #7
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Heat Pump, is it performing within spec?


Quote:
Originally Posted by dawktah View Post
There isn't a return duct. The closet the air-handler is in has a whole cut in the ceiling which has a grill in it that is in the floor of the second floor. Inside the closet there is just a plenum just tall enough to clear the top of the air-handler. The plenum and the grill above is not connected. When unit is running and you open the door to closet the negative pressure slams the door shut.
The you don't have enough return coming from that grille in the floor.
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Old 02-22-2010, 02:45 PM   #8
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Heat Pump, is it performing within spec?


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The you don't have enough return coming from that grille in the floor.
I guess I'll be getting out the Sawzall! I am going to have to find a weight bearing grille though...
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Old 02-22-2010, 03:03 PM   #9
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Heat Pump, is it performing within spec?


Or install a second return in the wall of the utility closet.
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Old 02-22-2010, 05:31 PM   #10
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Heat Pump, is it performing within spec?


Just left the door wide open to closet and temp produced is now 90-91 degrees. So I am definitely having some return air issues. The only portion of the wall to the closet that is conducive for another grill is above the door. Will have to look and see what's available.

An increase empirically of 5,000 BTU. The room over the garage still has minimal air coming out of vents, will need to figure out why.

Living in Indianapolis how often should this unit be going into defrost?

Last edited by ChrisDIY; 02-22-2010 at 06:25 PM.
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Old 02-22-2010, 09:11 PM   #11
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Heat Pump, is it performing within spec?


Depends on what defrost timer is set for. 45, 60, or 90 minutes.

Could be that the duct to that room is undersized or damaged.
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Old 02-22-2010, 10:12 PM   #12
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Heat Pump, is it performing within spec?


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Depends on what defrost timer is set for. 45, 60, or 90 minutes.

Could be that the duct to that room is undersized or damaged.
The heat pump defrosts every 30 minutes.

Took the register off and the duct is a flexible plastic with rough sides which will restrict airflow. Will have to heat/cool this room by another means
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Old 02-22-2010, 10:15 PM   #13
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Heat Pump, is it performing within spec?


Old defrost board.
Probably could set timer to 60 minutes. If you don't see it icing up much at 60, set it to 90.
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Old 02-23-2010, 09:59 AM   #14
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Heat Pump, is it performing within spec?


Quote:
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In an earlier message


I am being harassed about my hydronic air-handler saying two coils will impeded my airflow anyway???

2 stage doesn't use 2 indoor coils.
Yes, I will have to coils. If I do the hydronic air-handler will have the hydronic coil and the the evaporator coil for the heat pump.

--Chris
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Old 02-23-2010, 10:34 AM   #15
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Heat Pump, is it performing within spec?


Sorry. Thought you meant to DX coils.

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