Heat Pump Efficiency

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Old 02-10-15, 06:53 AM
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Heat Pump Efficiency

I have a 12 year old Goodman heat pump and am considering replacing it this year with a high efficiency unit. My wife's electric bill at her house was only $65 last month because she has gas heat. She's home all day so the lights, TV, etc. are running all day long, whereas everything is off at my house from 8am to 7pm yet my electric bill was $240. This tells me that the heat pump is to blame. Will switching to a high efficiency unit make a substantial difference?

BTW, I had my air handler replaced last year, which is a Goodman, and I stayed with R22 because of the heat pump. However, I believe the air handler can also use R134, so I'll presumably be switching over when the heat pump is changed. Would the copper lines need to be replaced or do they simply evacuate them with some sort of cleaner?

And I've heard there are new technologies on the horizon for heat pumps. Notably the all-season heat pump, which can supposedly heat a home effectively even when outdoor temps fall below zero. Should I hold out for a while longer until something better is available on the market? I'm more interested in cold weather operation than warm weather because at least I can use fans in the summer.
 
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Old 02-10-15, 07:28 AM
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Do you have electric strip heaters in your air handler for back-up heat? Do you use a night/away temperature setback thermostat? Your high electrical costs could be from the electric heaters running far too often.

R-134a is the refrigerant used in automobile air conditioners and maybe some window units or refrigerators. The common refrigerant for residential heat pumps is R-410a. Under certain circumstances the copper line set from an R-22 system can be cleaned and used in with R-410a but unless it would be really difficult to run a new line set I would not bother reusing but go with new.

There are always new technologies just around the corner. If you wait until they are perfected or even available you will wait forever.
 
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Old 02-10-15, 07:51 AM
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Do you have electric strip heaters in your air handler for back-up heat? Do you use a night/away temperature setback thermostat? Your high electrical costs could be from the electric heaters running far too often.
Yes, my air handler has an electric strip heater for backup. Problem is I need backup when the outside temp gets below 30 or so. I have a programmable thermostat and set it to 68 at night and all day and 70 when I am home. I'm sure my high electricity costs are likely from the strip heater, which is why I am looking for a better heat pump that can effectively heat the house when outside temps are in the teens and 20's.

R-134a is the refrigerant used in automobile air conditioners and maybe some window units or refrigerators. The common refrigerant for residential heat pumps is R-410a. Under certain circumstances the copper line set from an R-22 system can be cleaned and used in with R-410a but unless it would be really difficult to run a new line set I would not bother reusing but go with new.
Yes, R410a is what I meant. It's only about 10 feet from the heat pump to the air handler in an unfinished area, so replacing the lines would be very simple.

There are always new technologies just around the corner. If you wait until they are perfected or even available you will wait forever.
Good point.

Will most newer units work effectively at sub-freezing temperatures, or do I need to specifically look for a unit designed to work at sub-freezing temps? Where I live, temps get as low as the single digits in the winter and triple digits in the summer, and natural gas is not available in the area.

I remember hearing it's best to match brands. Is there any truth to this? I see Carrier has a "Greenspeed" heat pump that supposedly heats when ambient temps are as low as 5 degrees.
 
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Old 02-10-15, 07:55 AM
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It was cold in VA last month my bill was 280 with my heat pump and some gas logs on. Your not out in left field with that bill. Setting a heat pump back will cost more to operate in HP mode. You will have to change the air handler to get a high efficiency unit.
 
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Old 02-10-15, 08:03 AM
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Depending on how the thermostat is set up having the setback function may be costing you much more than it saves. In most situations it is better to leave a constant temperature with a heat pump. The reason is that when the thermostat switches to the higher temperature it energizes the electric heaters to effect a quick recovery to the desired temperature setting. IF you can adjust the electric heater cut-in to a significantly lower temperature (how to do this depends on the heat pump and thermostat combination) you will prevent the heaters from operating except when absolutely necessary.

At this point I have to admit that I am beyond my area of expertise as I have not worked with these systems for many years and do not know the latest trends. Hopefully Houston or one of the other HVAC technicians will take over from here.
 
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Old 02-10-15, 08:23 AM
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Setting a heat pump back will cost more to operate in HP mode.
Huh?

You will have to change the air handler to get a high efficiency unit.
What's the highest SEER and HSPF I can expect when pairing a new high efficiency heat pump with my Goodman air handler? By the way, ever since the new air handler was installed, I've been having issues with the ducts in the basement sweating and ruining ceiling tiles. Will getting a better heat pump help resolve the humidity issue?

Depending on how the thermostat is set up having the setback function may be costing you much more than it saves. In most situations it is better to leave a constant temperature with a heat pump. The reason is that when the thermostat switches to the higher temperature it energizes the electric heaters to effect a quick recovery to the desired temperature setting. IF you can adjust the electric heater cut-in to a significantly lower temperature (how to do this depends on the heat pump and thermostat combination) you will prevent the heaters from operating except when absolutely necessary.
My heater strips don't turn on unless the temp difference is at least 3 degrees, and that doesn't happen very often. Typically when it is below 20 outside (usually at night), I'll have the t-stat set to 68 and the heat pump will maintain 66.5 and the strips will never turn on. I'm hoping that if I get a new heat pump with HSPF of 10 or so, that it will be able to heat the home to my setpoint even when it's in the single digits.
 
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Old 02-10-15, 08:34 AM
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You will have to see what matches up with your new air handler but id guess no better than 14 SEER which is the lowest in VA you can get. Removing humidity will take care of the duct sweating. A matched system should remove humidity better than an un matched system.
 
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Old 02-10-15, 08:39 AM
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You will have to see what matches up with your new air handler but id guess no better than 14 SEER which is the lowest in VA you can get. Removing humidity will take care of the duct sweating. A matched system should remove humidity better than an un matched system.
When you say "match" do you mean the tonnage? If so, it sounds like my air handler will determine what heat pump I get, unless I replace the air handler again (which I'm not going to do). If that is the case, then I guess I'll be getting a 2.5 ton heat pump. I don't quite understand why the SEER would have to be the same. Isn't that just a measure of how much electricity the until uses compared to it's BTU output? If so, I don't see why you couldn't have an 18 SEER heat pump with a 15 SEER air handler. Why do they have to have the same efficiency? Doesn't make sense. If I had two DC motors connected with a belt and both were spinning at 100 RPM, if one uses 1W to run at this speed and the other uses 0.5W, so what? The important part is that they are both spinning at the same rate (analogous to system tonnage). Can someone explain in detail please?

What is the best 2.5 ton heat pump I can get that will heat my home when temps drop to the teens and single digits? From what I've read, I should get a heat pump with two-stage compressor and demand defrost.
 

Last edited by mossman; 02-10-15 at 10:22 AM.
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Old 02-10-15, 11:54 AM
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SEER is the efficiency of the unit. You get the efficiency up by using less electricity. One way of doing this is increasing the size of the indoor and outdoor coils so it will remove/add more heat. Coil size will follow SEER a 13 Seer AHU can not be used on a 16 SEER outdoor unit.
 
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Old 02-10-15, 12:36 PM
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Tonnage must match and so should SEER. In a pinch you could run a slightly higher SEER outdoor but performance will be compromised.
 
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Old 02-10-15, 12:58 PM
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Tonnage must match and so should SEER. In a pinch you could run a slightly higher SEER outdoor but performance will be compromised.
I understand. And what about matching brands? Does that matter as long as the SEER and tonnage is matched?
 
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Old 02-10-15, 01:05 PM
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Its always best to stay with the same brands. You will typically get a matched system (indoor and outdoor made to work together) that way. Plus I don't know any manufacture that will warranty there equipment if it is not matched.
 
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Old 02-10-15, 01:07 PM
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Well, I have a home warranty, so I'm not really concerned about that. Nonetheless, I'll likely go with a Goodman heat pump--the best I can get in whatever SEER my indoor unit is.

Any reason why I couldn't just buy the heat pump online, set it in place, wire it up, and call a technician to come out to evacuate the old freon and charge the new system? Or do most places not sell to the general public? I found a good deal on a 2.5 ton 14 SEER Goodman SSZ14 heat pump online for $1,100 with free shipping and liftgate service.
 

Last edited by mossman; 02-10-15 at 01:38 PM.
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Old 02-11-15, 06:04 AM
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Okay, I looked at the air handler. It is a Goodman ARUF303016CA and was installed two years ago (maybe three). I don't know what the SEER is. If my memory serves me right, it can be used with either R22 or R410a, and currently has R22 in it. I'm going to take a guess and say a 2 1/2 ton unit is undersized for a 30 year old 2,000 sq ft 3-level home with leaky windows and skylights on the top floor. If a manual J confirms so, can the 2 1/2 ton evap coil be swapped out for a 3-ton? Since I will be switching from R22 to R410a, it seems like replacing the coil would be best anyhow so I don't have to worry about it being flushed properly. I'm looking at the manual and the cabinet sizes for the 2.5 and 3.0 ton units are exactly the same, and the static air flow numbers are also exactly the same, so it seems like it would work.

Cabinet Dimensions
ARUF303016: 46 3/4" 22" 17 1/2" 19 1/2" 10" 14 1/2" 11 15/16" 17 1/8" 17 15/16" 2"
ARUF363616: 46 3/4" 22" 17 1/2" 19 1/2" 10" 14 1/2" 11 15/16" 17 1/8" 17 15/16" 2"

Static Air Flow
ARUF303016:
High 1455 1385 1330 1205 1090
Med. 1340 1290 1230 1140 1050
Low 1075 1030 980 910 840

ARUF363616:
High 1345 1290 1230 1150 1070
Med. 1270 1210 1140 1075 980
Low 1045 1005 955 885 805

Only difference I could find between the two units is the blower on the 3636 is 6" wide and the blower on my 303016 is 8" wide, which is why the CFM numbers are different. Even so, the medium speed of the 303016 is just about the same as the high speed of the 363616, so this shouldn't be an issue. Other than that, all electrical and mechanical specs are exactly the same. I'm waiting to hear back from Goodman, but I think it's safe to say I can replace just the evap coil to a 3 ton (and replace the flow rater with a TXV)
 

Last edited by mossman; 02-11-15 at 08:30 AM.
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