Heat Pump not working right?


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Old 02-12-05, 01:24 PM
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Heat Pump not working right?

Thanks in advance for any help that anyone can offer. My dilemna is this...

I have a newly constructed home, 2500 square feet, and has for the most part been constructed with energy efficiency in mind. By that I mean 2x6 walls, 2x10 ceilings, and insulation installed in proportion to that. I live in Kentucky, and winters here are not severely cold. There are days that the temp will get down to 0 degrees at night, but the norm here is 40-45 degree days and 25-30 degree nights.

I have a Tempstar 4-ton unit installed on the first floor, and a Tempstar 2-ton unit on the second floor. My electric bills are outrageous! I have used as many as 6000 kWh in a single month. That led me to some serious investigating.

I don't think that my heat pumps are working properly. I have spent countless days now doing research on heat pumps, and have come up with what I think may be a problem. In reading what I could about the "temperature rise" of a heat pump, I am not getting anywhere near what most people say...Other than the technicians that installed the units, and to whom I am stuck with for the next 10 years in accordance with the "HELP" warranty that I have.

Here are some numbers, and I hope that someone can look at these and tell me if they look normal.

On a 40 degree day, with a return air temp of 70 degrees, my register air will only be 80-82 degrees or so. So...temp rise of 12 degrees.

At 60 degrees outside, with a return air temp of 70 degrees, heat pump is outputting air around 86-88 degrees. Temp rise of 18 degrees.

I say these are way too low. HVAC techs that installed the unit don't seem concerned, and say it's not that far out, and then wanna get on the subject of most figures are average and not set in stone. I understand that, but...still I think they are TOO low.

In essence, I think my 25kw strips are running tooooo much, hence the high electric usage. I log my kWh usage daily, and my thermostat has a daily and weekly usage meter, and I log it accordingly. It is obvious that there is a direct relation between heat pump usage and high kWh usage.

Also, pressures on a 40-50 degree day are low-side (62), high-side (170).

OK...Question....Does it look like I may be low on refrigerant, or something else is wrong? Shouldn't my temp rise be a lot higher? Any help is greatly appreciated.

Henry
 
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Old 02-12-05, 01:57 PM
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Id say Oh boy Where to start here. First 2500 sq ft in kentucky with a 4 and 2 ton for 6 ton in the home. Did they run a heat loss and AC load on this home?????? 6" outside walls and and you say10" ceiling I take it thats a R 19 in the walls and aR 38 in the ceilings. Id say its colder in Missouri and we do a 4600sq ft home lots and lots of glass with just 6 tons of heat pumps.
I take it that the filters are clean????? Is it wired right??? The strips dont come on for first call for heat . Any of them stuck on. Does AUX or EM heat come on a lot .Blower set for right speed. When units are on heat is the big copper line hot. When you go to AC big copper line cold and wet???Did you get the pressure reading, are they from them? 170 psi on R-22 should be about 90o on the line. A amprobe would sure help here to see if any strips are on. If out door units are drawing what they should.

Post back in same post.

ED
 
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Old 02-12-05, 02:07 PM
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Heat Pump Not Working Right.

Henry,

I am not a expert, just a homeowner with a heat pump. I have been in my home for almost a year. It was my first experience with a heat pump. I had the same frustrations you have. I had to work over a period of time with my HVAC contractor to get it just right. My home is located in north Texas and has 2000 sq feet living space. My average heating bill is about 245.00 dollars a month.

On a 40 degree day, with a return air temp of 70 degres, my register air will be about 96 degrees. I dont notice much diffrence if its sixty or forty degrees, the air temp is still about 96-100 degrees. Now, if the aux. or emergency heat kick on it will register about 125 degrees.

When we first moved in I watched my aux. heat light on my thermostat alot. I noticed it would come on when my unit went into defrost. You can tell when it does because the fan on the unit outside will not turn when its in defrost. When this happens the electric stips come on to warm the air because the unit then acts as a a/c unit to defrost. The more it does this the more your bill will be. Im sure you already know this. To make a long story even longer, my unit was low on refrigerant and it went into defrost more than it should. We had a small hole that allowed refrigerant escape. Once that was fixed it worked fine.
 
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Old 02-12-05, 02:09 PM
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Thanks Ed for the quick reply....

Yes...the big line gets hot....Not REAL hot, but hot nonetheless.

Filters are clean and it is wired right. The strips are not stuck on, and are coming on when they are supposed to. It's just that the heat pump on its own cannot keep up with the demand, so the strips are working more than I think they should.

Did the amprobe thing, as I am certified in electricity and electronics, but probably am not an expert in the HVAC field (tho I have done quite a bit of work in that field). The compressor does not seem to be drawing full load as it should. About 3 amps shy of rating. That coupled with not enough temperature rise leads me to believe that I have a heat pump problem (refrigeration side). Pressure numbers are mine. I checked them.

Auxiliary strips are working properly. My Tempstar has TWO auxilary stages. I use the Y wire for the compressor, W1 for stage one aux and W2 for stage 2. I think that 1st stage aux is 5kW, and 2nd stage is the full 25.

Again, I feel that the "pump" is not up to snuff.....

Henry
 
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Old 02-12-05, 02:55 PM
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When units come on none of the strips come on at all??
Till there is a 2o drop then they should come on. Sounds low on freon. lost a bet one time company tech said he could charge a unit no gauges just by amps, And he did. You checked psi??? you EPA??? Hoses clean ,you didnt get any noncondensables or contaminate the system?? There should be a charge chart inside the unit there.Run AC and check head on it. That should be a good cross check.
Have you ran the AC yet what did it do?? I still think 6 ton for 2500sq ft is over kill it will pull the temp down but wont get the humidity out of the home. So you will still feel hot.
lost on the tstat dont know it. But on a ct 3611 Y jumper to W1 ritetemp 8030c its jump Y to W

ED
 
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Old 02-12-05, 03:36 PM
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No strips come on at all, until they are required. (2 deg drop)

Everything is working as it is supposed to as far as sequencing and such. Its just the heat pump cannot keep up with the temp like I think it should. Unit calls for the strips too often it seems.

A/C worked fine this past summer.

As to what kkmcewen posted....I have NEVER seen 96-100 degrees out of the heat pump. It may have hit 90 at one time, but it would have been rare. 84-88 is the normal output temperature....

I think it's low on refrigerant....

Henry
 
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Old 02-12-05, 03:54 PM
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Hey when I have a problem that just doesn't sound right I go back to the basics.
I would check the air flow to see if it is right by temp rise method.
Get the temp rise off emer. heat mode and let it run 5 or so minutes.
Get the amp reading of the air handler less the fan amp reading.
then get the watts and multiply that by 3.414 then divide that by 1.08 times temp rise.
This should give you the air cubic feet per minute.
That should be 400 per ton or 1600 CFM.
Then with Tempstar they have a good detailed charging chart on the inside cover of the outdoor unit.
Check the pressures according to the inside and outside temps.
If I am not mistaken there should be a line in that chartthat indicates a symbol T/R this is heat rise. All this should coinside.
The amp draw should be apporpriate to the chart if voltage is 230v but most places I have been it is closer to 240-245v
 
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Old 02-19-05, 06:40 AM
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Here is some more info...

This morning it is 20 degrees F outside. At 8:35am, my thermostat shows that the heat pump has run 8'35". So...It has run non-stop since midnight. Thermostat also shows that the aux has not run at all.

Temp rise is 8 degrees. Air in house is 70 degrees, air from vents is 78 degrees. Chart says that T/R should be 14 degrees at 20 degrees outside temperature. So...looks like to me that my heat pump is NOT providing the heat rise that it should.

Everything else is running OK. HP is keeping the temp within 1 degree, so aux strips are not coming on. I can up the thermo 1 more degree, and the first stage of aux will energize and vent air temp goes to 96 degrees. I can up the temp 2 degrees and the second stage aux strips come on and the vent air temp climbs to 120 degrees.

Basically...what I am asking is...Shouldn't the temp rise from the heat pump be MORE than 8 degrees? If it were to get ANY colder outside I would be using the aux heat a LOT. That is when my electric usage goes out the roof.....


Henry
 
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Old 02-19-05, 10:30 AM
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Henry

I too am not a heat pump expert by any strech of the imagination but I agree with Scottg on checking air flow. High air flow = low temperature rise. Presuming the air flow to be correct, I would suspect the system to be light on charge.
 
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Old 02-19-05, 10:44 AM
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Yes as it gets colder outside you will use more AUX heat. I think you should do are have some one do a heat loss on the home. To see if you have the right size unit in there

HP is keeping the temp within 1 degree, so aux strips are not coming on.

I can up the thermo 1 more degree, and the first stage of aux will energize and vent air temp goes to 96 degrees. I can up the temp 2 degrees and the second stage aux strips come on and the vent air temp climbs to 120 degrees.
It all sounds right are how it should work
ED
 
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Old 02-19-05, 02:38 PM
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Yes as it gets colder outside you will use more AUX heat. I think you should do are have some one do a heat loss on the home. To see if you have the right size unit in there
I did a heat loss on the home and came up with the specs.

First floor - 30520 btu
Second floor - 17350 btu

TOTAL - 47870 btu

Isn't it 12,000 btu/ton? That would be 2.54 for the bottom floor and 1.44 for the top floor. If I recall correctly, the reason that we went a little bigger on the size was due to the fact that my house is on the "north side" (sees VERY little sunlight in the winter), and...I have nearly 800 square feet of the bottom floor with 17' celings....

I can cool the home very economically. Comparable new homes around here are heating with heat pumps for HALF of what I am....

As to this morning....I was sure that I should be able to heat the home very easily with an outside temp of 20 degrees, by using the compressor only. But...it was struggling to keep the temp there. After my last post this morning, it did in fact take the aux strips to keep the home at 71 degrees....

would check the air flow to see if it is right by temp rise method.
As to my calculations, I came up with 379 cfm / ton...Is that close enough to 400?


Henry
 
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Old 02-19-05, 02:59 PM
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I'll tell what I would do.


Call and talk to the owner and explain that the units h/p function is unable to keep up no matter what the outdoor temp is and that he tech that came out is of no help. reqest that they send out a better tech to figure out what is going on. If they find out that you put gages on the unit they may be able to void any warranty you have with them.

I agree that 6 tons is way to much. The units will short cycle which will shorten their life and you will now remove humidity the way they should and with a home as insulated as yours is the inability to properly remove humidity will promote mold growth.
 
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Old 02-19-05, 10:02 PM
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Thanks to all that offered help and advice....

Call and talk to the owner and explain that the units h/p function is unable to keep up no matter what the outdoor temp is and that he tech that came out is of no help. reqest that they send out a better tech to figure out what is going on.
Well...I live in a rural area, and the company is family owned. The tech IS one of the owners. They came with several good references, and had one of the better bids, so I chose them. Their installation work is very acceptable. However, I think they may lack a little in trying to get every ounce of efficiency out of the unit. My opinion, and I would have no problem telling them as well.


scottg said:

Then with Tempstar they have a good detailed charging chart on the inside cover of the outdoor unit.
Check the pressures according to the inside and outside temps.
If I am not mistaken there should be a line in that chartthat indicates a symbol T/R this is heat rise. All this should coinside.
I looked and there is indeed a very informative chart in the Tempstar cover. I even scanned it into my computer, and looked over it closely. T/R and pressures are NOT what Tempstar says. Low pressures are somewhat close, but the high pressures are not. (BTW...I said in an earlier post that the pressure readings were mine...clarify....I VIEWED the readings...One of my employees IS certified, but ALL of our company's work involves mobile equip...don't have any R-22 or the such laying around)

Not trying to beat a horse to death here, but $500/mo electric bills are killing me. Especially when I see a lot of $150-200 ones. So...If I am getting annoying, just pass me by....Anyway.....Here is a comparison...

Tempstar specs at ambient of 40, thermostat at 70:

T/R = 23.3
Amps = 15.7
kW = 3.3
Hi = 235
Lo = 47


My observed measurements:

T/R = 12
Amps = 13.1
Hi = 185
Lo = 64

Oh well....Guess I'm gonna have to be vocal enough to make them want to shut me up, and make a service call.....


Henry
 
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Old 02-19-05, 11:35 PM
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With these readings something is not right.
It seems that the unit is low on a charge.
I would try putting in some refrigerant and see if the high pressure comes up.
At the same time the amp draw should come up and the low pressure should drop some.
 
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Old 02-20-05, 12:35 AM
David Haynes
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Lightbulb Install Geo loops next season

When you get a chance you can improve efficiency by converting to a ground exchange versus an Air exchanger.

Temporarily you can run Water through the coils, which will probably give you a 30 deg F increase in temperature vs your air temp.

The problem with that is the water will freeze unless you disable the fan and insulate the unit.

I have had good results with the water exchanger in Florida running in Normal AC mode as the Air temp cooling on HOTT days decreases the heat exchange. The water will be 20 to 40 deg F cooler from my deep well.

Well, some of the experts here will say that I am crazy, but that's ok.

The problem with heat pumps is they run most efficiently in the mode that you do not need.
 
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Old 02-20-05, 07:22 AM
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I'll bet I know what they did. After the vacuumed down the line set and released the refrigerant from the outdoor unit they are relying on that charge to be correct. I've seen this thousands of times and I couldn't count how many times that the factory charge was so far off that it isn't funny.

Another problem goes back to the oversized equipment. This is another scenario I've encountered. With the heat pump being to big it needs more refrigerant in the winter to properly heat then in the summer it ends up haveing to much.
 
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Old 02-21-05, 11:11 AM
David Haynes
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Talking Buy a water heat exchanger, pays for its self



Heat pumps running in reverse mode (heating the inside of the house)
decrease their efficiency as the outside air temperature drops.

One way around the low air temperature is not to use air but a water exchanger. Such units are more expensive but pay for themselves in
greatly reduced power consumption.

Since I cannot post ads I post the following description of a water exchange heat pump.

Product : 3.0 Ton Water Cooled Heat Pump
Pcode : EMO35-VLHR
Weight : 300 lbs. 0 oz
The ENERGY-MISER units are recognized as the most efficient and economical way to meet all your Cooling and Heating needs. Available in Vertical, Split, Horizontal and Counterflow configuration 1/2 through 6 tons. The EM Series is our Premiere product line. This works with Well Water Systems above 50 F, and with the extended range option for geothermal conditions. Even during temperature extremes, FHP equipment maintains its superior efficiencies. Therell be no nasty surprises during hot summer days or frigid winter nights.

REAL COST SAVINGS
Save from 50% to 70% in heating costs and up to 40% in cooling costs... Plus you can get low cost HOT WATER during the summer months with our Heat Recovery option

RELIABILITY
With over 30 years of experience in heat pump technology behind every FHP unit, you can be sure of a quality product that will give you many years of trouble free service.

Since there are many configuration options such as return and supply location,you will get a technical support call to configure your system to your specifications.
See full specs on .pdf file on right, 44 pages long!

 
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Old 09-01-05, 01:38 PM
NavyChief
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Heat Pump not working right

I am in the Navy, stationed in Virginia Beach. My wife and I live in a 1600 square foot apartment that is heated and cooled by a heat pump. Don't know about the tonnage or the BTU's since it is an apartment. Here is the problem, I am keeping the thermostat set at 70-72 degrees during the day and when I get home it is 76 degrees in the house. It doesn't get to 70 degrees until late at night well after sunset. Outside temps here have run anywhere from 85-95 degrees lately. My wife asked the maintenance guy if this was right and he told her it was not unusual for a heat pump to take 12 hours to cool our apartment from 90 degrees to 70 degrees. This does not sit right with me. I'm not an AC guy but still that doesn't sound right. Can anybody give me some help here? I can be reached at "No e-mail addresses" Thanks in advance for any help!
 

Last edited by mattison; 09-02-05 at 04:55 AM.
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Old 09-01-05, 02:07 PM
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You can have a lot of ifs ifs ifs here for sure. Is the attic insulation good?? Does the attic have good vents in it to let out the hot air??? Is the inside unit clean??? the coil the blower wheel and the filter???. Is the freon charge ok on the unit if it is the big copper pipe out side should be cold and wet??

See if you can check that all out and post back in same post here.

ED
 
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Old 09-01-05, 02:44 PM
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NavyChief

What size heat pump do you have? Model, Brand, Age?

Apt complexes are notorious for undersizing HVAC equipment.

You may want to ask maintenance to check the blower speed of the air handler and make certain it is on high.

Check the supply vent register temperature. It should be in low 60s-no higher.

As Ed stated, in AC mode big copper line should be cold and wet. Small line warm.
 
 

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