I recently remodeled and moved into a forclosure equipped with an 11 year old heat pump. I purchased a home protection plan, and the heat did not work. Warranty people sent out a repair man who continually said he hated heat pumps, and that they were not a good system for my climate (suburban St. Louis Missouri area. Replaced thermostat, still didn’t work. Replaced some type of board on the unit, still no heat. then he realized he didn’t need the board, he just had not programmed the thermostat correctly. Still, the heat pump would start to come on, run roughly for 1-2 seconds, and not go any more, just go to furnace. Does this every couple of hours. He says that this is the way it is supposed to work, and that it kicks off because it is too cold out side. This doesn’t seem correct, but I am an idiot when it comes to this and can’t dispute it. Someone please tell me how this thing should act, and if I am getting the right advice from this man, who by the way is an appliance repair man who just happens to also work on hvac.
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They will do a reverse cycle occasionally (set on an internal timer) where, when the selector is set to heat, it will run the AC to heat & defrost the outside unit. I think you ought to drop the change for a service call for a good HVAC contractor to take a look and give up on the warranty-sponsored-cheapest-bid-I-hate-Heat-Pumps-guy. IIRC locally it's $100 for a HVAC service call.
My plan is to call the warranty service and insist on a different vendor. I am, so far, happy with the service I am getting from the warranty service.
The guy doesn't know his A from a hole in the ground. You should first call the warranty people and ask them to send out a real HVAC guy. If they refuse, hire one yourself and sent them the bill. If they reject the bill then try small claims court.
Down to 0 degrees or so (this may be different from set-up to set-up and from manufacturer to manufacturer), when there is a call for heat, the unit should initiate the first stage of heat, which is the reversed refrgeration cycle. The compressor runs, the fan runs and the system generates heat after a start up period. IF this is not enough heat or the discharge air low limit is not met in a given time period, the second stage of heat comes on usualy an electric resistence heat coil or a gas furnace. If the temperature outside is too cold for the unit to start or for the unit generate enough heat, it will automatically go to the alternate heat source.
I agree with Dan that the individual they have been wasting your time with is wholly unqualified to service anything other than what he might find with his hand in his pocket.
Request a qualified service technician.
Below 40 degrees a heatpump is worthless.
And inside of a dog it's too dark to read.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Below 40 degrees a heatpump is worthless
HUH!!!
Mine works just fine down to 8F (coldest it has gotten here)
One I installed at Mom's house in IL works just fine at -10F, even without the aux heat strips.
Agree with all that the tech sent to the OP for service is an idiot.
Junkhound,The compressor part of your heat pump is worthless under 40 degrees F - the "heat strips" are your "auxiliary heat" - and not your actual heat pump. I have a heat pump that just happens to use an oil furnace as it's auxiliary heat instead of heat strips. Above 40 degrees I get the heat pump, below 40 degrees I get the oil furnace - I hope that helps!
Once again, it depends on the heat pump. Many units that are primarily for air conditioning are simply undersized for heating below 40F or so. But a properly-sized unit designed for cold weather can be effective (and sufficient without aux heat) to 20F or lower.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Your unit has a low temperature lockout that prevents the compressor from running below its setpoint. Compressors can and do operate in temperatures well below 0 degrees F. Junkie knows more about refrigeration systems than most.
I work for the manufacturer. We publish heat pump heating capacities down to -8 degF. For instance a 3 ton, single phase unit, with indoor air temp at 70 and outside air temp (OAT) at -8, will produce, using the compressor only, 8,800 btu/hr of heat. At 32 degF OAT, that increases to 27,200 btu/hr. Point is the unit compressor operates below 40 and the manufacturer tests it and catalogs the perfomance.
I work for the manufacturer.
yeah, but what do you know about heat pumps?
;^)
Thanks for the info that you post.
Like I said below 40 they are worthless. Yea it might work, but it gets less efficient as the temp drops and that is exactly when you need it doing a better job. Perhaps some like a cool breeze blowing 24/7 in winter.... not me.
I have a heat pump with propane backup about three years old. I did a lot of research and talked to three companies before purchasing. They all suggested the same size unit for my house. It's set to go to propane at 32 degrees, but below 40 degrees I manually switch it to propane. If it's below 40 degrees outside it feels like cold air coming out of the vents. I guess I would look at it this way. At the lower outside temperatures, I think we can all agree that propane heat feels better then heat pump heat.....agreed? .View Image
Damn skippy. When the 2nd law of thermodynamics is bleed my house of heat I'd much rather have an occasional 100 degree breeze then a constant 69 degree draft.
What you're saying about heat pumps used to be true, but no longer applies to the newer models using Puron refrigerant. I have a HP just installed this summer) with gas back-up. It switches to gas below 20F. It's 28F right now and the air coming out of the register is toasty warm.http://www.quittintime.com/ View Image
And there's the new Acadia heat pump that can produce considerable amounts of heat even in below-zero temps.
http://www.gotohallowell.com/acadia.html
113497.19 in reply to 113497.8
Junkhound,
The compressor part of your heat pump is worthless under 40 degrees F - the "heat strips" are your "auxiliary heat" - and not your actual heat pump. I have a heat pump that just happens to use an oil furnace as it's auxiliary heat instead of heat strips. Above 40 degrees I get the heat pump, below 40 degrees I get the oil furnace - I hope that helps!
FWIW, my heat pumps have NO auxilliary heaters. It has gotten down to 8F here and my 4T with R22 air-air HP can heat my 5300 sq ft house. That said, I do switch from air-air to wshp when air temp drops to 45F, but 'simply' for economic reasons. BTW, the wshp is a 'home built' and I do have the epa license for freon.
Think most the other replies have already explained and addressed the gross misconceptions of those who think HP do not work below 40F, wondering where that falacy originated.
These type threads do help me understand why the aerospace company keeps me around to explain this stuff to those with gross misunderstandings <G>
If one cannot plot enthalpy/pressure/temperatures on a mollier chart and compute the cop they have no business misleading those who ask questions with blanket statements like 'no work under 40F'.
The oil company does like you, will admit that. You could save yourself a few $$ a year by running your HP down to at least 15F.
"The oil company does like you, will admit that. You could save yourself a few $$ a year by running your HP down to at least 15F."Junkhound,Maybe you could educate me then. I understand that air source heat pumps "work" under 40F, but that they aren't very efficient. The installer and person who recommended my setup actually told be that they were going to set up the "crossover point" at 35F but they ended up setting it at 40F - why I don't know. He originally told me that 35F and above is more efficient with the heat pump, and below that the oil heat was more efficient. I have been having some trouble with it in heat mode lately - it's a 3 year old Armstrong unit. It starts up, runs for 3 minutes (blowing heat) and then the outdoor unit starts making kind of like a sound that a bearing going bad would make and then not so much heat and it just runs constantly without bringing up the temperature in the house. If I shut it off for a few minutes and then turn it back on, it does the exact same thing. I've heard the noise since new, but not constantly - makes me think it's stuck in the defrost mode or something. Anyway, I don't recall it making that noise in cool mode. The way I came up with this setup is I had a local company who thinks very highly of themselves give me a quote on a replacement oil furnace -vs- an all electric heat pump - that's what my parents had in their house for 20 years. They recommended the 2 1/2 ton unit after measuring the house and looking around some. Then I talked to a co-worker's friend who installs on the side (he also installs full time, but does it for friends and family on the side) and he suggested the heat pump/oil furnace combo. He installed the units in my house for me - all told I got the heat pump/oil furnace combo for only $500 more than everyone else was quoting for just a replacement oil furnace. I'm happy with the results - I'm using one less tank of oil than I was with only the furnace replacement and no insulation upgrades yet.At any rate, I have a 2 1/2 ton unit in a 1,400 square foot 1890's two story farmhouse. It is balloon framed and is poorly insulated - I'm just starting to find this out and am rectifying this situation as I can. 90% of the windows are vinyl replacement units and seal pretty well. Does it sound properly sized to you, or is it undersized? If I could make it work down to 35 or 30, I'd do it - my Honeywell TH8000 thermostat only allows changes in 5 degree increments. I'm thinking that my unit may be undersized, but as it gets tightened up, it will be O.K. I'm insulating one room at a time with 1-2" of closed cell foam, and then probably fiberglass bats. As many other posters have mentioned - it may work down lower, but it doesn't seem very efficient or comfortable. Maybe in a well insulated house, or with a ground source heat pump, or maybe a properly sized unit, other people would have a different impression of heat pumps?It's only 20 degrees out right now - the oil furnace is doing it's thing!Thanks for your input!
Below chart will give you an idea of typical air-air commercial HP performance
Understand your conditions now.
Since you have a poorly insulated house with only a 2.5T HP, I can see why you could be led to beleive that 'your' HP will 'not work' below 40F. In your case, it is true the HP dont work, if you define 'dont work' as an undersized HP being unable to keep the house warm.
At 40 F, a 2.5T HP can deliver only 2T worth of heat, so if your house loses more than that, you will get cold. However, note that at 40F the COP is still >3, so it is cheaper to run than the oil (assuming 10cents kwhr = approx $1/therm at cop of 3.5; whereas 80% oil furnance delivering a therm uses about 0.9 gallon of oil (at any temp). For the particular HP below, at about -15F the HP is worse than straight electric heat for economy.
So, if you can get oil for $1.12/ gal, oil is cheaper at 40F. Otherwise HP is more economical. However, say your house loses say 60,000 BTU/hr at 20F, you would need a 5T HP to keep warm, costing you about $1.50 a therm. Thus, at 20F, gas heat with a 95% furnace would be a breakpoint if gas cost approx $1.30 a therm, or if oil costs less than about $1.70/gal - number calc in head, probably off a little.
Most would likely agree that for your poorly insulated house, your $$ would be best spent on FIRST upgrading insulation (esp if installed DIY)
Outdoor Ambient Temperature
65 60 55 50 47 45 40 35 30 25 20 17 15 10 5 0 -5 -10
MBh
33.7 31.9 30.0 28.1 26.8 26.0 24.1 22.2 17.4 16.1 14.8 14.0 13.5 12.1 10.7 9.4 8.0 6.5
COP
4.09, 3.95 3.79 3.62 3.50 3.42 3.24 3.05 2.45 2.31 2.18 2.09 2.03 1.86 1.69 1.51 1.32 1.11
Outdoor Ambient Temperature65 60 55 50 47 45 40 35 30 25 20 17 15 10 5 0 -5 -10MBh33.7 31.9 30.0 28.1 26.8 26.0 24.1 22.2 17.4 16.1 14.8 14.0 13.5 12.1 10.7 9.4 8.0 6.5COP4.09, 3.95 3.79 3.62 3.50 3.42 3.24 3.05 2.45 2.31 2.18 2.09 2.03 1.86 1.69 1.51 1.32 1.11"Thanks for your input and response. Please help me with two things to help me understand what you are saying. I'm not sure what the 'COP' means. Also, my oil furnace is rated at 85,000 BTU with a .65 GPH nozzle and is roughly 80% efficient and we just paid $2.32/gal. When I asked the previous home owner how much oil he used during the winter (with just the oil furnace) and he told me "about 300 gallons" He was off by about 300 gallons - I guess he was more interested in selling the house than telling the truth. Also, is MBh "thousand BTU/hour?" Did my description of the problem with my HP give you any clue as to what the problem may be, and could a technician diagnose and repair it when it's this cold out? The guy who put it in says that he's not very good at repairs - he just does installations - at least he was 'man enough' to admit it:-)Anyway, thanks again for your help! I am enjoying the education that I am receiving on this site.
Just to update everyone, the warranty company has been unbelievably good to work with. Sent out a second company, and that tech diagnosed in short order. The compressor on the outside unit would start up, only to immediately switch off as a safety feature to prevent the compressor from burning up. Was low on freon. He advised that the second stage would get to within a couple of degrees of satisfying the thermostat, and would think that the heat pump was going to finish the cycle, but that the heat pump timed out, or that is the best he was able to explain to me. Ran perfect for one day, and then back to the old routine. He is coming back out shortly suspecting a freon leak somewhere. This warranty shure is coming in handy.
Can you share the name of the warranty company?! I have never ever heard of a warranty company doing the right thing!Glad you getting closer to a solution/fix.TFB (Bill)
sorry for the delay, the home warranty can be found at 2-10.com I am less than thrilled with the contractors reliability address the problem, the ones that diagnosed and temp fixed are not returning calls to come back out and fix perm. but the warranty company conference called them along with me and rode them pretty hard to respond to my needs in a reasonable amount of time. They also advised that if the current contractor fails, I can choose my contractor and get a quote to submit for payment. Like I said, so far money well spent, (I believer we actually paid less than $500 for one year including the pool equipment)
Thanks. Sounds like a stand up company.TFB (Bill)
I'm not sure what the 'COP' means
Coeffient of performance
Merry Christmas Papa and all, first snow on the ground here for Christmas for at least 10 years, 10th time since 1981 according to the TV Weather channel.
MBh = thousand BTUs per hour
COP, as said, is coefficient of perfomrance. For every 1000 BTU worth of electricity as measured by resistance heating, a COP of 3.0 from a HP gives you 3000 BTUs of heat. 1kW-hr = 3412 BTUs
Thanks Junkhound! Merry Christmas to you and to all! I'm glad the snow made your Christmas. We get it here quite frequently. I'm happy to have 5 days off straight and it's supposed to be warm Friday and Saturday, so I can FINALLY do the front brakes on the old van - '95 Chevy Astro - 190,000 miles.]Thanks for all your help!
"Maybe you could educate me then. I understand that air source heat pumps "work" under 40F, but that they aren't very efficient. The installer and person who recommended my setup actually told be that they were going to set up the "crossover point" at 35F but they ended up setting it at 40F - why I don't know."
I know around here 15-20 years ago, nearly every installer would do and say the same thing. The real truth I suspect is that they were tired of getting phone calls from people telling them the HP wasn't working because they didn't feel that huge blast of hot air like they were used to getting and the customers were worried about the longer run times of the HP thinking about the bill.
Partly that was the installers fault for not explaining the HP (manage expectations) and partly it was the result of replacing the AC unit with a heat pump but not the air handler. A single stage old style air handler on an old NG furnance would put out some serious CFM. If you just add a heat pump to that, you are going to get serious air movement at a much lower temp.
Advances in HP equipment came fast and furious and now HP are the #1 seller around here if not #2 behind geothermal HP and you don't get that reaction from customers or techs anymore.
Heck, Doug Rye the radio guy calls us the geothermal capital of the US.
I would suggest that any statement that heat pumps are worthless under 40 deg shows a minor misunderstanding of heat pumps.
Edited 12/2/2008 8:00 pm ET by HammerHarry
I may not understand heatpumps but I do understand the laws of thermodynamics.... and unless they have changed recently, I'll stand by my statement.
So it's no colder than 40F in your refrigerator?
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Well thanks for the heads up.... My fridge just disproved all the laws of thermodynamics.
Perhaps you could give us all a perpetual motion machine design too....
Bawahahahahahah!!!!!!
There's heat in the air down to just above absolute zero. It's just a question of how much, and how much work it is to get it out vs getting heat some other way. A heat pump becomes uneconomical before it quits working entirely, and generally that cutover point is somewhere below 20F.An undersized heat pump may not be able to supply enough heat to heat the house below some higher temperature, but that's a different issue.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Just to add to what DanH said, it's all a matter of what environment a particular heat pump is designed for. They have been more prevalent in mild climates, where the coldest temperature found most of the time is in the 40s (F). Below that and, yes, the pump may not work well, and much colder it won't work at all. Then the electric resistance kicks on.It's all a matter of selection of refrigerant and operating pressures. The liquid refrigerant must evaporate at some pressure where its temperature is below that of the lowest air temperature for which the unit is designed. The compressor boosts the vaporized refrigerant, heating it as it compresses, and the refrigerant condenses at some temperature higher than the air (or water) where the heat is being rejected.There are heat pump designs (as other posters have mentioned) that can run successfully at outside temps in the single numbers or below. The Acadia (Hallowel - sp?) has run down to -30 F. Your freezer runs at air temps below zero.Use ethylene as a refrigerant and you can pump heat from -150 F, reject the heat to a propylene-based loop, which pumps the heat up to cooling water temperatures. How cold do you need to pump from, anyway? Not far from absolute zero? No problem, just pick the right refrigerants and equipment. Unless the laws of thermodynamics have been repealed.
Call me for piling on. I disagree with both of your statements. ALL refrigeration cycles operate within the laws of thermodynamics, and you do not have a complete understanding of either. Are you a serviceman?
I understand Thermodynamics well enough to have taken Thermo 1 and Heat Transfer 2 twice each!
I will reply this again, when it comes to HVAC repair, open the phone book and find the oldest company, at least since 1976. Find one with thirty trucks. on HVAC its all about reputation, you want one that will be around another thirty years, not somebody who has a pickup and a tank of freon.You will pay more, but it be done right, the first time and they will stand behind their reputation.
Mine is doing this right now, but I know why - the fan on the heat pump isn't running. As soon as I have a chance, I need to see what went bad, the fan motor, or something else.
Go outside, and look at the unit when it's 'making noise'. Is the fan running? My guess is, not.
If the heat pump is running ... the condenser fan (outside) should be running and the discharge air should be VERY cold (it's taking what little heat there is out of the outside air ... making it even colder). That's a simple laymans way of first check. If that ain't happening, then something is wrong.
I agree ... ask warranty to send a qualified technician to look at it. You don't warranty something and then send a carpenter to do all the work that might need to be done.
good luck.
Two things come up for me.
One is a really dislike home warranties because they just don't work well a fair amount of the time. Just what you are experiencing.
And I dislike heat pumps. They are noisy and I'm never sure if they are working or the the heat strips are.
Just don't like either one.
I know this doesn't help right now maybe down the road it will.