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Heat pump output correct?

3K views 25 replies 6 participants last post by  carl333 
#1 ·
Hi, I have a Lennox XP17 2.5 Tand installed a year ago. Just wondering in my temperature output at the registers is just about normal.

With heat pump running and no heat strips engaged, I am receivng a temp of 80 degrees at the registers.

conditions:

house temp: 68F
outside air temp:14F

Is 80 that I am receiving at the registers normal or am I below what it should be??

tks
 
#4 ·
At 14 deg the HP isn't very efficiant.

With out knowing pressures I would say it's doing the best it can do.

When was the last time you had the system serviced.

If you don't have an outside thermostat I would advise you to have one installed. So that when the temp outside gets below 25 it cuts out the condenser and turns on the 2nd stage heat. At 14 deg you may be spending more money for very little results versus the same money being spent on 2nd stage heat and providing a better return on heating

I have always told customers that a system needs to be serviced twice a year spring/fall but with heat pumps you should atleast have the system serviced at the end of the summer. Charging techniques are quite different with a HP in the winter. It is much easier to check out a HP in the A/C mode.
 
#5 ·
The HP is a year old. Actually I have a dual energy system with oil as back-up. The HP will run until 10F or so, then the secondary source oil kicks in.

I haven't considered having it serviced just yet. What servicing would be done on a unit this old?

Right now, its about 15F, and its running about 60% of the time. Do you think its not efficient to run and I should have expensive oil kick in?

I live in Quebec and our electrity rates are very, very inexpensive.

Are you impressed with the 80F at the registers or should I have it serviced? I just want to get the max. efficiency out of the HP and not sure what I am getting at the registers is about normal.
 
#6 ·
The HP is a year old. Actually I have a dual energy system with oil as back-up. The HP will run until 10F or so, then the secondary source oil kicks in.


I haven't considered having it serviced just yet. What servicing would be done on a unit this old?


Right now, its about 15F, and its running about 60% of the time. Do you think its not efficient to run and I should have expensive oil kick in?

I live in Quebec and our electrity rates are very, very inexpensive.


Are you impressed with the 80F at the registers or should I have it serviced? I just want to get the max. efficiency out of the HP and not sure what I am getting at the registers is about normal.
 
#7 ·
The HP is a year old. Actually I have a dual energy system with oil as back-up. The HP will run until 10F or so, then the secondary source oil kicks in.

10 deg is too low I normally set kick out at 25 deg. HP loose their efficieny drastically below 27 deg

I haven't considered having it serviced just yet. What servicing would be done on a unit this old?

Even at a year old freon can leak out. Though it shouldn't I would still have the charge checked every year.

Right now, its about 15F, and its running about 60% of the time. Do you think its not efficient to run and I should have expensive oil kick in?

At 15 deg no I don't think it is very efficient. When you compare the BTU's you get from electric at 15 deg compared to oil I think you will benifit from oil.

I live in Quebec and our electrity rates are very, very inexpensive.


Are you impressed with the 80F at the registers or should I have it serviced? I just want to get the max. efficiency out of the HP and not sure what I am getting at the registers is about normal.[/quote]
 
#8 · (Edited)
That is a VERY high end unit and should be checked once a year. The covers on the outdoor unit need careful removal and the coil washed with a hose. Freon levels should be checked. GENERALLY if there is a freon leak it shows up in the first yr of operation and if it still has any of the 1 yr labor warranty left you should get it checked ASAP. Tech will check the superheat/freon level/outputs etc. To keep the warranty going properly ( has a 10 yrs parts warranty on that unit I believe) it should be checked once a yr. We have another tech Marty who may be here later (if not watching the Super Bowl) who does a lot of Lennox and has a XP15 himself. Hang in here.
 
#11 · (Edited)
14F = -10C sounds like you are running it WAY too low and I don't do a lot of heatpumps. Like Plumber101 says 25F sounds reasonable to me. 32F = 0C so you would be around -4C which is as far as I would go. Good advice from him. What you are doing now is basically wearing out the compressor and a VERY expensive outdoor fan ECM type so I would rather extend the life of the unit and pay for another fuel source. Your output is probably OK but the ROI return on investment /COP co-efficient of performance is poor at that temp. Why is elec so expensive in Quebec and Ontario. You guys have LOTS of it like Manitoba. Must be due to getting rid of the old nuclear plants and export deals etc. We may get nailed with that as the Manitoba govt/Hydro want to build this Bipole 3 line and more plants up North and guess who gets to pay for it. Moi of course.
 
#12 ·
Yuri,

Update. I am doing some accurate measuring as we speak.

Outside temp: -7C
HP kicked a few moments ago at 1:07 and it completed a cycle in10 minutes to maintain temp. Shut off at 1:17
HP re-kicked in at 1:32 (15 min. after completion of last cycle) and completed a cycle this time in 12 minutes or 1:44

My earlier post said my electricity rates are very, very INexpensive. Especially due to the fact that Hydro Quebec has a dual energy program where they discount hydro rates at 30% less that all the other hydro uses around me that are not on a dual energy program. Our electricity rates are probably second to now in the rest of Canada and I am being further discounted. YAAA!!! So I don't mind running elect. to run my HP for as long as it wishes just as long as its less expensive than oil. If running a HP involves a lot of wear and tear on compressors etc...then I may consider having the oil kick in sooner rather than later but not sure where the trade off is exactly. So many variables to consider, so that's why i need advise from the experts here. Comments?

Right now, the system as it is set up, oil takes over and kicks in at approx. --14C. Sure, the HP runs almost continiously just prior to hitting that temp....

Am I exerting the HP recklessly or am I on track to to run the HP as is considering the low elect. rates I am receiving?

I am going away from my 1st question which was about getting your opinions of the 80F reading at the registers solely from the HP. Am I doing good? Comments?
 
#14 ·
OK, I did not read the IN expensive part, apparently Ontario is expensive but they have some old nuclear reactors off line and needing expensive repairs. The compressor is designed to run continuos and the outdoor motor has ball bearings but I would rather not wear the unit out. Most people can't stand that low of a supply temp but obviously you can and your cycles are nice and short so if the shoe fits wear it. I doubt you can get more than 80 deg supply as the output drops like an inverted bell curve in proportion to the outdoor temp. Obviously Lennox does not have a problem with that setting and the new modern high efficiency units are designed to run longer and more efficiently than the older ones. Yours is 17 SEER and that is very high. Get it properly serviced when it is at least 70 F or 22C in the spring and then you have no worries. It has lots of safety controls to monitor itself so I doubt any damage can occur but it still needs checking. When you buy a Lexus you want to protect your investment not like some cheap thowaway car. With the outdoor coil now being dirty after a yr you may be losing some performance.

Beenthere knows a lot about them so I guess the consensus is let it run if you don't mind the wear and tear aspect and cool supply temp.
 
#15 ·
Thanks for all your replies guys. I appreciate it. Just 1 last ?? if I may.

Is the temperature at -14C when the oil kicks in decided by Lennox as a factory setting or could it have been the tech guy who installed it that made that decision? I would think Lennox.

opps! One last but just out of curiousity. Can the oil kick in temperature be decided by me at adjustments made at the thremostat? I have a White Rogers kick ass thermo as implied by the teck guy who uses nothing else. Old school or what? Good thermo?
 
#17 ·
Does the tstat you are using have an outdoor temp sensor, or is the cut out temp determined in the outdoor unit? If the stat has an outdoor sensor then you can likely pick whatever switch over temp you want, if it's done in the unit, you may have to add additional controls to make the switch over temp change.
 
#18 ·
I 'm pretty sure no tstat temp. sensor exists. This is a built for Canada pump and I can only think that the factory presets the controls to what it is capable of doing efficiently. If I am right, I am not looking at setting the kick off time sooner unless absolutely necessary and letting oil take over sooner than necessary.

Am I on track here? Even if the HP runs 90% of the time during our cold spells and maintains a comfortable level isin't it wise in all respects better than 50% oil 50% on the pump? From an economical standpoint, I think yes but at what point is it less economical to run the pump than oil?

My train of thought is to maximize the use of the pump as a 1st priority but I may be wrong. An earlier post suggests to run the pump as long as I could. So it appears that I shouldn't look at purposely limiting the time the pump ceases to kick in and have expensive oil take over.

Remember, my secondary source of heating is oil and not heating elements and as mentioned earlier, my electricity rates are 2nd to none.

Thoughts??
 
#20 ·
I would look into the possibility of adding heat strips. It's not very common but it has been done.

1st stage heat = heat pump
2nd stage heat = eletrict heat strips
3rd stage heat = oil heat

They make thermostats for 3stage heat. May be a little expense but it may let the compressor last longer.

Just my $.02

Hopefully Yuri or Beenthere will chime in
 
#23 · (Edited)
If your elec rates are that cheap why not get rid of the oil furnace and install an electric furnace like a Nortron with an energy saving ecm motor. Only drawback but it is a reasonable one time cost is that you may need a larger electrical panel service to the house. I would do that as it will easily pay for itself in a few yrs if your rates are that cheap. Very well built and been around 4ever and easy to get parts for. Need to get your installer to contact Lennox and make sure they have a dual fuel adaptor kit to use an electric furnace. Not listed on Davenet but they may have it.
http://www.broan.ca/product-detail.asp?ProductID=100544
 
#25 ·
I can’t consider this. Hydro Quebec offers a dual energy program to its customers of which I am. Your primary source of heat must come from a HP and secondary from a fossil fuel. A HP as primary and an electric furnace as secondary are not eligible. The reason for this is that they want their customers to use the least amount of electricity from the grid so they can sell more of their excess to my friends south of us (bordering US States) and elsewhere in Canada.

My kwh cost is .043 under the program. My only drawback but minor is that my electricity rates increase to .183 per kwh when it reaches -15C. A red indicator light installed in the house kicks in and tells us that we are paying premium rates so our usage habits change a bit. ie. the dishwasher can wait until tomorrow. -15C is few and far between so my savings running an efficient HP and the low rates have been quite outstanding. I needed air conditioning so the HP serves that purpose as well.

Thanks all for your inputs. My initial request for advice concerning normal temps received at the register has been answered. I was just attempting to see if my HP was tuned to max. efficiency and realize now that these readings involve various variables including a well oiled machine. I will get it serviced in the spring as suggested here. My attitude “if it ain’t broken, don’t fix it” has changed. Though we went off topic a bit, I was delighted to read comments from everyone who posted. What a wealth of info here.

Thanks guys. Don’t hesitate to comment further should you wish! I have more questions and I’ll post them later.
 
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