Heat Pumps and Electric Heating - Not convinced Heat Pump working properly?

I am hoping you can help me feel more convinced my Heat Pump is working correctly. Would really appreciate some help here

I live in Montreal. In Dec 2008 as weather got colder I noticed the heat was running almost all day. To me it did not seem to be able to heat the house as easily as it did in previous winter. I remember it being able to bring house temperature up a degree or so quite easily.

I also noticed that the heat pump's coils did not frost up as much as it used to. The heat pump used to frost up quite a bit and the defrost used to create quite a bit of steam. There were times when the coils were almost all white with frost. Since Dec I have only seen frost appear on 3 or 4 small bands around coils (maybe 2 inches wide). I have never seen it completely frost up for months.

I perceive that something had changed and not for the better.

The service person came. He checked the high & low pressure in the system (which was perfect). He also checked the temperature difference between the air intake vent on furnace and the air coming out of furnace. The result was a 20 to 22 degree difference. He claimed that was very good.

I have a thermometer to check things. Usually the temperature of air coming out of furnace with heat pump on runs around 90 to 92 degrees.

Does the fact that there is a 20 degree gain in temperature prove that the heat pump is working as it should?

I am not convinced it is working as it should but I hesitate to call for service again as I pay for the service call.

PS: Since the time I suspected having a problem my electrical bills have been noticeably higher (compared to last winter). Maybe due to long heat pump cycles or fact that I tried running blower fan 24/7 (on techs recommendation).

Not having frost buildup is a good thing, with excessive frost buildup indicative of various problems such as low charge or defrost subsystem problems.

The tech definitely checked some things that should be checked. If the tech wrote down pressures on your service slip can you post them?

Frost buildup on the outdoor unit is a function of several things such as humidity and unit run-time (low humidity and short run times will prevent frost buildup).

How much higher is your electric bill, taking into account the temp differences from this year to last and your fan on 27/7?

Other than lack of frost, and a higher bill is there any other reason to suspect the unit is not working properly?

It is a Lincoln SX2300 (made by Carrier). The pressure readings he wrote down were 75PSI low and 310PSI high. I think these vary depending on outside temperature.

My electrical consumption jumped to 96 KWH/day over a 49 day billing period. I was averaging around 65 KWH/day during winter months in past. My highest consumption on a bill was 70KWH/day. Do not know if this is just do to running fan 24/7 or if it has something to do with malfunction of unit.

That is about a 35% increase in consumption.

I have switched my fan back to auto.

The tech kept stressing that if it gives you a 20 degree gain then all is OK.

It is a Lincoln SX2300 (made by Carrier). The pressure readings he wrote down were 75PSI low and 310PSI high. I think these vary depending on outside temperature.

My electrical consumption jumped to 96 KWH/day over a 49 day billing period. I was averaging around 65 KWH/day during winter months in past. My highest consumption on a bill was 70KWH/day. Do not know if this is just do to running fan 24/7 or if it has something to do with malfunction of unit.

That is about a 35% increase in consumption.

I have switched my fan back to auto.

The tech kept stressing that if it gives you a 20 degree gain then all is OK.

Pressures and temps sound good. Did the tech check the current draw of the unit during steady state (after startup)? This could indicate a problem with the unit, but does not correlate with your good pressures and temps. The fan would cause an increase in KWH but 35% seems extreme. You should investigate other possible causes of your increased KWH usage.

what kind of furnace or air handler do you have? What kind of blower is in it? What size of Heat Pump and furnace do you have?

How's your airflow?

What kind of filter do you use??

I will try and provide details ask for.

The heat pump is a Lincoln SX2300 2 ton, 13 Seer with R410A gas. Made by Carrier and installed in summer of 2007.

The furnace is also a Lincoln. I think it is about 15 to 18 years old. Oil furnace with forced air. Model # LBO100DA. Cannot find any info on this furnace on web.

I use "Premium" brand pleated air filters and change them every 45 days or so. Not a high end filter that removes allergens etc etc but is is the pleated paper kind I was advised to use.

Nothing else has changed in my house. No new appliances, no renovations. Trying to determine if increased energy consumption due to using fan 24/7 or if partially due to heat pump issue.

I have set fan to auto to see if future bills fall into line again.

Running your blower 24/7 will surely increase your energy usage. Heat Pumps output is directly related to the outside temperature. The colder it gets outside, the less efficient they become. They don't put out a set temp like a gas fired furnace would. If your weather has been colder this year versus last then your KWH consumption will be greater. If your getting a 20-22 degree rise at the vents and not the coil, your probably fine. The real question is if the HP is maintaining the set temperature of you T-stat. If it is, then the unit is performing as it should.

Running your blower 24/7 will surely increase your energy usage. Heat Pumps output is directly related to the outside temperature. The colder it gets outside, the less efficient they become. They don't put out a set temp like a gas fired furnace would. If your weather has been colder this year versus last then your KWH consumption will be greater. If your getting a 20-22 degree rise at the vents and not the coil, your probably fine. The real question is if the HP is maintaining the set temperature of you T-stat. If it is, then the unit is performing as it should.

Agreed. Please check your average temps from this year to previous. I am not that far from you and know it has been colder than average. Combine your HP running more, blower on all the time, and possible slight increases in electric usage in other area for this year might explain the increase.

If your current draw on the unit and blower are within spec then they are likely bad.

FYI, from my HP reliability testing days, a unit that draw higher than spec current usually has a problem.

If your getting a 20-22 degree rise at the vents and not the coil, your probably fine.

Just to be clear.....

I am getting a 20 to 22 degree gain right at the vent exiting the furnace. This would be 2-3 ft from coil. It is running around 90 to 92 degrees near furnace.

I am comparing it to temperature at intake vent coming into furnace. Measuring right at the furnace.

I an not measuring at floor registers.

Again that supply temp is totally dependent on the outside temperature. Whats the outside temp when your getting 92 deg. at the vents??

Whats the orientation of your air handler? It's hard to believe you have a supply vent 2-3 feet from your coil. Your supply ducts usually branch off your supply plenum.

I should not have used the term vent. I am measuring the temp in the duct work going into and coming out of the furnace.

Lately it seems that regardless if it is 21F (-6C) or 46F (8C) the temperature on the exit duct runs around 90 to 92 degrees.

The tech seem to focus on the temperature gain of 20 to 22 degrees achieved and was happy with that.

Last winter tech was at our house due to thermostat problem. I am quite sure he measured the exit temp at that time and told me it was running around 107F. I sure it was only about 26F at that time. When I see it putting out 90 to 92 degrees it seems to support my suspicions that the heat pump is not working as effectively as it once did.

That is what I suspect but the techs say otherwise.

You mentioned you have oil as your stage 2 heat. are you sure your stage 2 hasn't come on and perhaps last year this accounts for the temp difference?

What raises a flag for me is that if your saying that when just your heat pump comes on the output temp doesn't change no matter what the outside temp is, that would indicate your charge is off. I've experienced that condition myself when I had a e-coil leak and didn't know it.

What kind of filter do you use? Try a cheap fiberglass one for a couple of days and see if things get better.

Your best bet is to wait for a warm day, call your tech back or a new one and have them ck. the charge by superheat.

A quick info note..410a runs at higher pressures than R-22.While a 75 PSI may be good for 22 its low for 410a which may be at 130 PSI. suction and 400+ discharge.Also even if pressures are close superheat and subcooling could be off.In reality your system could be low.

One more note..its normal for some frost to build up on the outside coils dependent on moisture conditions.That is why they have a defrost board.The defrost board will allow the coils to heat up and allow the coils to start cooling agin after the frost is gone.

I had a similar problem back in February. HP was running all the time and maintaining the temp but had a chill to it causing a cold nose. I had a difference of about 15 degrees which was borderline. Also the outside coil was on a average day was frosting on the upper third of each section. When it did get more say when it snowed or rained the defrost seemed to never work. I could force it into defrost and melted it fine but still marginal heat. First call to a friend of a friend he said freon was low. He put some in but never checked the head pressure which I thought was odd. Later vent was nothing but cold air only about 4 degrees difference at it's best. I could hear compressor working harder than normal and drawing more current than last time I checked. So I called a local Professinal company and after considerable troubleshooting found freon flow low and replaced filter drier in outside unit and damaged expansion valve. I then had a 30 degree difference and defroster working again. The partial frosting of coils went away. House has not been as warm in years. Electric bill went down as much as $100 compared to last year a month. Apparently electric heaters were cutting in out more than I thought. If you think your airflow is the same then it could be freon problems. I had called the original installer which is defunt now they would say the difference I had was OK. The filter driers they put in at the factory are very small and the Tech straight pipe it and put a bigger bidirectional one on the small line where it came out of the house. When split system are installed and precharged lines are not used, the off roll lines could have trash and moisture in them. My first HP had the sealed lines and never had the freon checked in 22 years of use. Lightning finally got the compressor. The new HP seemed to not perform right several years ago. With the power rates going up so fast it was hard to tell if anything was wrong. I am supposed to get them back when we start running in cooling as they can better get the freon levels more accurate than in the cold weather. Hope this is some help.

One might ask how do you check for a stopped up filter/drier? Most HP's have two, one in the outside that is used when heating and one inside that is used in cooling. Also there are two expansion valves and directional valves which control the flow direction when heating or cooling. Plenty of mechanical things that can cause wierd problems that takes a good Tech to find. Of course one way is to have in my case a direct line to the Trane Factory Reps. That is what the cell phone in the pocket is for. I asked how they determined it was the filter? Simple, there should be very little temperature drop across it. This one had more than a enough to say not enough freon flow. As to replacing the expansion valve, it was damaged during troubleshooting. As many Tech's know it is easy to break the capillary tube especially when it is 15 degrees outside. Some will say there is the possiblility it was the valve anyway. I watched him check it using warm water and it worked at first, but taking the well off and on several times and way to much capillary line gets in the way. It doesn't hurt to ask questions sometimes. We learn more by accident than on purpose anyway. That is life.

If you have electrical resistance heat as the auxiliary / emergency heat, you can use it to decide if the heat pump is delivering its rated BTUS . Here's how:
- note the outside temperature, call it TO
- switch (at the thermostat) to emergency heat only so that the heat pump compressor doesn't come on.
- time how long it takes for the inside temperature to rise one degree, from 69 F to 70 F, say, - that is: from the time the system cycles on, raises one degree, cycles off.
- you need to know the size of your electric auxiliary heaters.
- if you multiply the size of your electric heaters by 3412 you will know how many btu/hr your house requires, at outside temperature TO, to raise the inside temperature 1 degree. For example, when I test , using 10kw of resistance heat, I know that the heating rate is exactly 34120 btu/hr.
- now repeat the experiment with your heat pump only. (usually there are circuit breakers that allow you to disable the electric / auxiliary heat - so be sure that no electric heat comes on so that you can measure only the heat pump)
- the heat pump manufacturer provides btu/hr ratings for your system - you need them; in my case with a 3.5 ton unit, the rating on the heat pump at 32F outside temperature is around 34000 btu/hr.
- now compare how long it took the heat pump to accomplish a one degree temperature rise to how long it took the electric resistance heaters- in my case, with TO=32F, the electric resistance heat took 36 minutes, but the heat pump alone took 80 minutes ... so I know that the heat pump is not producing. Since, at 32F the manufacturer claims 34000 btu/hr, the heat pump alone should take roughly the same time as a 10KW heater to make 1 degree.
- The elecric resistance heaters can similarly be used to establish an accurate load line for your house - that is: what is the heat loss of your house as a function of outside temperature by timing the electric resistance heaters alone at various outside temperatures. The heat pump operating characteristics can be compared to this load line - and you will have a pretty good idea about whether the heat pump is performing or not.

It seems that heat pump manufacturers do not provide much help in actually monitoring heat pump performance in the field ... their methods are crude at best, monitoring air temperatures is subject to all manner of mistakes. It seems that there are no definitive measures of freon temperatures, pressures, flow rates that would tell the story exactly. The installers / repair people can only operate on hunches and folklore, sigh.


Also ... when the indoor fan is run continuously, all of the energy that goes into turning the fan ends up as heat - so it really doesn't matter if the fan runs non-stop during heating season - but who wants the cool breeze ? This is just another bit of folklore that the manufacturers / installers use to try and shift the blame for their bad designs, poor manufacture, and crude installs.

Disregard. I erred. ...................Thinking if listed in watts, not KW's.