Energy Savings. Where are they?

[kcrossley]

In February I replaced my 15-year old Trane XE800 heat pump and single speed air handler with an XL16i and matching variable speed air handler effectively going from a 10 SEER unit to a 17 SEER state-of-the-art system.

Today I just received my first electric bill using the new system and I don't see any savings at all. Now keep in mind that it's somewhat difficult to compare Apples to Apples since the average monthly temperature was different this year versus last.

I don't know the formular for calculating energy effieciency but perhaps someone here may. Here is my latest usage:

Mar 05 - 29 days - 3583 kWh - Avg daily use 123.6 - Avg temp 36
Mar 04 - 31 days - 2764 kWh - Avg daily use 89.2 - Avg temp 42

On both systems I have a programmable thermostat and used the exact same settings. 68 degrees during the day, 65 degrees at night (11:00 PM - 6:00 AM).

The only thing that may be negatively affecting my energy efficiency is that I had an Aprilaire whole house humidifier installed at the same time and the HVAC tech connected it to the hot water line. Of course their may be some other issues as well. I appreciated any suggestions or advice.

Thanks,
Kelly

[berad]

It may be possible the power company estimated the power usage for the month as well.

[Shophound]

I had an Aprilaire whole house humidifier installed at the same time and the HVAC tech connected it to the hot water line.

WHOOPS!

Off the cuff I'd say a month's time is not enough to conclude anything yet. And keep in mind your heat pump isn't the only thing in the house spinning the electric meter. Was there other things going on compared to the previous year?

Also if I recall correctly you had some kinks in your system to iron out before you got some decent performance out of it.

How's your overall comfort with this system compared to your old one?

[kcrossley]

According to the statement these are actual numbers. The billing period is Feb 15, 2005 - Mar 16, 2005. The meter was read on Mar 16th.

Just for fun the usage for the month prior was 5122 Kwh. This was when my old XE800 was running on emergency heat almost the entire month.

[wormy]

Going from the lower seer unit to the higher seer unit, you should get a savings, its really hard not to.

Things that can effect the effeciency in a negative way would be....
Air leaks left during replacement of equipment
Improper refrigerant charge

Being that your average temp was so low...
your unit may have been cycling on the aux heat alot more than the prior year you are refering to. The aux heat can use about 3 times as much electricity when it kicks in
(unless you use another source of heat for aux heat other than electric heat strips such as gas). The aux heat will start kicking in at around freezing. The actual temperature varies from house to house, but should be close to freezing.

Out of curiosity... where you more comfortable with the new system?

[kcrossley]

Off the cuff I'd say a month's time is not enough to conclude anything yet. And keep in mind your heat pump isn't the only thing in the house spinning the electric meter. Was there other things going on compared to the previous year?

Also if I recall correctly you had some kinks in your system to iron out before you got some decent performance out of it.

How's your overall comfort with this system compared to your old one?

I was thinking that too. No, there's nothing else that we're running today (electric wise) that we weren't running last year.

Yes, all of the kinks (mostly cosmetic) were worked out. If the heat pump isn't charged properly will that affect performance? By the way, I am purchasing the 10-year Trane extended warranty just in case.

The comfort is great! The air actually feels a little warmer than my old system and it's much quieter.

[Edited by kcrossley on 03-22-2005 at 12:36 AM]

[kcrossley]

Originally posted by wormy
The aux heat will start kicking in at around freezing. The actual temperature varies from house to house, but should be close to freezing.

Good point.

By the way, I recall the installer saying that he charged the system but because the termperatures were so low when it was installed (around 20 degrees) he needed to return in the spring when the weather is warmer to more accurately measure the charge and adjust it accordingly. Is this true?

By the way, my new thermostat which is a VisionPro 8000 doesn't seem to indicate when auxilary heat is running. Am I missing something?

[Edited by kcrossley on 03-22-2005 at 12:39 AM]

[wormy]

Here's a closer look as to what your weather looked like last year....

March 2004...
http://www.wunderground.com/history/....html#calendar

March 2005...
http://www.wunderground.com/history/....html#calendar


Looks like this year saw alot more potential for aux heaters than last year.

[wormy]

Yes... its a bit harder to charge one correctly when its that cold outside.

Unless he can get accurate line set lengths and calculate it (my prefered method)... sometimes thats not possible though.

[kcrossley]

Great web site! Yes, there were some pretty cold days this year. When is the earliest I can have him properly charge the system?

[BaldLoonie]

The Vision Pro does tell you when the backup is on. Instead of Heat on it says Aux heat on under the set temp.

I noticed something and haven't gotten any responses. I have a Vision Pro set up on my test bench checking out a twinning kit I made. It's set for 2 stage heat pump plus backup. The set temp has to be 5 degrees above ambient temp for the backup to turn on. I can't see that leading to a comfortable house. How close to set point does your system run?

[kcrossley]

Originally posted by BaldLoonie
How close to set point does your system run?

I have never seen the AUX HEAT indicator on since I've had the system. It may be that I have this set wrong. My recollection is that it's set on HEAT. It sounds like it should be set on AUTO if this is an option.

My system runs within a few degrees of the set point.

[Gunnery Sergeant Hartman]

I'd bet the system isn't set up correctly.

Didn't you have it installed by an unauthorized Trane dealer?
With as sloppy as your install looked, what makes you think it was charged and started properly?
Hire a reputable contractor to look it over and send the bill to the installer if anything is majorly wrong.

[dash]

May be too soon to tell,but as I remember the install photos ,there is a possiblity of problems.


For years now,we have a 25% saving guarantee,based on the heating and cooling expense,being 46% of the total bill.So 11.5% of your total bill ,for going from a 10 to a 12 or a 12 to a 14 SEER ,usually heat pump replacing heat pump.

There have been a few that didn't save,and everyone of them had a problem.Either a bad TXV,or high Static duct system.

The TXV is obvious,but not everyone gets what happens with high static ducts.When installing variable speed fans the literature usually talks about how little they cost to run,and may even encourage running the indoor fan 24/7.

VS is great ,when the static goes up,unlike a PSC motor they deliver the air needed or close to it.But at a much higher cost in wattage,at .9 or 1.0 static,then at .5 Static,fan watts goes up about 40%.Then if they run the fan 24/7,or switch to restrictive filters like 3M's ,the cost goes up even more.

[kcrossley]

Originally posted by Yellow Dot
Didn't you have it installed by an unauthorized Trane dealer?

The installer is now Trane certified. He has to be in order to sell me the extended warranty, which I'm currently buying.

[kcrossley]

Originally posted by dash
There have been a few that didn't save,and everyone of them had a problem. Either a bad TXV,or high Static duct system.

I'm assuming that the TXV is the air handler. What is a High Static Duct System?

[Gunnery Sergeant Hartman]

An improperly sized duct system.
Too small...

[kcrossley]

Originally posted by Yellow Dot
An improperly sized duct system.
Too small...

No, I don't think that is it. I had another Trane dealer do a comfort analysis and they said the ducting was fine for the system I was putting in.

[Shophound]

Originally posted by kcrossley

I'm assuming that the TXV is the air handler.

TXV stands for Thermostatic Expansion Valve. It is a refrigerant metering device. It regulates the proper amount of refrigerant to the indoor coil in cool mode to produce the refrigeration effect, and anøther one meters refrigerant to the outdoor coil in heat mode for the same purpose. When in cool mode, the outdoor TXV is bypassed and the indoor valve active. In heat mode the roles are reversed, along with refrigerant direction.

A malfunctioning TXV will improperly meter refrigerant. In heating mode the outdoor TXV not working right will affect system performance and capacity. Same holds true in cool mode for the indoor coil valve.

A check valve is often built into heat pump TXVs. If one of these valves are leaking by it could also affect performance. Same if one is stuck partially or all the way closed when it should be open.

Lastly, your system charge may not be right because many installers and technicians are fuzzy on how to charge a heat pump in the heat mode and/or during cold weather, when running the system in cool mode is out of the question.

[kcrossley]

[QUOTE]Originally posted by shophound

A malfunctioning TXV will improperly meter refrigerant. In heating mode the outdoor TXV not working right will affect system performance and capacity. Same holds true in cool mode for the indoor coil valve.

The system charge should be easy enough to diagnose, but how would you check a defective TXV?