Efficiency Disappointment?

[thegov3]

Well, it has been one month since my new Lennox XP 19 Heat pump and variable speed furnace has been in use. I am surprised to find that it is using more energy than my 22 year old Lennox 6 SEER. The system is working great in terms of cooling, but the energy use is 18% greater and when adjusted for my hot tub power being turned off at the same install time, the difference is even greater. The t-stat settings have been the same as before and when I look at the high outdoor temp and take that into account for that increase in June’s energy use it is still baffling why the new Lennox is more of a energy hog. Nothing else in the house has changed. The figures below came from my power company. I installed the new dual fuel system on May 30, 2008.

Is it possible that something is set up wrong? Thoughts?

Date, Total kWh, Max Outdoor Temp
06/26/08, 116, 88
06/25/08, 119, 93
06/24/08, 108, 86
06/23/08, 94, 84
06/22/08, 106, 86
06/21/08, 109, 86
06/20/08, 85, 83
06/19/08, 121, 86
06/18/08, 90, 84
06/17/08, 80, 82
06/16/08, 96, 78
06/15/08, 98, 82
06/14/08, 97, 86
06/13/08, 122, 82
06/12/08, 108, 85
06/11/08, 116, 88
06/10/08, 110, 84
06/09/08, 114, 74
06/08/08, 113, 87
06/07/08, 149, 87
06/06/08, 100, 83
06/05/08, 100, 85
06/04/08, 107, 88
06/03/08, 105, 89
06/02/08, 110, 81
06/01/08, 99, 88
05/31/08, 98, 89
Install Date
05/30/08, 112, 88
05/29/08, 93, 84
05/28/08, 83, 72
05/27/08, 99, 78
05/26/08, 134, 81
05/25/08, 147, 89
05/24/08, 100, 78
05/23/08, 92, 78
05/22/08, 96, 71
05/21/08, 98, 75
05/20/08, 109, 73
05/19/08, 115, 83
05/18/08, 126, 79
05/17/08, 122, 86
05/16/08, 93, 78
05/15/08, 96, 70
05/14/08, 87, 68
05/13/08, 105, 77
05/12/08, 94, 75
05/11/08, 82, 64
05/10/08, 96, 63
05/09/08, 91, 66
05/08/08, 100, 73
05/07/08, 95, 69
05/06/08, 101, 75
05/05/08, 85, 76
05/04/08, 97, 70
05/03/08, 71, 61
05/02/08, 83, 72
05/01/08, 126, 82
04/30/08, 91, 80
04/29/08, 62, 64
04/28/08, 69, 54
04/27/08, 76, 59
04/26/08, 63, 63
04/25/08, 73, 72
04/24/08, 100, 74
04/23/08, 93, 76
04/22/08, 103, 74
04/21/08, 79, 78
04/20/08, 109, 78
04/19/08, 96, 65
04/18/08, 82, 61
04/17/08, 78, 67
04/16/08, 64, 75
04/15/08, 67, 71
04/14/08, 75, 57
04/13/08, 81, 49
04/12/08, 68, 43
04/11/08, 64, 49
04/10/08, 62, 69
04/09/08, 68, 57
04/08/08, 69, 48
04/07/08, 62, 57
04/06/08, 118, 69
04/05/08, 112, 64
04/04/08, 74, 59
04/03/08, 78, 50
04/02/08, 72, 59
04/01/08, 74, 49
03/31/08, 100, 74
03/30/08, 95, 61

[adrianf]

Just looking at April 22 and 23 yes there is something wrong somewhere new unit or other wise.

[t527ed]

usage #s on days with the same temp are all over the place.......:cool:


sumptin ain't right, don't know if the unit or something else in the house.

i would think if the unit the #s on the warmer days would all be higher.

[bmathews]

If you're home isn't insulated properly and you have leaky windows and doors. Basically an older home. It doesn't matter what SEER rating you put in if it can't keep cold in and hot out or vice versa. You really need to look at the entire picture and not think that a fancy A/C system is gonna solve the problem. Maybe the ducts are too small as well, is the return undersized? It could be setup wrong. I've setup a few, they aren't that hard, but you do have to wire everything and cut jumpers and set dipswitches.

[Wheelbaron]

For 20 days before new system average temp was 80.5, and average KW 108.95
For 20 days after install average temp was 88.55, and average KW 110.9

Those numbers look better to me:confused:

What about relative humidity? You may be jumping the gun a little here. try comparing this summer to last summer. I am not saying that the new system is set up properly, there is not enough information to tell that from your post. And this is a kind of small sample. The numbers change a lot from day to day there so there must be a lot of other variables in this picture....

[captube]

Were their any modifications made to the 22 yr. old duct work ?

Post some pictures and ductwork sizes.

[frijoli]

wow, those numbers are all over. There are other things afoot!

Clay

[andserco]

Does this system have dehumidification controls?....

[smittyii]

ya gotta go by average. you can't cherry pick days with high usage or low temps. if your light bill is higher overall, maybe you should request an energy audit from the elect. co.

[frijoli]

wow, those numbers are all over. There are other things afoot!

Clay

[mark beiser]

Were their any modifications made to the 22 yr. old duct work ?

That's what I'm wondering. If it is the same old duct system as the old system had, and has the air leaks and inadequate insulation that are typical of old duct systems, heat gain and duct leakage will cripple 1st stage of a new 2 stage system.
When it is installed on an old leaky and poorly insulated duct system, it is not uncommon for a new ultra efficient 2 stage system to actually use more energy than the old inefficient 1 stage system did.

The reason this can happen is that the old system had enough capacity to still cool the house, despite the duct leakage and heat gain.
The new 2 stage system doesn't have enough capacity in 1st stage to overcome the duct leakage and heat gain, which is increased due to the lower velocity airflow in 1st stage, and still cool effectively, so you end up with much longer run times, and the system going into 2nd stage much more often.
We will see this more and more often due to the proliferation of 2 stage equipment.

I'm not saying that this is what is happening in this case, just pointing it out as a possibility.

[browntigerus]

What a mystery...

You replaced 3T heatpump with 4T variable speed unit....
What you really expected? That your new unit would be so efficient electric company will be paying you to use it?

Next you added IAQ and set humidity control.

And this on 60 years old house?

Wow....

I tell all my clients same thing. There is always something better, don't upgrade cause of some bells - upgrade when you have to. Expect new features to be added bonus.

[gonekuku]

A current clamp would tell a lot, but since you didn't already, you don't have one. Your backwards rolling date gives me a migrane...

Comparing the ratio of daily KWH consumption to daily high deviation from (lets say 70F), Appears that you have an electric dryer, and you do laundry 50% consistantly on Sunday nights, registering for Mondays? Is your spa electric? Appears that during the two months of log, you used it only on: Wed 5/7/2008 and Thursday 5/22/2008.

Since the plot started, you have gone from little heating season to cooling season, so analyzing the data is a bit complex.

Turn the HVAC off for 24 hours and carry on with your other consumption. Do you know at what time the KWH log starts? If so, turn the HVAC off that moment for 24 hours. If you don't know the start and stop time, turn the HVAC off for 48 hours. You will have at least on full 24 hour period with the HVAC off, which should be obvious in the KWH report.

[thegov3]

Does this system have dehumidification controls?....

Yes, the new system has humidity control. In my mind, that is the only plausible explanation for higher energy use since the system may be running longer to control humidity. I have no idea if it is running longer. I have the humidity set at 40%. Even so, the energy usage spikes are weird.

I have not changed any duct work other that what the install company did at the furnace to adjust for the smaller furnace size. My dryer is gas. My giant electric hog of a hot tub was turned off at the same time as the heat pump install on May 30.

While I was not expecting a significant savings, I did expect to see 10-15% in lower electric utility bills, not 20% higher. Again, all other electricity uses in the house are the same between May and June. The only variable is the hot tub no longer drawing power and the outside temp/humidity being higher.

[beenthere]

What thermostat is installed.

[teddy bear]

Yes, the new system has humidity control. In my mind, that is the only plausible explanation for higher energy use since the system may be running longer to control humidity. I have no idea if it is running longer. I have the humidity set at 40%. Even so, the energy usage spikes are weird.
higher.
Humidity control-dehumidistat or humiditrol? Fan "on" or "off"? Humidity control should approx. 50%RH. Lower is impossible under many conditions and use alot of electricity trying. Regards TB

[catmanacman]

call the company that installed it if they cant find the problem have them call a lennox tech rep to look at it

[thegov3]

What thermostat is installed.

Honeywell IAQ is the t-stat. I have it set to achieve 40% humidity (dehumidify) and it is on "Auto". Temp is set to 73* during the day and 76* at night. It easily achieves the 40% humidity. It has even gotten below that some times (38%).

I can have them increase the CFM. It was set slightly below the factory set point. Would that help reduce run times? I know humidity would be harder to control.

[beenthere]

Usually better off with the blower set closer to 400 CFM per ton and letting the IAQ slow the blower if the humidity gets high.

Most likely, your old system didn't keep your humidity anywhere near 40%RH. And now keeping it that low, you are increasing the run time the A/C has to keep the humidity that low. There by raising your electric usage.
If you set your humidity to 45%, and the blwer to 400 CFM per ton, you'll see a drop in electric usage

If you want to maintain a 40%RH. Either check into sealing your homes envelope better, or settle with having a high electric bill.