Another unhappy high electric use victim

I am brand new to this so bear with me.

In a brand new house built with 6" ICF walls for basement and 1st floor and with spray foam insulated 2" x 6" walls plus a very thick layer of blown-in insulation above the 2nd floor ceiling, my electric bills seem very high for a geo system. I am located in Northwestern PA. My geo system is a Carrier GT-PG (50YE) size 048 (2 ton?) with ground loop. The house size with unfinished basment is 4,349 sq ft - unfinished basement is 1,655 sq ft; 1st floor is 1,655 sq ft; and 2nd floor is 1,040 sq ft.

The system was turned on the first part of October. The electric bill (kwh cost of $.10104) through Nov 1 was $187. From Nov 2 - Dec 6 the bill was about $400 ($378 + $20 base amount). The Kwh use for Nov 2 - Dec 6 was 3,546. The Heating Degree Days for that time period was about 900. The thermostat was set at 70 deg and for one week it was set at 60. We have had a few colder days recently (Heating Degree Days of about 50 per day) and the daily kwh usage was close to 170 (with thermostat set at 70). The Carrier GeoDesigner estimate for the year to heat was 9,395 kwh (including electrical resistance emergency heat). Based on what I have experienced to date I estimate my annual usage for heat could be 15 - 16,000 kwh. This is almost double the Installer / GeoDesigner estimate of kwh usage.

Installer did a check at beginning of Dec and said the system needed to be recharged and they turned fan to max speed (fan on continuously). It does not appear either made any improvement. Something really seems wrong. Installer is to go back but based on recent check I don't what type of improvement to expect, if any.

Worst part is no one is living there now and no work is being done on house (it isn't quite done yet). The house is entered about once or twice per week and there is almost no other electric usage. Avg monthly usage before heat was turned on was about 300 kwh.

Thoughts?

 

General thoughts

From what you've described.

Your 4-ton'sh unit may be undersized and supplemental heat (electric?) is kicking in.

Just to confirm - you are seeing monthly measurements on your bill? Or does the utility estimate every other month (like around here)?

 

The usage is acutal (I have received a report by day) and the monthly bills are also actual based on daily usage for the time period.

I have received a daily usage report from the electric company. Also, the monthly bills are acutal (based on daily usage) not estimated.

 

Here's a bit more info on the system per the Carrier GeoDesigner System summary and recent conditions.

The system is a 50YE 048 and Slinky Horz - 8 ft/ft trench 0.75".

Carrier Unit:
Series: GT-PG Puron
Model: 48 (is this a 4 ton?)
Style: Single Stage
Hot Water Generator: Yes
Heating run time: 2,541 hrs
Cooling run time: 110 hrs

Geothermal source:
Source Type: Horiz Closed Loop
Soil Type: Damp Silt/Clay
Pipe Type: 3/4" IPS PE SDR 11
Pipe Config: Horz slinky 8 ft/ft
Avg Pipe Depth: 5 feet
Trench Length: 400 ft

Min Freeze Protect: 0 deg F
Max Source-cooling: 88 deg
Avg Source-cooling: 71 deg
Avg Source-heating: 29 deg
Min Source-heating: 20 deg

Deep Earth Temp: 49 deg F
Surface Swing 23.7 deg
Swing time lag: 24 days
Soil conductivity: 0.75
Soil Diffusivity: 0.60
Loop Conductivity: 2.92

Aux Heat:
Type: elec resistance
Style: Duct Heater
Aux Required: 3 KW
Optional Emergency: 12 KW
Efficiency: 100%
Aux Balance Point: 13 Deg F

Heating (Estimate?):
GT-PG Puron
- Elec Use: 9,261 Kwh
- Avg efficiency: 2.91 COP
- Annual Contribution: 100%
- Annual cost: $880

Elec resistance
- Elec Use: 134 Kwh
- Avg efficiency: 100%
- Annual Contribution: 0%
- Annual cost: $13

Conditions:
Thermostat is set on Auto, 70 Deg.

Hot Water is not on the best I can tell - Plumbing is not complete so no water can be used.

Outside Temp's for past few weeks have generally been overnights in teens and low 20's and days in mid to upper 20's / low 30's. Last week has been very consistent with temps in this range. The elec usage has also been consistent during the last week at about 155 - 160 kwh per day.

 

Im not an expert

But here are a few thoughts.
Depending on what your EWT is, your HP will use around 4KW per hour and since your weather is cold and you are operating at and below your design temperature of 20F it would be reasonable to expect long run times. If your are running just the heat pump 24 hours a day with no strip heat that would be 96KWH a day (it adds up quick). When we had the cold snap 2 weeks ago my unit was running 20+ hours of the day most of which was stage 2 with a HDD of 46.
http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/ca202.pdf


Anther thought is if you are having HDD at 50 or daily average temperatures at 15F. It is reasonable to expect strip heat to run from the information you provided. Most HDD Numbers are based at 65F to account for other internal heat sources Light, Stoves, TV's, and people if no one is living at the house and you have no other heat sources and it would be like adding 5 more deg to the 50 or HDD of 55 (darn cold).
You should probably check your EWT if for nothing else than to have a base point. It may also make you feel better knowing as long as your EWT is warmer than the the outside air and your unit is operating properly you are saving money as compared to an air source HP.


I have no idea and won't comment as to if the design and input are reasonable for your area of PA. Mine was designed to 22F and has been able to maintain at 14F (right at the edge) but I'm in Virginia.


I hope it just the colder than normal weather and not a problem. Good luck

 

HDD, Kwh, and Hi/Lo Temps

1) How do I measure / determine EWT (Entering Water Temperature?)?

2) Here's a breakdown of recent Heating Degree Days (based on BizEE / degreedays.net site with 65 deg base temperature), Kwh usage from electric company (I think readings were taken at approximately 1 AM), and Hi / Lo temps (nearby) from Weatherunderground.com. Sorry - chart will not retain spacing.

Date Hdd Kwh H L
12/14 51 175 23 17
12/15 48 177 26 21
12/16 49 166 25 18
12/17 43 163 28 22
12/18 47 154 26 15
12/19 47 158 24 18
12/20 42 165 31 24

 

HDD numbers dont add up?

On 12/14 you have 51HDD which at base 65 would be an average daily temperature of 14 deg F but you have the low listed at 17F. You may want to check that, one weather station is colder than the other. It depends on which one you are closer to as to how worried I would be. For me if my average temperature was 14F I would be running a good amount of strip heat, but if my low was 17F I would expect to run very little or no strip heat.
A simple home thermometer with a 5ft outside probe will work just fine to check Entering Water Temperature (EWT). Someone on this board or another was happy with a $10 aquarium thermometer from Pet-smart, but many places carry them. The preferred method from what I read on the board is wrapping the probe in aluminum foil and getting it on the pipe inside the unit. I have had good luck just sliding it between the insulation and the incoming loop pipe just outside the unit. It has a slower response but will tell the same story. Any measurements you take EWT, LWT, EAT, LAT should be as close to the unit as possible.

 

You surely have a problem, as stated the manual states with a 40° EWT your unit would draw a max of 4KW, this is actually a little high, but for calculations it's easy. If the unit was to run 24/7 something else would have to use 60-80 KWH each day.

My thoughts are that the heat strips are doing the heating, either the unit is not operating properly or the thermostat is not wired or set up properly.

FYI: from the model numbers you posted it is a 4 ton single stage unit.

 

You said thermostat was on auto-70*. Do you mean auto switch between heat and cool or were you referring to the fan selection?
Size appears right for your home.
Remember that the bulk of heating bills occur in just a few months of the winter. I'm not sure your usage is dramatically off base given the short usage sample.
Also bear in mind that if no compaction means were employed, you may not get your best performance in the first year.
Good Luck,
Joe

 

The Thermostat has only five (?) settings. Cool, Heat, Emer Heat, Fan (I think), and Auto. Installer said to keep on Auto. I believe that the Auto 70 deg setting is for system to automatically switch between heat and cool. System is programmed for fan to run continuously (at highest speed) per the installer.

I appreciate that the majority of the heat is needed in just a few months, but at the current trend i estimate the kwh usage will exceed the orignal estimate by 75 - 100%. That seems excessive. Normally, in Jan and Feb our temps will often range from lows in the single digits to highs in teens or twenties. We haven't even gotten there yet and the kwh usage has nearly approached 1/2 of the original estimate in just two months of heating (Oct and Nov).

The field system was installed in the late summer of 2009 but the heat pump was not installed until the spring of 2010 and not turned on until Oct 2010 so I expect that the loop field should have settled adequately.

 

Update - Additional information

I visited the house this morning about 10 AM. The thermostat has been set at 70 deg for weeks. When I arrived, the house temp was 69 on the thermostat. I then found the EWT and LWT connections at the side of the heat pump. They are completely insulated expected for a few inches at the 90 deg connection they make just outside the heat pump. (See attached photo). I wrapped my fingers around each exposed metal connection and found them to be the same temp. Also, there is exposed metal plumbing for a hot water tank coming from the heat pump. That plumbing temp felt the same as the water connections for the ground loop system. I expected a noticeable difference in temp between the EWT and LWT if the water had been circulating.

I then raised the thermostat to 74. 45 minutes later the thermostat temp had gone from 69 to 70 but the temp on a thermometer in a different room on the same floor remained the same. I spent considerable time at the heat pump and felt the ground loop lines. I did not hear nor feel any water circulation. Also, I did not notice any change in temp of ground loop EWT and LWT connections at the heat pump during the 45 minute period.

I then dropped the thermostat back to 70. I did notice a decrease in sound at the heat pump and wondered if maybe the heat strip turned off as the thermostat temp was showing 70. Do the strips make a sound when operating?

The outside temp was in the 20 - 22 deg range.

It appears to me that the heat pump is not using any of the geothermal system to produce heat.

Thoughts?

 

Temperature measurements

The differences between EWT and LWT may be small, ever system is different and will depend on size and flow rates. Mine only run a few degrees different because I have high flow rate so mine today are EWT 49 LWT 46 in second stage. I personally can't tell the difference from the two just by feeling them. They both just feel cold. You said they both felt the same and the same as your DSH lines. Did they feel room temperature or really cold? You will need to measure them to get any meaningful information unless your loop pump is not running at all. You stated previously you did not think DSH was connected and/or running. I would guess that the DSH lines to be room temperature or warm and guess the loop connections to be cold(30-50f)
Does the system have any faults?
Strip heaters (Resisters) don't make any sounds, but your fan may change speeds when they are energized.
When you changed the set point from 70 to 74 you probably engaged strip heat then and if the house didn't warm up much and they stayed in the 40 min you were there. When you moved the set point back to 70 the set point was satisfied and turned off strip heat, compressor (if it is running), and fan.
If your EWT, and LWT lines are at room temperature you are probably right that you are not using the geothermal part of your system. If this is what you are seeing I would think you would have a fault. Have you talked to the installer of the system?

 

I went to the house hoping to see the installer as he was to come today. I did not see him nor have I heard if he arrived after I left.

Metal feels cool to the touch anyhow (the basement is only about 60 deg), but if the water inside the pipes is in the 40's I expected the loop connections to feel 'cold'. To my hand the connections felt cool and no different than the pipes to the hot water tank which is not operating. There is no water to the hot water tank and the breakers are off.

Would I not hear the water moving through the pipes? I believe I've heard water flowing through them before. Also, if water is flowing would I not feel something (e.g. vibration?) when I held the connections or the insulated loop pipes that run from the basement wall to the heat pump?

Re: 'faults', not sure what I am to look for. No lights or gauges that I can see.

I appreciate the feedback I've received to date...

 

I dont know your system so I'm guessing at EWT but for this time of year I would think they would be fairly cold.
I normaly can't hear or feel the flow on my unit due to the noise and vibration from the compressor. I can hear the motor operating at the flow center (loop water pump).
You do have a fault light inside the system, but you may not feel good about opening the door High voltages are inside.
When you catch up with your installer I would get him to show you how the read faults, reset faults, and take some basic measurments. Your manual and post on this board will show you how to do most of this, but geting this informathion from him may be better.

 

My EWT is running 52-54 and LWT is in the 45-48, when I touch them you can tell they are cold, no questions.

When you turned the thermostat up as stated above you likely kicked in 2nd stage or more likely the heat strips. The blower speed will increase with either of these engaging.

I look forward to hearing about the resolution of this problem, keep us informed and good luck.

 

Positive Update - Fingers Crossed.

A tech for the installer came today. He determined that there was a short, but the specifics differ as I recieved a call from the tech who did the work and then later the owner left me a message relaying what the tech told him. The tech said the short was in a panel within the heat pump but the owner left me a message that there was a disconnected? / broken wire? for the thermostat and they replaced something. He also said something about 8 wire vs 6 wire. I'm assuming he meant that something was orignally connected with 8 wires and they replaced it with a 6 wire part they happened to have with them. I'll need to get a better explanation.

In any case, the short caused a lockout and the system had been running on auxillary heat. For how long, who knows, but I assume a few weeks if not longer. I'll be checking kwh usage and HDD readings to see if there is an improvement. Once fixed, the tech checked out the system and said it was running properly. He also told me where to look for LED fault lights on panel inside the heat pump, how to measure EWT and LWT using ports for that purpose on the outside of heat pump, and where in the manual to look for Operating Conditon specifications. He was very helpful.

I went to the house just a while ago and was surprised to hear nothing when I entered. Any other time I have been there since the system was turned on (first part of Oct) I could hear the system; a fan or something running. While there tonight, the heat pump started (I believe the compressor and / or pump started first). I could feel a little vibration in the water lines and felt the ports get cold to the touch (yea!). After a short while the fan kicked on and slowly increased in speed. The compressor / pump and fan ran for about 15 minutes and then shut off. Nice and quiet again. The house temp increased 2 degrees during that time. Outside temp was about 25 deg.

Question #1 - Should the fan have stayed on? Installer owner told me a few weeks ago the fan would always be on. Maybe the tech adjusted it so it turns off when the system isn't producing heat.

Tonight while running, I tried to measure EWT and LWT with a typical $10 digital meat thermometer (made by Taylor). I did not use the openings in the ports as they are quite small and I didn't want to puncture the rubber insert / gasket. Instead, I placed the probe under the insulation around the ports but not sure that was very effective. But, it did indicate there was a difference between EWT and LWT. Crudely, EWT was 47 - 50 deg and LWT was 44.

I have seen a few posts with different recommendations for reliable EWT and LWT readings, but I am unsure which way to go.

Question #2 - I wonder if I should find a thermometer with a thin probe to fit inside the rubber gasket inside the small port openings or rig up something to the outside of the ports. What has been found to be reliable, cost effective, and easy to use?

 

Here is a link for a thermometer with a small tip.

Edit to fix link

 

'Link' does not seem to work...

 

Sorry about that. It works now.

 

Constant fan

You can have the fan run constantly by setting the fan option at the thermostat from "auto" to "on"

In winter, constant fan helps even out temperatures, and it helps keeping fresh air in bedrooms with closed doors. It does use a bit of power, and depending on supply air grill placement and diffuser adjustments, may result in uncomfortable drafts.

In summer do not use constant fan if humidity is a concern, and humidity is a concern in all but the plains and desert southwest.