Posted By cad10047 on 21 Jul 2010 05:21 PM
Our bills with a combo of gas in the winter and elec in the summer were never over $200 either side.

I believe engineer was trying to determine the quantity
of gas and electricity (i.e, cubic feet and kWh) used to
heat and cool the original 1600 sq ft building.

Those numbers could be used as a "sanity check" on the
tonnage estimates from your geo HVAC contractors.

I made a mistake in my last post.... Original house was 1600 sq feet and the addition is 1500 sq feet. Total now 3100 sq feet for the house. Bills went from about $140/month total avg to about $600/ month avg ( $800 in winter and $300 in summer)using upgrades on windows, roof and geothermal. FYI

That $140 a month was the combined total of electricity and the gas bill; correct?   You aren't by chance forgetting that your original heat was provided by gas so you'd have to add that in, too?

I'm sure it's an oversight given all the Q&A going on here, but in order to help you, we need your actual usage information in kilowatt-hours and CCF of gas (or whatever unit they bill you in). The dollar figure is more or less meaningless.

For comparison, what we need is a few months of data from before and after the renovation.

Specifically, reviewing your utility bills, look at the bills for around April/May and Sept./Oct. You should find that the bills are at their lowest in those periods. Tell us what your kwh electric and gas usage are in those low months. That gives us your baseline consumption which is needed for other calculations.

Next, give us your January, Feb, June and July figures from before and after. Ideally, include the exact dates for the billing cycles. Knowing that, and the climate data from your area which we can get on-line, we can calculate the temperature-normalized usage figures for a usage per square foot of living space.

Other things must have changed with the renovations. For example, ow that you've got twice the SF, you're going to have a lot more lighting. That can add a hundred or more a month to your electric bill if you're not careful. That's why it's critical that we know your baseline, April/May figures.

Has anyone verified that the aux heat is not coming on every time the compressor turns on (due to a wiring error)?

Posted By tinoue on 22 Jul 2010 11:28 AM
I'm sure it's an oversight given all the Q&A going on here, but in order to help you, we need your actual usage information in kilowatt-hours and CCF of gas (or whatever unit they bill you in). The dollar figure is more or less meaningless.

Most interested in man J calcs. I can at least figure out percentages with those. From the get, this thread has been packed with content void of substance.
At this point I'm not convinced anything is wrong. Just too little data.
Sq' means nothing without cu', dollars or consumption mean nothing without load calcs.
OP there is a thread at the top of this forum that says "problem with your heat pump start here" read it and fill in the blanks.
Employ brevity in responses. Answer our questions (took many tries to establish previous furnace was gas).
Not trying to sound terse, but we are now 3 pages deep without even establishing if there is a problem (comparing usage to load) aside from you may be short looped.
Part of the repair bids should show you what to expect when they are completed. What are the loads, what are the suggestions, what are the op cost projections.......?

To responders, did want to mention one thing. It was suggested that adding one loop would have little impact aside from raising ewt slightly. I submit that if 1 loop adds 20% to the field and if the ewt is currently so low in winter that unit is locking out on low temp, this "one" loop could have a very dramatic impact on performance.
IOW's each system must have at least "x" feet of loops to keep EWT above minimum in heating dominated clims. Once that is achieved I agree that adding even more than a little loop has very modest impact on op cost.

Joe

Posted By joe.ami on 23 Jul 2010 09:43 AM
I submit that if 1 loop adds 20% to the field and if the ewt is currently so
low in winter that unit is locking out on low temp, this "one" loop could
have a very dramatic impact on performance.

Fair point. However, if that were the case, I'd expect the symptom to be
occasional lockouts during the worst cold snaps. From the (fragmentary)
information posted, it sounds more like a chronic "all-weather" problem.

Posted By Looby on 23 Jul 2010 12:20 PM

Posted By joe.ami on 23 Jul 2010 09:43 AM
I submit that if 1 loop adds 20% to the field and if the ewt is currently so
low in winter that unit is locking out on low temp, this "one" loop could
have a very dramatic impact on performance.

Fair point. However, if that were the case, I'd expect the symptom to be
occasional lockouts during the worst cold snaps. From the (fragmentary)
information posted, it sounds more like a chronic "all-weather" problem.

If system is designed in the 92-98% style relying on aux. at a high teen or low 20 balance point, undersized loops could cause lockouts as soon as weather hits even high 20's as heat pump would run 100% of the time. Around here that would be a problem virtually all winter.
j