The following stumper is presented in BPI's October Performance Matters e-Newsletter.

This month's stumper comes from a chump who's actually stumped! Ed Revers of Michell Timperman Ritz Architects in New Albany, Indiana has been scratching his head about this one and is wondering if you can help.

Ed explains that he has been working on a 50 year old house that has a four ton top-of-the-line Florida Heat pump system, with all the energy saving bells and whistles (hot water de-super heater, four-zone stats on Arzel control board, etc). After 2 years of utility bills, the energy savings are nowhere near what the geothermal manufacturers claim they should be. The new energy bills (gas and electric combined) are the same as the past 20 years, during which an old forced-air conventional gas furnace was used. The mechanical contractor has come out several times to check things and reports that it is working fine. The house was super-insulated when the new geothermal system was made operational. It isn't easy to compare old to new systems equally, because an addition of about 25 percent was added to the house when the new system was installed.

Background: The house is in the Louisville, Kentucky area and is now a 2850 sq. ft. ranch with a basement. Mechanical installation costs exceeded $30K, with four grouted wells at 150' depth each. At the recommendation of the mechanical contractor, the house was zoned because the existing house limited duct work configuration options and R-values weren't equal everywhere. The new system performs well (70 in the summer and 68 in the winter), but the energy savings are disappointing. The weather has actually been pretty mild the past few years too. As a newly accredited BPI Building Analyst, Ed considers the house to be tight and well insulated; although no blower door test or duct efficiency test has been performed to verify this. Gas and electric usage is probably below average for a family of four. Any clue as to what would help lower the utility bills and make the system less expensive to operate?

Tags: BPI, Chump, Contest, Matters, Newsletter, Performance, Stump, the

Views: 237

Replies to This Discussion

Be really helpful to see the load calc and have a blower door #. 

The new system performs well (70 in the summer and 68 in the winter)

A 70 setting for comfort in summer indicates gross oversizing.  (poor latent removal means lower sensible is required to achieve comfort.)  From there you can suspect cycling losses/short cycling is partially to blame for lack of efficiency.  

They didn't expect to save on heating when they have natural gas, did they?  Exaggerated expectations by the sales person, and acceptance without research by the homeowner, can also be partially to blame.  

Are they tracking entering and leaving water temperatures?  Run times?  How about External Static Pressure?  These things will better tell how much of a design failure we have than "it maintains the temperature we set it at". 

looking at the information provided:

1 - is the system a multistage unit to better match load as well as zoning demands.

2 - is the heating capacity properly matched to to home demand - does the backup heat run?

3 - is the cooling capacity too large - so homeowner sets thermostat lower to dehumidify

When you say, "The new energy bills are the same as the past 20 years", my first response would be to show me the data so I can run a billing anlysis.  I put together a spreadsheet that analyzes gas and electric billing histories.  The analysis simply calculates the average energy usage for each bill and plots it with that month's average monthly temperature.   This normalizes the data for different number of read days in each month and adjusts for weather variations.



Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Dennis Heidner replied to Rod Fox's discussion Utility Meter Accuracy
"For Rod, second part... When I see really large electric services... my first reaction my be…"
4 hours ago
Dennis Heidner replied to Rod Fox's discussion Utility Meter Accuracy
"Rod,  I did see earlier that you had calculated the loads.  The key is even though a…"
5 hours ago
Grzegorz is now a member of Home Energy Pros
10 hours ago
Rod Fox replied to Rod Fox's discussion Utility Meter Accuracy
"Dennis, that's a ton of useful info and it will take me a bit to fully assimilate those…"
10 hours ago
Ben Haas replied to Rod Fox's discussion Utility Meter Accuracy
"Yup..... 1200 amp service to the compound.....  3 -400 amp panels, all single phase since 3…"
22 hours ago
Walter Ahlgrim replied to Rod Fox's discussion Utility Meter Accuracy
"The more I think about it if the problem cannot be the current transformers reading small loads,…"
Dennis Heidner replied to Rod Fox's discussion Utility Meter Accuracy
"Note to readers 0.5A instead of 5A for reading with A/D.... the edit to correct that didn't…"
Dennis Heidner replied to Rod Fox's discussion Utility Meter Accuracy
"Rod, I have some of the CT's that you referenced in the openenergymonitor system.  They…"

© 2015   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service