Question from energy homeowner:

 

Contractor has recommended installing a two stage Water Furnace Envision w/desup NDV049A system into a 2700 square foot cape cod, 1000 square feet basement, 1000 square feet first floor, and a 700 square foot second floor.  The house is all brick and was built in 1950, walls and attics are currently insulated using r 11.  The blower door test gave a  2800 cfm reading at 50.

 

Contractor is recommending a 4 ton geothermal system, According to his comments it is a two stage system that  will run at 60% capacity at the first stage and 100% at the second stage.  Contractor feels the 4 ton system will provide more heat using the geothermal without going to the back up heat.,

 

If the system is over-sized to accommodate the heating season, does this make sense.?  He says with a two stage system it does.  Will the system operate efficiently.  If we were installing a regular electric heat pump the manual J test called for a 3 ton system  (single stage)   Is the contractor correct in over-sizing the unit to provide more geothermal heat in the winter months?

 

One other question: What is the advantage of using galvanized ducts as compared to 1 inch rigid fiberboard ducts?

 

Thank you for responses

 

 

 

Views: 1140

Reply to This

Replies to This Discussion

Hi my name is Steve.

If the manual J suggested a 3 ton I would look at a 3 ton two-stage. The two stage units are usually a 1/2 ton larger in size. When I size my units, I try to shoot for a balance point of 5 to 10 degrees outside temperatures here in Michigan. The operating cost seems to be the best at these temps (even with the little back up thats needed). The reason is the larger compressors use most electricity. Now, it's not a lot of difference in operating cost. Having the next size larger is not devastating but you need to have larger duct system and extra loop installed driving up installation cost.

My question is? Did the contractor you are referring to complete a manual J load and does he know where his balance points are. If he can not show you he calculations he is guessing and not doing you a good job.

Note: The home generates a certain amount of heat and you can design at 77% of the calculated load. So if the manual J says you can install a 3 ton then it does not matter if it it two stage or not. Sorry I have to go now my wife i waiting, You can contact me if you have more questions at performancegeothermal@gmail.com.

Steve Shannon

PS, I like sheet metal for duct work.

If the contractor doesn't calculate a manual J,D, and S worksheet for the house then he's merely guessing. Also, galvanized ducting last much longer, is easier to clean, and is more rigid that fiberboard.

RSS

Videos

  • Add Videos
  • View All

Twitter

Latest Activity

Evan Mills posted a blog post

Looking Back and Looking Forward: Home Energy Pros at 5 and 5000

Over the past five years, the Home Energy Pros social network has grown from a twinkle in our eyes…See More
1 hour ago
tedkidd replied to Diane Chojnowski's discussion Poll: How confident do you feel about the future of home performance?
"Thank you for sharing this trend! Full disclosure, I did NOT ask Bob to post that! If you have 2…"
1 hour ago
Bob Blanchette replied to Diane Chojnowski's discussion Poll: How confident do you feel about the future of home performance?
"I see fixed monthly grid charges continuing to increase while cost per therm/kwh/gallon remain…"
1 hour ago
Quinn Korzeniecki posted a discussion

Vent Cap Systems and SENSIT Technologies Products Added to BPI Product List

The Building Performance Institute, Inc. (BPI) has recognized four new products in its …See More
4 hours ago
Simon joined Diane Chojnowski's group
Thumbnail

Online Training

Online training coursesIf you provide ongoing online training for home performance or…See More
yesterday
Simon added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase
Thumbnail

Wanted - Blower and door frame kit for Minneapolis system

Hi everyone,I'm new to this line of work and have bought some equipment (Minneapolis blower door…See More
yesterday
Simon replied to Steve Mann's discussion TEC Blower Door Frame in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi, I'm interested, but could you send to UK?,I'd pay shipping of course. My email is :-…"
yesterday
Simon replied to Jeffrey Anthony's discussion Blower Door Equipment - 9 shrouds, 10 fans, 5 fan controllers in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi, if you able to sell sepereately, I'd be interested in a blower and a frame kit. My only…"
yesterday

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service