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Manual J load question
Last Post 04 May 2015 04:07 PM by
arcamm
. 9 Replies.
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arcamm
Basic Member
Posts:119
01 May 2015 10:38 PM
I'm looking over a J load calculation and on the Design Information page, under Heating Summary, what are the "Ducts" and the "Central Vent" entry's for? I'm assuming the "Ducts" for duct loss. Would "Central Vent" be for flue loss?
BadgerBoilerMN
Veteran Member
Posts:2010
02 May 2015 09:54 AM
Ventilation.
MA<br>www.badgerboilerservice.com
arcamm
Basic Member
Posts:119
02 May 2015 10:12 AM
Thanks Badger. The Heating Summary calculation has;
Structure: 42395 BTU,
Ducts: 2724 BTU,
Central Vent (151 cfm) 9447 BTU
There are no ducts in the house or vents that would flow that much air. I guess I'll have to call the guy that ran the calc and ask.
arkie6
Veteran Member
Posts:1453
02 May 2015 12:26 PM
"Ducts" would be heat loss through the duct system. This is assuming you have ducts outside of the conditioned space, i.e in a ventilated attic or unconditioned crawl space. Ducts are typically only insulated with R6 or R8 insulation.
Central vent would typically be for fresh air makeup. Do you have a fresh air makeup vent or ERV?
BadgerBoilerMN
Veteran Member
Posts:2010
02 May 2015 12:39 PM
I stand corrected. Thinking of another screen.
Thanks arkie
MA<br>www.badgerboilerservice.com
arcamm
Basic Member
Posts:119
02 May 2015 02:45 PM
No to the ERV. Nor is there any duct work. Just radiant heat and mini-slits.
joe.ami
Veteran Member
Posts:4377
03 May 2015 08:28 AM
You need to communicate with the person that ran the calc. I hope you didn't pay a lot for this.
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
arcamm
Basic Member
Posts:119
04 May 2015 01:52 PM
The central vent calculation is based on current fresh air requirements. I haven't received an answer on the duct loss in a ductless.
Dana1
Senior Member
Posts:6991
04 May 2015 03:47 PM
The fact that they included any duct loss at all for a ductless (&/or hydronic) heating system would be enough to cast great doubt on the accuracy of the rest of it.
I'm with Joe- this level of competence isn't something you'd want to be paying a professional rate for. With corrections for the gross & obvious errors it may be better than a WAG, but if the rest was as just sloppy you can't really count on that.
arcamm
Basic Member
Posts:119
04 May 2015 04:07 PM
I got my answer on the ducts, his mistake and he reran the calculation for a ductless system.
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