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Thread: Fed up with Manual J!
03-23-2012, 09:16 PM #79
Good advice GA.An answer without a question is meaningless.
Information without understanding is useless.
You can lead a horse to water............
03-23-2012, 11:32 PM #80
Business practices aside, and back on topic, this home deserves a lot more than a small simple furnace. Tight construction, 3 story, many residents living in very different zones, one of them being senior, - there will be no comfort without an extensive zoning system. At least there is a good sized mechanical room in the basement.
Here's my recommendation:
Combined Heating/Domestic Hot water system in the mech room feeding baseboard heat throughout. 24-hour outside air ventilation from 'dirty' areas (bathrooms, kitchen, gym/sauna, mech room). Common areas to contain concealed mini-split fancoils for the inevitable, yet minor, cooling demand (1 per floor). This will be controlled by simple single stage heat-only stats in each zone, with heat/cool stats in the common areas.
03-24-2012, 05:46 PM #81New Guest
- Join Date
- Mar 2012
WOW, and Still Confused
It appears that residential HVAC is mostly a black art (i.e.: a process that is mysterious and difficult to master or describe.)
> Pretty much everyone seems to agree that a 60,000 btu whole house heat loss (bumped up, at my request, to a single 100,000 btu variable speed propane fired furnace) is ridiculously low, despite a Manual J, S and D design from an outfit that is experienced and credible.
> Some of you suggest that the contractor and designer should be the same firm. I like that idea, too, but how does that solve my problem- I can't find a contractor that designs systems based on science. They design them based on rules of thumb and experience (and, by the way, they have many satisfied clients). And of the designers that I've engaged with, one did the Manual J, S and D that I posted and the other had never heard of Manual J (a California licensed PE, by the way).
> Some of you suggest that this house needs a/c. I've attached a document that summarizes the temperature data from 1961 from the closest station to us (on the Pacific Coast, about 20 miles due North). We didn't think we needed a/c, based on this data (which mirrors our experience at the site). Are we reading this wrong- does anyone still think we need a/c?
> Regarding zoning, we had planned on the system mentioned by GA-HVAC-TECH. It's called My Temp, by Home Comfort Zones (Removed link ). It is essentially a room-by-room zoning system. HOWEVER, this zoning system does not eliminate the need to properly size a whole house heat source and distribution system.
So I ask again- "Can anyone tell me why I shouldn't just go with the bigger system (250,000- 300,000 btu) and play it safe? The additional cost is peanuts compared to the size of the project, we don't have any LEEDS, Energy Star, or regulatory compliance requirements, and the hassle that this is causing doesn't seem to be worth the effort to try and do it the 'technically correct' way."
Last edited by beenthere; 03-25-2012 at 12:10 PM. Reason: removed link
03-24-2012, 05:52 PM #82
Look for member "Paul42". He has a 4200 sq ft house, with a 2 ton A/C. he lives in Texas. So a 60,000 BTU furnace may be the right choice for your house.Contractor locator map
How many times must one fix something before it is fixed?
03-24-2012, 06:19 PM #83Professional Member*
- Join Date
- Dec 2010
Even in Toronto, where the design temp is -6f..... 300,000btu would do a 10-12,000ft2 house. It is a complete waste of your time and money to install something like that. It would have to be done with 2-3 furnaces anyway.
03-24-2012, 06:31 PM #84
The reason I suggest cooling, is that a home this big is likely to not only hold the few residents. Tight homes are especially prone to 'party heat', where you have a get together at the house, and everyone ends up sweating. As you mentioned, the system would be a mere fraction of the home cost, so why NOT be prepared for it?
As for oversizing the heating, this is partly why I (and a few others in this thread) recommended hydronic. No-one ever worries about oversizing their water heater, because having too much hot water is never a problem. Hydronic also eliminates the potential for air balance and distribution problems in a home this large.
Speaking of air balance, what does the home have for forced ventilation (meaning outside air refresh/exhaust)?
03-24-2012, 07:05 PM #85Professional Member*
- Join Date
- Sep 2005
- North GA
Science and what works are sometimes two different things. I realize that sounds like a contradictory statement... however when lots of contractors say the same thing... one should listen to them.
The issue is the size of the home and the ductwork required to distribute the air... just not a fit which will work.
And if it were me, I would take the post above which explains 'party heat' seriously. I would HATE to be the host of a 50 or 75 person party... and everyone is hot and sweaty because the $M+ house does not have AC...
What would YOU do if you attended that party at your friend's home? Yeah, we all know what we would think and what we would do... <grin>
The world is not going to come to an end if you install 3 or 4 systems in that house which are low capacity and run a small amount.
Good luck with your project.GA-HVAC-Tech
Galatians 2:20-21; Colossians 1: 21-22 & 26-27; 3:1-4; Romans Ch's 5-6-7-8
2 Chronicles 7:14
Quality work at a fair price with excellent customer service.
03-24-2012, 07:23 PM #86Professional Member*
- Join Date
- Jan 2002
- East Grand Forks, MN
I've noticed your Heat load calc and the CFM requirements that was done; I say you need the right amount of airflow capacity from appropriate equipment/s and yet not oversizing the equipment.
I think natural gas is more economical than electric according to what I hear from util companies there.
Your system/s can either be simplistic or complicated depending your requirements by you or city/state codes. Have you looked into possible codes that are required like fresh-air! This alone can mean an end to the type of system you might have to need or require!
Your region is unlike my region. I know how to design and what type of system to recommend for cases like yours (your house size) if you were in my area. But I'm very limited to helping in designing a system like yours when you have a much milder weather than where I'm from.
I say again, keep looking/searching. I remember hearing and reading about some good HVAC companies in the Sacramento area, i think!
03-24-2012, 09:07 PM #87Professional Member*
- Join Date
- Feb 2010
Unless you're building near the airport( your report's weather data) which I doubt, your data will be more like Morgan hill or Alamaden~90.
Plus, some day the house will go on the market, unlikely any qualified buyer for a large home will have tract home expectations.
03-25-2012, 08:53 AM #88
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08-22-2012, 04:25 PM #89
So, how many energy auditors are licensed HVAC contractors?Philippians 4:13 "I can do all things in him that strengthen me."
Apostle Paul inspired by GOD.
08-22-2012, 08:36 PM #90Professional Member*
- Join Date
- Jul 2006
The real reason many units get oversized is because there is more profit in a bigger box.