contractors give different tonage quotes
We are replacing the HVAC unit in our townhouse in Washington DC and are getting quotes on a dual fuel system from 3 contractors. All 3 levels of the building total 1200 sq ft. Depending on who you ask , calculated Heat loss is any where from 17,500 to 21,000 and Heat Gain is from 9,200 to 12,500.
Contractor 1: 1.5 ton 15 SEER
Carrier Furnace and Heat pump
Contractor 2: 3 ton 15 SEER
York (Luxaire Acclimate 9V series) Furnace and Heat pump
Contractor 3: awaiting his quote.
My questions are:
Why such a discrepancy between tons for quotes 1 & 2?
Is tonage a random concept and assigned by the manufacturer or does it refer to an absolute measurement? In other words could one of these quotes be configured incorrectly?
one of them is waaay off
I agree, did anyone take all the measurements of the home and do a manual J? That is the only way to tell. Sounds like someone is using rule of thumb...
Originally Posted by t527ed
We only want to do it, if we can do it right.
I take it from your responses (nashobasales & t527ed) so far that tonage is an absolute.
We purchased software from the link above and ran the numbers so that we might compare it to their results. Software support walked us through a couple of issues but it was determined that we had 17,500 heat loss and 9,200 heat gain.
Contractor 1 said his was at 21,000 loss and 12,000 gain. Contractor 2 did not provide any numbers. Maybe his was the "rule of thumb" as nashobasales suggested.
Thanks for your input guys. I'll keep you posted when quote #3 arrives.
I'd bet #1 is correct.Nobody wants to install an undersized system,so I guess he has the load calc to back it up,meaning he knows he has sized it right.
If the company is Cropp-Metcalf ,you are in good hands.
Dash what makes you say that?
Originally Posted by dash
I used to live in a 1200 sq ft townhouse, inside unit. 1.5 ton A/C, could hang meat in there even in upper 90s weather. There's a 3 story townhouse community across from our office, most have 2 ton units though they don't need it. When I run a calc, I get about 11K. Got another neighborhood we work in, 50k furnace is oversized, 1.5 ton air. They are 2 story 1200 sq ft, lots of windows.
Sounds to me like #1 is on it. 1.5 ton heat pump, the smallest gas furnae you can find. Wonder if a 7kw electric furnace might be better?
#2 is out of his friggin' mind.
Be interesting to see what #3 says.
I live in that general area and have a good recommendation for you if you're interested. I know this company can do heat load calculations. My email is in my profile. They are in MD but I don't think you will be too far away--I could be wrong, though.
what is your electric rate?
you will never be able to properly size a gas furnace.
what size is your existing AC condenser?
First part ,that's what we do ,size them ,and often find customer questio that what we propose is too small.
Originally Posted by second opinion
Second part,I've known Mitch Cropp for many years.
Why did you ask??
First of all how is anyone sizing ant thing without r values ,window sizing and ratings contruction materials ect,ect,ect,. The 2 nd bidder might be quoting a 3 ton to get the heating btu's needed for the heat side of heat pump, sometimes you dont nessisaraly need it on the cooling but have to upsize to get the heat side right. The other issue is just because a manual j is done does not mean it is the bible ANYONE can buy and TRY to calculate losses and gains and loads BUT remeber you only get out what you put in, so any joe blow can fudge a manual j to make their system look like ie is sized correctly.
It is very much like Baldloonie described. Long party walls and windows and doors facing north and south. We purchased the property and are gutting it. House will be fitted with new low-e glass windows, insulation to code and all energy star rated appliances and equipment.
I didn't want to overload you guys with too much detail. It was the statement that #2 made about manufacturers configure their systems differently so a 3 ton from one can be equal to a 1.5 ton from another that made me wonder.
A few weeks ago I attended a seminar from EarthCraft (Energystar and LEED) where they essentially said what Baldloonie did which is if you "seal the envelop" you can get away with a heat coil in your AC unit. My concern is if it isn't enough heat how expensive and troublesome will it be to retrofit a gas furnace if we go the heat coil route. Anyway sorry for the long post. Again it was #2's statement that drove me to this site. Which is great by the way.
Originally Posted by dash