For $39, I was able to do what none of the three contractors who came to my house was able to do: accurately size a replacement furnace. Each asked me for the square footage of the house, and told me what size I "needed." The first said 120k BTU, but later said he had deliberately over-sized it. The other two said 100k.
After carefully measuring and inputting data into HVAC-Calc, I found that my total heat loss, with no upgrades, is 62k BTU. If I add R30 ceiling insulation and insulate the ducts to R4, its only 50k. With R6 duct insulation, its 48k BTU. I'm no expert, but I do think I can use a tape measure with fair accuracy.
So I need a furnace half the capacity of what three experienced HVAC contractors recommended by rule of thumb. Not only did HVAC-Calc give me an accurate size for my present situation, it also let me compare the result after upgrading my insulation.
While I did not get quotes on A/C, the program says I need 1.5 tons before upgrades or 1.0 tons after.
Great program, try it! http://www.hvac-calc.com
Where the contractors relucant to perform the load calculation? Did they charge you for their calculations? It has been stated many times on this web site to go with a dependable experienced company. What brand(s), SEER & AFUE units were they recommending to you? What did you finally decide to do?
None of the contractors mentioned a load calculation. When I discussed my results with the president of the largest company, he said he thought a larger furnace would be better, but he would install one with the BTU capacity indicated by HVAC-Calc.
I'm looking at an 80k BTU 80% 2 stage variable blower furnace, either by Trane or by Ruud/Rheem. This works if I insulate my attic to R30. It's marginal if I don't.
I've decided against A/C at this time. California is short of electricity anyway; and I've survived 21 years in this house without it. We only would turn it on 10-15 days per year, anyway.
You may want to check your figures again. A 1 ton unit is extremely small. How many square feet did you say you had?
My home have 1,950 square feet. It is in Silicon Valley, where we don't get too many days requiring A/C. I agree that it sounds low, but I don't plan to get A/C at least not this year.
I'm looking at an 80,000 BTU 80% 2-stage furnace with variable speed blower. Rheem/Ruud and Trane are the most likely brands.
snitow, I suggest you have your dealer install an evaporator coil case when they install the furnace. It is much easier and less costly to do this rather than retrofit when you are ready for A/C. Good Luck!
after reading your post regarding the software I bought it
and have to say that even after falling for many of the standard "Adjustment Swags" such as adjusting the outside temp. by +6 degrees I still reduced my a/c load on my new home plan from 14 tons to 8.0. ton's on four units! Believe me I've double checked these numbers several times and the information I input is dead on! My original #'s came from
a mechanical engineer who called out 2 four ton units and 2
three ton units and didn't blink in charging $1300.00. My
detailed calc. calls out for one 3 ton, one,2.5 ton, one 1.0 ton and one 1.5 ton. BIG DIFFERENCE!
Thank you for the tip on this program, definitely a winner!
I'm from arizona we use one ton of cooling just to cover the Bathroom.We had one contractor use a Trane load program to do two sudivisions, 1600 sq. ft vaulted ceilings, they used a 3 ton gas pack, most owners can't get there house down below 78 degree's on the hottest days of the year,never quits running, 400.00 dollar utilitiy bills,you have to make sure and give yourself a little for those hotter than average degree days or that filter you forget to change or that insulation that was suppose to be in you attic ,but the contractor shorted you or the doors the kids keep leaving open. I know after about 20 of these people in this subdivision signed a complaint with the registrar of contractors,that contractor wishes he would of bumped it up a little. Gives the saying, It's hard to stop a Train, a new meaning.
Probably nothing wrong with the Trane program-the problem was how the house was built. If the program calls for certain R values, air leakage rates, non leaky ducts,ect. and the builder does not do the correct job, then all the programs in the world are not much good. What you need is cooperation from designers, manufacuters, and bulders to do the right job.
sarcool, I appreciate the concern on the tonnage. It works
out for the kitchen/laundry/family room @ 3.5 tons,dining/
living room @ 2.5, master bed/bath @ 1.5 and secondary bed rooms @ 1.5. All zones have been bumped to the next 1/2 ton
to compensate for peak days. But believe me, I'm building this house and I'm doing EVERYTHING to insulate and eliminate infiltration. I was going to tyvek wrap the house
but opted instead to completely sheath the exterior in 3/8 OSB tongue and groove to eliminate seams. To take it a step further I'm gluing the sheathing at the top and bottom plate lines and using a foam gasket against the slab, foaming ALL exterior cracks and then insulating with cellulose. I also reviewed the hvac plan with my contractor who wants to increase the coil tonnage and reduce the expansion valves.
My goal is a utility bill that averages $200.00 a month for 3900 sq ft single level.
Mr Allen--Lowering your load is the best way to save money per month and be more comfortable. If you are building, why don't you consider structural insulated panels? I helped a couple design a 4500 sq. ft home with only 2.3 ton load! Our firm guaranteed average heating and cooling costs at only $48.00 per month in Virginia with heat pumps. The couple also said it was the most comfortable home they had ever been in. The real key on comfort is both the house and the HVAC equipment!
? for sarcool
I've never been to AZ but my brother lives there so I get some reports. If the hottest days are 105 and even more with no humidity how could you expect the a/c to shut off when set as low as 78? I have installed a/c for people who never had it and then they ask what they should set the stat for, and they guess 68 would be good. I tell them to try 12 less than outside as a guide unless they like the utility co. deep in their pocket. This is from NW Indiana where we get some condensate running.
In arizona we like our house's cold and our women hot. I keep my house at 76 and I can get it lower if I want.We do have some humidity ,it's called our Monsoon season,Late July till Sept.Thats when everyones condensate drain backs up from all the previous dry dusty months and makes a mess all over the place. But seriously, you can save a bunch of cash by sealing and insulating your home, when your involved in the construction of your house that even better. We've been able to do some real neat things with zoning.One of our next projects will be a 3 ton gas pack on a 1600 sq ft new home,with the proper duct size and a 2 zone system, we'll see how it works. will keep you informed.