AboutBill Brainard Expertise I can solve most heating related problems with furnaces and air conditioners(natural gas,propane, electric)(no oil or heat pumps) & some boilers and most control problems. Iam a heating & air cond contractor with 30 some years behind me. I spent 12 years working for Sears doing this type of work.
Experience I have graduated from 10 or 12 factory schools on gas furnaces ( 70%, 80%, 90%+ AFUE), basic air conditioning, air conditioning service, advanced air conditioning, oil furnaces, wall furnaces, floor furnaces, air handlers, coils, compressors, multi-speed (1 speed to 12 speed) furnaces, mobile home furnaces and air conditioners etc...
Question We had a replacement 2 stage 100,00BTU Trane furnace, a 4 ton evaporative coil, new refrigerant lines put in this week.Our home is a little over 2000 square feet. We live in the Sacramento, CA area where we still don't run the AC very often (we don't turn it on unless it gets up to 80 inside), but do use the furnace a lot in the winter with frost in the early mornings. The contractor installed a filter box above the downflow furnace that takes only 2 12 X 20 inch filters at an angle. The installation instructions for the furnace say that 2 16X20 inch filters are required (which is what we used on the original furnace). The contractor is saying that the box is what the Trane supplier gives him and that is what he always uses. Larger filters can't fit in this 12HX17WX20D inch box. I am thinking that this is not good for air quality, the freqency of needing to change them, or for the coils. We are trying to get the contractor to reinstall a larger box above the furnace (14 inches high which complies with the installation instructions for the furnace) but there would be a lot of sheet metal work. Does that sound reasonable? The second option would be to install filters at the returns. We have two air returns that have outside dimensions of 16 X 8 inches and 14 X 30 inches. Are the returns large enough to install filter-holding frames there or would they have to be enlarged? We were thinking of getting cleanable electrostatic filters or going back to using pleated filters again. Also, the contractor hooked up our old programmable Lux thermostat to the new furnace. It keeps us comfortable enough, but was wondering if we would get more energy savings by installing a different thermostat where the furnace would not kick into the second stage always after 10 minutes. If so, what kind of thermostat would that be and is it something we could install ourselves? I know it's lots of questions, but I would like an unbiased opinion. I appreciate your help.
Answer 1. Since the filter area is (2 16 x 20) or equivalent, one 32 x 20 or 640 sq." of filter area. A 100,000 BTU furnace can get by with one 16x25 filter but a 20 x 25 (500 sq") is plenty. If you have 640 that is even better. I have not seen a factory suggesting that 2 - 16x20 filters are needed. They usually say "X" number of sq" per 1,000 BTU's. Here in Montana this is something we pay attention to. It is the sq" that must be adaquate. How they are shaped does not matter. Forget the returns, they work BUT what a pain to deal with monthly. *****************************************************************
2. Use HEPA quality, pleated filters or electro-static. (peroid) I suggest electro-static filters. They are good quality and easy to wash & re-use. Clean them monthly, no matter how dirty they look. Use a filter cleaner soap. (no residue) ********************************
3. Thermostat - Nothing wrong with the "Lux". They work good & program easily. If you want to save money, have the contractor wire the furnace to "never" kick in the 2nd stage. I say that tongue in cheek. The 2nd stage should only kick in, 20% of the time. Not much savings to be had messing with that "time peroid".*********************************************
Winter frost, Hahh... It gets to -40 here, every winter. Now thats COLD !!!!! Later. Hope this helps.
