Bungalow HVAC project
My Son bought a starter house, He's getting married. Its an old summer bungalow, remodeled for a year round residence,about 15ft wide and less than 60ft long with a gas fired forced air furnace in the crawl space. The inside was recently redone, but the furnace is old and my Son would like to add central air. If he had money He'd buy a larger house. My idea is to abandon in place the old heating unit. Drop on a pad a package unit gas heat/Ac (off the cuff 80k BTU/ 1.5 Ton) and run the duct into the crawl space and do the hook up (off the cuff about $3000. total). My back ground is Electrical/HVAC for retail. My son was talking to a residental HVAC contractor who complained about the idea not being efficent, and suggested taking the house appart to install a new attic unit ($$$). Since the house is 600~800 sqft I don't see the problem with 80% efficency: the payback on the difference of 90% in the ten years or less he expects to live there, is I believe, irrelevant. Comments please. Thanks Oldfoggy.
Re: Bungalow HVAC project
At least on an advisory basis, I would recommend that your son have another 2 or 3 licensed HVAC contractors (consult the Yellow Pages under "Heating Contractors") get involved to give their preliminary opinion as to what is the best way to go with a new heating/AC system.
For one thing, a computer-driven "heat loss calculation" has to be done to get an exact amount of BTU/hr that's needed for both heating and cooling; each house is unique; the HLC determines how many BTU/hr are escaping thru the walls/window & ceiling so that an accurate sizing of the heating plant & the AC can be done---it is estimated that 60% to 70% of the heating plants out there are way oversized & burning way too much fuel.
Before the heating/AC plant is installed it is also very important to have an Infrared Inspection Service (Yellow Pages) to determine how much heat/cooling is escaping thru the exterior walls, roof & windows, because the walls & attic are often not filled with adequate (or any) insulation, and the windows are heat-wasting single pane that let out a lot of heat in winter to burn gas/oil and let in a lot of heat in summer to burn a lot of electricity for AC---many people don't take these steps first, & put in oversized HVAC that means high electric & fuel bills for the next 30 years; it's not uncommon for homeowners to halve their utility bills if they do this first, before they buy the HVAC equipment.
The estimates from the Heating Contractors will vary considerably in quoted price & type of equipment.
Your experiences with this so far emphasize the need to get at least 3 estimates and opinions from different HVAC installers on this thing---without looking at the building, I would have some qualms about an attic installation due to possible noise issues & vibrations; it may be suggested that you consider using the crawl space where the HVAC system is now; I don't quite understand placing the new unit on a concrete pad (exterior ?); a small 8' X 10' partial cellar could be installed in the crawl space; on the other hand, the Unico System HVAC system is usually installed in the attic. http://www.unicosystem.com
For the above reasons, I don't recommend installing a HVAC system as a DIY project (if this is your son's intent); it's against codes for one thing, & quite often a DIY install ends up spending more $$$ for a system that can be installed at a lower cost & higher quality by a licensed HVAC installer.
Another possible alternative is possibly a forced hot water boiler/baseboard system that could be more easily installed in view of the crawl space, combined with one or two ductless mini-split ACs by Sanyo, Mitsubishi,Hitachi, etc.
Last edited by Pelton; 02-03-2013 at 09:44 AM.
Re: Bungalow HVAC project
Pelton's suggestion is a must, since the contractor you talked to is out of line. Your approach seems correct. The only thing you need to double check is the size of the furnace (80K BTUs may be too large).
Re: Bungalow HVAC project
I agree with you. You are talking about what we call a "gas pack" around here. You can get them in very high efficiencies, 92+ % but those are very expensive, most people opt for the 80% efficiency units.
I think the reason your son's HVAC contractor doesn't like these is the duct work is very difficult and it is hard to find someone willing to do it. Many HVAC contractors want to use flex duct for this because it is much easier to install, but this is not a good idea. Mice, rats and other critters will tear holes in the flex ducts and crawl inside to nest.
This is one part your son can do himself though. You say that there is already a forced air unit under there, if there are sheet metal ducts attached to it, I would remove the old unit. The seal and insulate the existing ducts. Then your son or the contractor can build a new trunk to feet the air from the gas pack to the existing ducts. You will want to locate the gas pack outside as close to the old heater as possible.
If the ducts are non existent or in really bad shape, then a completely new duct system should be installed. a good HVAC contractor that just doesn't want to mess with the ducts will probably be glad to design a system for you. don't forget that you will need a return duct, these are often cut into the exterior wall next to the gas pack.