Being both a plumber and an avid woodworker I know first hand that you are confronted with two distinct problems. 1. Enclosing the gas furnace will result in creating what is called a "confined space" and will require making provision for an outside source of combustion air. 2. The woodworking process will generate highly flammable micro-fine sawdust particulates in the working atmosphere as well as occasionally producing volatile fumes from the finishing process. By code definition a "Confined space" is any space, which has less than 50cu.ft for each 1kBtu per hour. To determine a confined space we begin by totally the BTU/Hr rating of all combustion equipment within the space. By example, a residential furnace will typically range between 50k and 200kBTU/hr. For the sake of illustration let us assume for the moment that the data plate on your furnace rates the burner at 100kBtu/hr. Now let us assume for the moment that you also have a water heater in the same space and the water heater is rated at 35kBtu/hr so your combined combustion load would be 135kBtu/hr. We are required 50cu.ft for each 1kBtu so we multiply 50cu.ft x 135kBtu = 6,750cu.ft. Allowing an 8Â ceiling we then get 6,750 / 8 = 843.75sq.ft. You then multiply the length x width of your proposed machinery space and if it yields less than 843.75sq.ft it would be classified as a confined space and would require an additional source of combustion air. The codes allow us a number of different configurations for ducting in outside air, and each configuration has a different formula, therefore you should really consult an HVAC specialist in your area that could give you the requirements for your jurisdiction. By example, you could have a single horizontal opening through an exterior wall, which provides 1sq.in for each 3kBtu/hr. (135kBtu/hr / 3 = 45sq.in) but there would be height above finish grade restrictions to compensate for average snow load or other considerations. You could have two vertical ducts through the roof, one terminating near the ceiling of your machinery space and the second one terminating 12" above the floor, in which case you would be required to have 1sq.in for each 4kBtu. (135K / 4= 33.75sq.in) This could then be done with 7" diameter flue pipe. Once you have provided the necessary combustion air you would also need to consider how the return air gets back to your air handler. In many residential structures the return air is drawn directly into the furnace and is returned to the basement by infiltration from the floor above. In this case you would need to install return air ducting from the living space. Because the airborne sawdust or volatile vapors in the woodworking area are potentially flammable the door between the woodworking space and the machinery space should be equipped with weather stripping to minimize air flow between the two spaces.

Based on the information you've provided, sounds like the York quote is the best option, but I don't agree with the 80% modulating furnace. That's a high-end furnace, and going with the 80% version doesn't make sense to me, especially in our region where it can get cold at times (I'm in Maryland). Is PVC venting an issue? The York Affinity is a nice line of equipment. American Standard isn't bad, either, but the equipment that the York rep. is quoting is better in my opinion. 3 tons is a bit much for your cooling load, but it's what you'd have to go with if you went with the Affinity line. The 2.5-ton Latitude unit would be the better fit. With the low stage on the Affinity approximately meeting the cooling load at design conditions (which won't be met on all days), I don't think you'll be getting those long run times that you should with a 2-stage system. Ask the York rep. if he can quote the CZB or YZB 2.5-ton single-stage Affinity unit with a 90+ efficient v/s furnace (modulating or 2-stage). Not sure where the American Standard rep. came up with his sizing. Do you like it cold in your house (68-70)? Did the York rep. do the load calculation?

Post your electric rate in cents per kw-hr, and your gas rate in either $ per ccf or $ per therm. The heat output of a gas furnace is very similar to electric resistance strips if enough kw are used. Utility costs decide which is cheaper. 5 kw electric strips put out air temps about 15F greater than room temperature. So a typical 10kw strip heat puts out 100 degree air if the room temp is 70F (70 + 30 = 100). This# is based on 1200 cfm air flow from the indoor fan. 15kw = 115F which is more in the range of gas furnace temps. The air handler must be sized to handle this heating load. These temps are for the strip heat only and do not include any btu's from the heat pump. The heat pump itself puts out air temps from about 90F to 100F based on outdoor air temps. The 90F supply temp air from the heat pump combined with 20 kw aux electric strips provides minimum 120F output air when needed. Heat pumps provide enough heat up until the balance point, which is around 32F or so based on home construction/insulation (mine is 25F). At temps lower than the balance point, aux heat is needed - either furnace or strips. The good thing with the strips is they can run along with the heat pump. The furnace cannot run when the heat pump is in heating mode; its one or the other. When the heat pump goes into defrost mode, the air output is in the low 50's. 10 kw provides 30F to temper the air into the low 80's so it doesn't feel too cold while the heat pump is defrosting. The furnace will provide 120F air during a defrost cycle. The heat pump is typically 300% efficient down to 35F ambient. Heat pumps make cheap heat. One comment about the XP-19. It's "up to 19 SEER". Not all combinations get 19 SEER. Model numbers can be used to determine actual SEER. Also, dual-compressor systems like the XP-19 are more for hot and humid summers than for heating. In the cooling mode, running on 1st stage saves $$ and reduces humidity. Once on 2nd stage, it loses its operating $$ benefits. A 14/15 SEER usually provides the best combination of purchase price and operating cost. If you can afford a "19 SEER" system, go for it. Whichever SEER you get, you want as close to 12 EER and 9 HSPF as you can get for low operating costs in cooling and heating respectively. Good luck.

GoTerps let's look at each system's numbers. option #1 3929268 Active Systems XC14 SERIES LENNOX INDUSTRIES, INC. XC14-024-230-02 CX34-25+TDR SL280UH090V36B* 24000 13.20 16.00 option #2 3929121 Active Systems XC14 SERIES LENNOX INDUSTRIES, INC. XC14-030-230-03 CX34-31+TDR SL280UH090V36B* 29000 13.50 16.00 option #3 3656259 Active Systems COMFORT 16 PURON AC CARRIER AIR CONDITIONING 24ACC624A**30 CNPV*3014A** 58CV(A,X)070-12 23000 13.00 16.00 1 option #4 3656288 Active Systems COMFORT 16 PURON AC CARRIER AIR CONDITIONING 24ACC630A**30 CNPV*3117A** 58CV(A,X)070-12 28400 13.00 16.00 1 all qualify for tax credit. three observations. 1.The Lennox furnace is oversized and should drop down to the 70K model. 2.It is important that lineset be sized correctly whether you select 2 ton or 2 1/2 ton condenser. Flushing is acceptable practice but refrigerant lineset size must be correct. If you elect the 2 1/2 ton condenser, it is unlikely that old lineset will be correct size 3.I do not like thermostat selection for these quotes. I would like to hear from Ryan's ideas/suggestions on this. I do recommend a good 4-5" box filter cabinet. I would not put down more than 25% upon contract acceptance. now to the fuel comparison between electric vs nat gas. to be fair, I will use 50 therms mthly usage to better average your nat gas mthly base charge. Cost per 100,000 btu of useable heat Heat Pump with COP of 2.75 $1.15 Nat Gas Furnace 80% eff $1.81 you can readily see that a HP above temp balance pt is the less expensive choice to heat your home. Keep in mind the main reason for the large difference is the 80% eff furnace. yes, if operating costs are important to you, then HP operation would save you some $$s. ask dealer for option on HP condenser version if interested. IMO