furnace questions
#10
ok, two furnaces, two sets of  questions.

First one:
i have an older lennox furnace out in the garage works ok, have no plans to replace it.  Sitauation: added a shop on the back of the garage.  The shop is insulated and seems to keep the heat reasonably well, keep it around 50.  Garage is made out of concrete blocks, not insulated.  The furnace is in the garage.  So right now it's source of air is the garage air which was 41 last night when the outside was about 30.  Does this affect efficiency much or the life of the furnace?  Seems like it would for efficiency?

I've thought about building a utility room around it, probably 12 x 12, insulate it.  Three sides already exist, I would just need to add a fourth wall.  Figuring I'd eventually house the air compressor and another tool or two that I don't use much in it if I did.  Would this help with efficiency if the above answer is yes?  



Second One:
Got a new Heil ac and furnace.  Love it.  In summer ran the ac lower and still saved money.  Haven't really been able to compare on the furnace part.  Has a skuttle air filter, DB-25-20.  It is 5" wide vs the 4" which appears to be more standard.  Data sheet that came with it says capacity of 800-2000 CFM.  Would a 4" wide one work in it ok? 

Not a huge deal, but I'd like to have my options open a little more for brand and price.  I'd like to change more often then the once a year they say so saving a little money having little more flexibity would be nice.
mark
Ignorance is bliss -- I'm very, very happy
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#11
The only problem with the furnace in the garage is it is against codes in some places. People tend to store gasoline and other flammables in garages and that makes it a hazard. Also many chemicals stored in garages can corrode the furnace and cause premature problems. Combustion air is a consideration, if the garage hasn't the cubit feet needed without the proper vents. Return leaks can pull vapors from gasoline and chemicals into the home. Enclosures (closets) need to be a specific size large enough for clearances, and combustion air supplied as well- check codes.

2,000 cfm for the filter is good up to a 5 ton system. The 4" should be fine.
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#12
thanks. The garage/shop are separate from the house.
mark
Ignorance is bliss -- I'm very, very happy
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#13
I would guess the 4" wide filter would not fill the frame correctly allowing dust to build up on the heat exchanger and AC coils. You can get aftermarket brands of filters that are quite a bit cheaper, or maybe rig something up that keeps the filter snug on the intake side. My observation is that there's a reason those aftermarket filters are cheaper.... they have a lot less media (at least the ones I've seen). So I've chosen to stick with the (expensive) OEM filters for ours (Carrier).
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#14
The garage furnace is a potential problem if it runs a lot with cold return air going in. Most are certified with return temps above 45 or so degrees. The issue is combustion products cooling and forming acidic condensate in the heat exchanger. The other issue is thermal stress when the fan slams cold air into the hot heat exchanger. Keeping both spaces above 50 or so will eliminate that problem.  Air circulation and adequate combustion air supply are other issues. 

You can make small filler blocks to wedge a 4" filter in a 5" housing.
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#15
(11-30-2018, 12:01 PM)blackhat Wrote: The garage furnace is a potential problem if it runs a lot with cold return air going in. Most are certified with return temps above 45 or so degrees. The issue is combustion products cooling and forming acidic condensate in the heat exchanger. The other issue is thermal stress when the fan slams cold air into the hot heat exchanger. Keeping both spaces above 50 or so will eliminate that problem.  Air circulation and adequate combustion air supply are other issues. 

You can make small filler blocks to wedge a 4" filter in a 5" housing.

thanks.  Yeah if go with the 4" I was figuring I would cut some blocks to keep it sitting like the other.

Assuming I did this:
I was figuring if I walled it off it would still likely have enough leakage like a house.  I could put the ceiling so it is higher then the eaves.  Seems like air from there while flowing through to vent would also flow into the room some.  Would running a pvc pipe from the furnace area into the garage provide enough air flow.  I know it would be a loss of some heat but...  There are some ducts in the garage, but I'm not wanting to fight with the whole garage and garage doors now although that maybe the better solution and may need to consider it.  I thought I might want to move one of the ducts to the room if I enclosed it.  The return vent is in the heated shop.  There is a single pane window near the furnace that does leak some air in.
mark
Ignorance is bliss -- I'm very, very happy
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#16
just wanted to add a thank you. Useful information and something to think about.
mark
Ignorance is bliss -- I'm very, very happy
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#17
We're talking about filter thickness right?

Some of the 5" thick filters are being replaced with 4" thick filters and as long as the filter is made for the cabinet, there should be no problems using it.
An example is the April Air 2200. The original filter was 5" and used the combs (difficult for the customer), the Honeywell replacement is 4" pop-out- is the same merv rating and static loss and is much easier to install.
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#18
yep, the filter they gave me is a skuttle 20X25X5, accordion style inside a cardboard box. Easy to replace, just slide out and slide in. For about the price of 2 to 3 I could have gotten 6 of the 4 inch type from my gas company with the discount deal they had going. The skuttle filter says a year, but I've always been one who likes to go by how clean the filter is rather then just time. I check it regularly and if in doubt replace it. The ones that I have looked at online and mon-power are the same merv rating. Figure I might as well save a little and have more options all else being equal.
mark
Ignorance is bliss -- I'm very, very happy
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