Both companies main trunk line insulated sheet metal supply and return trunklines
When comparing 2 companies and their duct work:
What are good questions to ask?
My quotes I have:
1st Company: 26 Gauge
2nd company: 24 gauge
1st company: hard pipe in first 6 ft of flex
2nd company: foil back flex, metal outer covering
1st company: Trane XB13c (13 SEER, 80% A.F.U.E.)
2YCC3048A1120A
2nd Company: Trane 13 Seer 4 ton
Both companies say their installers have been with them a long time and they do not subcontract.
Anything else I should look at???
Both companies main trunk line insulated sheet metal supply and return trunklines
Is there anyone who can input about the different gauge and different flex?
26 guage is ok up to a certain duct size and generally on a 4 ton system would be ok, this has alot to do with how the duct is made and installed as well. A lighter guage will bend more and may cause some popping especially on rectangular duct that is large. Shorter duct lengths with standing s-slips will prevent this as well. If they are a good sheet metal contractor they will know when to use what guage metal they need. Flexible duct is ok as well as long as it is installed properly so that there will not be any dips or sags in it and it is sized properly. The foil back is good, and you should ask for an r6 insulated flex instead of an r4, and make sure you trunkline will have 1" liner and not 1/2" liner inside it.
If this is an attic square duct would be much better (better than rectangular,better aspect ratio) and 26 guage will surely be fine, but 24 guage is just fine too, cant really oversize the guage.
I would look at going with a 90%+ afue furnace though, it will pay for itself in just a few years and not waste so much gas. If it is in an attic this may not be an option due to freezing issues, if so look at using a heat pump with the gas as a back up for fuel savings. Missouri is a good climate for a heat pump, alot of 30-60 degree days where that efficient heat pump will keep you warm and not burn that high dollar gas or propane.
Last edited by hivacer; 03-04-2008 at 01:40 PM.
Not enough info to make a decision either way about which is better.
This is an all in one system outside, duct work goes up the outside of the house into the attic.
The main trunk line will run down the center of the house almost run the length of the house which is about 60 feet long. The width of the house is 45 feet, that will be fed by flex duct.
If the duct outside will be 10x30, I prefer 24 guage, if its 12x24, 26 guage is ok.
What size are each of them proposing to use.
be sure the trunk is not at the centerline of the attic, unless there is enuf room beside it to craw/walk!
I have to craw over mine to even get up thru the scuttle hole! = P I A!!!
harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!
Who did the load calculation on the system? Which company did the Manual 'D' duct design? Experience counts for putting the parts together but if neither company did a load analysis or duct design by manual 'd', keep searching.
If YOU want change, YOU have to first change.
If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!
I would think round pipe for the trunk lines would be better than square. considering the length and and the fact that its climbing up the wall and then approx 60 ft.a reducing round trunk would have less air turbulance. and ask for an r-8 insulation on the trunk and the flex and dont have them line any of it have them wrap it. good luck with it......and remember these are only my opinion
i personally wouldnt let them use duct liner ..it means to insulate the ducts from the inside......
Good point, round or spiral trunklines wrapped with r8 would be Ideal with saddles coming off at 45s, but going up the sidewall I would think rectangular will look better and that it will have to be lined because of it being outide unless it is wrapped and the insulation is somehow protected.
So make sure that the duct liner they use is 1". This is more important than the guage, your insulation on your ducts will save you alot of money over time.
Ideal would be koolduct.
http://www.knaufusa.com/products/com...ct_system.aspx
100 times better than duct board. Already insulated. very sturdy
I don't understand with nat. gas prices the way they are why you would not pay the extra few bucks and get a 95% furnace. That is why I don't like outside units, looks kind of tacky with ductwork going up the side of your house!!
I checked flex duct: They use r4 with metal aluminum sleeve. He asked about r6 and r8 and he said companies here are not using r4 and the company he buys from doesn't stock it, but he would see what it would cost to get it. (I'm in Midwest)
It will have 1" insulation inside. (In future when I side my house, I was told I could build around the duct, insulate more and side it. Almost to look like a chimney. Then it wouldn't be so ugly. Several of my neighbors have it running up the side of the house. One landscaped it the other did not.)