New Installation

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  #1  
Old 03-27-03, 08:25 AM
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New Installation

I haven't realized how difficult is to buy HVAC equipment if you don't have a licence. I'm building a hose in Wisconsin where you can pretty much do everything yourself. It's a pretty small vacation home (1300 sq ft, single level with a basement). The furnace will be centrally located and I'll be using the "standard" ducts from Home Depot (8X20 I believe, but I could be wrong). The house is all new, with R19 insulation in the walls and R29 in the attic. There will probably be 10 6" "outlets", 5 on each side of the furnace ductwork. I have no problem buying all the ducts (thanks to Home Depot), or doing the ductwork (my father in law is a sheet metal guy). The only "problem' is that nobody wants to sell me a furnace (needs to be propane). I understand that I can't work on AC equipment since I'm not licenced, but there is no freon in a furnace. I would also like to put the A frame coil in the furnace now rather then later ( I won't install AC now, but maybe later). Why is it so difficult? I can buy stuff from Grainger, but their brand doesn't inspire a lot of confidence.
 
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Old 03-27-03, 10:04 AM
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I think one of the reasons is because a lot of equipment gets mis-applied. Wrong size, wrong installation, improper duct size, venting problems. You name it, and I have seen it. Manufacturers don't want liability issues and they don't want to have to honor a warranty on a heat exchanger that was damaged due to improper airflow or combustion maladjustment. I'm not referring to your job specifically, but the homeowner installers in general.

A few years ago I gave a customer a price to replace an oil fired mobile home furnace. He didn't like the price. (it included a new mounting base and all new flue pipe through roof) He bought one locally and put it in himself and in less that a year, the place burned to the ground. The origin of the fire was the furnace and I can't say it was because of his installation, but I suspect it was.

If I was you, I would look for either a local supply house with a salesman/estimator who would work with you or a small hvac contractor who would act as your advisor and purchasing manager. He might want a few bucks but you will be way ahead in the long run. I have done it for people in the past and it has rewards similar to the ones we get here for helping. A new friend and a person who is satisfied that he did it himself. Not everyone is capable and that decision lies with the contractor.

A few notes.
The duct size is related to amount of airflow required. If you are planning on having 10-6" duct runs, you should be starting with 20X8 trunk. After the first 2 takeoffs, you can drop to 16X8, after the next 2 you can drop to 14X8 and so on. There are a few tricks that can make your job easier and a contractor could explain them in a half-hour BS session. Do you know anyone in your area that you could ask?

I'm sure if you father-in-law is 'the tin man' you can cut and assemble everything without a problem but the job starts on paper and you won't regret a little extra planning.
 
  #3  
Old 03-27-03, 10:13 AM
Brewbeer
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Also include provisions for cold air return in each room having a door that can be closed.
 
  #4  
Old 03-27-03, 11:00 AM
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Duct size

Im with KField here you just dont go down and buy duct work from Home DE-pot and put it in. You said the furnace would be about in the center of the home. If so you dont put a 8"X20 on the furnace. Like KField said 2" per run and 2" for the pot.Looks to me like you want to come off the plenum with a 8"X12" going both ways here. Why the waste to put an A coil in now. You can get an A coil box to go in now or build the plenum so it will take the A coil later. And with Brewbeer get cold air returns from all of the room. Dont forget out lets in the basement also.Now with the LP we have to be state licensed to work on LP furnace and to run LP pipe lines. So I think you should go and check out you codes there. So yes your back in the hills but you do want to play it safe dont you ED
 
  #5  
Old 03-27-03, 12:09 PM
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The ducts will go on either side of the furnace, and the return duct will be parallel to that. With the exception of the bathrooms each room will have a 6" return duct. The LR/DR will each have 2 8" returns. Perhaps I'll use a larger square return in the LR, the LR is above the furnace. The ducts will start with a 8X20, and start on both sides of the furnace. They'll only go about 15' each way. The reason for the A frame is because I don't want to touch it after that. The A coil box would be the best as it looks much better.
I was thinking of a 80,000 BTU propane furnace, with a 2 Ton coil if I can actually buy it. The furnace will have to be wall vented, as i don't want to have the chimney go up.
Regarding codes and licences, I only needed to have a licence to do the septic field. I could even dig my own well, although practically nobody drills a 135' well by themselves. There will be an inspection of course. I can do all of the plumbing, electrical, heating, cooling (although I can't charge and work on the system after it's charged). I just got off the phone with the inspector right now.
On a side note, is it possible to use black steel pipe with propane or does it have to be copper? I just think that it's way too easy to break a copper pipe.
Also, do they make high efficiency LP furnaces?
On my current home I have a Westchester (very noisy, but very reliable so far ( 8 years old)) which is wall vented using a regular metal vent pipe (only about 6' away). i don't have to worry about fire since it's going through a concrete wall. I could have also used high temperature plastic venting, but that would have required a drip loop. I want to vent this furnace the same way, but the wall is about 12' away, and I prefer to have the pipe go between the studs. I believe I'll have to get a 90+ furnace that will use the regular PVC pipe as the vent.
 
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Old 03-27-03, 12:24 PM
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I will post this one and then I will stop badgering you.

80,000 btu (even input) sounds like about 50% more than you will need for 1300 sq. ft.

If your returns from LR & DR are close to the furnace, there is no reason to oversize them. Oversize the returns farthest from the unit. If you have 10 6" ducts you will be able to move 1000 cfm. That is equivalent to 2.5 tons of cooling which is more than you will know what to do with in 1300 sq. ft.

Like Ed said, use 12 X 8 on both sides of the plenum and go both ways. If you oversize the duct, you are wasting money on materials and losing air velocity. Use dampers in all supply ducts. If you get a furnace too large, the blower will be too loud and whacking so much air around that it will be a service problem before you know it. Get someone to do a heatloss/gain for you and start from there. I believe you can do it online somewhere and it will be well worth the time it takes you.

You can use black pipe for gas if you want. It is more durable, just harder to work with.

No more scolding from me. Good luck and work safely.

Ken
 
  #7  
Old 03-27-03, 01:16 PM
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LP furnace

Yes the 80% & 92%furnaces come in LP also. I would two stage the LP lines. Put a little joe on the tank and a low pressure reg. at the home.UP there where you are make sure the vent hole on the reg. cant get under the snow or it will shut off on you .On the septic tank we use only the airobotic ones they put air down in the tank. Used them for years there in Mo.They are starting to use them downhere in Fl. now ED
 
  #8  
Old 03-27-03, 01:28 PM
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Thanks Kfield.
The only reason I wanted to oversize them is because the LR and DR will each have 2 6" supplies, I was thinking of using a 8X8 squre return instead of the 2 6" ducts. But thinking about it i guess it looks better to have all registers alike.
They only reason why I said 80,000 btu because all of the furnaces I've seen (I'm in chicago) are 80,000, and the houses are only about 1000 sq ft. Also, this house is around WI Dells, and it gets pretty cold in the winter over there. We have a little guest house we built already (750 sq ft, 2 stories) that is currently heated by electric baseboards (6000 W total), and even when it was 20 bellow it had no problem keeping the place at 70C.
I don't mind hiring a pro to do things that I don't know or am not capable of doing. I would have never done the well or the septic, or pouring the foundation. But I built that house all by myself without hiring anybody. Even though I'm an electrical engineer, and have an electrician's licence I am pretty much well versed in anything (I'm not a plumber, but I've worked with enough plumbers to do the job as well they can).
The reason for the pipe question is because all the houses I saw over there (all had LP) had copper pipes.
 
  #9  
Old 03-27-03, 02:54 PM
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Thanks Ed,

The piping from the tank to the house (and maybe inside) will be done by the gas company. The regulator wil be about 3' above ground level (that's how high the basement wall sticks up).
 
  #10  
Old 03-28-03, 06:24 AM
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I don't believe what I am reading here. Trinitro...you say you are doing the ductwork and were thinking about oversizing to get more airflow to the ducts which KField has pointed out is not only a waste of money to do so but is also a waste of efficient airflow. What does this tell you about your qualifications to do the job?

You want to vent a furnace like the other one. Don't you think you better vent the furnace according to what the furnace requires? What does this tell you about your qualifications?

You also have to ask about what pipe to use for the LP after talking with the inspector but you said you could do the job just as well as any plumber? Any plumber worth his salt would know what the best piping is for LP. Again...what does this tell you about YOUR qualifications for HVAC installations?

It's no wonder hundreds of people die every year from carbon monoxide poisoning as well as fires and explosions caused by furnace do-it-yourselfers who are not qualified to install them.

Could this also be the reason you are having such a difficult time buying a furnace and why supply houses are so reluctant to sell equipment to just anyone?

Maybe now you can understand why manufacturer's expressly state in their warranties and installation manuals..."The equipment covered IS TO BE INSTALLED BY TRAINED AND EXPERIENCED service and installation technicians. Improper installation, modification, service or use can cause electrical shock, fire, explosion or other conditions which may cause personal injury, death or property damage."

Look...I understand the joyful satisfaction of building and accomplishing something myself and I hate taking this negative attitude but our industry already has a hard enough time maintaining a decent work ethic; so if your going to do the job, do it right and quit guessing about what will or won't work before someone gets hurt.

Get a load assessment and get someone to work up a duct design for you to meet your needs and for heaven's sake...consult with an EXPERIENCED installation person that can see your layout and talk over your needs.

Please do it properly so you can enjoy it for many years to come. Good luck.

Getting off my soapbox now
 
  #11  
Old 03-28-03, 07:18 AM
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Considering that in my area you can't use copper for gas lines I don't believe I should know that. I even called my friend (a master plumber with 20 years of experience) and he said he doesn't know what to use since he never installed a propane furnace, or even used propane. So I'm learning here. The propane piping won't be a problem, the gas company will do that. Free of charge too.
Regarding oversizing, all I ment to say is that I wanted to replace 2 6" round return ducts with a 8x8 square duct.
I may not know near as much as a HVAC installer, but i've seen some work, and I truly believe that I can do a better job then they can. The furnace I've installed in my current home (including the ductwork) has been working perfectly for 8 years. I'm sure that a pro will be able to do a better job then I can. I'm not questioning that. But to say that what I do is dangerous is a bit reckless. I looked at what it takes to became HVAC certified, and it's not difficult to pass the test. But I don't believe that having that piece of paper in my hand will make me any better. I'm not trying to be difficult, or step out of line. I appreciate the pros (I'm one myself, an electrician), but I really don't see any advantage in hiring somebody to do something I can do myself.
Regarding the venting, as far as I know all 80 and 90+ furnaces can be wall or chimney vented. The last 8 houses I've worked in (electrical) all had the furnaces vented through walls rather then the chimney.
I would love to be able to just hire somebody to do all the work while I sit back and enjoy the view, but unfortunately I don't make enough money.... and I love doing everything myself.
Again, I'm sorry for my rambling. All I wanted were some pointers and guidance.
 
  #12  
Old 03-31-03, 01:24 PM
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trinitro:

I don't think anyone is questioning your ability to assemble the components of an hvac system, rather are just suggesting a more detailed and thought out plan of attack.

Sizing ductwork and furnaces are not like sizing wiring and plumbing.
The difference in one duct size can mean the difference between a duct that is too small being noisy and providing inadequate air flow to one too big that will bleed off too much static pressure from the plenum and main trunk which will make balancing a nightmare.
I havn't found a good duct sizing freebee, but here is one that is not too expensive:

http://www.heat-loss-calculations.com/
 
  #13  
Old 04-01-03, 05:51 PM
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yep

too many variables here, especially with lp. the furnace will have a venting table with it, not strictly followed will cause intermittant lockout on cold startups. MUST have low gas pressure lockout wired in series with psi switch, orifices changed...don't do this to yourself! airflow, noise, static pressure and velocity are essential factors in this equation, at the very least get a pro's opinion
 
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