Power vent extention question


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Old 08-30-06, 07:43 AM
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Power vent extention question

Newbie here so be gentle....

I know they are not the best system, but I have an OIL FIRED tankless system with a fieldcontrols SWG-5 power vent. Right now it exits the foundation and is presently under a deck. Well I want to make it right and I took all the boards off the deck and took some pictures of the power vent. A chimney is not an option because its on the back of the house and we have a sunsetter awning there too. I don't think I can leave the deck open there anyway it too close to the doors (see pix) less than 4'. so I think If I extend it out to the corner of the deck near the bulkhead and mount the power vent there. I have been talking to the Town Fire Inspector and with fieldcontrols themselves. the fire inspector was checking with the State fire marshal for clarification he said. I have not heard back. Lynn at Fieldcontrols said that if I follow the spec for BTU/Hr output chart for my power vent I could do it. with a 4" pipe it can be 16' from the boiler, with a 5" pipe it can be 51' fro the boiler.
The fire inspector said I should use double wall pipe. Has anyone here ever done this or come across a situation like this?
What is involved? I have replaced the power vent motor myself 3 yrs ago so I know how it comes apart. I think all you would have to do is, extend the piping (what to buy?) , extend the wiring from the controller(inside) and maybe extend the copper tubing( vacuum line) out to the edge of the deck. Can anyone shed so light on this and here are the pictures...


http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/powerventanddeck004.jpg
http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/th_powerventanddeck004.jpg
http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/powerventanddeck002.jpg
http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/th_powerventanddeck002.jpg
http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/powerventanddeck003.jpg
http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/th_powerventanddeck003.jpg
http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/powerventanddeck001-1.jpg

http://i115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/th_powerventanddeck001-1.jpg
 

Last edited by DIYaddict; 08-30-06 at 07:59 AM. Reason: Fixed image for easier copy and paste
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Old 08-30-06, 03:27 PM
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Power vent

If you can keep the piping indoors & go out another wall it would be far preferable to entending the pipe outside. I think if you try to do it in an unconditioned area you are going to have condensation & it will rot out the pipe.
 
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Old 08-30-06, 05:51 PM
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Found out today from the town Fire chief that I can run the pipe under the deck and he will sign off on it I use 6" metalbestos stainless pipe. run the power venter at the end of that on the end of the deck. I have some pieces now but I would still need 11' and one more elbow. expensive like $700 for all. there is no way to run it inside because the deck runs the back of the house and where it could be put through a wall that part of the basement is finished.
 
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Old 08-30-06, 09:00 PM
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Vent extension

With stainless you might be able to get away with it but I think another call to Field is in order. Be sure to tell them how far the pipe would be exposed to the outdoors. If they say OK, go for it. Just make sure you maintain the specified slope.
 
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Old 09-28-06, 06:03 AM
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Power Vent Extension Pictures

here are the pictures of my power vent extension. I had to go to the town fire inspector and he went to the state fire marshal for clarification on how to install. The Fire inspector has inspected it and it is good to go.

http://s115.photobucket.com/albums/n298/scottinmass/power%20vent%20deck%20photos/
 
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Old 09-28-06, 04:03 PM
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Scottinmass

Glad you got your approval & it was him & not me. No way would I ever approve of that. I hope it does well for you but don't hold your breath.
 
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Old 10-04-06, 05:50 AM
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Question

Originally Posted by Grady
Glad you got your approval & it was him & not me. No way would I ever approve of that. I hope it does well for you but don't hold your breath.
Why wouldn't you approve it? I have a vacuum under 4,which is good right? the system is all stainless, wont rust. The power vent runs approx. 30-45 seconds after the boiler shuts off. The power vent can do 51' with a 6" pipe.
What can go wrong?

thanks, Scott
 
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Old 10-04-06, 07:43 AM
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I think Grady's concern is that this application really pushes the envelope. I agree. Disclaimer: I'm not a pro, but a reasonably educated homeowner. I currently have an atmospheric gas boiler with an SWG4 power vent.

In glancing briefly through the pictures, I trust you did the Total Equivalent Length calculation correctly. Yes it's 51 ft, but that's TEL, not measured in a line along the piping run. Things like elbows, tees and reducers/increasers create friction and thus have a greater equivalent length than a straight piece of pipe. See the Field Table 3 at

http://fieldcontrols.com/venting.php#swgsize

In your installation, think I see

1 90 elbow 6"= 11 ft TEL
1 45 elbow 5" = 4 ft TEL
1 6" tee = 38 ft TEL
1 increase 5-6" = 2 ft TEL
1 reduce 6-5" = 2 ft TEL
1 reduce 5-4" = 2 ft TEL
~ 16-20 ft straight pipe indoors and out = ~18 ft TEL

That's a total of about 77 ft TEL. I'm not exactly sure the way you have the tee (blocked on one end) would count as the full 38 ft. But at the very least it would count for an elbow. In which case call it 11 ft instead of 38 and you're at 50 ft TEL.

Also not sure what the damper/tee would add. I'm sure it's a couple feet.

So under the worst case, you have far exceeeded the specified total equivalent length for that vent application. In the best case, you are right on the margin.

Sure it might work, but I'd be a bit concerned, to put it mildly.

I would also be concerned about condensate accumulation in a long run of exposed exterior pipe. I'm going to guess the possibility exists for condensing somewhere along the way. Is the piping pitched in some way to allow condensate to accumulate in a place that is not the blower or the boiler? Is there provision to drain that condensate if it occurs?
 

Last edited by xiphias; 10-04-06 at 07:54 AM.
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Old 10-04-06, 04:26 PM
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I think I read the chart wrong it says 95' for a 6" pipe and yes it's reduced to 5" only at the power vent. The pipe out of the boiler is 6" glavanized. as far as condensation is concerned it is slightly pitched toward the vent. i didn't realize the elbows and tee accounted for that much TEL but if you say 77' is what i'm at then according to the chart I am under that. Right?
 
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Old 10-04-06, 05:49 PM
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30-45 second post purge

My experience with power vented oil burners tells me to run that venter for close to 10 minutes after the burner shuts down. Failure to do so often results in a burner all fouled with carbon.
 
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Old 10-04-06, 07:09 PM
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do the math

If you go from the boiler all the way to the venter with 6", just tally up using Field's Table 3 and see what you get.

You might have to ask Lynn at Field what the TEL of the damper/tee is. I don't see it in the table.
 
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Old 10-06-06, 07:54 AM
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Originally Posted by Grady
My experience with power vented oil burners tells me to run that venter for close to 10 minutes after the burner shuts down. Failure to do so often results in a burner all fouled with carbon.
thanks, I'll have that adjusted to 10 minutes, I thinks it runs for 5 now.
 
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Old 10-06-06, 07:55 AM
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Originally Posted by xiphias
If you go from the boiler all the way to the venter with 6", just tally up using Field's Table 3 and see what you get.

You might have to ask Lynn at Field what the TEL of the damper/tee is. I don't see it in the table.
I'll check with Lynn, Do you know him personally?
 
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Old 10-06-06, 09:17 AM
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I do not know him (or her) personally. I asked a question on their forum a while back, hence my familiarity with the name.
 
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Old 10-06-06, 03:47 PM
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Post purge time

"The power vent runs approx. 30-45 seconds after the boiler shuts off."

This is why I mentioned the 10 minutes, the five minutes might be ok. It depends on how much heat the boiler retains in the chamber. If you have a problem with the nozzle assembly getting black, you can go to the longer post purge time. By keeping the venter on longer, you are sucking more heat out of the boiler. Energy is costly enough without wasting it. Try the five minutes & if you have trouble then go 7.5-10 minutes. Sometimes it becomes a balancing act between energy conservation & the burner getting nasty, costing you money for a service call.
 
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Old 10-06-06, 05:43 PM
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thanks,Scott
 
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Old 10-06-06, 08:10 PM
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Scott

As we get into & thru the heating season, please keep me up to speed on how the system is operating. I have never seen a power vented, oil fired system that worked well. I hope yours is the exception.
 
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Old 12-14-06, 07:49 PM
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Just reporting in, The power venter is still running flawlessly. Not once has it backfired or popped the reset. Scott
 
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Old 12-14-06, 08:07 PM
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Cool

Originally Posted by scottinmass
Just reporting in, The power venter is still running flawlessly. Not once has it backfired or popped the reset. Scott
Sounds like you have everything under control. I haven't looked at the pic's, but from what i have gathered, it sounds like an acceptable application. The important thing is that fields OK's it, the fire inspector OK's it, and your burner is set up to run at optimum efficiency. In 2 years, the sulfur content of home heating oil will be reduced by 97%, decreasing condensation concerns. Also, if you run a biofuel blend, it will burn cleaner. Monitoring it every month or so wouldn't hurt. Good Luck!!
 
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Old 12-15-06, 06:26 PM
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Power vent

Scott,
Thanks for the report. Hope your luck holds.
 
 

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