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eric_40 Member Posts: 4
in Gas Heating
a Friend has an 80% efficient, 10 year old Forced air Tempstar furnace. The Chimney collapsed because there was no liner installed. She had a sidewall vent installed and I think there should be an barometric damper installed. What do you think its Only an 8 Foot run with 2 90's.
You can't just stick a flue pipe out the side wall with an 80% furnace. It needs a Field Controls or Tjernlund side vent kit for that. And I believe a damper is part of it or a needed component.0
You can only sidewall vent an appliance with a power venter or inducer if the appliance is certified to use a SPECIFIC one. Otherwise it is an illegal installation! And it can be dangerous to the occupants of the dwelling!0
I do not believe any appliance can be certified for a power venter or inducer because it is field installed. It may be listed by the manufacturer as acceptable but that would be it. When it comes to venting most manufacturers, they say follow everyone else's instructions and use approved materials.
All power venters and inducers are either UL or CSA listed for use on gas appliances and that is all the approval that is needed.0
sidewall power venter
Jim is essentially correct with one caveat: if a mfr. of an appliance specifically forbids sidewall power venting, then no. Otherwise, there is a "transfer of liability" or an "assumption of risk" on the part of the power vent mfr.. Regardless, a few rules: the power vent must incorporate a pressure switch that proves a pressure change signifying supposed sufficient air flow. This is not bulletproof but is considered an acceptable safety control. The powerventer must be interlocked. Basically, on a call for heat, it pre-purges, senses sufficient negative pressure, closes the contact to the furnace controls and allows the normal sequence of operation to continue. Should be vent become blocked, loss of power, or thermostat satisfied, the fan de-energizes, vent pressure equalizes causing the pressure switch to open causing the furnace to shut off. Now, some can incorporate a post purge cycle, which is desirable to mitigate condensation.
You still must maintain stated clearances to combustibles on vent pipe unless specifically tested as listed as a system. Same with vent sizing, unless engineered system accepted by the AHJ. Check local codes for vent termination restrictions over and above national codes and the product listing. The most restrictive requirements apply such as height above snow line.0
I am sure if it is a new sale no manufacturer is going to jeopadize a sale. Existing installation might be different.
The odd installation was the standard water heater. Because there was no electric, the water heater had to come on before the venter. A gas pressure switch on the pressure tap of the gas valve turned on the venter. No air proving switch, just spill switches mounted on the barometric. Happy to say in 30 years not one unsafe failure.0
As a voting member of several national gas codes and once an appliance certifier, the appliance must be certified to use a specified power venter! One cannot use whatever on an appliance that is NOT certified to use it! if it ain't in the certified instruction manual of the appliance, then one CANNOT modify the installation with a power venter!0
retro-fit venters can work great
The Tjerlund power venters I have installed are basically a mechanical 'B' vent. They are certified to connect to any appliance rated as a cat 1 or B-vent appliance. When correctly selected and installed; the appliance is interlocked so it can only fire once a vent proving switch is closed.
The simplest wiring arrangement has the venter interrupting the thermostat circuit so when the t-stat calls for heat; the venter powers up, after the vent switch closes a pre-purge timer counts down and then a relay closes and the call for heat is passed on to the appliance that then fires. At the end of the call for heat the venter has a post purge that runs before it shuts off.
Apart from issues surrounding initial noise, and increased noise/vibration as the unit ages, they work great. My own view is they are a better B-vent. A standard B-vent can spill if venting conditions aren't perfect, these units shut the appliance off before that happens. They are a great alternative to trying to make a long, cold, exterior chimney work.
Make sure you check the instructions for the specific unit you are installing, but generally if the appliance it is attached to has a draft hood, then the draft hood stays and no baro is needed. if it is an induced draft appliance with no draft hood, then a barometric damper has to be added as per instructions. You will need to get a permit, and ask your inspector to have a look at the instructions before you start.
The key here is the unit has to be carefully selected (they have dozens of different versions for different applications) and you must, must, must follow the instructions exactly.Home Owners Please Note:
You are receiving advice from some very skilled pros completely free of charge. One of the reasons I participate is to sharpen my own troubleshooting skills. So; did we get it right? I would be grateful if you extend this courtesy back by posting the final outcome of the issue you are inquiring about. Thanks0
Power venters and inducers
According to the National Fuel Gas Code the mechanical fan must be listed. It most cases the installation must follow the mechanical fans instructions. When it comes to venting manufacturers of equipment rarely provide their own instuctions and only refer you to follow someone else's.
I never allow a power venter or inducer to be installed without a barometric. Even with a mechanical fan, pressures change, wind changes, temperatures change etc. which will affect the combustion process. Barometrics nullify these effects.
Only a O2 or CO test at the outlet of the heat exchanger verify if flue gasses are venting. Match tests, smoke tests and draft tests only verify the chimney is functional, but do not identify what is going up it.
I keep hoping some day they will remove that crap from the Code book.0
As a voting member of B149, I can attest that if the appliance is not certified for a power venter, it CANNOT be vented by one! That is the code! NFPA54 has a similar requirement. So no power venting if the appliance has not been certified for it in the certified I & O manual!0
Per tech services at
Tempstar that furnace can't be sidewall vented. That being said I would also check with local AHJ. We all know how checking with the manufacturer works as they are very careful not to stick their necks out.0
I am pretty sure when Ultra Vent was recalled the approved repair was to use a power vent system. I do not know any that were specifically certified with any appliance, only recommended by certain manufacturers. This wasn't a choice, it was mandatory.
As far as I can tell, there is nothing in NFPA 54 that states you can't use power venters on anything you want. Some local authorities may not like them but they are approved venting devices. Power venters are part of the flue system, not the equipment which means it has nothing to do with the equipment manufacturer. They only state the appliance should be vented properly, not how.
The only reason not to allow them would be the lack of trust in the knowledge or mechanical skills of the contractors. A power vent sytem is considerably safety than a conventional flue. It has safeties to verify it is working whereas standard flues do not.0
""A power vent sytem is considerably safety than a conventional flue. It has safeties to verify it is working whereas standard flues do not. ""
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