Power Venter: Terrible Idea?

iced98lx · October 2021

Hey all! We've got an older Natural gas boiler that is working great and we are trying to keep it in service while we renovate the house and theoretically decrease the heating load (leading me to want to wait to replace it until we need a smaller one). Unfortunately, it is vented poorly (it works fine but is not well done) and the vent pipe (not a chimney) runs up through a wall we are planning to remove. We have a six inch outlet on the side wall (walk out basement) that previously served a down-draft stove vent that I could re-use for a power vent and solve the other issues... Will I regret this?

Local HVAC companies are used to mostly forced air systems and don't really want to put one in, they are all saying just replace it with a new one (of the same size) that is power vented, I want to consider multiple system design changes when the time comes to change the boiler.

Thoughts, opinions? It's a 250k BTU boiler so I'm looking at a Field Controls SWG-5. This will be the only appliance served by it (the water heater is already a power vent).

Damien · October 2021

Very interested in following this discussion, as this is similar to my situation.

We removed a wall and found the b-vent for the boiler running through it. We want to get rid of the b-vent on the first floor. Our options are 1) have a chimney company replace existing vent with an exterior chimney or 2) replace the entire system with a direct-vent system.

I'm leaning toward the new system but would love to hear some advice, thank you!

SuperTech · October 2021

Why not use the same power vent that the water heater uses? I'm not a big fan of power venting. A chimney just works, nothing to break down and fail when you need it. And they tend to be noisy. I'd go with a chimney if possible.
250,000 BTUs? Must be a very big house. Would 6" venting be adequate for such a large boiler?

Another thing to consider is that a power vent isn't as simple as just installing it and letting it run. Power venting alters the combustion and the draft over fire needs to be set and proper combustion confirmed with a digital analyzer. Safety switches need to be installed. This is not a DIY project.

iced98lx · October 2021

SuperTech said:
Why not use the same power vent that the water heater uses?

I mis-typed, it's a direct vent water heater, meaning, it's built into the water heater with just a PVC pipe off the heater for venting.

SuperTech said:
I'm not a big fan of power venting. A chimney just works, nothing to break down and fail when you need it. And they tend to be noisy. I'd go with a chimney if possible.

The "chimney" is just a single walled 8 inch galvanized pipe that has made every HVAC professional shake their heads when they see it and needs to be moved anyhow. I don't disagree the simplest option is the best in any case it can be used for. Perhaps I need to evaluate building an exterior chimney and running it over to it. Sadly the boiler is sort of in the middle of the house.

SuperTech said:

250,000 BTUs? Must be a very big house. Would 6" venting be adequate for such a large boiler?
;

we're heating about 4100sqft, the boiler is very over sized. This is the size field controls suggests for the BTU rating with my estimated 25ft of horizontal run:

SuperTech said:

Another thing to consider is that a power vent isn't as simple as just installing it and letting it run. Power venting alters the combustion and the draft over fire needs to be set and proper combustion confirmed with a digital analyzer. Safety switches need to be installed. This is not a DIY project.

This is the part that is most concerning to me, I want to have the combustion tested and adjusted this fall anyway but it will certainly require a visit.

iced98lx · October 2021

A call to field controls yielded interesting results. Their answer was basically "Yeap, you can do that keep the 8 inch over to a PVG-300 then from the PVG run 4 inch out the house."

EBEBRATT-Ed · October 2021

@iced98lx

I am not a big fan of power venters either. I wouldn't want to have one long term they can be finicky but if i's a year or two and then you change the boiler then go for it.

That being said even if it's not going to be in use long it needs to be installed and adjusted to code and the boiler combustion checked.

In fact it wouldn't be a bad Idea to combustion check the boiler first so you know what your getting into

Carbon monoxide doesn't care

pecmsg · October 2021

the weathers still mild have you considered downsizing now?

iced98lx · October 2021

EBEBRATT-Ed said:
@iced98lx

I am not a big fan of power venters either. I wouldn't want to have one long term they can be finicky but if i's a year or two and then you change the boiler then go for it.

That being said even if it's not going to be in use long it needs to be installed and adjusted to code and the boiler combustion checked.

In fact it wouldn't be a bad Idea to combustion check the boiler first so you know what your getting into

Carbon monoxide doesn't care

Boiler was converted from LP to NG in May and was combustion checked/tuned then after I requested it, it runs great despite its age.

pecmsg said:
the weathers still mild have you considered downsizing now?

No, we are in the middle of a 2-3 year renovation and part of that includes insulation and enegery improvements to the house, I'd really like to wait until we know more about what we'll need then vs now if that makes sense. I'd also like to ditch the slant fin in favor of floor heat, but that's another post for another day

Power Venter: Terrible Idea?

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