Heresy-don't try this at home...

[pybyr]

While thinking/ asking about condensing propane water heaters....

another thought crosses my mind.

My 1840 VT farmhouse has a lot less "air exchange" than when I bought it, but still has a long way to go.

I've never been comfortable with the "ventless" propane conventional combustion units of any type.

But with a condensing type propane units, the combustion efficiency and effectiveness must be pretty huge, and the condensate is removed.

I'd never run one "unvented" in a "tight" building or without CO detection.

But in my non-tight house that can use all the extra BTUs that it can get from any source, would it be utterly insane during the winter to put in a CO detector and just let a condensing water heater warm the old stone cellar a little?

 

[heaterman]

Yes, to answer your last question.

It may be fine for who knows how long and then one day something goes wrong with the burner and it starts belching out CO in the thousands of ppm.

• Waking up dead is not advisable for a good start to your day.

I had a CO call Friday, LP gas Buderus boiler and a water heater vented into an old brick chimney. The old clay liner didn't like the mid efficiency Buderus and disintegrated into chunks blocking off the flue opening.
All the exhaust from both appliances had obviously been getting dumped into the basement for a long time. There were stalagmites running down out of the cleanout opening that did not happen overnight.
So I was wondering what sent 3 kids to the hospital all of a sudden

Turns out the homeowner in an effort to winterize the old house, had taped plastic over all the downstairs windows just 2 days before. There must have been enough leakage to prevent CO poisoning from happening. Once they sealed the windows though, things got bad in a hurry.

It's not worth it. I have to say that the more "efficient houses are made, the more dangerous and less healthy they become.

 

[pybyr]

Yes, to answer your last question.

It may be fine for who knows how long and then one day something goes wrong with the burner and it starts belching out CO in the thousands of ppm.

• Waking up dead is not advisable for a good start to your day.

I had a CO call Friday, LP gas Buderus boiler and a water heater vented into an old brick chimney. The old clay liner didn't like the mid efficiency Buderus and disintegrated into chunks blocking off the flue opening.
All the exhaust from both appliances had obviously been getting dumped into the basement for a long time. There were stalagmites running down out of the cleanout opening that did not happen overnight.
So I was wondering what sent 3 kids to the hospital all of a sudden

Turns out the homeowner in an effort to winterize the old house, had taped plastic over all the downstairs windows just 2 days before. There must have been enough leakage to prevent CO poisoning from happening. Once they sealed the windows though, things got bad in a hurry.

It's not worth it. I have to say that the more "efficient houses are made, the more dangerous and less healthy they become.

Ah, good points, all of them. Are there CO detection devices that can cut power to a device? I ask only because I may want to do a very short term unvented arrangement 'til I can plumb the vent line. If efficient houses are unhealthy, my house still has no shortage of fresh air moving through it... not quite the wind that very literally blew through it when I started, but it- especially the basement- are still far from air-sealed...

 

[tom in maine]

There are a lot of ways to jerry-rig things.
Not venting any gas appliance should not be one of them.
I would be somewhat concerned about what does come out of the vent of a condensing device even if it is not CO.
The chemistry of combustion is a bit different than non-condensing units. You do not want to test this.

 

[pybyr]

There are a lot of ways to jerry-rig things.
Not venting any gas appliance should not be one of them.
I would be somewhat concerned about what does come out of the vent of a condensing device even if it is not CO.
The chemistry of combustion is a bit different than non-condensing units. You do not want to test this.

OK, consider me convinced. The two of you are individually and collectively more knowledgeable than most of the rest of us here put together. Now I just need some input (please) on whether certain makes of condensing tank type heaters are worth seeking or worth staying away from.

 

[tom in maine]

I just peeked at your other posts.
I would consider a Japanese (Rinnai, Takagi or Noritz) tankless water heater as a backup.
Some have decent efficiencies. If it is solely for occasional backup, I would be reluctant to use a condensing unit.
My 2 cents worth is that the extra efficiency (again, if for back up) might be a long payback and I am suspicious of the
longevity of condensing units.

 

[BoilerMan]

I am suspicious of the
longevity of condensing units.

I think you are absolutely correct Tom. While any condensing gas appliance will save on gas due to the phase change of the flue gasses (latent heat extraction) the combustion blowers, printed circuit controller, modulating gas valve, and miniscule flue passages, think Giannoni HX. All of these things lead to a technically superior unit with 90+ efficiencies, I do not think they will see the 20 year mark. An 80% CI, natural draft (atmospheric) boiler will have a long life, but suffers from lesser efficiency, the demand of the two units and cost of gas all should play a role in the choice to be installed. Condensing units for the occational backup can be a waste, and prove to be less than reliable when not used for extended periods.

My 2cents from a woodburner..................with no backup.

TS

 

[BoilerMan]

Another thought.
Some would say that you should install the highest efficiency unit and not waste any natural resources. You need to make the decision based on what it will be used for and how often the unit will be asked to produce heat. Just don't get anything with a standing pilot unless it is grossly oversized and cycles like mad

TS

 

[arbutus]

You've been convinced to not run and hopefully not to test the unit inside.

I was in an equipment room once that was maybe 30' x 60' when someone else fired up a pressure washer in an adjacent room the same size. They had the large overhead door open and were using it near the door. Even so, It took less than two minutes for me to develop a splitting headache because of the CO that little Honda engine was belching out. Strange enough, nobody near the pressure washer was affected.

Don't do it. Not even to test for an hour or two.

The hole saw for your vent is less than $15, and you can buy a longer 1/4 inch bit if you don't have a drill with a large enough chuck to grab onto the hole saw shank, if that is what is preventing you from doing the install properly..