Huge combustion air vents are making my house too cold!

[motoguy128]

I disagree. One tankless would rarely give the same preformance when a contractor thought that two 50's were appropriate. Custom homes usually mean more bathrooms than typical and high end tubs/ multi-head showers, etc. On top of that you are almost certainly not accounting for the reduced BTU capacity that goes with most locations in Colorado, a fatal thing to disregard in this state. That being said, niether of us knows without more information.

It would depend on the BTU capacity of the water heaters. IF they are both 75k BTU units, then I would tend to agree that 1 300k tankless would fall short. However, keep in mind that's it's atill a single family home, and I'm well aware of winter water temps. We hit record lows of 35F incomming water temps here this winter. That still gives you 5gpm at 112F. Plenty to fill a soaking tub and still use a handwash sink. But it might fall short if there was one of those stand-up showers with 20 heads that uses 15gpm. In that case... well in that case, even the 100 gallon storage would run out quick.

A compromise could be to add an electric water heater just as a storage tank and have it just maintain at 120F for hygenic reasons, set the tankless to the same and use a mixing valve to drop it to 115F. IMO there no need to run domestic water over 115F.

[jmac00]

It would depend on the BTU capacity of the water heaters. IF they are both 75k BTU units, then I would tend to agree that 1 300k tankless would fall short. However, keep in mind that's it's atill a single family home, and I'm well aware of winter water temps. We hit record lows of 35F incomming water temps here this winter. That still gives you 5gpm at 112F. Plenty to fill a soaking tub and still use a handwash sink. But it might fall short if there was one of those stand-up showers with 20 heads that uses 15gpm. In that case... well in that case, even the 100 gallon storage would run out quick.

A compromise could be to add an electric water heater just as a storage tank and have it just maintain at 120F for hygenic reasons, set the tankless to the same and use a mixing valve to drop it to 115F. IMO there no need to run domestic water over 115F.

the OP said the tanks are 40K btu (which I think is light for a 50 gal) but read up a few posts and you'll see the BTU rate.

[firecontrol]

An economics point of view. By the time you insulate and add a space heater and the cost year after year to operate the heater you might find that it would be cost effective to change out the 7 year old water heaters with sealed combustion units of some kind.

Some of the aspects are cost vs cost comparisons, but others are comfort and practicability issues. If your home's hot water system has a constant circulator installed that assures hot water at your taps all the time, or even on a timer, you might be able to use a sealed combustion instantaneous water heater with a large electric water heater in line with it. Just a thought.

[RAMHS]

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[beenthere]

RAMHS, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here.

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Further infractions may result in loss of posting privileges.

[ckartson]

You may consider Installing MOD's ( motor operated dampers) in the combustion air ducts. You would need a pro to do this because the dampers would need to open on any burners call for heat. Both dampers would have to open and provide proof of opening before either burner can fire. This is commonly done in boiler rooms. This may not be possible because many resi hot water tanks don't have provisions for this sequence but some of the direct vent models do. You would need to have someone assess the equipment first.

[darctangent]

dampers are not possible. If you check the OP's post above you will see he has natural draft water heaters. f.y.i the OP appears to have vanished. he appears to be a semi DYI personality.

in my opinion this thread is getting filled with all sorts of extraneous posts that cloud his need for onsite pro. depending on the nature of his issue, the OP may actually have a dangerous condition. He needs a pro.

[randyl712]

I've not vanished, just taking it all in - were there questions of me still unanswered? I'm very appreciative of the replies here, it's a troublesome issue for us and we want to get it resolved.

I'm open to having a pro out to the house - would I just want a standard HVAC technician? I've had bad luck with young kids who didn't know what they were doing in the past.