Water heater Advice

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Phog

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Hi, new poster here but I have been lurking on & off for several years. Every time I have a question about anything plumbing related, I just come here and search through old forums posts. I have learned so much.

Here is my question for today. I presently have a natural draft water heater that vents into an old chimney stack (my house is 110 years old). I am getting a new roof put on in about a month and a half. I am going to have the chimney taken down below the roof line as part of the job. The full chimney will come out at some point in the future but for now it's just the external stack coming down, so that I don't have to deal with a hole in the roof down the road.

This means I have to figure out what to do with the water heater. The existing unit is only 2 years old (Kenmore 65 gallon 9-year high recovery unit. It's a rebranded AO smith). There are of course two basic options. I could build a 4" B-vent up through the chimney stack and put a termination cap on the roof. Or I could move to something that is direct-vented.

Other concerns that come into play are as follows. First, there are 3 units in this house including mine (all 1BR), with common utilities (I am the landlord). Second, in winter the incoming service water is very cold -- I have not measured it but I would guess around 35deg. I upgraded from 40-gal standard to 65-gallon high recovery and I still can definitely feel the water cooling down if I get in the shower immediately after one of the tenants. And finally, I travel for work. A lot. Reliability is extremely important, I have ways of getting repair work done while I'm out of town but it is definitely sub-optimal.

So far I have had 2 big local HVAC companies come through and asked for their recommendations. Both are highly pushing tankless, and specifically Navien NPE-240A. I am not feeling good about that -- I don't think I'll get the water temp rise out of it that will be needed in the winter, even with the 199k BTU input & recirc loop, to supply multiple units. I also am skeptical of of the reliability record. But these HVAC sales reps don't even seem to want to talk about power vent tanks. I am wondering if they get kickbacks from the manufacturer or something.

Another option I'm considering is the HTP Phoenix light duty. I am scared of the condensing units from Rheem & especially AO Smith, they seem to have lots of problems, but lots of good things being said about HTP. The problem is that there doesn't seem to be any information about local installers or servicers. I sent out an inquiry the other day to HTP, waiting to hear back from them. I could definitely tackle the install job myself, if I had a lot of free time, but with the work travel + the 6 week deadline to coordinate with the chimney removal, I just don't see that happening. I suppose I could pick up an electric tank as a temporary stopgap if needed, but slow recovery would get old really quick when winter starts. And if the HTP ever breaks down, and I'm not around to diagnose / repair, I am not sure I could get it serviced. But I do really like the extremely high recovery + the stainless tank. Seems like I could get 20-30 years out of it.

Last option I'm considering is regular power vent. I think a 8-year 75gal Rheem high recovery, for example Pro+G75-76N RH, would probably suffice. If I put in a tempering valve and crank up the setpoint to 140 it would probably outperform my existing system (have my present unit set to 125). But again I am a little scared of the reliability. Not that there is anything wrong with these units as far as I can tell, it's just that there are more moving parts when compared to a natural draft / pilot light system for "forget about it" factor. At least if something happens while I'm out of town I should be able to get a plumber in there to diagnose & repair quickly.

Or, the thought has crossed my mind to perhaps get a pair of 40-gallon power vent tanks, plumbed in series. This way if one goes out it is just a reduction in hot water for the tenants & not a show stopper. But I'm not sure how the venting would work -- can multiple power vent tanks share a single intake/vent system?

Anyway I know the people here eat up this kind of stuff, and I am very interested to see everyone's thoughts and suggestions. There doesn't seem to be a clear cut answer to me. Thanks!
 

Dana

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There's nothing wrong with going with a regular power-vent, but if your place is heated with a hydronic or steam boiler (like most 100 year old homes in Rochester are) you'll probably be better off adding an indirect hot water heater operated as a zone off the boiler. It'll be more money, but it should last 2x as long, and deliver better hot water service than a big-burner tankless.

So, if there's a boiler that could be used here, what is the make/model/vintage of that thing?
 

Phog

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There's nothing wrong with going with a regular power-vent, but if your place is heated with a hydronic or steam boiler (like most 100 year old homes in Rochester are) you'll probably be better off adding an indirect hot water heater operated as a zone off the boiler. It'll be more money, but it should last 2x as long, and deliver better hot water service than a big-burner tankless.

So, if there's a boiler that could be used here, what is the make/model/vintage of that thing?

Thanks for the response Dana, this house never had a steam boiler/radiator system, it previously had a gravity induction air furnace -- also very common around here in that era. Anyway it now has a high efficiency forced-air gas furnace.

I think I am now leaning back toward keeping the existing natural draft water heater, and just installing a 4" B-vent in place of the masonry chimney that's being removed. The main reason I was thinking of direct-vent before was a misunderstanding of the 2015 changes to the WH efficiency standards. Someone told me that large (75gal+) natural draft water heaters were being phased out, and that only power vent was going to be allowed in the future. This seems to be incorrect though. So if I can just keep getting natural draft water heaters into the future, and go out through the B-vent, why throw away my 2-yr old tank?

The only small drawback is that I wanted to reclaim all of the square footage freed up by chimney removal (it's about 2ft x 4ft and goes through living space on 3 floor before going out the roof). I am looking into oval B-vent instead of round, to try and fit in inside a 2x6 wall.
 
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