Water heater energy choice & instant hot water - new construction

[Chicagoan]

I received a lot of good advice & info in the boiler forum about radiant heat in my new construction home. Thanks everyone! I now had a couple of water heater questions and would appreciate any advice.

1. If you had a choice (new construction) which fuel would you choose for a water heater - electric or power vented natural gas? Normally, I'd take natural gas but have no experience with power venting. How reliable is it? How noisy is it? (I've replaced 3 water heaters over the decades in my current home due to leaking - not once did one fail due to an ignition problem - but these were all vented into a chimney.) I'm thinking maybe it's better to pay the extra fuel cost for electric than adding multiple failure points with a motor, blower, sensors, etc. Are these things pretty reliable over the life of a water heater?

2. Based on searching the forum, I gather the best instant hot water setup is with a separate return line, which I can do with new construction. I didn't find any discussion about specific pump brands. I've found that Grundfos, Taco and B&G all have instant hot water products. Is their reliability pretty much the same (leave it up to the plumbing contractor) or should I specify a particular brand?

Thanks in advance for any & all info and advice. Merry Christmas!

 

[Dana]

If you have a space heating boiler, use the boiler to heat the domestic hot water. Set it as the "priority" zone on the zone controller. Recirculation loops (if desired) would be the same as with any water heater.

The additional duty-cycle on the boiler increase the net efficiency, and the standby losses of an indirect are generally lower than a standalone power vent. It's important to insulate the near tank and tank-to-boiler plumbing though.

 

[Sponsor]

 

[LLigetfa]

If you had a choice (new construction) which fuel would you choose for a water heater - electric or power vented natural gas?

I had that choice when I built and chose gas but it was not power vented. Electricity rates here are high and recovery time on electric is slower which would have required a larger electric tank.

After the first tank failed, I had to change to a power vent as that was all I could find height-wise that could re-use the hole through the wall. It was a terribly noisy unit and I regretted it. I should have patched up the old hole and made a new hole up higher. When the second tank failed, the third tank was taller again and it could not use the existing hole. This third one is power vent too but much quieter than the previous.

 

[Chicagoan]

@Dana - Thanks, didn't know about that option. Will have to discuss it with my builder. Only worried about the initial cost vs. just plopping down a regular water heater.

 

[Dana]

In my neighborhood in competitive bidding, adding an indirect will run $800-$1800, depending on the equipment options and how hungry the local plumbing trades are that season. It's more expensive than a minimum-legal-efficiency standalone, but it'll last twice as long. Since it doesn't need an exhaust vent it has the advantage of using the cheaper energy source with faster recovery times than an electric tank, and it has lower standby losses than a cheap standalone.

An indirect doesn't usually need to be as big as a standalone to deliver the same more first-hour gallons, since many smaller boilers still deliver 2x or more the 30-32,000 BTU/hr output of a typical 50 gallon standalone. A 35-40 gallon unit is fine for most people. As long as it's big enough to fill your biggest tub, the recovery times are lightning quick, and most setups can deliver a continuous 2.5 gpm shower forever (but not two simultaneous endless showers.)

What boiler are you installing? Don't let them talk you into upsizing the boiler for the domestic hot water load, which is (almost) ALWAYS a mistake. Sizing the indirect for the hot water load, and sizing the boiler for the space heating load is with rare exceptions going to be the right solution.

 

[Chicagoan]

That's pretty reasonable seeing that it will last longer and be more efficient. Of course, though, all the 'reasonable' options add up. I'm not there yet. Don't know the boiler yet. GC just wanted me to put together my first pass want list - heating, trim, door style, hardware, plumbing fixtures, general type of flooring for all rooms, etc. I'm trying to spec out as much as possible at this point to get the build cost. After I get that and recover from the shock, I'll have to figure out what I can keep and what goes. But I might as well put in for everything that I want now - can always leave stuff out.

Thanks again for the info. This is all pretty daunting. Other plumbing stuff was pretty straightforward - just went with Kohler everything. I've had Kohler in my current house and have been pretty happy with it.

 

[Jadnashua]

SOme of the indirects have a SS tank, and have a lifetime warranty. Now, if they do fail, it doesn't include the labor to replace it, but the tank itself is 'free'. Unless you have a huge tub you want to fill, as Dana indicated, often, you can get by with a smaller one. The better indirects are very well insulated. I had a boiler issue over a weekend recently, and I didn't want to pay the overtime to fix it (couldn't get the part I needed). I took three hot, but short showers over the next three days until I could get the part and still had hot water. Course, I do have a large tank for a 6' tub, but still...a standalone gas-fired tank would have been cold fairly quickly (relatively speaking)...an electric one, might have stayed warm for awhile, but I do also keep my indirect fairly hot (with a tempering valve), so it functions as an even larger tank.

I've never noticed the house cooling off after using a lot of hot water from the indirect as a priority zone...the recovery rate is quite fast, and it gets back to heating the house without noticing.