HTP/Westinghouse water heater options and question for a new house build

[Mikesm]

Hi everyone... We're building a big house for our large family- 9000 sq ft, with 3 dishwashers, 6 showers, and 3 sets of laundry, and everyone loves having their hot water when they want it. The house is plumbed with a recirculating hot water system, but no radiant heat as that doesn't make a lot of sense here in the mild climate of the SF Bay Area.

While our plumber does great reliable work, he's very much old school, and has never installed a unit with a stainless steel tank. While we have a whole house water filter installed, no one is comfortable going with a tankless set of units, but I want a very efficient DHW system, since energy prices here in PG&E land are crazy high. And I want a very reliable system, and one that needs less maintenance because of the busy family life we all get to enjoy.

Based on research, I think going with a stainless steel tank based unit or units would be great on the upkeep side - no anode rods to deal with, and the HTP units seem to have great reviews for efficiency and performance. So I'd like to go that route even though the plumber would like to stay with the usual Rheem or AO Smith units, and a pair of 80 gallon ones.

I am trying to find a system with strong FHR ratings, and good recovery GPH. The plumber doesn't really do the math, so that's partly why I'm asking you all for help!

We could go with a big Phoenix unit, like the PH199-119 - very strong performance, with good insulation so it doesn't lose a lot of heat when idle, but plenty of recovery heat performance. But these units seem to be very expensive ($7000) and not very available locally.

Home depot carries the Westinghouse version of the Pheonix LD line, and the PH76-80 has very good performance with a 206 gal FHR, but I am not sure it would be enough if everyone was active at once. But they are much less expensive, and I could go with two of them. Would that be overkill though?

I have room for both, but is the insulation for the LD line the same as the big brother version? I worry about all that hot water sitting around losing heat at night when everyone is at work and school, and we have the usual housework going on at home.

The other option would be to use a couple of the new 100K BTU Crossover floor units, with 130 gal FHR ratings, but the ability to keep going, and and they are a lot cheaper than the LD units, and I would not worry so much about the smaller 20 gal tank losing heat through the day and night.

But these units are very new, and not a lot of reviews that I can find. Have folks here used them? Do they have modulating burners like the more traditional HTP models?

And is it OK to go with the Westinghouse version instead of the HTP version? Are they really the same unit?They are much easier to get here.

And if we go with two units, they would need to be piped in parallel right? Anything special to watch out for with these units that we should keep in mind?

Thank you all very much!

Thx
mike

 

[Dana]

The Westinghouse units really are identical to the HTP units, but the distributor & tech support chain is through Westinghouse, not HTP. Westinghouse moves a lot of product through Home Depot, but how good their support is in your area relative to HTP is unknown to me.

There is no advantage to plumbing them in parallel unless you anticipate instantaneous draws way more than 10 gpm. Balancing flows with parallel tanks isn't possible to make perfect, but plumbed in series you get 100% of the storage volume one tank and most of the second.

Unless all six showers are in close proximity to one another, it's probably to break the hot water distribution systems in half, each supported by it's own heater, three baths on one, three on the other.

At your likely water volumes the standby losses shouldn't be first & foremost in your mind. If overall efficiency is a driver, installing a drainwater heat exchanger downstream of the showers would be way ahead of standby loss issues.

 

[Sponsor]

 

[Mikesm]

The Westinghouse units really are identical to the HTP units, but the distributor & tech support chain is through Westinghouse, not HTP. Westinghouse moves a lot of product through Home Depot, but how good their support is in your area relative to HTP is unknown to me.

There is no advantage to plumbing them in parallel unless you anticipate instantaneous draws way more than 10 gpm. Balancing flows with parallel tanks isn't possible to make perfect, but plumbed in series you get 100% of the storage volume one tank and most of the second.

Unless all six showers are in close proximity to one another, it's probably to break the hot water distribution systems in half, each supported by it's own heater, three baths on one, three on the other.

At your likely water volumes the standby losses shouldn't be first & foremost in your mind. If overall efficiency is a driver, installing a drainwater heat exchanger downstream of the showers would be way ahead of standby loss issues.

Thanks for the quick reply. Unfortunately most of the drains from the bathrooms don't go through the mechanical room out to the sewer - it wasn't plumbed that way, and none of the plumbers we talked to out here ever have put in such a system. The basement drains do go through the mechanical room's sewer ejector pump, but not a lot of daily DHW use flows through that. To be fair, the water supply coming into the house is pretty warm - the ground never gets that cold out here compared to a lot of parts of the US. Also, the first and second stories flow to the sewer line through gravity feed, and was plumbed separately so they would still work even if the basement ejector pump failed.

So sounds like I shouldn't worry about the heat loss issue. Which of the three types of units would you suggest we focus on?

mike

 

[Dana]

Thanks for the quick reply. Unfortunately most of the drains from the bathrooms don't go through the mechanical room out to the sewer - it wasn't plumbed that way, and none of the plumbers we talked to out here ever have put in such a system. The basement drains do go through the mechanical room's sewer ejector pump, but not a lot of daily DHW use flows through that. To be fair, the water supply coming into the house is pretty warm - the ground never gets that cold out here compared to a lot of parts of the US. Also, the first and second stories flow to the sewer line through gravity feed, and was plumbed separately so they would still work even if the basement ejector pump failed.

So sounds like I shouldn't worry about the heat loss issue. Which of the three types of units would you suggest we focus on?

mike

The drains don't have to be anywhere near the mechanical room for a drainwater heat exchanger to work. Fifty feet of 3/4" PEX has less than a minute's worth of shower flow in it- the heat exchanger can even be on the opposite end of the house and still do pretty well.

The primary requirement is an adequately long vertical section of drain downstream of the showers to have decent return efficiency. Even a 36" x 4" EcoDrain V1000-4-36 delivers 50% heat recovery at 2.5 gpm, the six-footer recovers over 2/3 of the heat in showering mode. At higher flows and higher incoming water temps those numbers drop a bit, but they don't fall off a cliff.

To hit those efficiency numbers the output of the heat exchanger needs to feed both the cold feed to the water heater and the cold feed to the shower mixer, but if you have to choose just one you'll still get most of the performance feeding just the water heater.

It doesn't matter if local plumbers have never installed one- this isn't rocket science. It might matter to the local code inspectors though- some want to see all sorts of documentation & certifications, and even then look askance at any device that has both potable and grey water flowing through it. But they meet code in most of the US- I only know of one that was ever disallowed. (It was in the midwest, by an inspector who insisted on seeing a stripe marking on all potable tubing on the device, which in this case was a PowerPipe model manufactured by Renewability.) But there is often inspector education required.

FWIW: This technology is under active review for how it will be included in the 2019 California Title 24.

 

[Mikesm]

Ok, I'll take a look and see if it can be incorporated... So funny no one here ever heard of it.

Any advice on which type of HTP unit to go with?

Mike

 

[Dana]

A 76K burner can handle a 24/7 full-flow shower with margin to spare at Bay Area incoming water temperatures. A pair of them can handle more than 3 continuous showers. Size the tanks to the biggest tub you need to fill, and don't worry too much about the rest. Any big soaker tubs to fill? Are you ever going to fill 4 tubs in rapid succession (or at the same time)?

A drainwater heat recovery unit can roughly double the "apparent capacity" of a tank with a small burner in showering mode, and turn a 76K burner into a two full-flow 24/7 shower.

There are other drainwater heat recovery units out there, but the V1000s happen to be the "new kid on the block" 4th generation design that's kickin' butt on performance specs relative to the rest of the pack, knocking PowerPipe off it's long held position at or near the top of the performance heap. In the US most models of PowerPipe can even be had through Home Depot, but they can also be purchased direct from the manufacturer (as can the V1000). To compare apples to apples Natural Resources Canada has this handy website (and downloadable spreadsheet). The NRCan data is third party verified efficiency based on a test protocol developed by NRCan about a decade ago, standardizing incoming & outgoing water temperatures and flow rate to be able to make reasonable comparisons.

As stated previously, your actual return efficiency is both flow & incoming water temperature dependent, and in houses/apartments with long plumbing runs there is some amount of recovered heat abandoned in the plumbing between the heat exchanger,water heater and shower. So long plumbing runs cut into the as-used efficiency, but even 100' of 3/4" pipe is still only about 45 seconds of shower flow @ 2.5 gpm, or 1 minute @ 2 gpm, roughly 10% of typical shower times. Unless you go out of the way to make the runs extra long the abandoned heat is a non-issue.

A handful of driving hours north of you Oregon has had state rebate subsidies for these things for about a decade now, but I believe that is only for homes heating water with electricity. A few other states and some local utilities/governments have similar subsidies for drainwater heat recovery.

 

[Mikesm]

So if my plumber tells me the HTP Phoenix LD 76-80 is not big enough, what would you think about coupling that with an RGH20-75F Crossover Floor unit?

It would seem that if the Phoenix LD runs out of water, the crossover unit would be able to kick in up to 75K BTU more to boost temps and support sustained hot water flow until the demand drops off and the phoenix can heat it's tank back up to normal temps.

This would also eliminate the need for a tempering valve as the Crossover has one built in. The only issue is the tank storage temp settings are fix at 127, 147 and 165 degrees. I would think if these are plumbed in series and the Phoenix is the first unit, you'd want it supplying water at a much higher temp than the Crossover would be set to so that the Crossover wouldn't fire unless the Phoenix couldn't keep up.

The Crossover unit is much cheaper than another Phoenix too, and a combined storage of more than 100 gals seems plenty.

thanks,
Mike

 

[Dana]

I actively hate the 2-tank idea using the Crossover.

Going with a bigger burner 80 gallon Phoenix (not the LD) would probably be the better solution. The PH160-80 has more burner than the Crossover + LD 76-80, and would be a simpler/cheaper install, despite being several hundred more in hardware price. The PH130-80 would be comparable in price to a Crossover + LD 76-80, and almost twice the burner of the LD, cheaper to install than two water heaters.

A 160K condensing burner is enough to support three simultaneous 2 gpm showers at a 50F temperature rise forever even without the 80 gallons of storage (and without drainwater heat recovery.) The 130K burner could run 3 showers at 40F rise without the tank. Your annual average incoming water temp is about 60F, typical shower temps are 105F, so even the 130K Phoenix is likely to be more than enough, even without drainwater heat recovery.

 

[Mikesm]

I actively hate the 2-tank idea using the Crossover.

Going with a bigger burner 80 gallon Phoenix (not the LD) would probably be the better solution. The PH160-80 has more burner than the Crossover + LD 76-80, and would be a simpler/cheaper install, despite being several hundred more in hardware price. The PH130-80 would be comparable in price to a Crossover + LD 76-80, and almost twice the burner of the LD, cheaper to install than two water heaters.

A 160K condensing burner is enough to support three simultaneous 2 gpm showers at a 50F temperature rise forever even without the 80 gallons of storage (and without drainwater heat recovery.) The 130K burner could run 3 showers at 40F rise without the tank. Your annual average incoming water temp is about 60F, typical shower temps are 105F, so even the 130K Phoenix is likely to be more than enough, even without drainwater heat recovery.

It does seem easier to just use a bigger unit. I think we'll go that way, though Home Depot doesn't carry the non-LD versions, so it may take more effort to get one.

Why did you "actively hate" the idea? The complexity didn't seem that bad...

thanks!
mike

 

[Dana]

A big-burner little-tank in series with a big burner big tank just looks and feels like a band-aid. That's one thing if you were fixing an actual problem discovered after the fact, but since this is in the design phase it's just silly. Why start out with a broken leg and a crutch when you can start out with a sturdy enough leg from the get-go?