Best way to heat a demand of up to 35gpm?

CoachTonyM

We're looking to update our master bathroom which will feature a whirlpool tub and a new 'smart shower' system that may draw as much as 35 gallons per minute.

We plan on upgrading our water supply system, to include replacing almost all of our old equipment an, except the Boiler (>100K BTU).

My initial question is what would be the best (indirect) Boilermate unit for us (60 degree rise)?

The largest one we've found is 115 gallon tank, but I don't think that will supply the potential demand.

Any guidance for a layman homeowner?

Larry Weingarten

Hello, You could always add a second tank, but I'm curious about the 35 gpm. Seems it would be hard to breathe with that much water! I'd look into shower heat exchangers as they can cut the hot water need in half while still giving a big shower. Maybe look at lower flow heads as well.

Yours, Larry

Zman

35 GPM is a lot of water. Do you know what the duration is?
I would love to see the specs for a shower that uses that much water.

Jolly Bodger

What size pipe are you going to feed 35 GPM through? Without checking my resources it seems like it would be over an inch. That would be like taking a shower with a fire hose.

Jamie Hall

Your problem at 35 gpm isn't going to be heating the water -- it's going to be getting enough water at any temperature. As @Zman said -- specs on that shower, please?

B_Sloane

that could be 1mm btu/hr there ....

Jolly Bodger

Assuming a 60 degree Delta-T (50 EWT 110 SWT) you need a water heater with 1,045,800 BTUH to keep up. A 100 gallon tank would last 3.5 min, or mixed down 4.5-5 min.

Have you thought about the size of drain pipe needed for 35 GPM?

hot_rod

Is the water lateral suppling the home able to move 35 GPM?

A 4" shower drain?

SuperJ

Storage will be your friend. You can put tanks in parallel but they need to be piped carefully to balance the flow.
What is the total consumption over an hour? 35GPM can't be happening for that long?

Makes sense to buffer the load over a longer duration with some tanks. Maybe a 200kbtu modcon with an array of indirect tanks. I don't think a million btu boiler makes sense for intermittent loads. You would probably be running a whole new gas line out to the street.

Agree that heat recovery makes sense on the shower, and there are a bunch of ways to pipe it. Probably makes sense to just to preheat the cold line with the drain water heat reclaim to reduce the amount of hot water needed (probably by 50%).

With mixing valves you add capacity to your tank. If you keep the tank at 140-150f and mix it down to 115 you will get proportionally more gallons of hot water since you're diluting.

With those kind of demands, and the potential costs for the equipment you're talking about. I'd recommend getting the system engineered. Over sizing and throwing a lot of $$$ at it is not engineering :-), this might be what some contractors will be tempted to do initially.

B_Sloane

SuperJ said:

Storage will be your friend. You can put tanks in parallel but they need to be piped carefully to balance the flow.
What is the total consumption over an hour? 35GPM can't be happening for that long? I don't think a million btu boiler makes sense for intermittent loads. You would probably be running a whole new gas line out to the street.

.

A residential service can not supply that amount of gas

pecmsg

Smart Shower that uses 35 GPM?

not too smart!

Leon82

The smart spa modules I have seen had 3/4 connections.

Maybe a few body sprays would use 3.5 gpm

Is it possible the Jets in the tub itself will circulate 35 gpm? That would make more sense.

So if you want to fill the tub as fast as possible you would want to look at tank storage

mikeg2015

That’s like 16 standard 2.2gpm heads. Wow! The can’t be right.

You need an engineer to design that so you can sue someone when it doesn’t work right.

As mentioned, you would need probably two 100 gallon indirect Tanks on a 400k boiler and 1-1/4” pipe feeding it and a commercial cold water supply, larger sewer connection, gas supply.

I’m guessing it’s more like 6-7gpm and 35 is the whirlpool tub as mentioned.

Zman

One post wonder.....