Two different sized DHW heaters. How to pipe?

Matt_38

Four showers in the house. Two have 6 body sprays & a shower-head EACH! One 200+ gallon whirlpool and all the other (normal) stuff that goes into a typical McMansion. Customer's expectations are; one bather (showerer)at a time with time to recover tank capacity before the next in line. Super small mechanical room will not allow any more storage capacity. I just want to give them the bigest bang for their buck with what I've got. Taco 0011 will do both coils. They'll be piped reverse return not primary/secondary as stated in my original post.

Matt_38

Trying to pipe in two indirect water heaters and wondering what

the best way is to accomplish this on the domestic side.

If the two are piped in parallel won't the smaller tank run out first, then begin mixing cold water with the larger capacity tank?

The two indirect coils I believe should be piped primary/secondary so the boiler water temperature across the HXs should remain fairly evenly distributed with a lower delta T. (I think)

Seems to me that the domestic side should be piped in series with the lead water heater being the smaller, the lag tank being the larger and the sensor inserted into the lead tank's well. A thermostatic mixing valve will be used on the outlet side of the lag heater to mix down 140* DHW to 120* I believe this is the technically correct way but I thought I'd ask before it's done improperly.

Can't seem to find any links on either the BNP or Penton archives on this subject although I know thre have been articles written on this subject.

Your help is greatly appreciated.

Larry Weingarten

domestic side

Hello: I can comment on the domestic side of thing. Your idea for piping the tanks in series sounds good as long as it won't produce too much flow restriction. I would add three ball valves each to create isolation and bypass capability. Thars my two cents.

Yours, Larry

Tundra

What kind of a domestic hot water demand are you anticipating that you want to place two indirects in series? I would have a separate circulator for each unit.