# Parallel series ?



## ace4548 (Feb 10, 2015)

Hi guys, I'm doing my fist big commercial water heating job, with 2 water heaters. Because of space and duct work in the tiny maintenance room, we can't just T them in the middle for the waters for hot going out and cold coming in. We are doing the left heater going into the hot line first, and the right second. The right heater will then be fed cold water first and the left second. This makes sense except, the way I was told to pipe the cold is drop the cold straight down on the right and tee into the left heater. After the system is pressurized won't both heaters pretty much be getting fed cold water at the same time? The left heater will still be feeding the hot water first though. I talked to the fitter I am working with, and it didn't really make sense either. Then I asked our 5th year apprentice and he said the only thing he can think of is, the fittings create a little resistance. I have heard of the first in last out method before, but not sure if this is true parallel or not, and will the left heater feeding the hot water work harder then the right?


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## Redwood (Sep 8, 2008)

Try a Reverse Return Piping...


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## ace4548 (Feb 10, 2015)

The recirc line is tied into the cold to pre heat the water a little before it gets to the heaters... I'm a second year, so I'm not a 100% sure what you are talking about. But I think reverse return is having your return line piped almost identical to the supply to match the resistance. I have helped on a boiler awhile ago and I believe we did this.


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## Redwood (Sep 8, 2008)

This explains it pretty well


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## ace4548 (Feb 10, 2015)

Thanks a lot Redwood. This does explain it pretty well, and I understand now what mistakes we made piping now. This is why I love this site, when you are a young dumb plumber , this knowledge is very helpful


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