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DHW sizing

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Brad White_9
Brad White_9 Member Posts: 2,440
Hi Jeff,

Here is a posting I gave on March 25th. It has been years since I actually <i>did</i> any plumbing engineering on a regular basis but took the course back in 1987-88 for what it is worth. HVAC is my gig :)

See if this helps you. I should also look through my older notebooks in my "archive" and tickle those long-dead brain cells back in my head.


-Brad

<i> Date: March 25, 2007 04:40 PM
Author: Brad White (bewhite@rcn.com)
Subject: Fixture Units

The way I was taught (before software and perhaps other modern methods) was the Fixture Unit method proulgated by the American Society of Plumbing Engineers (ASPE), not to be confused with the Canadian Territories Plumbing Engineers (CANTPE). :)

Each fixture is given a value roughly proportional to the amount of hot water it uses.

These numbers are added then compared to what is known as Hunter's Curve (this is not a type of archery equipment; don't make the same mistake others have made! ;)

Hunter's Curve allows for diversity, that is, an allowance that all fixtures will not be drawing all at once and that the more fixtures you have connected, the fewer as a total percentage will draw at any one time.

In other words, a single apartment may have simultaneous shower, laundry and possibly dishwashing activities, but a half-dozen such apartments are less likely to be doing all things in each unit at the same time. Thus a single apartment will have a greater demand percentage than a larger complex.

I do not have my tables handy otherwise would spot you some better advice. But my point here is that you should ask to see your contractor's methods and assumptions both in GPM and GPH rates regardless of the type of system you choose to use finally.

Burnham and other companies may have tables available on their web sites for you to cross-check too.

(http://forums.invision.net/Index.cfm?CFApp=2&Message_ID=327870) </i>

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