Heat trap


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Old 11-06-06, 03:40 PM
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Exclamation Heat trap

I'm installing a mixing valve on my new indirect. Here are instructions for one I'm putting in http://giveme5.honeywell.com/Product/mixingvalve/AM%20Series%20Mixing%20Valve%20-%20Tech%20lit%20and%20installation.pdf

It shows to make a heat trap on cold supply side (fig.1.1) to prevent heat loss (at least some of it). However my indirect instructions have no provisions for one. http://buderus.net/Portals/16/S120-IOM-01.pdf
Do you guys normally make one or it's a waist of time/material?

Also, looking in indirect instructions, they install back flow preventer on supply and don't show expansion tank, WTF?
I'm definitely installing one, just wondering why would they do that?
 

Last edited by zaq123; 11-06-06 at 03:50 PM.
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Old 11-06-06, 04:37 PM
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Grady could provide more insight, but I can offer that indirect piping instructions seem to be among the more variable. Everybody does boilers essentially the same way, but indirects seem to have more options or at least more is open to interpretation in the application.

FWIW I have exactly the same mixing valve (AM101C-US-1, 3/4"). The piping is not specifically a heat trap in terms of the 6" called for in Fig 1.1 (it's less), but I do not observe significant heat migration, either. Nor do I have an expansion tank for the indirect. I think expansion tanks might be required above a certain size indirect, or perhaps by local code?

I will say that running the indirect at 140F and mixing down is really nice. Very consistent and predictable water temps at all taps; provides a an effectively larger reservoir of DHW for handling peak and dump loads.
 
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Old 11-06-06, 04:51 PM
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Prv

As far as I know, and I am a DUMB homeower, the expansion tank is only needed if you have a PRV or backflow valve between the supply and cold water inlet on the DHW tank. Otherwise, there would be nothing to take up the hot water expansion and you would be blowing the relief valve. I have the Amtrol indirect, and I did make a simple heat trap on the hot water port to stop heat loss. The trap is on the hot water side of my Sparco AM101 tempering valve. It seems to work, the pipe going to the U is hot, the other side is cool. I've noticed a lot of the indirect tank manufacturers are calling for the use of vacuum reliefs on their tanks, other the warranties are void. Did your instructions mention using one?
 
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Old 11-06-06, 05:19 PM
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radio, if you look at fig 6 (indirect manual) they call for vacuum breaker/purge valve. They are not going to get it in my install.
Shut off, check valve, expansion tank and maybe vacuum that's all for cold feed. Maybe put something like this at the highest spot http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/8311/cid/2047
 
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Old 11-06-06, 05:43 PM
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or something like this one perhaps?? http://www.kingsolar.com/catalog/mfg/conbraco/37-302.html

I think the device is there to protect the tank if vacuum or negative pressure developed. I surmise it which would damage the plastic liner, as is used in the design of my Amtrol indirect tank. The only way I could ever see that happening is if someone valved off a HOT tank, and allowed it to cool--the contraction would pull a vacuum. That shouldn't occur normally unless there is a PRV and a shutoff valve on the hotwater out. A bladder tank would certainly prevent a vacuum if it is always in line (in my opinion only!!).. I could never get a clear answer at the local plumbing stores, however. All conjecture on my part.

Pete
 
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Old 11-06-06, 07:13 PM
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Heat Trap, Etc.

My two cents:
I always install a heat trap. Got in the habit years ago.

Many local codes do require the expansion tank. Make sure you get one made for water heaters not a boiler expansion tank or well tank.

Never thought about it but R/C has a good point about the vacuumm breaker. Some of these tanks are pretty thin. They will withstand pressure but not much vac.

Okay, that's three cents, so shoot me.
 
 

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