Heat migration

jim post

I recently hooked up a side arm heat exchanger on my domestic hot water heater. I put a tempering (mixing) device on the hot water supply just past the water heater so I can restrict the temp of the hot water to 120 degrees at my faucets. However hot water seems to be migrating from the water heater back into my cold water line and can give me a pretty good blast of hot water out of my "cold" faucet. I imagine under the right (wrong) conditions this blast of hot water could scald someone. How should I fix this?

Thanks wallies!

jp

Weezbo

i think that looks like maybe the wrong mixer.

Weezbo

the reason i post this this way is because...

no good comes from telling someone how to continue in a thing that is bad from the gate.

you want an anti scald valve,maybe an ST-12 and a check valve or two or three if you have a recirc system for immediate hot water at a faucet.

jim post

check valve

The mixing valve I have seems to do fine on mixing down the hot water temp. It's the cold water side that is causing me trouble. I don't have a recirculation system but I think you are saying a check valve on the cold input to the hot water heater will fix my problem. Is that correct? Thanks.
jp

kevin coppinger_4

You have a serious...

code violation there...The t&p valve needs to be back in the top 6" of the water heater...you have the potential to blow your house up! The reson for the migration is the lack of traping the mixing valve. You look at the instructions again. A better mixing valve would also help.

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Weezbo

Jim What Kevin said was....

you are not allowed to gate the T&P from the heater/holding tank. It is supposed to go Into the heater as to be indicative of what the real temp and pressure are at any given momment , theoretically. "Theoretically" as there are certain conditions when these things can be compromised. taking readings as it were of the pipe outside the heater would be a fairly safe bet that the compromised part would have likely already happened one day....... it is difficult to see with my eyes .i say stuff different.:)

do yourself a favor, go ask a plumbing company for a honeywell Am series ,a couple brass T's ,a ST-12 a check valve and look at the writing for the installation of the tank and valve. They have pictures...pictures help alot. i like indirects i dont have a picture handy so you can see it and go 'Oh Yeah now i see what he is saying'.

jim post

T&P valve is not gated...

from the water heater...the picture may be confusing the issue. The cold water enters the water heater through the right hand tapping. The hot water leaves the water heater through the left most tapping. The center tapping has the side-arm loop and the T&P valve...there is not a valve between the T&P valve and the water heater.

I believe the heat is moving from the water heater into the cold water line by conduction. How can I prevent this?
Thanks.
jp

Dave_4

also if your getting hotwater into your cold water line it's because you don't have a expansion tank on your hot water heater. that will fix that problem

also to prevent someone from getting scald. just install a tampering valve on the system and turn it down to where you want it this will mix cold water into the line before the faucets

good luck

thanks
Jason

brucewo1b

Jim even though the TP is not gated it has to be in the top of the tank not in the piping, and to stop migration you need to make a heat trap wich means you drop the piping 12 inches below the outlet of the water heater then install the mixing valve that way the heat will not migrate down the pipe far enough to get into the cold pipe.

Bruce

jim post

Thanks Wallies

Thanks for the explanation of and solution to my troubles. I will correct the piping. I did some more checking this evening and the heat is definatly moving through the mixing valve. Probably wouldn't get hot enough to scald anyone through the cold water piping but I would rather not take that chance.

Just out of curiosity what prevents the heat from migrating back up the cold water inlet piping from the water heater? Is there an internal check valve on water heaters?

Thanks again.

jp

brucewo1b

Inlet

If it is just an inlet then it doesn't matter as when you turn on the water the heat is transfered into the heater, but with the mixing valve there it creates a loop and the water itself starts to migrate too.