Taco Mixing Valve Is Thermosiphoning

Glenn Sossin_2

Install check valves on both hot and cold sides. Could be a press differential between hot and cold sides at the tempering valve causing water to bleed across the valve.

pennron

hi:

I just had a Taco 5000 mixing valve installed with a watts expansion tank on my Burnham alliance indirect water heater. The heater is now set to 135 degrees and the valve is at 120 degrees. I will experiment with those numbers as time goes on.

The problem is that the cold supply side of the Taco valve is as hot as the hot supply side. This thermosiphoning goes all the way down the cold side to the inlet of the water tank. I'd say thats a good 8' run in 3/4" pipe. I bgt a 3/4" copper trap which the plumbing supply said will help. However I've read about check valves that should also be installed. The supply house did not know of this.

If this is the solution do I use both the trap and the valve (pz let me know what valve to get) and where does the trap and valve go. On the hot or cold side. Thanks...

Weezbo

cold water side sing check.

i think an ST-5 or 12 is also a Sound idea.

Big Ed

Longivity

The trap will help it last longer. The valve sitting in a pocket of hot water will break down faster. The trap if properly sized would work with the check .

Unknown

did a small job

Did a small job with water heater and flat plate with pump on both side... Customer complaining of overheating... Read it somewhere from one of St Holohan books and installed heat trap piping and springloaded check valve.... No more complains....

pennron

taco 5000 pic

hi:

Thanks for responses. I have included a pic of the installation. The watts exp. tank is installed on the cold water side. The hot water comes out the top of the indirect heater. The cold supply pipe coming out of the mixing valve, thru the exp. tank and all the way down towards the floor is HOT.

Can someone explain where and type, model etc, check valve I should install. The web literature says the check valve should go on the cold side. It also says I should have installed the mixing valve below the hot water outlet on top of the tank (8-12"). I can re-do that but rather not. I have a 3/4" copper trap that can also be installed but I don't know where. Any suggestions are appreciated.

clammy

thermal traps

When ever i have used a mixing valve for just about anything i pie in a thermal traps no promblems in many many years because of it ,here's a pic of one peace and good luck clammy

pennron

thermal traps

hi:

thanks for that pic. It seems that you do not have any check valves in that setup. At this point I would like to install a check valve. I just do not know which side it should go on. Logic says the HOT side so that when flow is stopped, hot water will not bleed to the cold side.

It seems that the way my setup was piped a trap is now not feasible and the check valve is the easier solution. What do you think?
thanks

clammy

my thoughts

Personally i usually always pipe in a thermal trap instead of check valves i would only use check valves for re circ wheather it was using a pump or gravity but in most cases just re orination of some piping with thermal traps usually elimates thermal siphoning ,in some cases i have ran into i have heard chattering of check valves on opening of large usage fixtures like tubs and in some cases washing machines .I usually just stick to what has worked for me in the past i firmly believe in keeping it simple and have used and found thermal traps to work well usually a 14 to 24 inch trap is more then enough ,i would also put some hangers on that expansion tank if the tank bladder ruptures and fills with water it would become a little heavy .here's another shot of a thermal expansion tank set up which allows for ease of checking water pressure and charging the bladder side alot easier to perform and change if need be sorry about the pic but if you look closer you will see what i'm touching upon peace and good luck clammy

pennron

traps and check valves

clammy:

nice setup. Thats your house. wow. Thanks on the hanger advice for the tank. I was going to do that just havent gotten to it yet because I think I may have to repipe this. According to Taco the thermal trap should be piped below the COLD water inlet of the water heater for this mixing valve. However, on my Alliance indirect, the cold inlet is about 2 " off the ground. It looks like you have the same Taco valve as I do with the green cover. looks like you were able to trap it because you did not have a problem going below the cold water inlet from what I can determine.

Since thats impossible for me we piped it as shown. So I am in the dark about how to trap this. ANY SUGGESTIONS? Lastly, if I open the piping up to re-do this how does it affect the expansion tank? Do I just have to make sure there is 40lb pressure in there before I close the piping up? Thanks....

clammy

how to

i would make a trap where your cold water lines ties into your mixing valve and on the hot water tank outlet i would turn the elbow down and drop it at least 12 to 20 inches and then tie it back into the mixing valve as you can tell i set them up that they can be easiely isolated or bypassed if need be you could also just make a inline trap for the tanks cold water inlet in general i always try to hook up the mixing valve so bith the cold and the hot water lines or better said that the mixing valve itself is below the traps ,i know this because i try not to ever do the same mistake more then once so you get a little anal retentive so that all the install go with any call backs peace and good luck clammy

Rookie

Taco 5000

Thermal traps are very important on piping systems where there maybe thermal syphoning or a system pressure differential. In the valve box there are installation instruction take them out and review them, in them you will find the suggestion that if you are having thermal syphoning you need to locate the mixing valve below the cold water inlet ( in this case to your indrect water heater)at least 12". The photo you posted doesn't show any isolation valves, as the instruction illistrate they are recommended for, isolation, servicing or maintenace of the valve. The Taco 5000 is an excellent valve, and should provide your client years of trouble free service, provided it is properly installed and under the correct water conditions. Good Luck.
More info:
http://www.taco-hvac.com/uploads/FileLibrary/102-080.pdf


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bob young

bravo

Picture perfect job. i might have added temperature gauge , pressure relief valve & draw offs for draining for service to mix. valve. insulators on kindorf straps nice touch. thought i was only one that would do that. lol.

don_185

DIY

Diy job..no doubt.

As you can clearly see it was not setup for service down the
road.It also clearly shows that the instruction were thrown
out with the box.

No biggie...we will talk you thru it.Amazing!!

pennron

DIY JOB

Hi:
Thanks for response. Yes no doubt this is a DIY job done by me. I am just trying to save some bucks by doing it myself. Let me state that I did install shut off ball valves. If you look high in the left corner you can see one of the valves with the yellow handle. I just chose to install them farther up the line. I guess most would have installed them closer to the mixing valve so you bleed less water when servicing...

I am going to re-pipe this on friday. I purchased a watts 601s check valve and liquid filled thermo gauge. While I will repipe this so that the mixing valve is 8-12" below the top of the tank to create a thermal trap my BIG QUESTION is this: In this setup in the pic, where DO YOU INSTALL THE CHECK VALVE??? The cold water supply is coming in on the RIGHT side of the expansion tank.

From what I read the check valve should go to the right of the expansion tank. That would place the expansion tank between the heater and the check valve. Is that correct?
Thanks...very important concerning the pressure build up...

Dave Larsen_2

check valve location

Yes, put the check valve on the cold side of the expansion tank. The temperature migration you are having is due to expansion of the water as the temp. increases. Thw water has to expand somewhere, and that place would be the tank! With your tank located so close to the tee in the cold water line and the slope of the pipe upward, I'll bet you get more migration north than the Texas border! A well placed 3/4" swing check will take care of your problem.

pennron

check valve location

Dave:

Yes thats what I thought. I'm a newbie but logic says that the hot water that is thermosiphoning into the cold side thru the mixing valve should go into the expansion tank first, expand, then hit the check valve which will stop any further siphoning into the cold line.

While the theory is when I re-pipe it trapping the mixing valve, I probably will not need the check valve, I will install it just in case. Its not supposed to affect my water pressure to my fixtures (pressure drop) and it supposedly is silent...just extra insurance and I don't see any drawbacks...

Dave Larsen_2

pressure change

I really don't think the trap will do you much good. what you are experiencing is caused by pressure change. That change will move up, down, and sideways, and right past your trap. The trap is designed to stop thermal syphon, not pressure change. Hope this helps.