Indirect Water Heater Aquastat Accuracy

Adam_2

I'm having a very strange problem with my Vaughn 50 Gal Indirect water heater. Despite the setting of the aquastst, the water is getting way to hot. (around 160 degrees)

I have tested the aquastat, and even replaced it, and the problem remains. I am now confident that the Honeywell Aquastat is good, and the zone valve is working fine. Even set as low as it goes, my water temp stays above 160. The problem this causes is regular blow-off from the overpressure relief valve, not to mention excessive running of the boiler system, and inefficiency.

It seems to me that the aquastat sensor is not getting a good reading from the water heater. There is a long thin copper "cylinder" about 6" into the tank that is supposed to transmit accurate temp readings. The aquastat bulb seems a little loose in the cylinder. Perhaps there is some kind of thermal transfer medium that should be used?

At my wits end. Basement flooded twice, now I have the blowoff plumbed into my sump pump. Thanks in advance for any suggestions.

Adam A
diverex@optonline.net

Bob Bona_4

postive that the

zone valve is closing? Yes, heat transfer paste is nice, but from what I've seen, the stuff gets like glue after a few years and you can pretty much forget about pulling the sensor out in one piece. The next suspect is a bad thermostat. Is the tank piped correctly..in/out? Ghost flow up the return?

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Steve Minnich_1

I use

Honeywell's L6006 1145 and find them to be very accurate. A little pricey at around 70 bones but well worth it.

I also use them in conjunction with new boiler's aquastats for the same reason. Accuracy.

Steve

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hot_rod

Take a piece of

1/2" copper about as long as the well. Slit it open the long way and flatten it out. Then cut a strip and bend it into an angle. Slide this in with the sensor buld to get a better "connection"

With a little practice you can build a taper into the piece so it tightens up as it nears the bottom of the well. Don't over do it or you may puncture the cap tube.

Heat transfer grease is still a good idea for corrosion and "ease of slide"

Used to see these copper strips shipped with some wells. They had a little tab on the end to allow removal, also.

Although there could be other problems, aside from the aquastet well, causing the overheat, as other mentioned.

hot rod

Adam_2

Thanks. You think like I used to...

Zone valve works for sure. Thermostat tested fine (I hooked up a continuity tester to it while dipping the sensor into different buckets of pre-heated water of known temp.) Replaced it anyway, as the plumbing supply house had one for me to try. Still same problem. So, I'm thinking its not the aquastat. As I'm told, these Honeywell units are pretty reliable.

As far as the plumbing, well, I'm pretty sure it's hooked up correctly. As I said, the unit works, it just doesn't shut off the heating zone when it reaches high temp setting.

I guess this is better than taking cold showers...

Thanks again.

Adam_2

Great Idea

That sounds like a great idea. I'm going to give it a try and let you know how it works.

Thanks!

Adam_2

Honeywell

That's one of the things I liked about the Vaughn, it came with a Honeywell Aquastat. I'm on the second one with identical results....

John Penwarden_2

Indirect Water heater Aquastat Probs

I have a similar problem with my Crown susper-stor. It gives me 140-150 water when set to 120. This only happened recently after I set the temp to 180 for a day of equipment sanitizing. Now it never gets below 130. I confirmed that the stat was working OK, although I've been told the Honeywell L4080B1295 is not the most accurate device. I also confirmed that the zone valve is working correctly. I will try the previously noted trick of adding copper to the well to try and get the sensing probe in better contact with the well tonight..

John_21

Indirect

You may want to drain tank and pull the well out it may have scale on water side. Scale is a great insulator. Have used Locktite C5-A anti-seize it is copper based for probe lube.Also on pump flange bolts. John

Adam_2

Too Little Space

There doesn't seem to be enough space in the well to allow for added copper. I even tried with a piece of 14ga copper wire, but couldn't make both the probe and the wire fit together. With such a close fit, I would think thermal transfer would be great. Oh well, manufacturers rep is supposed to call me today, I will let you know what I find out.

Adam

Adam_2

Scale...

That's a very good point. I'll let you know.

Thanks!
Adam