Aquastat Failure

[m_kenney]

Hello all,
When i moved to rural maine, one of the first people that I met was an aging farmer who quickly became one of my good friends. I end up tinkering on a lot of his stuff. He heats two of his houses (he owns 7) with wood boiler, his personal residence being heated by a heatmor. Last year was the first year that I worked on his wood boilers. That heatmor has been going through aquastats like crazy, I must have put three in that machine, and I have had to rewire it at least twice when the fire ran away on him.

He mentioned to me the other day that he lost another aquastat. All the aquastats he gave me to install were scavenged from old boilers. He was thinking that he hit the back wall too hard throwing a log into the firebox. I've never taken one apart so I can't speak to their cause of failure. Does anyone have any ideas? I was thinking about replacing the Honeywell aquastats with detroit switches, we used them in the navy and they were pretty reliable. They were also shock tested for use in naval combat. Im curious to know the thoughts of the group.

Thanks, matt

 

[all night moe]

Were those old boilers sitting out in the elements? Could be the aquastats had partially corroded leading to failure?
Why not just try a new stat of any good name?

 

[m_kenney]

Were those old boilers sitting out in the elements? Could be the aquastats had partially corroded leading to failure?
Why not just try a new stat of any good name?

Some were, he's got at least two sitting in a field, one in a 3 wall pole barn, and one inside a barn, but they didn't look corroded. I'll see if I can get the old farmer to spend some money

 

[gthomas785]

Are these 120v aquastats? I'd put an amp clamp on one leg and see how much current is getting pulled through, if it's a large inductive load like a blower that rapid cycles I could see that burning through contacts pretty quick. Maybe wire the aquastat to control a heavy duty contactor that carries the motor loads.

 

[mustash29]

Might want to try a Johnson Controls A419. I recall several folks using them on boiler build threads and heat pump water heater threads.

Page 12 of the pdf shows the contacts are about 2x higher rated than a typical boiler aquastat.

OpenBlue, Building Automation and Controls Knowledge Exchange

docs.johnsoncontrols.com

And they're about half the price.

https://www.supplyhouse.com/Johnson-Controls-A421ABC-02C-Single-Stage-Digital-Temperature-Control-120-240v-SPDT