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I just recently replaced one with an Emerson/ White Rodgers electronic control. I don't like the clamp to the bottom of the tank for the bulb. I used a piece of copper to take up the extra room in the clamp and insulated it well. Now we've eliminated the cap tube and wet/ chemical problems corroding the control. The electronic also has an adjustable offset so you can calibrate it to the milk actual temp. It has a probe temp digital display and a setpoint display . It's been working fine. Let's not even get into the flooded evaporator and subcooling valve on those Muellers.

What part of thermostat is failing if it is the points it is possible that it is a DC control circuit requiring snap action points to avoid burnout.

Just a thought, any chance the sanitation acids used in the milk house for wash down and tank cleaning are damaging the capillary tube when they drain off?

Originally Posted by btack

I don't know about milk tanks. I do know refrigeration. Is the stat pulling in the compressor directly or operating a relay? Occasionally I have seen when an OEM remote bulb stay is replaced with a stock stat off the truck. The problem is not all stats are created equally. Make sure the stat can handle the amp load going through it.

Good luck

Sent from my amazing 4G device

A Mueller 500 gal tank the t-stat will be pulling in a contractor.

Thanks btack. I'll check that. I haven't worked on this unit before, so the off the truck part is a strong possibility. The stat is wired to a panel that controls a diesel powered compressor (its an Amish dairy). John

I don't know about milk tanks. I do know refrigeration. Is the stat pulling in the compressor directly or operating a relay? Occasionally I have seen when an OEM remote bulb stay is replaced with a stock stat off the truck. The problem is not all stats are created equally. Make sure the stat can handle the amp load going through it.

Good luck

Sent from my amazing 4G device

The tank is a Mueller Model No. 10, S/N 20676 , 500 Gal. The present control is mounted with one screw and the probe slides into a U shaped strap or slot so it touchs the bottom of the tank. The probe was somewhat oxidized, so I cleaned it and we'll see what happens. I'm not really in the refrigeration business, (HVAC & Plumbing), but I'd like to help this customer if I can, since he's also a good friend and neighbor. Thanks again for any advice anyone may have. John

Thanks for the replies. I'll get that info and post in the morning. John

How are they mounted?

The screw pattern on the base can screw those up.
It twists the base and they go a bit wacky. What is in the well for heat transfer?

Originally Posted by tinnerjohn

One of my customers wants a replacement control for his bulk tank. He has replaced three Johnson A19ABA-40C Remote bulb temp controls in about a year and a half and would like to try a different brand. The only condition I can find that would shorten the life of these is the high humidity at times in milk houses, but the there is no noticable corrosion. Any ideas or suggestions would be appreciated. I like selling controls, but I'd like to try to help him get a little longer life out of them. John

What is the brand and model of the tank?
Regards TB

Milk bulk tank

One of my customers wants a replacement control for his bulk tank. He has replaced three Johnson A19ABA-40C Remote bulb temp controls in about a year and a half and would like to try a different brand. The only condition I can find that would shorten the life of these is the high humidity at times in milk houses, but the there is no noticable corrosion. Any ideas or suggestions would be appreciated. I like selling controls, but I'd like to try to help him get a little longer life out of them. John