Stumped

Steve Minnich

I was in a boiler room today that had a 1.4 MBH steam boiler, piped correctly, short cycling due to inadequate main vents.

Here’s what I don’t get. There was a strap-on aquastat on a vertical return above the water line, wired in series with the pressuretrols.

What is it’s purpose?

Danny Scully

What was it set to? Is there a tekmar control or a heat timer control somewhere?

Steve Minnich

It was set to 200F and there was an R & D Contol.

EBEBRATT-Ed

What's and R &D control?
Have seen aquastats on large steam boilers to keep the burner on lo fire until the boiler gets warm. Obviously not used for that.

Just a guess. Inadequate venting building not heating well radiation short of steam so they shut burner off if the return reaches 200. radiation cold returns hot. Maybe a banging pipe limit LOL. As mentioned could be a "heat established" sensor for a heat timer as mentioned above but not wired that way

Steve Minnich

R and D is a very popular steam control manufactured and used here in Chicago. I see that one more than Heat Timer or Tekmar.

KC_Jones

To detect steam at end of main for timing the cycle perhaps?

RayWohlfarth

Steve I have seen aquastats used to keep the burner at low fire until the boiler water reaches a certain temperature.

Steve Minnich

Thanks guys. I bet that's what it is, Ray. The aquastat for low fire and the operating pressuretrol for high fire?

Steve Minnich

Two stage Weil LGB-12

RayWohlfarth

@Steve Minnich Typically The operating control was set for the desired operating pressure and the aquastat will keep the boiler at low fire until the temperature reaches the setpoint. Once it does, the burner goes to high fire until the call the firing rate or operating control changes it

Steve Minnich

Thanks Ray. I appreciate the help.