Signs of bad pressurestat ??

#1: Post by **CSME9** » January 17th, 2011, 11:03 pm

Isomac TEA with 3 yr old mater P stat
Power light is on.
Boiler heats up, green and red lights cycle on/off ok.
Drain 5-6 ounces of water thru group and both green & red lights turn off, boiler pressure starts dropping from 1.2 to .06 then red light goes back on and cycles again to 1.2.

Problem started 3 days ago after a boiler and HX descale.

Thanks, WS

#2: Post by **another_jim** » January 17th, 2011, 11:29 pm

The red and green light are connected to the normally closed and open sides of the same switch. If both go off, that switch is jamming, and the pstat needs to be replaced. This is different from the pressure diaphragm freezing into one position, since that can sometimes be "exercised" back to life.

#3: Post by **Randy G.** » January 18th, 2011, 1:10 am

Started after a descale might mean that there is loose scale that worked its way up into the the plumbing of the pressurestat or the diaphragm. mIght try removing it and cleaning it. maybe.