Out of Control

coldinNE

The system is a Slant/Fin Sentry S120 continuous pilot gas boiler, FHW, 2 zones 2 circulators, each with a Honeywell R845A relay. The system has a Johnson Controls series M35 Y15 automatic damper system and a Honeywell L8148E Aquastat. The system has worked well since installed 11 years ago. When either stat is turned up to call for heat, the Aquastat contacts close and the circulator runs, but the damper does not open and the burner does not fire (the pilot is burning).  If I slap the Aquastat with my hand 2 or 3 times, the damper opens and the burner lights and burns for 30 seconds to a minute, then goes off, and the damper closes. Water temp gauge reads 75 degrees F, and pressure reads about 7 PSI, and the readings do not change materially during the short burn. Any help is greatly appreciated.

Ironman

Does Your...

Vent damper plug directly into the 8148E? If so, try checking the plug connector for good contact. Otherwise, you may need a new aqastat.

bill_105

Try this

Get the shaft in the open position. Then turn the power off to the boiler. Then remove the cover to the dampener. Remove the wire at terminal A and stick it on B. Turn power back on. Or, Move A to B and, using a wrench, rotate shaft in direction of arrows until vertical  If all is now well, be warned those things are not cheap.(for what they are).

coldinNE

reply to Bob

Bob,

Thanks for the suggestion. the damper has a harness that plugs directly into a molex connector in the 8148 aquastat. I disconnected it, connectors appeared sound and not corroded. I reconnected and the burner still does not light. I might try a new aquastat if i could be sure it was not something else.

Ironman

Also Try ...

Jumping a wire across the actual limit switch in the 8148E. It's the part with the dial on the side. Do it momentarily and see if the damper opens and the burner fires. If it does, the aquastat is bad. If not, either the damper is bad or the relay in the 8148E is bad. I'm suspecting the relay contacts since tapping the control opens the damper. Make sure all connections are tight.

Ironman

One More Option...

If the aforementioned didn't work. Try momentarily jumping "R" (red) on the limit switch to "B1". If the burner fires, the vent damper or connector is bad. If not, replace the 8148E aquastat.



Look at page 10 of the attachment.

coldinNE

Reply to Bob.

Bob,

Thanks for the roadmap for troubleshooting the circuit. I will take out the volt/ohm meter and jumpers tomorrow.

coldinNE

Reply to Bill

Bill,

Thanks for a good suggestion. I moved the damper to open, switched A to B, and powered up. The burner did not fire. I powered down, moved B back to A, and powered back up. The damper promptly closed, and the burner never lit. The green LED, which is supposed to light to signal that the damper is open, never came on, even though I slowly turned the damper into the fully open position. Slapping the Aquastat no longer operates the damper or the burner. Sounds like a problem in the Aquastat to damper connections, as others have suggested, or problems in the damper circuit board. I will test further tomorrow by opening the damper and jumping connections in the aquastat. Thanks to all for the help.

Tim Potter

exacr same problem

Had same prob, bad solder joint in 8148e, relay contact, circ would run fine, but no 24v to open the damper. On my slant/fin sx-150, int pilot,b1& b2 run the damper motor & the yellow wire on z supplys 24v to the gas valve when the vent damper switch closes. I had to bang on aquastat to get damper to open, and burner to light too. Jumper solved problem so I could have heat, Beckett aquasmart is on way to solve for good. Slant-fin wiring is diffrent than honeywell version when a vent damper is used. If you need further info, don't hesitate to ask.



Tim