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Steam boiler pressure too high on startup

Posted: Tue Apr 10, 2012 1:19 pm
by BeRad
Typcially I turn on the steam boiler (SB) twice a day sometimes I leave it on for 15minutes, sometimes for a few hours, either way I've never had an issue.

Well, I haven't used the SB for a few weeks and the other day I turn it on and leave the room while it warms up. Long story short the 'safety' on the SB activates and there's steam all over the kitchen. I look at the pressure gauge and it's reading about 2bar, the boiler light is not flashing. I purge some water and the pressure drops to normal but begins rising again (again I don't recall that the boiler light was flashing). The machine has no alarms. I turn the SB off.

I do a couple of checks, like making sure the vacuum breaker isn't stuck, and everything seems OK. 30minutes later I turn the boiler on again. This time it warms up like normal (I hear the vacuum breaker pop right before the pressure begins to build) and it remains fairly stable at 1.35bar. I consider my earlier experience to be a random event and shut the machine down for the day.

The following day I turn on the SB (from a cold machine) and it begins warming up normally but again the pressure continues to rise towards 2bar. The boiler light is solid during this time. I purge some water and it settles at 1.35bar. I turn the SB off, let it loose all it's pressure and then start it back up again and it remains stable at 1.35bar.

This scenario now plays out the same every day. From a cold start the SB pressure keeps rising (again the boiler light is turning solid when pressure is at 1.35bar). After the initial purge everything seems to be stable. If I shut the SB off, let it cool down for a while and then turn it back on everything is fine.

I checked the vacuum breaker (but didn't clean it) and it seems to function properly but perhaps it isn't. The temp probe also seems to be operating properly since it looks like it is turning off the heating element once the correct pressure is reached.

Any ideas what could be causing this? Or where I should be looking?

Re: Steam boiler pressure too high on startup

Posted: Tue Apr 10, 2012 7:36 pm
by az erik
Overfilling the SB on startup? I don't know as I just got mine but the SB pressure is dictated by the SB temp right? sound like the temp is reading wrong on start up. If you purge all the water from the boiler does it do the same? Oh BTW I noticed on mine the fill probe wire and one other actually got nicked some how by something. Possibly putting the back cover back on. My wire leads up from the back of the boiler, right up the center of the back.

Re: Steam boiler pressure too high on startup

Posted: Tue Apr 10, 2012 8:09 pm
by GDK
Just to make sure I understand. First time warm up, you say that pressure climbs to 1.35bar at which point light stops blinking and stays on solid as if the boiler heating element is off, though pressure continues to rise to 2bars despite of that.

Does your machine control the steam heater with a triak (which has a fan you can clearly hear when heater is on) or is it a relay?

Re: Steam boiler pressure too high on startup

Posted: Wed Apr 11, 2012 2:24 pm
by BeRad
Machine has the SSR, no fan. It's also a 220VAC version.

I tried to pay closer attention today to what was going on and of course things worked just fine. In the morning when I turned the boiler on the pressure went up to around 1.7bar (much higher than normal) and I did notice that the boiler light was flashing until ~1.5-1.7 bar, not turning solid at 1.35 as I previously stated. It then went solid and the pressure settled down to 1.35. I flushed the boiler a few times and each time the pressure went back to 1.35 bar w/ little overshoot. I turned the boiler on again after work and it went straight to 1.35bar. Flushed a few times and after every refill, it settled at 1.35bar.

I may put this issue into 'monitoring mode' versus 'active troubleshooting' until it starts happening consistently again. Thanks for the replys.