Re: Runaway Boiler
Posted by Greg on October 18, 2001 at 10:44:23:
In response to Re: Runaway Boiler
I have been working on my boiler lately as well. The aquastat relay sends a 24 volt signal to your thermostats. That should always have power. When the thermostat is turned up it makes a connection and sends the 24 volt signal to the zone valve and tells it to open. When they open it sends a signal to the aquastat and it tells the pump to kick on. I would first look at the thermostats and see if they are stuck closed (making a connection). Good luck.
: Coming home to an 80� house in 65� weather isn't good, especially when the zone valves are all set to 63�!

: I have a 2 year old Vaillant boiler with Honeywell zone valves and a Honeywell Aquastat relay, type L8148E. Since the zone valves were all energized, I assume something on the relay board has gone south. Does this seem reasonable? If so, does the board have to be replaced as a unit? OR, can the individual components be replaced? Of course, if this isn't the problem, does anyone have an idea where to start looking?

: Also, the water temperature had reached 190�, considerably higher than the output from our old boiler. Is this near the temp that you would expect to see the pressure relief kick in?

: Thanks. Any advice will deffinitely be appreciated!

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