Posted by Wes on October 26, 2001 at 23:35:13:
In Reply to: Re: Instant Highfire! posted by Robert on October 26, 2001 at 07:25:41:
It you can find a wiring diagram for your boiler because yours most likely is not wired the same as mine. Unfortunately wiring diagrams have a tendency to get lost or stuck to the inside of the control panel were they turn brown and get covered with dirt.
If your controls are set up so setting limits the fire rate when the boiler is on automatic then there would have to be some kind of controller between the pressure transducer and the modulating motor. If this is the case then I would check that control and the wires going to it.
If fire rate on auto is controlled only by the tranducer and boiler is going to high fire when it shouldn't need to I would check the following.
Setpoint on pressure transducer. Has somebody changed it?
Short or open circuit on wires going to pressure transducer.
Leak on control line or blockage in control line.
: Wes, if I understand you correctly, I need to check the pressure transducer then. And yes, when Boiler ignites it lights off in low fire mode and then moves to potentiometer setting ( while in manual mode), however, in auto mode, it bypasses setting and goes to high fire.
: : This is how our CB-350's normally operate.
: : When they are on manual the potentiometer controls the fire rate.
: : When they are on automatic the fire rate is controlled by a pressure transducer.
: : Normally when I test LWCO's the pressure drops enough that if it were on automatic it would go to high fire.
: : I am assuming that the boiler lights on low fire then goes to high fire. If it lights on high fire then your modulating motor or the wiring going to it is probably bad.
: : : I have a Cleaver Brooks 125 hp firetube boiler generating 100psi steam. This morning I discovered that after blowing down boiler and after prepurge boiler came on line as normal but went to 100% fire even though it was set to only go to 50%. In automatic mode it is bypassing the preset setting (ignoring it) and continuing to 100% fire. When I switch to manual mode it will stop at the preset mode of 50% fire. Where should I start looking for the problem? Modulator motor?
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