I'm going to attempt to help you out.
First i have a question for you. Was this problem an "all of the sudden problem" or was some type of was the unit worked on, manually shut off, or anything like that?
Ok, i've done a little bit of research online, and i believe i may have found something that may be able to help you.
Around page 11 it talks about faults.
Yes, it is difficult, but i will attempt to try. If i am not able, i will opt out and allow another expert to try and help you out.
Ok is there anyway you can reset the reset, so to speak?
Can you shut off power to the reset, does that reset it?
If you can get the unit to try to start and tell me what happens as its trying i should be able to help you figure out whats wrong.
I see, ok. Well the Venter Motor (fan) is designed to power vent the exhaust gasses out the flue. There is a pressure switch that is activated when this fan turns on that signals the board that it can begin the ignition process.
However what you've described to me is that the fan isn't running currently.
Which could mean one of three things, the fan motor has failed, or the thermostat isn't calling for heat, or the stat is calling for heat but the board isn't letting the fan turn on(which could be due to a failed circuit board or because of the lockout)
Do me a favor, try and hold the reset button in for a full 60 seconds and see if this resets the system.
Please could you let us have the light sequence on the blue light and the reset light. This is the worcester fault code.
For example blue light flashing fast and no reset light or flashing slow with reset light lit.
I see what you're getting at. Would a faulty fan prevent the pump from running? Also the thermostat you mention would be the overheat, flue or limit stat rather than the room thermostat.
Blue indicator light flashes slowly..on/off every second approx.
Reset button flashes on/off apprx twice a second.
Cool, sorry to interupt but always good to sart with the fault codes.I'll leave you in capable hands.
Fault codes pre 08 section page 58.
No problem alex, if you think you can better answer this question feel free.
A faulty venter motor or pressure switch would prevent the system from beginning its ignition sequence (gas valve open, ignitor initiates, ignition, flame sensor sensing flame, circulator circulation hot water)
As far as whether that could keep the pump from running, it really depends how the pump is wired in. If it is wired in that whenever the stat calls for heat that the circulator may start, or it may have to wait for the system to ignite.
If anyone of those switches you mentioned are open or faulty, it could keep the system from activating.
Well your best bet is to go with what the book says as to what the problem is. Sorry i was not able to better help you.
If you have more questions feel free to ask.