No heat or hot water!

[steve80]

Any ideas on this one please?

My central heating has started working intermittently. I turn up the thermostat and it might fire up then a few minutes or seconds later it just stops. When it works it all seems fine otherwise. Could it be a thermostat problem perhaps?

I have an Ideal Classic boiler with Honeywell st6400 controller and Honeywell thermostat with thermostatic valves on all radiators.

Any help greatly received ...its getting cold!

Thankyou

 

[keithkar]

Is the pump is working ok?.

 

[ddk]

What kind of Ideasl Classic is it? Sounds like it might be a boiler thermostat fault, if its the 'classic' im thinking of, there are three thermostats in the boiler, flow, return and a flue stat (which is located into the body of the fan). They are all connected to one wiring harness (blue, red and white wires) and the harness simply plugs into a connection on the right hand side of the PCB (circuit board). This is a common fault with the ideal classics. The parts shouldnt cost more than 20-30 pounds depending on where you buy them from

 

[twgas]

I'd be looking at pump first, when the sensors pack up the boiler tends not to work at all, although that is not always the case.

 

[ddk]

it may be the pump, but the fact that it works intermittantly suggests to me that it is a boiler sensor fault. dropping the bottom cover to expose the PCB will reveal several LED's which will tell you if it is a sensor/harness fault (LED 3 will be flashing when the boiler cuts out)

 

[gas4you]

First thing I would look for, after checking there is power to the system generally, is 240VAC to the live terminal on the terminal block on your Classic.

Classic's only have one live in, so if there is no power there it will be an external control fault, eg zone valve.

Check one thing at a time, logically, until you find where the power fails.

If there is 240VAC at the boiler termianl, then the boiler needs checking over.

First thing is to check that the overheat button has not popped out.

 

[steve80]

Thanks for all your replies.

The power is on ok.

The pump seems to be working ok.

I don't feel able to look at PCBs etc I'll get an expert. I wonder if it is a boiler problem. If I turn up the stat on the boiler it will fire up for about 30 secs then stop after making some vibrating noises.

 

[ddk]

good idea steve80, although revealing the PCB is merely a matter of removing 2 screws underneath the boiler and dropping the panel down to reveal the fault finding LED's. if you get an expert to check it out, make sure you go off recommendations, theres alot of cowboys out there!

 

[gas4you]

ddk, I can't remember ever seeing a pcb 25 with fault led's on it

 

[twgas]

if it fires for 30sec after turning up stat its almost certainly a circulation problem, could be pump, lack of water, blockage etc

 

[ddk]

i am assuming it is the same boiler as the british gas RD1, which im sure it is (minus the modem connection!), but an older version may not have the LED's on the board

 

[steve80]

Thankyou all again!

With any luck I have an expert coming tomorrow.