Y Plan Boiler Not Turning On

[Bobthebuilder95]

can you post a close up of the boiler terminal showing what the terminal not used is please

Hi see below:

 

[ianmcd]

OK there is a wire missing there, the permanent live to the boiler, the boiler must have a permanent live for the pump to work

 

[stem]

'P/L' is Pump Live. 'L' at the other end is the Permanent Live.

If the boiler has a pump overrun it's probably been connected directly to the boiler and hence the vacant P/L terminal.

 

[Bobthebuilder95]

Thanks for all the replies. I'll check tonight to see if all the switched lives are working as they should. If they are that basically only leaves the boiler circuitry and the pump wiring?

 

[ianmcd]

[yes your pump on that boiler has to be wired direct to the boiler, and not the wiring center

 

[Bobthebuilder95]

Just reading the manual for the boiler and one of the suggestions is to check the manual bypass valve is open, where is this and what would it look like? Bit of googling keeps coming up with automatic bypass being fitted now?

 

[stem]

As you have a Y-Plan they don't always have an external by-pass fitted because the 3-Port valve can never close both outlets (HW & CH) simultaneously and so there is always a circulation route open. Even if there was one I don't see how it would stop the boiler and pump from starting up in the first place, AFAIK it would just cause an overheat situation later on.

My expertise is electrical, so the gas guys can probably give a more definitive answer.

 

[Bobthebuilder95]

Not ideally, because there could be a fault in the wiring between the wiring centre and the boiler, and it wouldn't test that.

If you wanted to try a test, you could check the various parts of the controls are generating the required signal. Either of the below when the system was operating properly would cause the boiler to run, by generating 230V on the boiler S/L terminal.

1) Check the orange wire in the MID POSITION VALVE terminals with the heating only on and room thermostat calling for heat, should give 230V (hot water to be set off)

2) Check the wire in terminal 1 of the CYL STAT with the hot water only on and cylinder thermostat calling for heat, should give 230V (heating to be set off)

And in both cases is the boiler S/L terminal live also?

Just done this test summary as below:

With heating on and water off orange wire isn't live only the blue one is. Switched live on boiler is also off.

With water on and heating off cyl stat brown cable is live and switched live on boiler is also on (at 35-40v)

Any ideas?

 

[Bobthebuilder95]

Just done this test summary as below:

With heating on and water off orange wire isn't live only the blue one is. Switched live on boiler is also off.

Also cylinder stat is live when water is off but switched live to boiler is off in this case.

With water on and heating off cyl stat brown cable is live and switched live on boiler is also on (at 35-40v)

Any ideas?

And when the hot water is off the cyl stat is still live but switched live to boiler is off.

Finally there's no power from the honeywell relay (from the wireless thermostat) even when on, is this usual?

Many thanks Rob

 

[Bobthebuilder95]

Photo of the airing cupboard incase I am missing something obvious!

 

[stem]

With heating on and water off orange wire isn't live only the blue one is. Switched live on boiler is also off.

So that's wrong. The valve isn't switching the boiler on when heating only is selected. The blue wire is neutral and should be 0V, but you have to be careful taking adhoc measurements, as the components are interconnected and stray voltages and currents can appear. Also make sure you are measuring the voltage using a genuine neutral as not all blue wires are. The mains supply N or better still the N in a local socket outlet would be best.

Can you repeat the test, again, with the HW off at the programmer and cylinder thermostat and the heating on at the programmer and room thermostat. This time you are looking for 230V on the MID POSITION VALVE white wire. If there's 230V there can you check the orange wire again also. Without changing the controls from the above, can you check the manual lever underneath the motorised valve, is it loose & floppy or is there resistance when you slide it.

With water on and heating off cyl stat brown cable is live and switched live on boiler is also on (at 35-40v)

So that's as it should be and as you say the switched live is at 230V, the other end of that wire is the one I referred to below, so the boiler should have come on.

a check for 230V on terminal strip ST2, and terminal Lr

 

[Bobthebuilder95]

So that's wrong. The valve isn't switching the boiler on when heating only is selected. The blue wire is neutral and should be 0V, but you have to be careful taking adhoc measurements, as the components are interconnected and stray voltages and currents can appear. Also make sure you are measuring the voltage using a genuine neutral as not all blue wires are. The mains supply N or better still the N in a local socket outlet would be best.

Can you repeat the test, again, with the HW off at the programmer and cylinder thermostat and the heating on at the programmer and room thermostat. This time you are looking for 230V on the MID POSITION VALVE white wire. If there's 230V there can you check the orange wire again also. Without changing the controls from the above, can you check the manual lever underneath the motorised valve, is it loose & floppy or is there resistance when you slide it.

So that's as it should be and as you say the switched live is at 230V, the other end of that wire is the one I referred to below, so the boiler should have come on.

Thank you just as I tried to do that as I turned the boiler back on the pump kicked in. However the boiler had a fast flashing blue light and didn't ignite while the pump kept going.

Tried to reset the boiler by holding it on the reset position for 5 seconds to no avail so turned it all off and on again. Now back to how it was before with the pump and boiler being entirely unresponsive!

 

[Bobthebuilder95]

So that's wrong. The valve isn't switching the boiler on when heating only is selected. The blue wire is neutral and should be 0V, but you have to be careful taking adhoc measurements, as the components are interconnected and stray voltages and currents can appear. Also make sure you are measuring the voltage using a genuine neutral as not all blue wires are. The mains supply N or better still the N in a local socket outlet would be best.

Can you repeat the test, again, with the HW off at the programmer and cylinder thermostat and the heating on at the programmer and room thermostat. This time you are looking for 230V on the MID POSITION VALVE white wire. If there's 230V there can you check the orange wire again also. Without changing the controls from the above, can you check the manual lever underneath the motorised valve, is it loose & floppy or is there resistance when you slide it.

So that's as it should be and as you say the switched live is at 230V, the other end of that wire is the one I referred to below, so the boiler should have come on.

Just did this test and there was 135-140v on the white and orange and still the 240v on the grey.

 

[stem]

Sounds like a loose connection somewhere, or maybe a failure of the connections at the back of the wiring centre PCB, check the security of the connections around the area you were disturbing. If you can, would you be able to turn the power off and insert a wire link between the mains L and Mid Position Valve white wire (they are conveniently next to each other) so that they are electrically connected. Then restore power. What happens?

 

[Bobthebuilder95]

Okay so trying it again the heating settings have no effect however once the hot water is turned on by itself and thermostat up the pump kicks in and after a few seconds the boiler has the fast flashing blue light and the pump continues to run constantly.