Valliant Boiler - pls help troubleshoot

[Ambienz]

Hi,

Have a Valliant Ecotec Plus 637 system boiler that is showing no error codes and S.0 (no demand for heat), but it is not heating.

Have checked that it is receiving switched 240V heat demand from controller into PCB, so believe it's just a boiler issue.

Boiler was working fine up until needing to fix leak in UFH manifold and swap over TRV rad valve. When boiler and heating system refilled and turned on again, boiler didn't respond to heat demand. Water pressure showing 1 bar on the LCD.

I noticed that water pressure was very low when I switched it off, to the point that I would have expected it to stop heating but it hadn't.

Have tried resetting, power down and on. Have had a look at PCB and other than some spark discharge at the Ignition Transformer connection there are no obviously blown components.

It probably needs some pressure in the expansion vessel, but that wouldn't explain the S.0 code.

Is there a way to manually force it to heat, to try and isolate the problem?

My thinking is that if it is getting demand for heat but responding that no demand for heat then it may be PCB.

What else should I be thinking about?

Thanks

 

[John.g]

If its a combi is it firing up on DHW demand?, if heating a cylinder is it firing with a demand for cylinder heating?.

 

[Deleted member 120897]

If its a combi is it firing up on DHW demand?, if heating a cylinder is it firing with a demand for cylinder heating?.

Op states system boiler, starts with a 6 too. @Ambienz - does the boiler fire for hot water demand? I doubt it’s the pcb.

 

[Ambienz]

If its a combi is it firing up on DHW demand?, if heating a cylinder is it firing with a demand for cylinder heating?.

its a system boiler, but its not firing up at all - despite getting a request for heat from controller

 

[Ambienz]

Op states system boiler, starts with a 6 too. @Ambienz - does the boiler fire for hot water demand? I doubt it’s the pcb.

no boiler doesn't fire at all for either heating from controller or hot water from cylinder thermostats

 

[Deleted member 120897]

Have you looked at the motor valve(s)? Are the temperatures set properly on the display? I would check the voltages in the wiring center.

 

[John.g]

S.00 says "NO heat demand" so, as above is a motorized valve(s) opening?, if so the end switch of this should give a run signal to the boiler via orange wire, grey wire to the motorized valve is permanently live.

 

[Ambienz]

Have you looked at the motor valve(s)? Are the temperatures set properly on the display? I would check the voltages in the wiring center.

perhaps Im wrong but there are only 2 relevant wires into the boiler. The permanent live and the switched live. I've checked that the switched live is providing 240v . Is there something else I should be checking?

Yes temp settings are OK.

Which motor valves - external ones are OK. Internal?

 

[John.g]

The motorized valves are external, zone valves and supply the switched live to the boiler which you say is live so would point to a boiler problem, you could switch off the CH and HW demand and check for no voltage on the switched live to prove it, when you switch it back in with either CH or HW demand listen for the fan starting up and check the d and s parameters again if no fire up.( and any f fault codes)

 

[Deleted member 120897]

perhaps Im wrong but there are only 2 relevant wires into the boiler. The permanent live and the switched live.

Depends on boiler and type. If it’s the same as the EcoTEC pro Combi then it’ll be pins 3 and 4. Are you testing between a known Earth and the lives?

 

[Ambienz]

Depends on boiler and type. If it’s the same as the EcoTEC pro Combi then it’ll be pins 3 and 4. Are you testing between a known Earth and the lives?

I have Live, Neutral and Earth and Pins 3-5 are switched live, so testing between the Neutral and Live pins

 

[Ambienz]

The motorized valves are external, zone valves and supply the switched live to the boiler which you say is live so would point to a boiler problem, you could switch off the CH and HW demand and check for no voltage on the switched live to prove it, when you switch it back in with either CH or HW demand listen for the fan starting up and check the d and s parameters again if no fire up.( and any f fault codes)

Yes. if it turn off control zones then I have no power to switched live and you can hear motorised valves retracting.

When switch live comes on there is no noise or action from the boiler, nor are there fault codes

 

[Deleted member 120897]

I have Live, Neutral and Earth and Pins 3-5 are switched live, so testing between the Neutral and Live pins

5 is a neutral connection. Also on these boilers, if the cover is removed it should be checked for safety afterwards using 26.9 of the gas safety installation and use regulations 1998. If nothing is firing up, then it could be the pcb, but I would engage with a gas safe registered engineer to progress further.

 

[Jerry]

Gut feeling is PCB
Time for someone registered.
Switch on your immersion and get some fan heaters