17 Year old Vaillant...fix it, or put it down?

[Heggsy]

I've now fitted a new pump and diverter valve (both confirmed as faulty) to this boiler - a VCW GB 221H. The DHW is fine, but the CH is still problematic.

To get the CH to start, the boiler has to be switched off, drained, have at least one of the banjo pipes at the bottom disconnected, refilled and then switched on. This will start it 99 times out of 100 (Yes, I've done it that often!). However, the CH will then run for an amount of time ranging between 30 mins to several hours.

Should I just accept that 17 years is a pretty good run and replace it, or is there life in the old dog yet?

Cheers,

Heggsy

 

[ChrisR]

WHat? It's only just run-in!

I suspect the servo valve needs attention, but one of the older-gits-than-me will know more.

 

[Heggsy]

WHat? It's only just run-in!

Yeah, I've been told these boilers are pretty much bullet-proof...maybe this one was hit by a grenade!

I suspect the servo valve needs attention, but one of the older-gits-than-me will know more.

Any particular reason for your suspicion, or just a hunch? Either way, it's worth exploring.

 

[ChrisR]

That's what sends the pressures to the diverter to move it, and make the CH go. Check the microswitch in there too, iirc

 

[Heggsy]

That's what sends the pressures to the diverter to move it, and make the CH go. Check the microswitch in there too, iirc

Thanks, Chris.

A mate of mine has just removed a working boiler of the same type, so I think I'll go rescue the SCV from it.

 

[chrishutt]

Rescue the PCBs as well, plus...erm, let's see....the secondary heat exchanger if it's a plate type, differential valve (on gas valve), maybe water section and rocker mechanism above it.

On your boiler you ought to check the banjo connection to the diverter valve. If this has a tiny valve mechanism in it, looking like a little bit of wire, just rip it out. They can block the hydraulic tubes and cause the sort of problem you have.

 

[Gasguru]

Do a search this has been covered before.

To start with check:

The auto air vent is working (ie there's no trapped air in the boiler).

The water section pin (and microswitch) is adjusted correctly and not sticking.

The servo valve operates correctly and the ceramic inserts inside are working properly.

All the control tubes are clean.

The small orifice in the end of the control tube is clean.

The diverter diaphragm is not hole'd or too flexible.

The microswitches on the end of the diverter are correctly adjusted.

etc.

etc.