Worcester Heatslave Highflow (bf) pilot not staying lit

[Mloclam]

I had a problem with water leaking out of the Automatic Air Vent. Skip forward 2 nightmare days or leaks at the air vent , at then at the drain cock, and the system is now refilled and not leaking, however the pilot won't stay alight.

When I drained down the system I only vented the first upstairs radiator closest to the boiler.

First time I restarted the system the pilot did light and stayed lit. Boiler fired up for domestic hot water and was heating fine. Then I switched on the CH and went off to check for air in the radiators. A few mins later when I came back to the boiler the gas/pilot was out and radiators had not yet heated up.

Going through the fault finding in the manual...

Pilot light is a good big flame when holding in the Gas Control Knob but goes out when release the Gas Control Knob.

It then says to
"Check E.C.O. connections at the thermocouple and gas valve following procedure 5 in the multimeter handbook. Minimum closed circuit voltage 8mV. Does Pilot stay alight?

if NO then

Change Overheat thermostat"

There are a number of things about this I find confusing and have questions.
1/ What does E.C.O stand for?
2/ How do I check this thermocouple is producing minimum 8mV via procedure 5 or otherwise? (I do have a multimeter)
3/ Would I be correct to assume that if the thermocouple is producing less than 8mV then I relace the thermocouple, otherwise I replace the Overheat thermostat aka Boiler Limit Thermostat?

Very grateful for any help you can provide.

Hopefully,
Malcolm

 

[ScottishGasMan]

The boiler usualy has one or two over heat thermostats (with the big white front cover off there normally seen as a red button under the contol panel, if it over heats they can pop, and you need to press them back in (will feel and hear a click if they go)

other than that thermocouples/saftey devices etc etc is gas work, which on this DIY forum we cannot give DIY gas advice and any responsible person shouldnt.

 

[Mloclam]

ScottishGasMan,

Thanks for getting back to me. Unfortunately mine does not have any red buttons to push.
Looking at the instructions they were written 1987. Boiler is basic but preforms well and reliable.

Thanks again,
Malcolm

 

[ScottishGasMan]

87? so possibly a heatslave 9.24, would still have a resetable oveheat stat, can you take a pic of the boiler with the white front pannel off?

 

[Mloclam]

I should have done that sooner but I didn't find how to do it the first time I tried.

While we are talking... if a Thermocouple produces good values when tested with a blow torch, is it safe to assume it works fine?

Cheers,
Malcolm

 

[Mloclam]

Might be called a Highflow 3.5 bf
Max output is 23kW if that helps identify it!?

 

[45yearsagasman]

While we are talking... if a Thermocouple produces good values when tested with a blow torch, is it safe to assume it works fine?

No. Flame temperatures. ECO. Energy Cut Off

 

[ScottishGasMan]

Last option then, lift the white panel off the top of the boiler, comes off just the same as the front pretty much, on the top of the control pannel over where abouts the temperature knobs are, look for a small push button (possibly red) and click it back in then try pilot again.

They all had them Im sure, your model is particularly old so should be above the controlls as opposed to underneath it.

if not, call someone in (ideally ask if theyve worked on these before as if not they will more than likley struggle too)

 

[Mloclam]

Thanks ScottishGasMan and 45yearsagasman.

AAAAAAAAAAAaaaaaaaaaaaaaaaaaaaaagggggghhhhhhh!!!

OK. Having got that out of my system, the latest is that the Pilot Thermocouple and the Boiler Limit Thermostat have both been replaced and situation is unchanged. Pilot lights fine and stays lit while holding the Gas Control Knob in but when released the pilot goes out.

Exact model is Heatslave Highflow. I looked at the Highflow 3.5-4.5 operating instructions and the Heatslave 9.24, got the manuals of the Worcester Bosch web site, and neither of these is the correct model. Lot of similarities but not the same. The Worcester Bosch web site doesn't have a user manual for a Heatslave Highflow which doesn't fill me with confidence that even if I got them in they would know what to do.

 

[ScottishGasMan]

They won't work on boilers that old I don't think.
Did you replace these parts?

 

[Mloclam]

Lets say for arguments sake yes but if that is a problem then no.

 

[ScottishGasMan]

Just get someone qualified to look at it, your playing with safety devices on a gas appliance, and if you want to keep going then be my guest but there's no diy gas advice on here, and we're past resetting things here

 

[Dan Robinson]

The bit I think it is is long obsolete anyway.

 

[ScottishGasMan]

Probably