Boiler Advice - Worcester Heatslave Junior

[toad]

My old combi boiler refused to fire up today. It's done it a couple of
times in the past and seems to sort itself out when left alone.
However I'd like to get to the bottom of it.

The pilot light is lit fine.
All the switches seem to work. (I can hear relays operating as apporpriate)
According to my multimeter the boiler control thermostat is working
and joining (shorting) the two terminals to the thermostat doesn't
have any effect so I think we can rule that out.

The problem is when you click the switch you hear the relay, you hear
something else happening (low hum) but there's no big flame to heat
the water.

How can I test the gas valve/pump? Is there some kind of reset switch?

Needless to say I'm not planning to mess things around or risk doing plumbing work myself for fear of becoming red mist but I can't do too much harm checking and cleaning up the odd spade connection etc and I want to have a good idea how the boiler works and what the problem is before calling someone in.

Anyone offer some specific help or general boiler diagnosis advice?

TIA.

 

[namsag]

It will prob be the solenoid operator gone on the gas valve . pretty sure these are 24v so where the wires attach to it will be light blue in colour ( occasionally dark blue) if it`s black it`s 240v. If your getting voltage there and nothing happening change the operator cost about £45 nearly same as whole valve but only take 5 mins to change.

Heatslave junior got to be over 20 year old now and where very prone to scaling up..

 

[toad]

It will prob be the solenoid operator gone on the gas valve . pretty sure these are 24v so where the wires attach to it will be light blue in colour ( occasionally dark blue) if it`s black it`s 240v. If your getting voltage there and nothing happening change the operator cost about £45 nearly same as whole valve but only take 5 mins to change.

Thanks a lot, that's a massive help.

Heatslave junior got to be over 20 year old now and where very prone to scaling up..

I would imagine it's 1984, I suspect it may not be the most efficient boiler in the world.

Personally I'd rather avoid the costs of replacement but I'm planning to let the house out soon and I'm tempted to replace it for the sake of the tennants. Will I be required by law to get a better boiler?

Do you have any recommendations for a replacement?

 

[Agile]

Without a number I cannot visualise this model.

If it has a fan then I would expect the problem to be the APS as its been intermittent before.

If the gas valve coil had failed then it would often be a one time becoming open circuit which is easily measurable.

Some of these things are best dealt with by a competent CORGI.

Tony

 

[namsag]

no fan.. balanced flue wall mounted worcester with built on HW storage tank

 

[toad]

Some of these things are best dealt with by a competent CORGI.

Have no fear, I'm not planning to *do* anything beyond investigate. If the problem seems trivially easy to solve or a required component trivially easy to fit I might do it. If I've got the slightest uncertainty I'll get a CORGI in. I don't want to get blown up or suffocate in my sleep. (Well not for a good few years yet anyway) Mind you if I get a CORGI in I'll probably cut my losses and go for a new boiler.

 

[pannierstan]

no fan.. balanced flue wall mounted worcester with built on HW storage tank

Are you sure Namsag. I thought these were the old floor mounted thorn M with a heat bank strapped on the side.

Or is that the Senior.

Ahh those were the days

Stan

 

[namsag]

Pretty certain seniors where all floor standing and the juniors where the wall mounted with low water content boiler with about a 10 gallon stored hot water tank on the right hand side . Over heat stat up on right of boiler but before heat bank like the ones that used to be on feulsaver 15`s but you had to use a nail to push reset button in.. 2 stat knobs on bottom trim CH and HW with same size knob to select various hot water / heating combinations and built in clock on right hand side of same trim

 

[toad]

Pretty certain seniors where all floor standing and the juniors where the wall mounted with low water content boiler with about a 10 gallon stored hot water tank on the right hand side . Over heat stat up on right of boiler but before heat bank like the ones that used to be on feulsaver 15`s but you had to use a nail to push reset button in.. 2 stat knobs on bottom trim CH and HW with same size knob to select various hot water / heating combinations and built in clock on right hand side of same trim

Christ, you guys know your stuff.

Right, here's the gas valve:
http://tinyurl.com/tofb6t

You get 240v across those terminals when the water switch is 'on'. DOes that tell us anything? Is the solenoid behind the round alloy cover?

Here's the cct:
http://tinyurl.com/ua39tx

I've checked what I reckon to be the overheat thermostat (left hand side at the top, jubilee clipped to a pipe) and it's fine.

I think it's time for the CORGI guy but I've got the bit between the teeth!

Final shot. Retro boiler p*rn for the real enthusiasts!
http://tinyurl.com/o4r4mq


Finally, can anyone reccomend a good CORGI in the Gatwick Area. Also what's buying a new boiler and getting it plumbed in likely to cost me?

 

[Agile]

If there is 240 vac on the solenoid you may be able to isolate and measure the resistance of the solenoid.

If its about 2k-4k then next needs a corgi to measure the gas pressure at the inlet and at the outlet.

Stupid I know but is the grey button rotated to the correct operating position ???

Tony

 

[toad]

If there is 240 vac on the solenoid you may be able to isolate and measure the resistance of the solenoid.

Next question is how to I measure the resistance of the Solenoid. How do I get at it? Or is measuring the resistance across the two spade connectors on the gas valve effectively the solenoid resistance?

 

[toad]

If there is 240 vac on the solenoid you may be able to isolate and measure the resistance of the solenoid.

Next question is how to I measure the resistance of the Solenoid. How do I get at it? Or is measuring the resistance across the two spade connectors on the gas valve effectively the solenoid resistance?

Resistance across the terminals in the pic is about 600-1000 [1] when on, and 0 when off.

[1] Dunno what the units are.

 

[Agile]

Its always the same resistance!

You must measure with the leads disconnected!

If you dont know what the units are then one might say you should not be measuring it.

Its probably OK though. But much lower than I would have expected though.

Now what about that knob ???

Tony

 

[toad]

snip

 

[toad]

Ok have checked again. Thanks Agile.

Set to 20K Ohms the multimeter reads 5.3 across the terminals shown here. http://tinyurl.com/yofb6t

I'm guessing that's 20*5.3 - 106000 ohms.

Given the suggested figure of 2k-4k, does that suggest a knackered solenoid?

Can anyone recommend a good CORGI guy near Gatwick? Is it worth repairing in a boiler of this age given I'm planning to let the house out which (I suspect) may require a new boiler. What kind of cash is a total replacement of the boiler going to come in at?