Ravenheat LS80 no DHW, thermistor and diaphramn changed

[Mickymoody]

Hi all, as above, the boiler isn't firing when hot water turned on, CH works. Prior to the hot water failing, the reset button tripped intermittantly.

Where the thermistor sensor goes into the pipe near the divertor valve, the water goesn't get warm at all.

Thanks in advance for any help.

 

[ollski]

Not overly familiar but it probably has a diverter valve with a diaphragm in it.

 

[Agile]

The heading says the thermistor has been changed!

Which one?

Did you measure the sensor resistance or just change it?

Diagnosing faults on boilers is not just a matter of changing parts!

When you turn on a tap does the boiler make any noise at all?

If not then the diverter valve has probably failed.

Tony

 

[Mickymoody]

I *mistakenly* purchased the CH thermistor, in the belief that the 2 sensors are interchangeable. (clip on type); the resistance was somewhere in the region of 1750 ohms for CH sensor, 1800 ohm for DHW sensor, and 1750 ohm for new sensor. I'm unsure exactly, as I personally did not test this.

When hot water tap turned on, the boiler does NOT make any noise or attempt to fire up.

The wiring from each sensor has been swapped around to the alternative sensor, but this made the radiators warm up, but no hot water. When tap was running, the boiler pressure reduced accordingly.

The new sensor was clipped onto DHW, CH worked as normal, no hot water.

The new sensor was clipped onto CH pipe, no hot water, CH operates as normal.

The microswitch on the 3 way valve was removed, and this caused the boiler to fire when unpressed, but no hot water.

We have spent so long testing various combinations and scenarios, that I've got boiler fever, and confusing myself! Hope this makes sense, please feel free to ask anything, as a difficult-impossible to fit £122 part doesn't sound a good outlook.

 

[ollski]

Your tallking about the diverter valve with the clip on flow switch same as on the old alphas. Run a hot tap and unclip the flow switch, if the rads get hot you need to remove the complete diverter valve and either replace the whole unit or just the diaphragm (get yourself lots of spare o rings for everything else too!). If the rads don't get hot then you may be lucky and just need a new flow switch.

 

[Agile]

Are you very sure the resistance of the sensors is correctly stated? All the later Ravens have a nominal resistance of about 25k although the LS is probably a boiler they might prefer to forget!

Yes, it does sound as if the diaphragm unit on the diverter valve has failed.

In theory you can just change the diaphragm but commercially its such a pain to change that I would always replace the whole diverter valve. Otherwise there is a big risk that the old one would start leaking or jam up and we would be blamed and expected to replace it free.

British Gas do a fixed price repair for about £175 and that might be a best option for you.

When you start changing parts yourself you are rapidly spending more than a professional repair might cost.

Tony

 

[Mickymoody]

I can see which way you guys are going here; in the manual, the fault chart says 'does main burner light' - no - is microswitch on shunt valve being operated mechanically - yes, replace 3-way microswitch.

Do they mean the flow microswitch on the 3 way valve/divertor valve.

What Ollski says is correct; unclipped flow switch, rads get hot. System pressure goes down. Has this on/off microswitch got 3 positions, it only has 2 wires.

Agile, really unsure about meter readings, I understand what you mean about throwing parts at it, as was assured that 'Them Ravenheat LS80? thermistors all the way!', as I had a bad experience with a LeBlanc boiler before this; the guy came out to repair, simply popped a fuse out the front, replaced it, and was away. It worked for 2 minutes. I checked fuse he popped out, and he replaced a 300ma fuse, with a 3A fuse. He was then rude and offensive, wouldn't come back to fix it, or give me a refund. New boiler required..and what do they fit? The wonderful Ravenheat LS80. I'm not going to be attempting to replace this valve, but want to be totally assured that this is faulty, and I'm getting a decent job done at a fair price.

Still confused about this switch; but looking highly likely to be diverter valve diaphragm. Wish everyone out there was as open as you guys have been regarding this.

 

[Agile]

Turn on hot water tap while heating is switched OFF.

Remove diverter switch.

Does boiler fire up?

What gets hot?

If rads the diverter valve failed as we said.

If hot water then go and have a shower quickly!

Tony

 

[Mickymoody]

I *think* when we attempted that scenario...holy hell let loose?

summer switch on, so no CH OK?

removed divertor switch, so forces boiler ON to fire up.

Boiler makes all kinds of gushing/banging noises, vents steam outside, pressure fluctuates between 1 and 4 bar. I ran away.

NO HOT WATER!

Orange flame failure light comes on. If pressed, it comes back on after the boiler wrath.

Do you think the divertor valve is broken then. lol

I must say; although all through testing it never happened as CH wasn't on, is that when the CH has been on, there is scalding hot water in the tap for like 30 seconds? But assume thats the heat exchanger doing its job, as the boiler doesn't fire for hot water. But I never experienced that, I think my girlfriend has boiler fever too..

 

[Agile]

I am still waiting to know if rads heated up during that test.

Repeat with rads cold.

NEXT test!

Replace switch on diverter valve.

Heating off.

Turn on hot tap.

Does boiler make noises?

Tony

 

[Mickymoody]

The rads were kind of lukewarm, but that could be because of the previous tests? The kitchen double rad (near the boiler) gets mad hot when in use, whereas the living room rad is only lukewarm, unable to get the bleed key to fit properly.

Not replaced switch on divertor valve, as I don't own one, and buying one to test is another £18 down the drain.

Is the microswitch on divertor valve multifunction, or is it on/off? It works OK for CH. IF it had another setting to turn on DHW, then I'm sure it would work, as this switch isn't operating to fire the water up.

As soon as the switch is unpressed, the boiler fires, but only heats up CH, or if CH is turned off, sends boiler into a fit.

Traditionally microswitches, with 2 wires attached are either on or off. This switch works as it says on the tin, as far as microswitches go, does it have a third setting, used for HW?

I turn on hot tap; no noises. no relays, no clicks, no ignition, nothing.

Can the HW potentiometer be faulty?

 

[Agile]

Please do THIS test!

I am still waiting to know if rads heated up during that test.

Either with rads hot OR cold.

NEXT test!

Put back the switch on the diverter valve.

Heating OFF.

Turn on hot tap.

Does boiler make noises?

 

[Mickymoody]

Ok - no the rads didn't get warm, as the gas cutoff came on. And steam was vented outside.

Diverter attached as per, heating off, no noises from boiler. Not a flicker of activity.

 

[Agile]

Thats confusing.

How can steam be produced if the boiler is totally quiet.

One test at a time.

One result at a time!

 

[Mickymoody]

Summer mode=CH off = no boiler function.

Normal mode = CH works OK, no hot water

microswitch removed on divertor valve = boiler fires up regardless; if CH is selected the radiators get warm.

microswitch removed on divertor valve and summer mode selected = boiler heats water up, but vents it, makes lots of banging and running water noises, (like there is water trapped, and its leaking out?) still cold water from tap, then pilot light goes out.

microswitch fitted as normal, CH works, DHW does not work.

Summer mode = boiler inoperable on DHW.

Winter mode = fires as when requested.