Grant External combi oil 21e burner lockout.

[WBRacing]

Hi folks, once again I am in need of your expert help I am afraid!

Just before Christmas my boiler was losing all pressure in about 24hours. For months it had had a very slight pressure loss that took about 8 weeks to drain but it sped up. After re-pressuring a couple of times it got even quicker, down to about 2 hours. Long story short (and with the help of a borrowed thermal camera as it was raining outside) it turned out the water was coming out the pressure relief pipe. The pressure relief valve and expansion vessel (that was the culprit) were replaced by the engineer and all was well and pressure wise - and now continues to be. That is apart from one thing which is proving now to be an absolute git of an issue to cure.

Since those parts were replaced, the Riello RDB burner now keeps going into lockout. It didn't do this before and the boiler for the last 18months or so had been faultless, apart from the pressure loss...

The lockout occured once the house has reached the thermostat temperature and the boiler had been off for more than about 2 minutes. I should also mention that the house is fitted with a Netatmo "smart" thermostat so it is prone to turning the boiler off/on quite a bit more than a mechanical stat.

Over a period of the last three weeks in order (roughly) the engineer has:
Cleaned all filters
Checked oil pressure
Checked tank for water and debris
Replaced: Nozzle, Photocell, Capacitor, Solenoid (possibly?), Control Box, Pump, Motor.

Not sure if I have missed anything but after all of this the motor seems to of had the most success. For two days now the boiler heated the house to the desired 18degree temperature and once reached, held it there for six hours almost exactly. At this time though the burner then goes back into lockout which is infuriating! The engineer (who I trust and think has been very good, methodical and attentive) is running out of ideas so I am here hoping you can help us.

If there is anything I can add or answer that may help diagnose this issue please ask. Thank you!

 

[oilhead]

With what has been changed, everything points to a fuel supply problem. Does it always start on pressing the reset or do you have to press the reset several times?

 

[Andy4444]

Check the fire valve.
Disconnect it and see if there's a blockage either in valve or where the fittings connect to oil line.

I've had nuisance intermittent lockouts caused by sludge blocking the fire valve.

When your oil/filters were checked was there a lot of sludge/muck in evidence?

Did your oil guy check to see if there was any resistance in the oil line with his vacuum gauge?

 

[WBRacing]

Hi guys, thanks for your replies, really appreciate the input.

The boiler always starts immediately on reset and whilst heating the house fires on and off merrily, it only seems to have issues once the gap between fires gets slightly longer. The last two times are what confuse me though as the thermostat shows the boiler as being on for about 25% of the hour whilst holding 18degrees and then almost to the minute, locks out after six hours. Maybe that is just a coincidence?

When the filters were cleaned they were apparently full of muck (I didn't get to see) which was disappointing as they were only 12months old. I don't know if he measured / was able to identify any resistance in the oil line. I'll ask him when he comes over this week and perhaps recheck the filters again? I don't know anything about the fire valve, is it something that I can check or is it best just to replace. Will ask in case that has already been done as well.

 

[Andy4444]

You will have to break the oil line which means that the oil pump will need bleeding once you reconnect. If you know how to do this then you can check the fire valve.

Turn off the oil supply at the oil tank isolator (and turn off boiler). The fire valve should be outside the boiler on a capilliary (brass fitting with KBB written on it is a common fire valve). Loosen the nut upstream of the fire valve (hold container underneath to capture oil) and see if it runs with a good flow.

Reconnect and then loosen nut downstream of fire valve. See if you get the same flow rate through the valve. At this point it may be evident that there is sludge in the valve and given that there was muck in the filters then you will likely find some in the fire valve.

If there is disconnect the fire valve and blow through with air duster. You may need to replace the valve if it is chocka!

This is basic stuff for an oily and if it is a fuel supply issue then throwing parts at the burner is a waste of £££.

Good luck!

 

[Andy4444]

Just a note. A line blockage is consistent with the symptoms you describe. Oil line fills when boiler off and runs perfectly well. Once the burner is running and using oil the supply becomes strangulated by any obstruction and then locks out. Oil line refills and the cycle begins again!

 

[WBRacing]

This is great stuff, thanks so much Andy. Will give it whirl and see what I find and will report back.

 

[WBRacing]

Hi Andy,

Well I did what you suggested this week and although the flow appeared fine I gave the fire valve a quick blast with the air duster anyway as I was there. Once back together and bled the boiler is running fine but now rather than the burner locking out, the boiler control unit seems to be!! The Burner LED has started flashing.

Basically, it is almost all the exact same symptoms (i.e. the boiler runs fine when on full demand, heating the house all the way up from 7 degrees to 20) at which point the house thermostat clicks off for a few minutes. When it clicks to come back on, no heat and on checking the boiler, the Burner LED is flashing. I am going to sit outside today to see if the LED starts flashing once the stat turns off, or if it is triggered once the stat clicks back on.

Could this now be a sensor / main boiler control board issue?

The attached image is an old photo, it shows is the Burner LED I'm referring to.

If I power the boiler off/on then it seems to reset and work fine straight away, right up until the house thermostat clicks off/on again. Gah!!!!!

 

[Andy4444]

Sounds like a pcb issue.

If you check manufacturers instructions a flashing burner led states this.

I'd give Grant Tech a call to confirm

 

[WBRacing]

Blimey Andy - thanks for the incredibly fast reply!!

I did see in the installation manual about that, thought it worth double checking.

Thanks so much for all your help, will see what they say.

 

[oilboffin]

I think you while get the oil tech to put the parts he took of back on again it's obvious you didn't need them, with what he changed you could have fitted a new burner cheaper.Bob

 

[WBRacing]

Hi Bob, he's actually already done that without my having to ask, he has been great about it all - he's not taking the mickey I don't think and seems to be treating it more as a personal challenge than to rack up big bills.

I have just sat outside (in the blimming pouring rain! ) watching it and noticed that whilst it was working normally the pressure was reading high - well over 2bar. I am waiting for the system to cool so I can see what the pressure is at rest, if it is still high I shall bleed some water off.

Is it possible that this could be the cause of the issue? That the boiler (once the water has been heated and expanded) is basically locking the burner out to avoid over pressuring the system?

 

[Andy4444]

This wouldnt cause burner lock out.

It has 2.5 bar pressure relief valve which will lift if this limit is exceeded. Your prv termination pipe will emit a flow of water to release pressure and you will then find that you have to top pressure up.

If you lose pressure the low pressure warning light will illuminate and then you simply reset the fault by topping up with the fill loop

 

[WBRacing]

Ah nuts, thought it might be a bit too good to hope for! The pressure relief valve was replaced at the same time as the expansion vessel so at least I can be confident that it will be working properly.

 

[Andy4444]

Was the PRV lifting then?