Oil burner problem

Magilla Gorilla

Hi.
Just looking for advice on where to go next.
The issue is my Riello RDB2 won’t cut out immediately when it’s supposed to. The time clock is shutting off the motorized valve which I’ve already replaced so that is not the cause. The burner keeps running for a minute or more and then eventually shuts down. It was stopping immediately.
I’m fairly handy so would be happy to replace a component on the burner. I just wonder where should I look next?
Thanks.

jimf

sounds like the motorised valve

nothing on the burner to cause this symptom

Magilla Gorilla

Already replaced the MV on downstairs zone. Other two MVs are responding to control panel also one was replaced a few years ago. No problem with burner starting on clock.
Any idea as to the mechanics involved in the burner running on?

agusta

Is the same thing happening on all zones or just on one zone.Do you have wall stats on a cylinder stat

Magilla Gorilla

Stats on walls upstairs and downstairs and cylinder stat for hot water.

If it’s happening on other zones what would that indicate? I only noticed it in downstairs so far but can’t say for certain.
Thanks.

agusta

Id say it only happening on downstairs zone
1/turn on boiler on downstairs zone for a minute
2/then turn down downstairs wall stat to zero
3/if boiler still runs for a min or two its a faulty motorised valve[sticking micro switch in valve]

Magilla Gorilla

Sorry to be a pain but I put a new MV on the zone on Saturday so I think that should be covered.

If it’s happening elsewhere any ideas? I’ll check this tonight.

Thanks.

K.Flyer

Magilla Gorilla wrote: »

Sorry to be a pain but I put a new MV on the zone on Saturday so I think that should be covered.

If it’s happening elsewhere any ideas? I’ll check this tonight.

Thanks.

Depending on the type..
If it has two screws holding the actuator on I have seen over tightening causing the actuator to take a while to close.
Otherwise it may be that the spindle in the valve is sticking.

Magilla Gorilla

Valve seemed to be free enough I could turn it easily.

Magilla Gorilla

Further experiments reveal-


1. Boiler is not shutting down immediately on all three zones.
2. Time to shut down varies- 45 seconds on downstairs; 3 minutes on upstairs; 2 minutes on hot water, but probably not a factor.



Control panel is definitely shutting off all three MVs- I can hear and feel them working. This seems to me to rule out MVs completely, as all three cannot be faulty at once (and one is brand new).



I'm guessing the stats are not a factor as once the control panel switches off the circuit they should not matter- is this correct?


I'm convinced it's something at the burner/boiler end- solenoid, stat, photocell, control box?


Any suggestions welcome.

Dtp1979

Is there a pipe stat fitted for pump overrun wired arseways?

Magilla Gorilla

No changes to the wiring. There is a stat/control box beside the boiler with two copper wires running to the probes that take the temperature- could there be something failed there? How would that cause the boiler to keep running?


Thanks.

jimf

nothing at the burner is causing this issue

failure of the stat would cause completely different problems

Tom44

jimf wrote: »

nothing at the burner is causing this issue

failure of the stat would cause completely different problems

Ah Jim, did I teach you nothing? Some boilers have frost stats that could be faulty or set wrong

Personally I suspect that one of the other MVs has a faulty micro switch.
OP is the boiler still hot when the clocks have been off for a few hours?
Touch the coppor pipe at the top.

Magilla Gorilla

Hi Tom.


I've left the heating off since earlier- I'll check the boiler as you suggest later on and report back tomorrow.


Thanks.

Wearb

Give me a shout lads if you get stuck :pac::pac::pac:

jimf

Tom44 wrote: »

Ah Jim, did I teach you nothing? Some boilers have frost stats that could be faulty or set wrong

Personally I suspect that one of the other MVs has a faulty micro switch.
OP is the boiler still hot when the clocks have been off for a few hours?
Touch the coppor pipe at the top.

agreed tom

but the over run is too consistent to be frost stat related In my very very limited knowledge :P:P:P

jimf

Wearb wrote: »

Give me a shout lads if you get stuck :pac::pac::pac:

SHOUT

as a mod your not allowed to be a smart arse its beyond your pay grade

Wearb

jimf wrote: »

SHOUT

as a mod your not allowed to be a smart arse its beyond your pay grade

Only joking Jim. You have all made the same stab at it as I would. I would only add that he needs to get a multimeter on it to see where the power is coming from.
btw was dtp's question about pump over run answered?

jimf

agreed

no dtp question wasn't answered but it would really have to be screwed up wiring wise but hey they are out there

Magilla Gorilla

OK, the boss came home and put the heating back on so I'll have to wait til morning to check pipe at boiler.

Maybe I'm being paranoid now, but the pump seems to be running constantly with everything switched off, which I don't remember from before. Am I losing it or is this normal?

agusta

No,i dont think your getting paronoid.your getting a permanent live to the boiler
If you turn up the stat on the boiler now to max will the burner fire with the time clock off?
If so your in danger of damaging the circulating pump as it probably has no where to pump to

Magilla Gorilla

No, turned it up full but no firing.

agusta

Top of boiler was probably above 85 degrees so it wouldnt come on.leave the stat on lowest setting,if the circulating pump is running,id be turning off the circuit breaker for the heating at the fuse board when you dont need the heating on,until its resolved
If it is a motorised valve issue,it could be any one of them.the switched live on the microswitches in them are all connected to each other

Magilla Gorilla

So I just checked boiler before anything is due to switch on. Pipe on top is very hot and pump is whirring away. Pump is hot too.
System has just started up as normal.

Tom you were on to something, what do you think is going on?

TECH85

Is there any bypass or three port valve fitted on the circuit?

Magilla Gorilla

Only the three MVs for the zones, which are two way open close.
Can’t say about bypass- what would I be looking for?

jimf

at a guess at this stage

permanent live going to boiler

when motorised valves shut off no circuit for water to circulate

so boiler going over temp and shutting down on stat at boiler as it should

stat probably not set high enough for hi limit stat to activate

maybe all gobbly gook but my guess so tom is probably correct as usual

Magilla Gorilla

Made no changes to any settings so I’m confused as to why it’s started now.

K.Flyer

Definitely something wrong with external controls / wiring, either a frost stat / pipe stat, but something is not wired correctly and its throwing a live over to the boiler.
Time to get a multimeter out.

agusta

Magilla Gorilla wrote: »

Made no changes to any settings so I’m confused as to why it’s started now.

motorised valves have two moving parts,the motor and the micro switch.they do break down.if you dont have a frost stat,it is a motorised valve

Magilla Gorilla

Thanks all.
I’ll see if I can identify which of the MVs might be causing the problem.

Magilla Gorilla

So, it was one of the other two MVs that was the problem, as correctly predicted by some on here.



I disconnected them one at a time and checked to see if the pump was still running. Hot water MV made no difference, nor did downstairs MV (replaced on Saturday as this was the zone I initially noticed the issue on). With just upstairs MV still connected, the pump was still operating- it stopped when disconnected.


I was able to switch off both of the "good" zones immediately as before from the control panel with upstairs MV out of the picture.


I'll buy a new one at the weekend as I don't think it would be wise to put the (still working) 20-year old one back on.


Thanks to all who contributed- I've learned a lot.

jimf

glad you got sorted and well done they are known to cause this issue

but its only guess work on our behalf that might point you in the right direction

thanks for coming back and letting us know the outcome many don't once they have a fix