Venting boiler

[SandLake]

Hi

I am having a strange problem where my boiler will come on of it own accord without the pump on or any valves open and boils over into the expansion tank, yesterday morning the heating was on from 6:30 to 8:30 and around 11 this happened (next on is at 4:30pm). It happened again at 5am this morning. This has been happening for a year, since the boiler had to be replaced but was actually OK during the summer. I have had two plumbers look at it but they were stumped.

It is a Grant Vortex 50-90 oil boiler with a Riello RDB1 pump and a Honeywell Smartfit S Plan controller

I have been delving into it myself today (and I don't know what I am looking at) and I have found that the wiring from the controller to the boiler should be (there are only 3 wires)

Boiler L - SL on controller
E - E
N - N

but is actually

Boiler L - L on controller
E - E
N - N

I don't know what SL is but it looks to me that this is something to do with overrunning, I have changed the boiler L to go to the controller SL and will wait to see what that does, it has initially come on OK.

Is this likely to be my problem?

Also there is no auto-bypass but 2 radiators do not have TRV's

Thanks

 

[SandLake]

In an integral garage

 

[jtsplumbing]

Dont know anything about oil boilers, but most gas boilers have 4 wires L / N / E & SL (Switched Live) from controls.

 

[SandLake]

OK, Switched Live makes sense. That must mean that SL on the controller switches power on and off to the boiler as required instead of passing on Live all the time - potentially allowing the boiler to fire when it shouldn't!

Thanks

 

[Terry_the_piper]

Is the pump failing?

 

[SandLake]

I don't think so

 

[Terry_the_piper]

Boiler will only fire if it is getting a signal (ie a voltage) so either controller or wiring is faulty. You say it fires without the pump running? This should never happen.

 

[SandLake]

As I said in my opening post 'I have changed the boiler L to go to the controller SL'

The installer had wired it - boiler L to controller L - but that is not what I see in the installation instructions.

I am now guessing that that 'incorrect wiring' is what was causing the boiler to run when nothing else (pump or valves) was getting power.

As I don't have much experience with all this, I will be monitoring the new wiring but am HOPING that it will resolve my problem of the system boiling over when it shouldn't even be on!

 

[Rob Sale]

sounds like someone has bypassed pump proving device but i ain't a oil man.

 

[SandLake]

Sorry I don't know what that means?

 

[Dotty]

Moving this to the oily forum.

 

[Subby]

Is the boiler in a cold location?
Is it possible that the boiler has a built in frost stat that turns the boiler on when the temperature drops below, say 5 degrees?

 

[migoplumber]

what subby says makes sense.
frost stat of some sort turning on boiler to prevent freezing.
if the boiler does not send a signal to the pump to run in frost condition that is why it pumps over.
sounds like its all been wired externally.
normally 2 frost stats wired into an external control system.
one turns on the pump at 5 degrees ( first stage )
the other turns on the boiler, signal to SL at 2 degrees ( second stage )
wiring is definetly the problem. call in a good local sparks to set it right for you.

 

[SandLake]

Are you saying that changing the wiring so that the boiler Live is now connected to the controller Switched Live instead of the controller Live is NOT going to fix my problem>

 

[dontknowitall]

I've not read all the above so I could be talking tripe (nowt unusual).

You've L, N, E and SL.

LNE are for normal running and if the boiler is toddling off on it's own then there'll be a frost stat in it. The SL will take the signal from the programmer and room thermostats and stuff like that. They will tell the boiler when they want it to work and when they don't (hence the switched bit).

Hope I'm right here or I'll have to get my size 12's out ... again ...

 

[SandLake]

I've been thinking about this as I find it hard to keep it all together in my head. The centre of my system is the controller, it takes readings in (thermostats) and sends power out (boiler and pump) The controller has the option of connecting to the boiler via L, SL, E, PL and N but the boiler only has 3 connectors L, N and E. N goes to N and E goes to E and we are left with what goes to L, if it is the contollers L, then the boiler is always live but if it is the controllers SL, it is only live when the controller tells it to be.

It was connected to the controllers L and that was when it was boiling over very occasionally, possibly frost protection was kicking in although I don't think it was always cold enough to explain that, the boiler is in a garage which is not that cold, it is a double skinned garage attached onto the house. There is no way for anything on the boiler to tell the controller it must get power

I thank you for your response but I am going to monitor the system the way it is now for a while to see if any boil overs occur or any other stranger things happen

Thanks you

 

[peteheat]

A thermostat calling for heat opening a two port valve switching on the boiler, possibly a link where it shouldn't be in the programmer.

The pump should come on which again suggests a wiring or programmer fault, suggest you contact your local OFTEC registered technician as they will either sort out the fault or can recommend an electrician who understands wiring programmers.

 

[Subby]

Are you saying that changing the wiring so that the boiler Live is now connected to the controller Switched Live instead of the controller Live is NOT going to fix my problem>

No, He is saying, call in someone who knows what they are doing

Hi

I am having a strange problem..blah blah...

I have been delving into it myself today (and I don't know what I am looking at) and I have found that the wiring from the controller to the boiler should be blah blah..

 

[SandLake]

Touchy!!!

I have had 2 plumbers (aka people who know what they are doing!) out to look at it and they both 'tried' a few things but didn't make any improvements - am I meant to just keeping calling plumbers till I find one that knows something? - I thought I would come on here to see if I could get some good advice or pointer on how to proceed. Yes I don't know what I am doing but when I trawl the internet and find an installation guide that shows a diagram of the boiler L connected to the controller SL but that is not how mine is wired, what am I meant to do? I changed the wiring to match the diagram - was I wrong? Why didn't the 2 plumbers notice that?

It's been 2 days now and I am not aware of any more boil overs - I must have gone to the right plumbing school, but thanks for your advice anyway!

 

[peteheat]

Touchy!!!

I have had 2 plumbers (aka people who know what they are doing!) out to look at it and they both 'tried' a few things but didn't make any improvements - am I meant to just keeping calling plumbers till I find one that knows something? - I thought I would come on here to see if I could get some good advice or pointer on how to proceed. Yes I don't know what I am doing but when I trawl the internet and find an installation guide that shows a diagram of the boiler L connected to the controller SL but that is not how mine is wired, what am I meant to do? I changed the wiring to match the diagram - was I wrong? Why didn't the 2 plumbers notice that?

It's been 2 days now and I am not aware of any more boil overs - I must have gone to the right plumbing school, but thanks for your advice anyway!

Dear Sir,

Perhaps I can help clarify a few things for you.

1) You are the person standing in front of both the the boiler and the programmer, we are effectively in the dark.

2) You were advised to contact a local heating specialist who understands and works with oil systems, including a link to the OFTEC web site where you find such people.

3) Plumbing is a wide and varied trade with many different specialist subjects, material and manufacturers of those materials, to get a glimpse of how many take a look here BES

From what I have read you received good advice based on the information provided, sorry we couldn't meet your expectations.

Kind Regards,

peteheat

 

[tickdoc]

could it be a motorized valve head need replacing ?