Expansion tank swan neck dripping and steaming

[Evsusername]

Hi
I am not a central heating engineer, I am an electician but hopefully with some help I may be able to sort this problem. I have recently moved into a bungalow with an oil fired boiler. This provides heat for central heating and hot water. It is an open vented system with 2 tanks in the loft, 1 big, 1 small.

The problem I have is that it seems to be using lots more oil than I expected, so much so that I am worried I won't be able to afford to run it. The boiler seems to be coming on a lot more frequently than I would have expected, even though until last week it has not even been very cold here.

While I was in my loft today I noticed the swan neck overflow above the CH expansion tank was dripping water and steaming constantly. The timber beams above are saturated with water and stained, so it looks like this has been happening for a while. I am guessing that the high oil usage may stem from this problem, as I am using oil to heat this water which is in turn vapourising and heating my loft!

Having the issue, it looks as though I may have one of a few problems, namely a faulty boiler stat (causing the ch water to overheat and expand up the vent pipe) or possibly a corroded or split immersion tank coil, or maybe something else.

How can I trace the actual fault, or eliminate possibilities one by one?

 

[stevetheplumber]

a split coil would make the lower tank overflow by backing up the cold feed boiler stat is the more likely have you tried setting it lower see what happens the other possibilities are pump speed to high cold feed blocked on ch tank or it was all put in wrong to start with bungalows tend to be low head instals and there are ways round this one is to put an over sized section of pipe in the exspansion pipe

 

[jase158]

photos would be good,
cant remember how to check for split coil, but boiler stat would be gas safe engineers job.
have you checked the pump speed? thermostats, valves, i.e.

 

[Evsusername]

I have tried turning the boiler stat down. It goes from 0 to 7. Originally it was on 4, and I turned it down to 2. It didn't seem to make any difference.

The expansion pipe looks like 22mm. How oversized would it need to be and for what length?

 

[SimonG]

photos would be good,
cant remember how to check for split coil, but boiler stat would be gas safe engineers job.
have you checked the pump speed? thermostats, valves, i.e.

It's oil Jase

 

[jase158]

It's oil Jase

D'oh
Been a long weekend,
Oftec engineer then

 

[erpkid]

If the boiler can be run this way I would convert it to a sealed system once the stat or pump issue is resolved - it could also be that the pump is in the wrong position and over pumping. This would get rid of one tank in your loft and a source of damage to your timbers.

 

[erpkid]

You do not often see these things now but you could also try a surge arrestor. This was popular on low head installations.

 

[stevetheplumber]

if you turned stat down to 2 and it made no diffence there could be a clue there

 

[Evsusername]

Thanks for all your advise chaps, I have sorted the problem. The pump was set to max speed. I turned it down 1 notch and the problem disappeared. Thanks again.

 

[stevetheplumber]

I suggested that a week ago

 

[Evsusername]

Thanks Steve, I sorted it a week ago. Just thought I'd let you know tonight.