Worcester 28i Junior boiler problem

[DeLavel]

Hi,

hope that somebody may be able to offer advice on a problem with this boiler, about 5-6 yrs old.

With the heating on, the system pressure rises until the pressure vessel operates and allows water to escape, at around 3.5 bar. When the system cools down again, the pressure drops too low and the ignition lockout operates. I think that upon refilling, it may have been over pressurised, and so I made sure that the next time that water was allowed in, it only went up to around 1.5 bar - but there's still a problem somewhere.

I took the front cover off today to have a look, and found blue-green corrosion on the undersurface of the heat exchanger, with bits of corrosion lying on the plate beneath the burner - hope that the photos may show this.

I had hoped to check the pressure in the release vessel, but the fitter has installed a pipe in the way of the valve

So, does this corrosion suggest a leaking heat exchanger? Many thanks for any help/advice...

 

[OLLIE20]

The build up on the HE is normal, it happens all the time, and is a reason why regular servicing is important, to clean it away, the fins on them low water content copper HE's dnt take much to block. This need 2 be done by an RGI

I dont follow you're pressure problem, if it was high from when you filled it, then obviously when you run it it will rise, once it gets to 3 bar the pressure relief valve will let the pressure out

You say youve pressured it to 1 bar and now its at 1.5 - no problem there?????

Although note, these boilers have cross flow HE's on them and are prone to ruptering internally, which causes pressure rise constantly, unless you isolate CW in to boiler, if this is whats happened atlest you wont have to worry about getting the current one cleaned

 

[Ray84]

HE might have ruptured but faults most likely due to the expansion vessel being burst or flat. check posts on that but probably better to get the boiler serviced, HE cleaned and ask the RGI to check your expansion vessel + also that the safety valve is not now dripping outside

Ray

 

[DeLavel]

Many thanks for the quick responses. Regarding the pressure...I had allowed water in until the pressure gauge was in the middle of the thicker line, assuming that this would be about right. I then ran the heating for about 20 mins, by which time the pressure had risen to about 3.5 and the boiler started venting water to the outside. After switching off and allowing it all time to cool, the pressure was below 1 bar. I repressurised it to about 1.5 (the start of the thicker line on the gauge), thinking that perhaps the lower pressure might help. However, after the boiler had been on for a while (I wasn't present this time) the same fault occurred.

Unfortunately, the fitter has placed a pipe about 1/4" above the valve on the pressure vessel, and I can't get a pressure gauge on it to check this.

Hmm, will have to have another look tomorrow, but it's a relief to know that the HE is probably ok, thanks again.

 

[DeLavel]

I haven't had chance to look at this again until today, am still puzzling.

What can cause the system to overpressurise? Having allowed water in to set the pressure at 1 bar (the minimum required) - and switched on the heating, the pressure gradually rises to about 3.5, whereupon the pressure vessel allows water to escape, just as it should. But what might be causing the pressure to rise like this?

 

[PEDANTICVINDICTIVEMAN]

Duh