WB HEATSLAVE 18 25 losing pressure

[DAVID BISHOP]

Hi all
I am new to this forum so if I put in too much information please forgive me. I have a WB Heatslave 18 25 oil combi boiler. I have had it for a number of years. I know WB has a great reputation which is why I bought this boiler but it has been temperamental, to say the least.
It has always had a propensity to lose pressure. I have called out engineers on many occasions and even WB came to look at it but it remains unreliable. It is serviced regularly. Currently it is losing pressure again and from my limited knowledge I think it could either be a faulty pressure relief valve or a faulty expansion tank. The latter is almost new so I suspect the pressure relief valve.
My question is, how do I safely check to see if it is this valve that is malfunctioning?

 

[Millsy 82]

Worcester dont really have a great reputation especially when it comes to oil.

But if you have had several engineers look at it it may not be the boiler.

Check all your radiator valves for a green stain on crumbly greenish stuff that is a sign of a leak.

How long is it taking to lose the pressure? What are you pressuring it to?

 

[Sharp Point]

Is there water coming out of the pressure relief tube outside, when the heating is on? That’d determine a leak from there.

 

[DAVID BISHOP]

Worcester dont really have a great reputation especially when it comes to oil.

But if you have had several engineers look at it it may not be the boiler.

Check all your radiator valves for a green stain on crumbly greenish stuff that is a sign of a leak.

How long is it taking to lose the pressure? What are you pressuring it to?

Thanks for the reply. There are no leaks in the system and the rads are new. Pressure loss is variable in that it can lose pressure over a couple of days and on other occasions, it stays fine for a few weeks. There is a new stain on the wall outside under the pressure relief pipe so I guess that pinpoints the problem.

 

[DAVID BISHOP]

Thanks for the reply. There are no leaks in the system and the rads are new. Pressure loss is variable in that it can lose pressure over a couple of days and on other occasions, it stays fine for a few weeks. There is a new stain on the wall outside under the pressure relief pipe so I guess that pinpoints the problem.

Oh and I only pressure it to 1.5 bar. Thanks again for responses.

 

[Millsy 82]

Sounds like a problem within your boiler that you would need an oil engineer to sort out for you. A good one should find the fault relatively quickly from what you have said.

Maybe post your location up on here and one of the oil lads on here might be able to help.

 

[Sharp Point]

How many radiators do you have? Your internal expansion vessel, may not be big enough volume to accommodate your system, you may need an additional vessel.

 

[Best]

Well known fault - your boiler expansion vessel is only 12 litre and will not be big enough for all the total volume of water in the rads, pipes and boiler.
Your engineers don’t know much if they didn’t suggest it.
Have a second expansion vessel installed to return pipe, preferably near to boiler if possible, but not essential.
The existing boiler vessel and the extra vessel will need the air charge to be same and this also requires checking and air recharged each year.
You probably do not need to have your system at 1.5 bar. Usually 1 bar when system cold is plenty, but your engineer, if you can find a decent one, will advise.

 

[robdog6000]

You can test the prv by putting a plastic bag over the pipe. Put a tie-wrap or rubber band on in to hold it in place.

 

[DAVID BISHOP]

Well known fault - your boiler expansion vessel is only 12 litre and will not be big enough for all the total volume of water in the rads, pipes and boiler.
Your engineers don’t know much if they didn’t suggest it.
Have a second expansion vessel installed to return pipe, preferably near to boiler if possible, but not essential.
The existing boiler vessel and the extra vessel will need the air charge to be same and this also requires checking and air recharged each year.
You probably do not need to have your system at 1.5 bar. Usually 1 bar when system cold is plenty, but your engineer, if you can find a decent one, will advise.

That is new to me and really helpful. Thank you. Finding a decent engineer is another matter entirely where I live. Recently my sister had a leaking tap (I was out of the country), she phoned a local firm and two weeks later they sent out an "engineer" who said, "Yep you have a leaking tap but I don't have any tap washers on the van". (???????!!!) He went away but two days later a bill for £50 arrived!

 

[Millsy 82]

That is new to me and really helpful. Thank you. Finding a decent engineer is another matter entirely where I live. Recently my sister had a leaking tap (I was out of the country), she phoned a local firm and two weeks later they sent out an "engineer" who said, "Yep you have a leaking tap but I don't have any tap washers on the van". (???????!!!) He went away but two days later a bill for £50 arrived!

Where abouts are you? Maybe one of the oillies on here can help you.

 

[antoine irving]

Give fernox F4 leak sealer a try, you might have a weeping leak somewhere under the floorboard

 

[Millsy 82]

Give fernox F4 leak sealer a try, you might have a weeping leak somewhere under the floorboard

Not if there is staining under the prv I wouldnt.

 

[michael sweeney]

how do you put presure in boiler

 

[John.g]

If the E.vessel pressure rises to > 2.8/2.9bar with the system hot then you will loose pressure, the PRV can also then weep at normal pressures but very easy to check as shown.