New expansion vessel needed?

[omega015]

Boiler maintenance/repair company already notified and due out Thursday (providing my claim is valid for the policy) I am just asking for clarification/confirmation so I know what to expect. If the flue seal part cannot be answered due to fear of DIY please omit this question.

Long post so I underlined my actual questions. thanks.

Noticed a water drop from the pressure relief external pipework from the combi (Worcester Greenstar 25Si) this morning. Pressure when heating was off after being on, slowly went to almost 0 bar. No air in radiators, topped up to 1 bar and heating back on and confirmed PRV activated and above 3 bar pressure. I have an internal expansion vessel at the back of the boiler as part of the fixing frame and can just about reach the air valve.

Gave the air valve a little press and immediately water came out of it. It that a 100% guarantee that the diaphragm is no good and the vessel needs changing? Re-pressuring the vessel isn't going to achieve anything (except maybe a short term fix?)

The boiler is housed inside a cupboard and the flue goes out over the top of the boiler, so they cannot do an in-place replacement of the vessel without either taking off the boiler or could they remove the flue and go above? If they remove the flue should they replace any gaskets/sealant with new? Or is this not required/applicable for this part?

I haven't had this company do a service before as my policy auto switched over to these from an energy supplier no longer doing this cover so I don't know the quality/thoroughness of their work. And on reflection I believe the previous company barely did a service on the boiler (dirty condensate trap, previous leaks where the green corrosive stuff hasn't been cleaned off, no vacuuming the combustion area etc...

As its likely they will need to drain down the system replace the vessel should they be re-adding any inhibitor? Oh and after having a bag loosely attached to the PRV outlet, the water colour was medium brown (maybe slightly green).

Again this all comes down to them accepting that the vessel is part of the boiler and not external to it. Not sure if they would try to get out of it that way or not.

Few pics so you can get idea of what space is like.

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[Madrab]

If there's water where there's supposed to be gas then yup 99% guaranteed the EV's membrane has gone. If that's a void/empty space above the boiler cabinet then a remote vessel could be installed on that return pipe and the vessel located in that space and then a piece of board matching the cabinet put on the front to hide.

 

[omega015]

Thanks Madrab. If I can get them to replace the faulty one then that would be preferred as I don't want to have to add another thing to my to-do list. If the vessel is part of the boiler cover I have I don't see why they shouldn't go to the trouble to swap it out. I shall see what they say/do Thursday, although the call centre did suggest they only come to identify the fault first so I doubt they will repair it then even though I did explain what was the issue.

 

[Madrab]

Yup, leave it to them, that's what you pay for.

 

[Aquaheat]

@omega015 just because water was ejected does not mean the vessel is FUBAR. They are prone to condensation and will always hold a bit if water.

What you need to do is isolate the boiler, drain the boiler side of all pressure, leave an open end (drain point) and then test pressure in the vessel. Pump up vessel with the open drain point open to MIs. Normally about 0.5bar. If this holds then vessel is all good.

Jon

 

[DP]

@omega015 just because water was ejected does not mean the vessel is FUBAR. They are prone to condensation and will always hold a bit if water.

What you need to do is isolate the boiler, drain the boiler side of all pressure, leave an open end (drain point) and then test pressure in the vessel. Pump up vessel with the open drain point open to MIs. Normally about 0.5bar. If this holds then vessel is all good.

Jon

Agree 100% with above
Agree 100% with madrab's pos also
Am going to do a Tony Agile and say not many know how to pump up the expansion vessel so bang in secondary expansion vessel when existing is perfectly ok

 

[omega015]

Yeah I prefer to try narrow down problems before trying different things and wasting time/money. If I get chance tonight I will do some further tests as above to see if the vessel truly has had it or not, if not then will have to trust the engineer coming tomorrow will be on the ball.

Will post update as/when I get them and thank you all so far.

 

[Agile]

There is often a little water on the air side.

If it has lost all it's air pressure then you might well get 10-20 cc of water out.

So my advice would be to let the water out and see just how much you get.

If the diaphragm was holed ( very rare ) then the water would keep on coming as it would flow from the heating side.

In most cases only a limited amount of water comes out and then it is possible to repressurise with air. As long as this is done with the system depressurised all the time you are pumping it up.

All this can be done by a DIYer when the EXV air point is accessible without opening the boiler sealed cover as in this case.

If you try to leave it to a boiler cover firm you run the risk of them trying to get out of it as changing an EXV like yours can be a big job sometimes meaning removing the boiler from the wall.

Most independents would add an external EXV instead of replacing the one in the boiler if that was more work.

Tony

 

[DP]

Most independents would add an external EXV instead of replacing the one in the boiler if that was more work.

Not I sir, I prefer to replace internal vessel almost every time

 

[Agile]

So if it is easy to fit an external EXV, you will want to charge the customer say £200 to remove the boiler from the wall to fit the manufacturer's own expensive part?

Usually fitting an external EXV is far cheaper and the part itself only about £30 compared with the manufacturer's part which can be more like £60.

 

[Aquaheat]

Not I sir, I prefer to replace internal vessel almost every time

+1

 

[DP]

So if it is easy to fit an external EXV, you will want to charge the customer say £200 to remove the boiler from the wall to fit the manufacturer's own expensive part?

Usually fitting an external EXV is far cheaper and the part itself only about £30 compared with the manufacturer's part which can be more like £60.

Don't be obtuse.
How often does the Vokera, plethora of Baxi/ Pottertons and a host of other makes require boiler removal off the wall. Some of these boilers have EV so situated that it is faster and ECONOMICAL overall to fit genuine part instead of sourcing external EV, modification of pipe, afixing the vessel to structure, making sure the charge point is well sited etc.

Perhaps you would be charging £200, sorry has to be a multiple of £84.00, so £168 or even £210, by the time the bus takes you to the supplier to select necessary parts etc. Plus the material.

Granted there are times when an external vessel needs hooking up. But to 'save' the customer money is not an excuse. It is the customer who decides if external unsightly vessel is order of the day

Again quoting figures that are pointless and just plucked from air to make a (weak) point

Some of the stuff you are posting currently seems to suggest you lack authentic repair skills.

 

[Phill Peck]

As above

Most manufacturers have the foresight to put the expansion vessel where it can be removed without the boiler coming with it.

I'll fit external if it is more practical than internal, usually on worcesters. Also it is quite common that the internal ev in undersized anyway.

Op I don't think you've got enough height/space even with the flue out do they'll probably have to take the boiler off the wall

 

[Agile]

Don't be obtuse.
How often does the Vokera, plethora of Baxi/ Pottertons and a host of other makes require boiler removal off the wall. Some of these boilers have EV so situated that it is faster and ECONOMICAL overall to fit genuine part instead of sourcing external EV, modification of pipe, afixing the vessel to structure, making sure the charge point is well sited etc.

Perhaps you would be charging £200, sorry has to be a multiple of £84.00, so £168 or even £210, by the time the bus takes you to the supplier to select necessary parts etc. Plus the material.

Granted there are times when an external vessel needs hooking up. But to 'save' the customer money is not an excuse. It is the customer who decides if external unsightly vessel is order of the day

I was very careful to say that fitting an external EXV was likely to be a cheaper option where it is difficult to replace the original in the boiler.

How difficult to replace the original depends on where and how the boiler has been fitted.

I always explain the options ( and costs ) to the customer.

 

[Aquaheat]

I was very careful to say that fitting an external EXV was likely to be a cheaper option where it is difficult to replace the original in the boiler.

How difficult to replace the original depends on where and how the boiler has been fitted.

I always explain the options ( and costs ) to the customer.

But regardless, even if the boiler is required to com off the wall it's a couple of hours? A new EXV is an hour to fit anyway so why not do the job properly?

As for the comment about original EXV being undersized, how often do you come across a system over 100 litres? Even then there is a leeway which allows the EXV to be given an additional precharge to compensate for additional system volume.

Surely this was down to original design and you would mention this to them should you come across it?

Jon