Grant Combi 90 losing pressure

[mrbriggs]

OK, I think it's the pressure vessel...

When I got home today, the heating was on as it's set to start just as I walk in the door(!) and the water was leaking out of the prv pipe. Got in and the readin was 2.5 bar so I presume the PRV is doing it's job. I powered it all down, released some water and let it cool. Checked the pressure vessel and water came out of it. Does that mean it's knacked? I'm presuming the boiler is getting high pressure when operating due to the pressure vessel not having any air in it and it's full of water?

Where can I get one of these from?

Also, Should I get a bigger one? I currently have the 10 litre one. Any benefit buying a 12 litre one? Will it fit....

http://www.oilboilerspares.co.uk/acatalog/Grant_Combi_90.html

Thanks

 

[oilman]

See if you can mount an external one somewhere, they are cheaper, and you can have a bigger one. From what I've seen they are more reliable than the ones supplied in boilers.

I suggest you ring grants and ask them for a manual, of course if you have one, you had better read it as it has the answers to many questions.

 

[mrbriggs]

Hi, I don't think I have any space to mount an external 1. I know they are cheaper, but there is nowhere for it to go.

Do I need some sort of compound to make a tight seal on the joint when connecting the new vessel?

Thanks.

 

[oilman]

It's just a fibre washer. 1/2" bsp I think. I don't have to know, I just pick the right size out of the box.

 

[mrbriggs]

OK, thanks.

Can someone just confirm for me, is it DEFINITELY the expansion vessel? Like I say, when I pressed the "tyre like" valve, water did come out. Is this confirmation it is faulty? Was it worth replacing the auto air vent too? (just because it's cheap £8, and while I'm working on the boiler may as well do it, plus someone said these are "cheap" on the grant boilers as in unreliable!)

One other thing, I would like to do a flush and was trying to work out where to drain the system from. There is a tap on the front of the boiler at the bottom and obviously I have the two top up points. How do i use these 3 connections to flush the system?

Thanks.

 

[mrbriggs]

ANYONE?!

I got an email back from Grant directly. They are doing the PRV for a mere £17 + vat, should i get 1 of these as well as it's cheap?

Cheers peeps!

 

[JPH/01]

Sounds as if your problem is the vessel, if there is crud and wet round the top of the auto a/v then it is knackered, the p-r-v will most probably be fine.

 

[mrbriggs]

I have ordered the vessel and auto air vent from oilboilerspares.co.uk

Is it just a case of topping up the system (after a flush of the heating system and topping that up first obviously!) Will the vessel come pre charged to the correct pressure? What should the pressure be set at?

Thanks

 

[mrbriggs]

Forgot to ask, when fitting the Auto air valve is there anything I should know? Do I have to open it when filling the system and close once it's filled?

 

[mrbriggs]

Just fitted the new parts after doing a flush, Filled with inhibitor, bled system, everything appears to be working and is actually better than before. The rads get roasting now!!! Pressure is 1bar when cold and 1.5 bar when in operation.

Just want to say thanks for all your help on this.

Lee.