Fully Pumped Sealed System / Potterton Suprima 60L / Replace expansion vessel?

[marky9074]

I've got what the Potterton (Suprima 60L) manual defines as a fully pumped sealed system. We've seen water coming out of the overflow outside and assume this is because the expansion vessel bladder has zero pressure (well I think that's why water is seen).

To pump this up I have turned off the mains, cracked open the hot and cold at the nearest outlet by the tank, and pumped to 2.5 bar. I 'think' it's an Imera M18 but am not 100% sure as it's in a wardrobe and obscured somewhat. However, am reasonably confident it does not hold pressure for long, so am wondering what to do. Can you replace the bladder, or do you replace the whole thing?

With the mains off and pressure released at the outlets, is it then empty/de-pressured and can just be replaced easily (looks one one nut only)?

Just read this link:
https://www.diynot.com/diy/threads/faqs.37170/

Indeed if I try to pump without shutting the mains off then there is pressure and water does come out of the Schrader valve.

Any help would be much appreciated.

 

[trojanhawrs]

If water is coming out of the valve the bladder is burst and there's nothing you can do, needs to be replaced. Once you've bled the system pressure you can isolate, check again for no pressure in shrader and remove, water will be in the vessel unless drained down, and even then the ruptured bladder can block the hole and trap it in the vessel.

 

[marky9074]

Thanks for the confirmation. I've ordered a GWS 18L as a replacement. I'm not sure how that is going to fit as the Imera has a flat part which the installer used to sit flat on the wardrobe shelf. I'll work something out and report back.

 

[45yearsagasman]

If that's attached to an unvented cylinder, then you really should get someone with the correct ticket (G3) to change that.

 

[oldbuffer]

1. As its coloured white, that is probably the expansion vessel for an unvented cylinder, not for the boiler.
2. If for an unvented cylinder, there should be a tun dish near the hot water cylinder through which any drips should be visible.
3. If the drip is coming from a copper fitting outside, and particularly if that fitting is 15mm, then likely to be the pressure relief from the boiler, not the unvented cylinder.
4. As 45yearsagasman has stated, unvented cylinders and their accessories should only be worked on by those holding a valid "G3" ticket. Unvented cylinders have the potential to explode if the three level safety system is compromised. They also require an annual service.

 

[marky9074]

Yup, correct, for cylinder and not boiler (apologies should have mentioned that before).

Drip is coming from 15mm outside but assumed from cylinder plumbing as in same location. I'll look for the tun.

Noted on servicing, I wasn't aware of that (and it wasn't passed on - ironic given he was a heating engineer). I'll start looking for someone reputable in Ashford, Kent area.

 

[marky9074]

OK, changed over the expansion vessel yesterday. Biggest issue I had was trying to get a 1"BSP to 22mm coupler from Screwfix as tried to click and collect and then payment didn't go through and it then showed as out of stock (as reserved for me presumably) and no amount of persuading to the 'computer says no' at the counter resulted in a mad dash to the next Screwfix at 17:55.... Anyway I digress....

The old vessel was quite nasty....

 

[trojanhawrs]

Yeah, because expansion vessels are plumbed end of line the water just sits there.

 

[ChrisJP]

I'm curious to know what the advantages are of sealed systems with expansion tanks. The old fashioned vented HW cylinders and vented boiler radiator systems with feed and expansion tanks in the loft do not have the "potential to explode" if not serviced regularly and correctly. So why are sealed systems now apparently so popular?

 

[trojanhawrs]

I'm curious to know what the advantages are of sealed systems with expansion tanks. The old fashioned vented HW cylinders and vented boiler radiator systems with feed and expansion tanks in the loft do not have the "potential to explode" if not serviced regularly and correctly. So why are sealed systems now apparently so popular?

Means you can run off mains pressure without the need for a pump. If I remember right you need 10m of head for every 1 bar of pressure. Also more efficient at retaining the heat

 

[oldbuffer]

1. Central heating systems without a feed and expansion (F&E) tank but with an expansion vessel are called sealed heating systems rather than unvented heating systems.
2. Hot water systems without a vent (generally over the cold water storage cistern CWSC)) are called unvented hot water (DHW = domestic hot water) systems.
3. Sealed heating systems have the advantage that they do not require the F&E, which is a ready source of oxygen entering the system water and causing corrosion. Also a generally minor space saving without the F&E.
4. Unvented DHW systems offer the advantage of mains pressure hot water as well as cold. Also, in conjunction with a sealed heating system, they enable the CWSC to be removed. A space saving, particularly in flats.
5. The above does not include the points against sealed / unvented systems.