Worcester Heatslave 3.5

[roadhouse3211]

Hi all,

I have one of these Worcester Heatslave 3.5 gas combi boilers.

It has had a long term problem with the preassure vessel which now looks like its finally givien up the ghost (preassure loss, down to around 0.3bar when cold, rising to over 3bar when hot. If i top it up to 1 bar cold, it looses it overnght and the hot preassure gets even higher).

The heating guy i use got round it once by draining it and pumping air back in, that lasted about a year. This time the loss has been fairly sudden and it now looks as if its had it.

No great problem, the spares are available but how do you actually replace the vessel ?

I cant (and neith can my heating engineer) see a way of physically getting into the boiler to remove the faulty unit !

How do you go about dismantaling the boiler in order to replace the preassure vessel ? What do you need to remove and how ?

if anyone can assist that would be great.

Cheers
Shaun

 

[Agile]

If you are quite sure thats the fault then you usually take the boiler off the wall and replace the expansion vessel.

Its good to be sure!

Tony

 

[roadhouse3211]

Hi Tony,

I#m fairly sure its the preassure vessel. This problem has happened before and we fixed it by re charging the air up. But back then, it lost preassure over a long period of time. This time it was over a few days...

This boiler is floor standing with the flue directly through the wall. The vessel itself is located at the bottom and the read of the boiler, there doesnt seem any way of getting to it without either totaly removing it from its installed location, or removing just about all the 'guts' from the front.

I was hoping there may be a way of removing the side panel, which would help enormously.

any ideas...?

Cheers
Shaun

 

[Agile]

Its easier to repressurise it first in case that cures the problem. See FAQ.

Tony

 

[namsag]

Leave existing vessel in place and fit another one elsewhere . Is an option

 

[roadhouse3211]

Cheers for the info guys, I will try repreassurising it first i think.

just to double check the process...if i have understood it correctly....

1; empty water from the pressure vessel using the black valve under the lid of the boiler. As i recall, you open this (its also where the water is expelled from if the over pressure saftey is activated) and what ever water is in the vessel will be expelled from the overflow, the pressure guage should drop to zero.

2; with the pressure guage at zero, check the pressure at the pressure vessel, and if required pump air in to a max of 10psi

3; shut the black valve

4; fill the boiler until the pressure valve reads 1bar

5; fire it up and watch the pressure

Is this right ?

Cheers
Shaun

 

[gas4you]

Don't drain the boiler via the prv, as this can cause debris to foul the rubber seat and leave you with a dripping prv afterwards that will need replacing

 

[roadhouse3211]

Thanks for the avidce,

On the heatslave, where do i drain the vessel if not from the prv ?

I can see a drain cock at the front right side of the boiler, behind the gas valve and infront of the pressure vessel, is this it ?

Also, i had tried opening the prv (before i read your reply) and couldnt get it open, it has arrows pointing clockwise on it but if i try and turn it it seems like it just rides up on a 'cam', then clicks back down and stays shut. A bit like a safety cap on a bottle of tablets. is this right ?

Cheers
Shaun

 

[gas4you]

That is how the prv works. It is not an open or shut valve, just a 'last resort' safety valve on a spring that should open if the system pressure goes above 3 bar. Not sure where the proper drain is on this boiler but sounds like you have found it.

 

[roadhouse3211]

Thanks Dave,

I am draining it now, although i have noticed that the only way i can get water to flow from it is to open the PRV as well..even though the pressure guage shows .05 bar.

how long should it take to loose this pressure ? I have let out some water from the drain (about 5 litres or so) and the needle has hardly moved..if at all.

is there something wrong here somewhere ?

also, I notice that there is no air in the pressure vessel (expected), as a test i did manage to pump a small amount in, and it is retaining it. so I have let it back out until i can get the main guage to read zero.

Cheers
Shaun

 

[gas4you]

Have you shut the ch flow and return isolaters on the boiler. If not you will be draining the rest of your system as well

 

[roadhouse3211]

hi Dave, Many thanks for helping me out with this..

Have had a look at the boiler, the only valves i can find are on the connetors which attach to the in and out sides of the pump, there are no valves on the actual pipework.

They seem to be stuck fast as well, if i cant get these shut will I just have to continue draining the CH as well until the reading is zero ?

Cheers
and many thanks
Shaun

 

[gas4you]

usually there are valves on the flow and return connectors under the boiler. They may just have square heads or a slotted screwdriver slot. These turn 90D to shut them off.

If you are draining entire system you need to open radiator air bleed valves to let it drain quicker

 

[roadhouse3211]

Thanks Dave,

The boiler is floor mounted but all the pipework is at the top of the boiler.

I can see the flow and return pipes, and the only vlaves on them are the ones on the connectors to the pump.

They do look exactly as you describe them though.

I have removed the bleed screws from the upstairs radiators, more water came out, them stopped. The guage still reads .05bar and the downstairs rads, are still full of water.

the pressure just wont drop to zero

Thanks for the help
Shaun

 

[roadhouse3211]

sorry, that should be 0.5 bar not .05 bar...

Cheers
S