Alpha CB24 constant pressure drop - HELP!

[Zip]

ALPHA CB24

Hi

About 2 months ago, I bled the upstairs radiators.

A lot of air came out, so they needed topping up.

I topped up via the combi boiler - and from that point on, my Pressure Gauge drops to zero around every 2 hours - ONLY WHEN THE C/H IS NOT ON.

At first I thought it was a leak under a floorboard - so I waited for the leak to start somewhere. Nothing.

BUT I have just noticed that my overflow pipe is soaking wet underneath, because it's constantly dripping.

Someone said that by bleeding/topping up, I might has disturbed a bit of muck which has stuck in the pressure relief valve. Yesterday I kept turning the valve to release the water and topping up. This hasn't helped.

I know this seems a silly question - but could it be anything else other than the "3 BAR (red) Valve"?

I ask this 'cause I've read somewhere that they rarely breakdown.

This boiler is around 8 years old.

One other point, when the central heating is on - the pressure drops very slowly. When the C/H is on the pressure gauge reaches 2 to 2.5 bar.

I finally found the expansion vessel and tried to pump it up - but it would only take two strokes (car foot pump).

Any help or pointers would really be appreciated.

Thanks in advance, Stephen

 

[Bahco]

You are losing pressure through your prv if it is constantly dripping.

Call someone in to replace.

 

[Agile]

You have not correctly pressurised the expansion vessel. Follow the instructions EXACTLY as stated in the FAQ here.

The PRV is probably Ok but until you have sorted out the problem with the expansion vessel you will not know.

Tony

 

[Zip]

Thanks Tony - just one point, the FAQ sates that it's "imperative that water or air is allowed to escape from the heating system"

Does this mean while I'm pumping I get someone to 'hold open' the PRV (sort of half way?)

Cheers, Stephen

Below is from the FAQ


4.6) During this phase it is imperative that water or air is allowed to escape from the heating system as it is pumped out of the Pressure Vessel. Otherwise the system pressure will resist your pumping and give a meaningless reading. If you aren't sure, let some more water out of the system when you have the air pressure at the right level. If that makes the air pressure drop, pump a bit more and release water and so on, until it doesn't.

 

[eccoboy]

Hi I have a similar issue with my Alpha CB24 boiler. When pressurised to the correect water pressure (cold) and then fired up water passes to the outside and ends up in a small visible pool on my garage roof. When the boiler cools down the pressure has dropped to the point at which it won't then fire up again.

Is this the pressure vessel or the PRV that needs replacing?

Any help greatly appreciated, I dont really want to plumb in an external vessel if it then turns out that its a faulty PRV! Vessel is about £30 all in from Screwfix, PRV is £20 and is easier to fit!

Cheers Ben

 

[ianmcd]

Thanks Tony - just one point, the FAQ sates that it's "imperative that water or air is allowed to escape from the heating system"

Does this mean while I'm pumping I get someone to 'hold open' the PRV (sort of half way?)

Cheers, Stephen

Below is from the FAQ


4.6) During this phase it is imperative that water or air is allowed to escape from the heating system as it is pumped out of the Pressure Vessel. Otherwise the system pressure will resist your pumping and give a meaningless reading. If you aren't sure, let some more water out of the system when you have the air pressure at the right level. If that makes the air pressure drop, pump a bit more and release water and so on, until it doesn't.

you can do it that way but your risk getting grit sticking to the seat of the PRV and it will drip, it is not recommended to manually operate the PRV, either open the system drain or open a bleed valve at a radiator and have someone hold a container to catch the water as you pump up the expansion vessel and dont be tempted to over pressurise the EV

 

[eccoboy]

Hi, though that I'd post back the results of the work done on my CB24.

Eventually fitted an external pressure vessel bought from Screwfix (8 litre one) and fixing collar (all in about £37) Cut this in to the return of the heating system after draining down , fitted with a compression t joint with a stab of 22mm copper pipe sticking out and then bought a 900mm length flexi hose again with compression fitting onto the stab end of the t joint and then tightened straight on to the new expansion vessel. (flexi hose again from Screwfix at £5.00 - don't go to B&Q!)

Refilled with the filling loop, bled the radiators and it works at treat, no more lost pressure at all. Will need to add some inhibitor through the top radiator at some point soon though as I didn't do this (this is about £8 and can be squirted in with a silicone gun)

Hope this helps people along the way.....

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• eccoboy
• 11 Mar 2013
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• eccoboy
• 11 Mar 2013
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• eccoboy
• 11 Mar 2013
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[ianmcd]

You could have saved yourself a lot of expense and a lot of time if you had just followed the advice given to properly re-charge your existing vessel

 

[eccoboy]

A check of the pressure vessel had already been undertaken and showed that this was losing pressure from the 0.8 recommended in the user manual.

Cheers Ben