Cannot Precharge Expansion Vessel

[Syd98]

Continued from my last post.. (no more replies)
Unvented system losing pressure..! I have checked with car pump pressure of expansion vessel = 0 bar, when i blow it up, the gauge on the pump slowly fals back to 0 (sytsem pressure acording to RWC (maker) should be 0.5bar).
Could the fault be leaky Schrader valve. (would this cause my pressure loss when system is ON)
If i top up cold and leave off stays good?

 

[doitall]

The pre-charge in the vessel and the system pressure are different.

You need the system pressure on zero to check the pre-charge, if however it is not holding the pressure then the vessel has gone toes up

 

[Syd98]

The systen pressure was 0 when I checked with footpump c/w gauge. Also air is escaping when I remove pump. Presume valve as gone.
Would this account for pressure loss in the system?
If so wheres all the water gone i've been topping up with the past 2 weeks. Local engineer says CH coil could be leaking within the water cylinder (Megaflo) Asked how you check? He says fit a new one..!

 

[doitall]

The systen pressure was 0 when I checked with footpump c/w gauge. Also air is escaping when I remove pump. Presume valve as gone.
Would this account for pressure loss in the system?
If so wheres all the water gone i've been topping up with the past 2 weeks. Local engineer says CH coil could be leaking within the water cylinder (Megaflo) Asked how you check? He says fit a new one..!

Can we decide if you are pressurizing the system or the vessel.

The local engineer is most unlikely to be correct, in fact I'll put money on it.

If the vessel has lost it's charge the boiler pressure will raise and dump the water from the pressure relief valve.

 

[ChrisR]

Would this account for pressure loss in the system?

What system do you mean? Heating system? Probably not anthing to do with hot water system . Leak unlikely between the two on a Megaflo.

 

[Syd98]

Pressurizing the Vessel. But. I have had a bucket on the discharge pipe and have collected no discharge from the PRV? I did think the local engineer was talking ****, So much for recommendations, I think I will get a new vessel and try it for the cost? Presume you buy them pre-charged.

 

[doitall]

Pressurizing the Vessel. But. I have had a bucket on the discharge pipe and have collected no discharge from the PRV? I did think the local engineer was talking ****, So much for recommendations, I think I will get a new vessel and try it for the cost? Presume you buy them pre-charged.

before you go doing things like that where is the vessel, what is the make and model of the boiler etc

 

[Syd98]

Boiler is an Ideal Minimiser SE (8yrs Old), Cylinder is Megaflo, Vessel is RWC 8Litre pre-charged to 0.5bar.

 

[doitall]

So with the system pressure on zero, you have tried to pressurize the vessel to between 0.5 and 1bar, and the vessel does not hold the charge.

 

[Syd98]

Yes that is correct, must be a leaky shrader valve?

 

[chrishutt]

Yes that is correct, must be a leaky schrader valve?

Or a leaky diaphragm. It's easy to check if either is leaking - just immerse the valve or the threaded pipe connection in water and watch for bubbles while it is still pressurised.