Help needed re Unvented Hot Water Storage System.

[Michael02]

Hi. I am very confused.
I have an unvented hot water storage system.
The system appears to be working ok.
In the airing cupboard there is a Tribune hot water cylinder with a Varem 24 litre vessel on the top of it.
I thought I should check the precharge pressure.
So I turned off the mains water and opened the nearest hot water tap to the cylinder. Then I checked the pressure (with a tyre gauge) at the Schrader valve on top of the Varem unit.
The pressure was zero - which seemed wrong, the label on the Varem said the precharge pressure should be 2.1 bar.
I tried pumping it up but it stayed at zero.
I turned off the hot tap and turned on the mains water.
When everything had settled I checked the pressure again and it was 20psi. No water comes out of the Schrader valve so I guess the diaphragm is ok. And the system works.
I guess I am doing something wrong here...!
And I definitely don't understand what I am seeing...!
Could one of you experts please explain things to me..?

 

[heatingman]

I suggest you call a qualified engineer, its not something to fiddle about with. Potential for all sorts of nasty things.

 

[wetshoes]

These can take quite a while to pump up, especially if you are using a pants £4.99 foot pump from Halfords !

Even though it gives a precharge pressure on the side of the expansion vessel it might have been set at a lower pressure for a reason.

As per the previous post, could be a good idea to get someone experienced (and qualified) to take a look.

rgds

 

[rojaca]

If you had any charge in your vessel you have now lost it, if you pushed down long enough on the schrader to check for a split diaphragm.
You need a car foot pump (maybe one costing £9.99?) preferably with pressure gauge on.
Turn off hot water and open all hot water taps so you have no head of pressure above vessel. Now connect and pump and get up to pre-charge pressure. Are you sure that's the only reading on data label? Doubtful plumbers would have adjusted charge to specific requirements of install anyway.
As posted above Unvented Hot Water isn't something to fiddle about with, but it is better that you run vessel with a charge in rather than no charge at all. I would then get suitably qualified person in to check what you have done as soon as possible.

 

[Michael02]

Thanks for that.
On the label all it says is :-

Varem 24 litre
Precharge pressure 2.1 Bar
Max pressure 8 Bar
Working Temp -10 +100 degrees C
Date 07/96

The strange thing is everything seems to work ok.
Even the shower is good.
So I've no idea how long it has been like this.
That's why I was wondering if what I am seeing is normal.

 

[kevplumb]

according to the mi's ex vessel precharge is 3 bar

 

[ajstoneservices]

Thanks for that.
On the label all it says is :-

Varem 24 litre
Precharge pressure 2.1 Bar
Max pressure 8 Bar
Working Temp -10 +100 degrees C
Date 07/96

The strange thing is everything seems to work ok.
Even the shower is good.
So I've no idea how long it has been like this.
That's why I was wondering if what I am seeing is normal.

The data above doesn't matter it won't help you charge the vessel correctly.

What you've described isn't normal.

You need to get someone to check and re-charge the EV.

 

[Michael02]

Many thanks for all the suggestions.
I got myself a better pump and with this I set the Precharge Pressure to 2.1 bar as per the label.
Four days later I checked it again and it is holding aok.
Thanks again...!