Help with an unvented hot water cylinder please!

[highside23]

Please bear with me I have a new born baby in the house and I want to get this sorted so I will try and be as concise as possible.

I have a Heatrea Sadia Electromax electric combination boiler.

The original problem I had when the system was fitted was water hammer every time the toilet was flushed (upstairs only) or a tap was opened fully (again upstairs), the pressure was high then the hammer would happen and the pressure would return to normal. I closed in the stop cock a bit and this helped.

Then months later (a few weeks ago) I noticed the overflow was dripping whenever the water in the cylinder heated up. If I opened the expansion valve on the cold water combination valve (which was very easy to do, like it was a bit open anyway, obviously) the pressure would go and the valve became harder to open. I.e working as it should. I emailed Heatrea sadia and they said check the pressure vessel pressure (it should be 3.5bar) I did there was no pressure and I found a faulty valve. I replaced the valve and recharged the vessel. The water hammer is now back and worse than ever!! (It now happens with the downstares taps too) So I emailed them again and they said that the vessel should be pressurized to match the incoming water pressure. I phoned the water board and they don't know what it is and won't come and measure it.

What can I do to stop it!? I know you can get arrestors to put on the toilet, but it’s not just the toilet that does it. Will opening the stop cock fully help? would matching the pressures really stop the hammer?

Please help!!

 

[CBF]

as it's an unvented cylinder you shouldn't be touching it, you need to get someone to look at it who has the G3 unvented cert

 

[Dan Robinson]

If you are competent to work on an unvented cylinder, you should already know how to measure water pressure?

 

[batco]

You have a problem with cold water pressure. Is your cold water circuit balanced? (connected through the pressure reducing valve?)

 

[Agile]

You need a qualified person to work on it.

Many will not be able to sort out your problem though because it could be caused by the size of pipes used in the installation and that needs original thought as its not covered by installation instructions. You have an hydraulic tuned circuit and that needs to be damped.

I have sometimes needed to fit different sized pipes to cure that problem!

Tony

 

[highside23]

The system is connected via a combination valve which has a prv.

I am not a plumber by trade but an electromechanical engineer. I know there are professionals but i have a go at most things myself, so came on here to see if I could get advice to fix it myself. Looks like that may not be the case. Where would I find a G3 engineer?

 

[batco]

Is your cold water circuit connected to the PRV port.?

 

[highside23]

Yes I think it is.

This is the system:
http://www.google.co.uk/imgres?q=el...p=29&ved=1t:429,r:11,s:141,i:223&tx=156&ty=63

 

[Agile]

That is just the installation diagram.

They are often not installed corrrectly!

Tony

 

[batco]

If your installation is matched with diagram then you may have to look in to expansion area. There is a company called surrygas.co.uk try to speak to them. they are very small but best in heating business. masters of heating problems.

 

[dcawkwell]

Pressurise your expansion vessel with the water off
and a hot tap open to about 1.5 to 2 bar should sort it.

 

[Dan Robinson]

Let's hope for this new born baby's sake the OP knows how to check the safety devices

 

[highside23]

Thanks for the helpfull replies.

 

[HDRW]

The "high pressure" from the taps then dropping sounds like the expansion vessel isn't doing its job, and the water hammer may be caused by that too.

The expansion vessel has a rubber diaphragm or bladder which has the water on one side, and pressurised air on the other, with a schrader (tyre-style) valve connected to that side. The air pressure may need topping up, or the vessel may need replacing.

Find the expansion vessel and briefly press the pin on the schrader valve - you shouldn't get any water coming out, and if you do it needs a new expansion vessel, which is a professional job.

If you just get air, check the pressure with a decent tyre pressure gauge with the supply turned off and a hot tap open, so you're measuring the air, not water, pressure. Find out what the pressure *should* be, and pump it up to that.

Good Luck!

Cheers, Howard