22mm compression isolating valves

[boydell]

Hello,

I am a newbie to this forum, so I hope am not going over old ground.

I have a 10 year old Worcester 240RSF Combi which I have managed to repair from time to time (non gas side that is), and as a result the 22mm central heating on/off flow and return pipe isolating valves slot head screws have become mangled and very difficult to operate. These would not be easy to replace, so I would like to add two standard 22mm isolating valves just below the offending originals where they enter the bottom left of the boiler.
Can anybody tell me if this is the best solution? Would gate valves be a better idea? From reading other plumbing forums I understand some plumbers in the trade don't bother to turn the CH flow and return off when draining the system because of the risk of them leaking. I have tried this, but when I fired it up (after filling to 1.5bar) I got an alarming banging and clanking noise from the boiler, and the thermal trip popped out. However, after resetting it and trying a second time all was well. Is there a trick of the trade to doing it this way?

regards,
boydell.

 

[helpsy]

Gate valves are for low pressure use

 

[traineedrip]

Id stick to the usual brass ballofix valves. The problem with gate or lever valves are they are to easy to fiddle with or be turned off accidentally... something the combi wont like. As said gate valves are for gravity and even then their not brilliant.
Ballofix cant really be accidentally turned off and they dont tend to fail.(as long as you have a good fitting driver)

 

[Puddle]

I very rearly close the valves ,as said they will propably leak and most of the time there is not need to do so
If you have banging when you first fill up,you probably have the auto air vent closed.this needs opening to let air out when you are filling the boiler
also turn the temperature dial to its lowest setting

 

[boydell]

Many thanks Lads for your help... it is appreciated.

This forum is the third I have joined in an effort to find answers to my questions, and has been by far the best!

Even so any more advice on this subject would still be welcome.

regards,
boydell.

 

[Bernie2]

You can buy gate valves for a pump if you want them. As you say the 1/4 turn slotted ball valves usually wear out.

The problem with ball valves is that in some situations they can cause water hammer as they shut off so quickly, not that that is a problem if you only intended to use them on central heating systems.

Incidentally a Conex gate valve is rated as being able to withstand 16bar pressure and a temperature of 30C, the same as a 1/4 turn ball valve.

A Conex stop or screw down valve is only rated at 10bar but a temperature of 65C.

The screw down though has a more positive off than a gate valve and its the only one they allow on mains water. And the screw down with a loose jumper can act as a none return valve which is basically ideal to protect drinking water.

But gate valves come in all kinds of types and pressure ratings. I've used specials on steam lines. So its a case of a gate valve isn't just one valve it covers many different types of gate valve.

 

[chrissyposs]

the best valve to use are quarter turn 22mm full bore lever valves, then take off the handle, that way the home owner usally won't touch as no handle and they are full bore so they won't impeed the flow rate on the system and poss lock out the boiler on overheat as ball o fix reduce.

 

[boydell]

Grateful thanks to Bernie2 and Chrissyposs for their info... much apreciated once again.

regards,
boydell.