Service valves in a central heating circuit.

[Rednadnerb]

Service valves in a central heating circuit. Is this a no no? I've put some to help moving a rad and now it hardly warms up. Pretty sure that nothing else has changed.

Thanks

Brendan.

[Roger Mills]

Do you mean the small in-line ball ball valves, with a screwdriver slot to rotate to turn them on and off?

They *do* cause a flow restriction, so it's better not to use them on big radiators. They're ok for small ones though. The larger full-bore lever isolation valves are far better when you don't want any restriction - but you don't too many of those on show in your living room!

In your particular case, my guess is that you've somehow succeeded in getting an air-lock in your system while moving the rad, and that a thorough bleeding[1] will probably clear it.

[1] Close both radiator valves, and then open them one at a time and bleed quite a lot of water (maybe a litre) out each time. That should get rid of any air trapped in the pipes. If it's a sealed system, keep an eye on the pressure and top up with the filling loop as necessary.

[Tricky Dicky]

I had to do similar when I put in the kitchen at the last house and had no problems although I did use full flow types not the standard types which do have a slight restriction. Are you sure you have not got an air lock some where, I used to get them on the Micky Mouse CH system I inherited which ha d a lot of drop feeds to the downstairs radiators but no drain off valves o n some. Due to the trapped water when refilling the system radiators would fill even vent but air locks in the pipes prevented them getting any heat.

Richard

[Mr Pounder]

Out of interest, will the boiler need to be topped up with inhibitor if two or three litres of water is lost from the system? Please excuse me if its a silly question.

[newshound]

That should be a fairly small proportion for a normal sized house, perhaps more significant for a tiny flat? How long has it been in service? You can't really over-dose.

[Mr Pounder]

Bungalow. 5 rads. New boiler about 6 years ago. Lost about 2 litres after a pipe to a rad pissed out. Looks like I'm okay. Thanks.

[Andrew Gabriel]

The other problem is that there isn't a valve which will operate reliably after many years of not being operated. You need to make sure your annual test/check of the system includes opening and closing all these valves, or after a few years, you will find you can't do it anymore. There are 4 x 22mm full bore valves in my system for isolating some sections in case of any leaks which I ignored for 10 years, and then found they will no longer turn.

[fred]

In article , Rednadnerb writes

Even crappy ones will have a 6mm orifice which should pass enough water to heat all but the largest of radiators.

For the future, my personal choice would be a full flow ball valve[1] with a handle. If the handle would look out of place then it can be removed and the valve actuated will pliers or grips, or the handle stored and re-fitted. Screwdriver actuated valves are notorious for leaking, possibly due to the shorter support for the actuating shaft.

[1] the orifice in the ball is the same bore as the connecting pipe, easily recognised by the bulge in the body around the ball.

[harryagain]

Some valves (intended to be fitted under sinks for tap servicing) very much resrtrict the water flow. Totally unsuited to central heating.

You can get "full bore" valve that offer no restriction. (They have a much bigger body than the previously mentioned ones). These would be OK.

Sounds like you have the wrong ones.

They look pretty similar externally apart from the body size.

[Tim Watts]

Yes - I agree. Remember the balancing valve on the rad is usually no where near fully open for most rads in a typical house, so adding a small point of restriction is very unlikey to totally break it.

I go with an earlier suggestion that there's an air lock.

[John Rumm]

Even a fairly small system with have >60L typically (and commonly 100+) so a couple here or there is not going to make much difference.

[Andrew Gabriel]

Points of narrowing also present the opportunity for debris to block them. IME, this happens with stop valves that only need to be open a crack - in an older system, you can find the flow rate dimishes over time, but is restored by opening the valve fully, before restoring it to its original position. I always open them fully as part of a wash-through prior to refilling a system.

[fred]

In article , Andrew Gabriel writes

Yep, a valid point, particularly in the long term or on an old system.

[Rednadnerb]

A thorough bleeding as described by Roger seems to have sorted it out.

Thank you for all of the replies.

[Weatherlawyer]

o problems although I did use full flow types not the standard types which do have a slight restriction. Are you sure you have not got an air lock so mewhere, I used to get them on the Micky Mouse CH system I inherited which had a lot of drop feeds to the downstairs radiators but no drain off valves on some. Due to the trapped water when refilling the system radiators woul d fill even vent but air locks in the pipes prevented them getting any heat .

I wonder if I've got that. I have a mickey Mouse landlord that is for surr ten.