No hot water from boiler feed

[woodio]

ok let me explain the problem and then what occurred to prior.

I have a gravity fed system, two tanks in loft small one feeds boiler larger one feeds hot water cylinder. this has a motorised valve which does HW, CH or both. The cylinder is also fitted with an immersion.

I'm unable to get HW unless I use the immersion. CH is fine.

Now what took place before this all stopped working.

Being a gravity fed system the en-suite shower is naff. I fitted a shower pump to the feed for the shower only (not taps). On doing this I stopped all water so turned off 4 valves to make sure all located within same space as cylinder. Upon restarting the system the above problem occurred. I called out an engineer as the boiler kept cutting out (doesnt now) and he fitted new valve and motor. this has not resolved the HW problem, he then suggested I flushed the system I followed his instructions and still not HW.

we can live with the immersion but as you can imagine the short amount of water it heats and length of time it takes means bath time is a nightmare.

I have done a bit digging around in various forums and have noticed that the feed (middle of boiler) gets hot when HW switched on but the return stays cold, there is a valve on the return but this only turns 1/4 inch and nothing happens.

Happy to take photos etc and appreciate any advice before having to pay for extra visits and work.

thanks

 

[Whitespirit66]

What were the '4 valves' that you turned off?

Pics may be helpful.

 

[woodio]

ok I have have some pics.

3 of the valves are above the boiler showing in pic and the 4th was on the return pipe which only moved slighty.

thanks
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[Whitespirit66]

The valve that only moved slightly, is this the headless one on the cylinder's return pipe below motorised valve?

If yes, maybe it's seized. It's a balancing valve, which shouldn't be open much, but if the head doesn't turn, it might not be open enough, if at all.

 

[woodio]

on the first picture its the one without head yes at bottom. would this need replaced or is there anyway to test

 

[Whitespirit66]

on the first picture its the one without head yes at bottom. would this need replaced or is there anyway to test

How much does the valve's head turn? Most gate valves are rubbish and usually seize or break when you need to use them.

With your symptoms it would be one of the first things I looked at - along with the motorised valve, which you say has been replaced. Did you plumber do anything with it?

Difficult to test, so I would replace it with a Pegler gate valve or full flow lever valve.

 

[woodio]

all he done when he came out was to move it a few times with pliers. he then said all were getting hot and off he went. Just to clarify is this was broken / stuck would it not allow water to circulate around the coil and in turn vent alll water up out the boiler??

I only ask as I notice the pipes out the top of boiler are quite hot.

thanks

 

[Whitespirit66]

With your symptoms and the fact that the valve only turns 1/4", I would be surprised if it wasn't the cause.

The valve is a cheap part and broken, so needs replacing.

 

[woodio]

thanks very much for advice I wil let you know how I get on.

When I fit the new valve how open does it need to be?

 

[woodio]

Just to update, changed the valve this morning and all systems go.

I cant thank you enough for the advice has saved me another small fortune

 

[Whitespirit66]

Good to hear it's working again.

May take a bit of adjustment to get it set right. Try half open to start, then choke down a bit if rads cool when ch and hw on together. Shouldn't close it down much more than !/3 open though or will be insufficient flow through boiler when hw only on.

Hope you replaced with a quality GV or full bore lever for reliability.