Help, Central Heating Hot Water Problem

[denzildexter]

Hello Forum,
I was hoping to get some advice for a problem we have with our central heating hot water. I'd just like to make doubly sure there isn't a quick/obvious fix before calling in a gas fitter/plumber as good (trustworthy) ones seem to be like hens teeth where we live. Anyway, the problem is that the hot water takes an age to heat up.

The system comprises a cylinder in airing cupboard, a baxi bermuda back boiler, tanks in the loft, a pump under the floorboards in the living room (I think as there's an access panel and I can hear it). I assume there's a diverter valve somewhere but I've not seen it. Both tanks in the loft have water in them. The central heating works fine and the radiators heat up nicely and quickly.

I've uploaded some photos of the tank in the airing cupboard as I think something isn't right here. Please take a look at these photos...
https://onedrive.live.com/redir?res...82&authkey=!AP3Trgt5JPAUm1Y&ithint=folder,jpg

The first photo shows the pipes into the tank (rear lower) and the return to the boiler (top front) [My assumption please advise if wrong]. The lower of these two pipes gets red hot when the hot water is ON. The other pipe comes out of the tank (see picture 4) but stays pretty much cold all the time. At the top of this pipe (see the 2nd picture) there is an air bleed valve [again please tell me if I'm wrong].

I'd expected for both the pipe into the tank and the return to get hot but this is not the case. Having read other forums I wondered whether air might be trapped in the system and so I un-screwed the air bleed valve shown in picture 2 - nothing happened, no air release and no water either.

So anyway, am I on the right track? Are my assumptions right or (as per norm) am I way off track. Any advice would be much appreciated.
Regards,
DD

 

[picasso]

It looks like you have gravity hot water/pumped central heating so I would think the cold feed is blocked, try bleeding a down stairs rad and see if the small tank in the loft starts to fill.

 

[denzildexter]

It looks like you have gravity hot water/pumped central heating so I would think the cold feed is blocked, try bleeding a down stairs rad and see if the small tank in the loft starts to fill.

Thanks very much. Unfortunately I'm working away at the moment so can't get to the system till Wednesday evening. I'd like to understand your logic though so would you mind expanding? Is this the kind of system you mean?
http://www.muswell-hill.com/foxandco/images/openvent.gif

 

[Bitzerdisandat]

Try getting a big old towel and get that manual air vent opened up. See if it is full of air. If you have a blocked cold feed, then the water / air will stop coming out of the vent. As you have a cylinder stat, it is possible that you could have motorised valves. Look under the floor for the pump. The mv's could be next to it. Have a look round and get to know your heating system. Can you operate just the heating without heating the hot water??

 

[Bitzerdisandat]

Oh, and if the cold feed is blocked, you will find it where the cold feed / expansion pipe coming from the bottom of the tank goes and connects to the rest of the system. Usually, I find that the problem is an airlock on the cold feed/ expansion pipe. This should run vertical, dead flat or preferably, rise up to the tank to clear any air. If it rises as it leaves the tank, then that's the culprit. Either raise the tank with a bit of wood or alter the pipe.

 

[denzildexter]

... get that manual air vent opened up ... If you have a blocked cold feed, then the water / air will stop coming out of the vent. ... Can you operate just the heating without heating the hot water??

John thanks, I was able to undo the knurled nut on the top of the valve all the way .. nothing came out at all, no air or water. The central heating works fine standalone. Just can't get the water in the cylinder to get hot (without using the immersion heater).

 

[Agile]

Keep the towel in place and prick the hole with a needle in a cork.

Keep the cap handy.

Tony

 

[denzildexter]

Thanks for all the help and advice so far but the hot water still doesn't get hot. Here's what I've tried.
1. I bled a downstairs radiator (very slowly) and eventually the small F&E tank in the loft started to fill.
2. The knurled nut on top of the manual bleed valve (in picture 2 of my original post) I undid all the way. Couldn't get a pin in anywhere so eventually I just undid the whole thing with a spanner. Nothing came out initially but a bit of poking with a pin got lots of muck flowing out of the pipe followed by nice clean water. I screwed in back up.
3. The cold feel into the cylinder travels horizontally for about 10cm then straight up. I can't see where it joins the rest of the system so I didn't do a magnet test. If I understand correctly checks 1&2 above imply the cold feed is not blocked.
So, I'm still not much further ahead. Any ideas or can anyone recommend a reliable/competent plumber in the Weymouth, Dorset area.
Cheers,
DD

 

[Bitzerdisandat]

Hi mate. Ok, what you probably have is a motorised valve with a faulty syncron motor. Before the fault, was it possible to run the heating without the hot water on? Try this now with the programmer. If this is possible, then you need to start tracing the pipework, looking for that m v. What kind of gas boiler do you have? It's rare, but some boilers have m v's inside them, but that is very, very rare indeed. A motorised valve is a rectangular box with a wire coming out attached to a brass body.
The magnaclean is a magnetic filter that pulls most of the rubbish out of heating systems. They are really good at prolonging the lifespan of heating systems. Seriously consider fitting one.
Bitzer...

 

[denzildexter]

Managed to find the pump and valve(s) - there are two and they are under the downstairs floor (hence the mess). Take a look at the 5th and 8th photos here https://onedrive.live.com/redir?res...82&authkey=!AP3Trgt5JPAUm1Y&ithint=folder,jpg. The 5th shows the valves and the 8th the pump.
Is there anything I can do to check these valves are functioning properly?
DD.

 

[75pete]

So, you cleared the air blockage and can get hot water if you use the immersion. The valves are for the isolation on the pump and will be open so unless you wish to change the pump, that's not part of your problem. You need to check the motorised valves and the tank stat

 

[denzildexter]

... You need to check the motorised valves and the tank stat ...

Pete, I thought these were the motorized valves.
https://onedrive.live.com/redir?res...authkey=!AKGEosdSYDfcZuU&v=3&ithint=photo,jpg
There's another picture showing the isolation valve for the pump.
There's no problem in the boiler firing when the cylinder/tank is cold so I'd ruled out the stat. Is there a way to check the valves?
Thanks,
DD

 

[gasmanstu72]

you need to work out which valve is for heating and which one is for water,
you say your heating works ok, so we know the heating valve must be working, what to do is turn on your heating and see what valve opens, these type of valve you have on your picture are Danfoss type, they will have a small lever at the opposite side to where the wire is, you should see that move when its opening.
turn your heating off and on a couple of times to make sure you got it right, when it moves right the way over, the pump should come on and the boiler fire up,(you will probably hear it moving too) it might be more obvious to poke your head underneath the floor and see some radiator pipes tee'd in off the pipe its on.

so by elimination you now know which one is the hot water valve, do the same as before but this time turn you hot water on and off, does it move? if not its bust and needs replacing. or it might move but doesnt bring on the pump, either way its broke
you can prop the valve open as a tempory fix, do this by moving the valve lever across, it might bring on the pump, if it doesnt, dont panic, it just means the switching inside might be bust as well.

to replace it, unscrew the two screws either side the head will come off, replace it with a new one, to make it easier you can snip the wire and use a suitable junction box to join the old wire to the new, just make sure the power is isolated first!

edit: you might not see the lever moving, but you will notice a stiff resistance when in its default closed position and it go slack when its open

 

[denzildexter]

.. you need to work out which valve is for heating and which one is for water ... Danfoss type, they will have a small lever at the opposite side to where the wire is ...

Thanks very much for that, it's very useful. I think I know which is which but I'll test as you explained to be sure. I'm working away again so I'll try it on the WE. A couple of things though, I did look for the small lever you mentioned and I couldn't see one? Maybe I just missed it or is it possible they don't have a lever? Is there a chance that the valve on which the actuator sits is up the swanney?
DD.

 

[Bitzerdisandat]

Hi. Ok, so you found the m v. Take on board what's been said about identifying which is which. Use a marker pen and write ch or hw on them as appropriate. Take the two screws out and remove the actuator head. It's safe so be cool. No danger. Grab the protruding spade and try to turn it by hand. If needed, then try plyers. If it's stiff, then that's the culprit; the sticky valve has cooked the actuator. If the valve is really sticky, go get a new complete valve and actuator. If the valve turns ok, then it's just the actuator that you need.
Take it from there.