Problems with central heating

[shoot66]

There are a couple of problems but first I'll try to explain my setup.

I have a Ferroli Tempra 24 boiler, an unvented mains pressure Ultrasteel indirect 150L water tank and 10 radiators of various sizes over 3 floors. The upstairs radiators are controlled separately to the downstairs ones. There is a 12L 3Bar expansion vessel fitted.

The first problem which has been going on the longest is that the overflow from the mains pressure water tank constantly leaks. I think it is leaking from the expansion release valve. I have fitted a new valve a few months ago and the problem persists. It also leaks whether the system is hot or cold which makes me think it's not a problem with the expansion vessel. I just tried replacing one of the motorised valve but that didn't work either. I was thinking it might be the cylinder thermostat that's faulty.

The other problem is that the radiators aren't turning off once on. The room thermostats say they should be off but they stay hot. If I manually adjust the cylinder thermostat I hear the other two motorised valves come into action and the radiators turn off.

I don't know if they are related at all but the problem is really bothering me now. Any advice or suggestions would be greatly appreciated.

 

[simond]

You have a wiring fault. This cannot have suddenly started so I guess there is more to this story than we know....

Are you sure the water overflow is from the cylinder and not the boiler? Sometimes they are teed in together before the tundish.

And are you aware that there are two valves on the unvented cylinder which can let off in a fault situation? Plus possibly the boiler, as above.

 

[shoot66]

Thanks for quick reply.

Yes it has been going on for quite a while. Not sure about boiler of cylinder, the boiler is situated about 10 feet from the cylinder in a different room. I'm pretty sure it is leaking through the expansion release valve by the cylinder (is the other valve you mention the expansio release valve? I don't think it is coming from this one). Also the boiler has a separate overflow pipe which isn't leaking so I don't think it's the boiler.

I haven't changed the wiring so would the problem not have been there since it was installed if it was a wiring problem? Could it be a faulty cylinder thermostat? Or another thought I had was a faulty pressure reducing valve.

Thanks.

 

[petit_pablo]

You could do with getting an engineer qualified in unvented to take a look at the problem. There are a few things that could be causing the drip

 

[crockett]

Another reason for the dripping relief valve is pressure, as these valves are temp and pressure relief. May want to get a plumber in to check the static pressure, and then, if your unvented cylinder came with one, check the PRV, as this may be faulty. As is mentioned, make sure that the plumber has an unvented ticket.

 

[shoot66]

Thanks for the advice. I wanted to try and fix it myself before I had the exspense of calling someone out.

I don't think it's the pressure reducing valve or the incoming pressure that's the problem because i turned the mains water off and then it stops leaking, so I turned the mains water back on but only opened it slightly so there was very little pressure coming in (turned on cold water tap to check this) and it still started leaking again within minutes.

I don't know if this matters but I've noticed that the cold inlet pipe is very hot as well, right back to the pressure release valve which is next to the pressure reducing valve. Should the cold inlet be very hot?

My expansion vessel is also connected after the pressure release valve (as in between the PRV and the hot tank), should it not be before the PRV?

 

[crockett]

Doesn't matter if you've only opened the mains stopcock only a little bit, the pressure will still increase to whatever it is you've got there. I still feel that it is a pressure problem. The expansion vessel is normally fitted after the PRV

 

[simond]

Bearing in mind how dangerous unvented is when the controls are changed by amateurs, I shouldn't be saying this.

But if the incoming cold pipe is hot back to the PRV then that is what is leaking.

Why is it leaking? Seating could have failed or be blocked with crud.

Is this the valve you replaced once already? Did you replace it like for like with a valve from RCM Copperform?

If it is, then the pressure is too high. The incoming pressure reducing valve (combi valve) may be letting by in excess of 3-3.5bar. So this needs the seating cleaning out too, and possibly completely replacing.

 

[crockett]

Well said Simond, and I hope that S66 takes the advice on board, and then calls a reputable plumber to check / test, and carry out remedial works. Replacing the parts may look simple, but fekking it up may cost you more than new components

 

[shoot66]

crockett - if you open the stopcock just a bit, is it the flow rate that is affected and not the pressure then?

simond - sorry it's hot back to the expansion release valve and yes I've already replaced the this and I got it directly from the hot water tanks manufacturers. The cold inlet comes in, there's a 3 bar pressure reducing valve and then the expansion release valve and then the expansion vessel before it goes into the cold inlet on the tank. It gets hot back to the expansion relief valve.

Thanks for all your help and thoughts on the problem.

 

[crockett]

S66, you've got it. just the flow rate, not static pressure

 

[petit_pablo]

Id say you had the pressure reducing valve failing and allowing more than 3bar pressure through.

What bar pressure relief did you fit after the reducing valve

 

[Arnold31]

this will look stupid question , but do you use any termostatic showervalve, and do not hear any stupid noise from that?

 

[shoot66]

petit_pablo - I didn't initially fit the system, just trying to stop it leaking. The pressure reducing valve is first and set to 3 bar (if working!), then the expansion release valve is a 6 bar valve, and the temperature/pressure release valve coming from near the top of the cylinder is 7 bar.

Arnold31 - there is a shower with thermostatic control but I don't think there is any strange noise coming from it when used.