central heating on when it should be off?

[Steve]

I have a gas boiler that provides the heat for radiators and water. I have an electronic timer that allows me to set two on and off times each day. The boiler will run at those times if required and I can select "off", "auto", "once" or "on" for heating and water separately.

My normal summer setting is "off" for heating and "auto" for hot water.

In the last week, I have noticed that the radiators are heating up when the boiler is running, even though the controller is set to "off" for heating.

I have no room thermostat, but each radiator has a thermostatic valve, so I can turn them all off, but that isn't really the point. I want to get things running smoothly before the winter comes.

I had the boiler serviced two weeks ago, but he just hoovered the boiler out, checked gas pressures etc., so I can't see how he could have caused this problem.

The only other components of the system that I can see are one motorised valve (I'm not sure if that controls the water or the heating), and a pump - presumably for the heating.

Can anybody suggest where the problem might be and whether I need to call in professional help to fix it. I can do basic electrics and plumbing, but I've never drained down a central heating system.

TIA

Steve

[Christian McArdle]

The most common arrangement when you have fully independent control is a 3 way valve to choose heating, hot water or both and a pump that pumps both water and heating. However, you do sometimes get arrangements such as having a gravity loop on water controlled by a zone valve, whilst having the heating controlled by the pump.

Looking at the zone valve, does it have 3 pipes coming out of it, or 2? We need to identify if you have S-plan (unlikely unless you've missed a zone valve), Y-plan, C-plan or some other control arrangement.

Your modifications/repairs should include ensuring that you have either a room thermostat or a flow switch that turns off the boiler when the flow through the radiators drops down low.

Also ensure that you have a cylinder thermostat that does the same for the hot water.

Christian.

[Roger Mills]

Did the problem start when the boiler was serviced? Even if no other parts were touched, the system could have been tested after the service and - if you have a 'sticky' zone valve - that could have jammed in the mid position.

I am assuming at the moment that you have a Y-Plan system - which is fully pumped, with a 3-port valve to direct water either to the heating coil in the HW cylinder or to the radiators or to both at the same time. The valve has a small motor to move it to the mid (both) and CH positions, and a spring to return it to the HW position. Sometimes, if the 'wet' part of the valve gets a bit stiff to turn (particularly in the summer, when it doesn't get any exercise) the spring is insufficient to move it back - and it sticks in the mid position so that whenever the HW is on, the radiators get hot too.

Many - but not all - 3-port valves allow you to remove the electrical bit (actuator) from the wet bit by undoing a couple of screws. If yours is like this, remove the actuator and check how easy it is to rotate the shaft of the valve. You should be able to move it by gripping it with your finger and thumb - or certainly by using *light* pressure from a pair of pliers. [It only moves through 90 degrees, with the mid-position being at 45 degrees.] If it is very stiff to turn, you may be able to free it by gripping with pliers and moving it back and forth. If not, the wet part of the valve will need to be replaced - which involves a partial drain-down.

While the actuator is off - but still connected electrically - you can test it by selecting all permutations of HW and CH at the programmer/thermostats and check that the actuator moves to the expected position in each case.

If your system isn't like this, we'll need to think again. In that case, answer the questions posed by Christian about the number and type of valves etc.

[Owain]

Motorised valve or its actuator or microswitch stuck.

Owain

[Steve]

Thanks to all for the info so far.

I've had a closer look and there are 3 pipes going in to the zone valve.

I assume one comes from the boiler, one goes to the HW cylinder (which does have a cylinder thermostat) and one goes to the pump. There is a smaller pipe that comes back from lower level on the cylinder and joins the pipe going to the pump.

The electrical box on top of the zone valve only has one screw on it - high up on the opposite end to where the cable goes in and the little lever sticks out. I haven't tried unscrewing it yet - is this wise with the power still on? It doesn't look like this screw would release the electrical gubbins from the valve, but I suppose it might give access to screws that do.

I have fiddled with the little lever that sticks out. It was in the central position, but if I move it to one side or the other, it seems content to stay where I move it to.

I have also tried putting the lever to the central position, then switching on just the heating - the lever doesn't move. Same thing if I try putting on just the water.

Does any of this give a clearer idea of exactly where the problem lies?

[Roger Mills]

Is there any chance that you could take a photo of the pipework round the

3-port valve and pump - and stick it somewhere on the net, and post a link to it here?

Is there any make/model information on the actuator? If you tell us that, someone may be familiar with your type of valve.

If the valve is working, it should certainly move when you change heating selections. It's a very low geared motor though - and may take a minute or more to move from one position to another. Are you giving it long enough?

From what you've written so far, the prime suspect is still the 3-port valve.

One more thing you can try. Remove *all* power from the system by turning it off at the main FCU - not just at the programmer. You should then see and hear the valve move to the HW position under the action of the spring return. If it doesn't, something is definitely wrong with the valve. If it does, try running the system again - it may just be ok this time. These valves do sometimes get confused, and need to be "re-booted".

[Steve]

here are some photos that might make things clearer

pipework

end of electrical bit end of electrical bit now had a closer look, its a Honeywell 9123. Info on the "other end" gives a part number for head replacement - is that likely to mean that the electrical bit is removable?

I have tried "rebooting" but nothing moved. On closer inspection, the lever slot is marked Auto on the left and Manual On on the right.

I have now found one combination of lever position and on/off settings where the lever does move under its own steam - If I push the lever to the right, then put Water ON while heating is OFF, the lever moves back to the centre position

Thanks for taking the time to help me to understand this

Steve

[Roger Mills]

Nice photos! It's a fairly conventional fully pumped Y-Plan system, but I think you mis-described it a bit in an earlier post.

Water comes from the boiler, through the pump, and up to the central inlet of the 3-port valve. The LH outlet goes to the radiators. The RH outlet goes to the cylinder coil. The bottom water pipe (not the gas pipe) comes back from the coil and returns to the boiler. It is probably joined by the CH return under the floorboards. The small pipe with the gate valve on it is a by-pass so that if the heating is on but all the radiator TRVs are closed, the water still has somewhere to go.

The fact that a part number is quoted for replacing the head almost certainly means that the actuator can be detached. Maybe there are screws going up into the bottom of it, through the brass flange on the top of the wet bit of the valve?

Are you absolutely sure that the valve isn't returning to the HW position? When it does, it requires pressure on the lever to move it elsewhere. when it is in the mid or CH position, the lever flaps about without doing anything. Note that in the manual position, the lever only moves the valve to the mid position. There is no way of moving it manually to the CH position.

[Steve]

Sorry I confused things before - my ignorance knows no bounds on this sort of thing. I thought the water was flowing in the opposite direction

Emboldened by your advice, I removed the cover from the actuator and inside the casing I found two screws connecting it to the brass flange. I removed them (carefully, as the thing was still electrically connected) and tried to lift the actuator off of the brass bit. It didn't want to come off - it wiggled about a bit but would not come clear. Then there was a ping, like a spring jumping out of place and I decided to put it back together and seek more advice. As far as I can see, the spring is still in place.

I have checked again and the only situation where the lever moves of its own accord is when I push the lever to the right (Manual), then put Water ON while heating is OFF. This causes the lever to move back to the centre position.

Something else that struck me as odd is that when I stopped fiddling with this earlier this morning, I left the lever pushed over to the left( Auto). When I went to test all this just now,some 7 hours later, the lever was still on the left but the actuator was hot to the touch, even though neither water or heating had been on for about 7 hours and all of the surrounding pipes were stone cold. When I had the casing off of the actuator, the heat was coming from the silver coloured drum shaped object - presumably the motor.

Is this making any sense yet?

[elite-heat]

I was expecting this to be a Honeywell 4073 mid position valve before I saw your photo. It still 'looks' like one but clearly isn't.

Generally, the motorised valves with a replaceable actuator have a dimple on the top of the casing. it is not clear from yours whether you have this or not.

Anyway, the problem is one of two things; mechanical or electrical. In order to diagnose the fault you will need a multimeter and will have to poke around in the wiring centre. An electrical neon screwdriver will not be sufficient to do this.

Are you confident of not electrocuting yourself?

[Christian McArdle]

It sounds like the head is totally knackered. Persist with removing the thing. Any springs are part of the head and it is of no relevence if they are damaged or lost.

Once the head is off, make sure the spindle turns relatively easily. If so, you can probably just put a new head on it. You might even get away with replacing just the motor bit. It is called a "synchron motor" and is easy to source if you don't mind a little soldering.

Christian.

[Steve]

It is getting on for 15 years old - might it be an earlier model?

There is a dimple on the top of the casing, just above the out of focus screw you can almost see at the top centre of the "other end" photo - with that, and the info about head replacement on the casing, I hope I am safe in assuming that it can be replaced. Still need to figure out if that's what needs replacing though. Are we talking about a lot of money here?

I am never confident around live electrics - that may be why I have avoided electrocution so far. The trouble is I don't have a multimeter and I almost certainly wouldn't know how to use one.

[Steve]

I have since left the lever in the central position and the motor has cooled down.

If I do this, can I safely continue to use the system for water heating until I can find a replacement?

It's 15 years old, so I think I'd probably be happier renewing the whole actuator.

Am I right in thinking that a plumbers merchant is the place to go for this sort of thing?

[The Natural Philosopher]

However that means draining down the pipework.

What happened to one of my 20ways was that the motor got tired somehow, and the valve got stiff.

Removing the head allowed me to wiggle the valve, and a new head cured all other problems.

Yes. Take copious photos, try and get the head off and work teh valve manually. It its reasonably free, disconnect electrics and take head in.

ISTR I got a new head online somewhere tho.

[Steve]

Thanks to the advice given here, I persevered and got the actuator off. I tried to turn the spindle on the brass valve, but it won't turn it with my fingers, or even with medium pressure with pliers.

I take it that this means the brass bit needs replacing. That is not good news - I have never drained down a system and I don't even know where the drain c*ck is for this one.

I had found a replacement actuator on the net, but I'm not sure now if I need one - when I run the heating with the actuator off, it clicks throgh 90 degrees, switches off, then a few seconds later does the same again. Does that mean it's OK?

Even if it is OK, I haven't been able to find the right brass bit to go with the existing actuator so presumably that means I'll have to get a complete new assembly.

This raises so many questions for me - must it be honeywell like the junction box it connects to?, must it be a particular type?, what size does it need to be?, will the wiring requirements of a different valve exactly match those of the old one?, where is the draincock?, do I have to drain the whole system?, etc. etc.

This may be blasphemy to this group, but I'm beginning to think I might be better getting a professional in to tackle this. What do you think?

Even if I do sell out and call in a pro, I'd like to thank everyone for the excellent advice and support - it's improved my understanding of how all that stuff works no end,

Steve

[Christian McArdle]

If you are replacing the entire valve, the main compatibility issue is that the connections are at exactly the same place and the thread (either fine or medium) matches the original nuts. If so, no pipework modification or olive removal is required.

The other main issue is making sure it is the same type of valve (i.e. mid position, diverter etc).

However, you might as well replace with another Honeywell. They are well regarded and not that much extra in cost.

Christian.

[The Natural Philosopher]

Oh bugger..

Possibly. Howver as you point out..

Almost certainly

These things are fairly standard, but, yes, you may need to mod the pipework slightly for a new one.

I think you are probably right. Its a days work for a competenet plumber (if you can find one) but if you get in a muddle it might leave you with water on the floor or a non functional heating system for several days..

e> Even if I do sell out and call in a pro, I'd like to thank everyone for

[Roger Mills]

Have you tried working the spindle back and forth, while gripping it with pliers? You might *just* be able to free it up, and avoid having to replace the valve.

If you *do* need to replace the valve, you only need to drain the system to below the level where you're breaking into it, rather than the whole lot. I've no idea where the drain c*ck is - every system is different. You may have one or many - but hopefully there will be at least one!

It's a good idea to turn off *both* ends of all radiators in order to keep them full when you drain the pipework. If you do that, count and record how many turns it takes to close each lockshield valve, so as to be able to put them back to the same position (assuming the system has been balanced!) You can reduce the amount of water to be drained out even more by bunging a cork in the fitting at the bottom of the fill & expansion tank, thus keeping the water in the tank when you drain the pipework. Don't forget to remove the cork when you've finished, though!