Motorised valve stuck

[patagonia]

When I turned up the hall thermostat to bring the ground floor heating on, there was a horrendously loud banging noise which echoed all round the house including in the upstairs rads even though that circuit was not switched on at the time. I went down to the cellar where the boiler is sited and there was a very loud noise which I thought was coming from the boiler b ut now think was coming from an adjacent motorised valve since turning down the hall stat and even turning the ground floor off at the programmer didn't close the motorised valve (but stopped the noise) and the boiler continued to fire and the heat continued to circulate round the ground floor. Can anyone tell me whether it is just the valve head which needs replacing, which I presume cd be done without draining down, or is it an electrical fault or will the whole valve need to be replaced. I know we need a power flush since the boiler is kettling and don't want to have the system drained down twice. Can scale/sludge in the system affect motorised valves and trvs? Some of the latter seem to be sticking as well. I have phoned umpteen plumbers, leaving messages on answerphones, but so far have not succeeded in getting anyone round. Just as well it's not stuck in the closed position or we'd be freezing. The boiler seems to be coming on every couple of minutes. Is this because the valve isn't working?

 

[ChrisR]

Valves an stick open and keep the boiler on, but that doesn't cause banging.

 

[wapsap]

Is that new or old one?

 

[patagonia]

The valve is about 5 yrs old.

 

[bengasman]

Only reason I can think of is boiler is actually boiling due to lack of flow. Trvs and zone valves could be stuck. Is there enough water in the f&e tank?

 

[patagonia]

It can't be because the boiler is boiling because the banging noise starts as soon as we turn on the hall stat when the boiler has been off and is cold. We've left the hall stat off and the heat is still circulating through the ground floor because the motorised valve is open. The boiler turns itself on and off depending on what it is set at. I turn it fairly low during the day when I just want background heat as this is the only way I can now control it.

Even when we pay a lot, we still seem to get monkeys!

Patagonia

 

[patagonia]

Incidentally, as I think I said before, we don't get the banging noise unless we turn on the hall stat.

Patagonia

 

[D_Hailsham]

You mention upstairs and downstairs circuits and motorized valves, but don't say how many and what type of valve (2 or 3 port)or whether you have separate thermostats upstairs and downstairs.

Can you describe your system in more detail, including boiler type etc?

 

[patagonia]

Thanks for reply, D Hailsham. We have 3 2-port Siemens motorised valves which are governed by the hall zone thermostat, the first floor landing zone thermostat and the cylinder stat. The boiler is not supposed to fire unless one of these is calling for heat but now that the ground floor valve is stuck in the open position, the boiler fires even when the other stats are off. The boiler is a Kingfisher Mf conventional flue 100k btu; the pump is a Grundfos Alpha l5-60 130 variable speed. We have it on a low setting as otherwise we get hissing in some of the rads. Since we had the new boiler, pump and valves about 5 yrs ago we have had air accumulating in the bathroom towel rail (which is hot whenever the boiler is on but does not fire the boiler) and we get a ticking noise in the upstairs rads whenever the upstairs thermostat turns itself on. It sometimes wakes me up and drives me mad. I don't know whether this is due to the fact that modern boilers have a smaller water content so heat up more quickly or the initial surge one gets when the pump comes on; I presume this surge happens if an additional zone switches on as well. We would like to downsize but feel we can't sell the house with these problems and don't know what to do about them. The ticking noise seems to start in the cellar and continue in the pipes going through a cupboard in the study and then round all the upstairs rads. Very occasionally we get a sharper ticking noise in some of the downstairs rads at intervals. All very mysterious. Any other questions?

 

[patagonia]

I should have said that we have trvs on most of the rads as well but there is one rad on each floor with an ordinary hand wheel valve. We also have two fan convectors: a kickspace in the kitchen and a large Myson in the dining room. These are not always switched on. The house is quite big and we try to economise, now that there are just two of us on a not very high pension, by turning down the rads in rooms which are not in use and turning off the upstairs circuit during the day unless it is very cold. We still seem to be consuming a lot of gas, however.

 

[D_Hailsham]

We have 3 2-port Siemens motorised valves which are governed by the hall zone thermostat, the first floor landing zone thermostat and the cylinder stat.

Ah so now we know! you have a S-plan plus installation, which looks like this:

The boiler is not supposed to fire unless one of these is calling for heat but now that the ground floor valve is stuck in the open position, the boiler fires even when the other stats are off. The boiler is a Kingfisher Mf conventional flue 100k btu; the pump is a Grundfos Alpha l5-60 130 variable speed. We have it on a low setting as otherwise we get hissing in some of the rads.

2-port zone valves are normally closed; they need to be energised to open them. Modern valves can have the actuator (box on top) replaced without disturbing the pipework; in any case the cover can come off so the motor can be replaced. So it would be worth removing the cover and checking what happens when the thermostat is turned up/down. You should hear the motor run and see the valve spindle turn. Remove the complete actuator, if possible, and check that the valve shaft turns easily (it only turns through a few degrees) from open to closed.

If the motor works and the valve opens/shuts then the switch in the actuator is probably faulty. Check there is 240v on grey (valve closed) grey and orange (valve open). If faulty, replace actuator/valve.

The Grundfos Alpha automatically adjusts to the load as the TRVs open and close. You say it is on the lowest setting, which setting exactly? There are six positions, three left and three right. With the size of house/installation you must have, I am surprised you only need the pump at the lowest setting.

we have had air accumulating in the bathroom towel rail (which is hot whenever the boiler is on but does not fire the boiler)

It sounds as if the towel rail has been plumbed in as a bypass after the pump but before the valves. This helps dissipate the excess heat. And it keeps the towels warm.

I expect you have tried bleeding this rad several times, but are you doing it the right way? Bleeding should be done with the boiler and pump turned off and the water cold.

we get a ticking noise in the upstairs rads whenever the upstairs thermostat turns itself on.

This could be the TRVs operating. Take the TRV heads off and note what happens

I don't know whether this is due to the fact that modern boilers have a smaller water content so heat up more quickly or the initial surge one gets when the pump comes on; I presume this surge happens if an additional zone switches on as well.

The Kingfisher is not a really low water content boiler, so this should not apply.

You say that you have kettling noises. To quote from the DIYnot FAQ on kettling:

If a boiler is kettling its because the water is not flowing quickly enough through the heat exchanger. The temperature increase is too great in one slow pass of the water so it literally boils creating the noise.
To find a remedy you have to think of things that would slow down the flow or cause the excessive build up of heat within the heat exchanger.
Heres a few ideas.
Sludge/scale in the boiler and or system ... Remedy = fernox system restorer or similar. If that doesn't work a chemical powerflush and if that doesn't work then your heat exchanger and or pipework is probably seriously crudded up

You mention the need to powerflush but this will not deal with limescale in the heat exchanger (or a pump set too low)

I would do the following:

1. Check the motorized valve and replace motor/actuator/complete valve as necessary.

2. Install an Automatic Bypass Valve (ABV)between flow and return after the pump. This is more effective than the towel rail as it will open and close as required when the TRVs close/open. There are instructions for adjusting the ABV Here

3. Bleed all rads.
Lock all motorized valves in the Man position while doing this, otherwise there is no flow from the header tank to make up water lost but don't forget to reset them to Auto.

3. Balance the system
Instructions for balancing systems with TRVs are
Here (It's for Drayton TRVs but the principles are the same)

The pump should be set to a fixed speed when balancing.

 

[patagonia]

Thanks again D Hailsham and sorry for delay in replying; haven't been too well for the past couple of days.

1. I'm afraid I don't know how to take the covers of the m.vs. so all I can tell you is that the arm which is supposed to whizz over and go rigid when the zone stat is turned off no longer does so.

2. The pump doesn't have any numbered settings - just a knob with a pointer to a band which goes from thin to thick with a circule at one point which I presume is the half way mark. We have it pointing to about 2/8th inch from the starting point. If we turn it up higher we get a whooshing noise in the rads nearest the boiler. The boiler has no numbered settings either; we usually set it to about three quarters of the way from the start.

3. I used to bleed the towel rail nearly every day (always with the boiler and pump off) till I discovered a small leak from a rad valve and tightened the nut; since then I only have to bleed it occasionally. However, this situation went on for a long time so may be set up corrosion. It was actually hydrogen as it was possible to ignite the air coming out. None of the rads have air in them but one or two don't feel as hot at the bottom as at the top, particularly one in the sitting room where there is quite a difference between the flow and return pipes, even with the lockshield fully open, so may have sludge in them, unless it is that the underflow pipe sizes are not correct or the pump not high enough.

4. Since we have some sludge in the expansion tank (despite the fact that an inhibitor (Sentinel) was supposed to have been added when the new boiler was installed about 5 yrs ago (how long is it supposed to last?)as well as these other problems, we thought we had better have a power flush. However, I note your scomments that this would no deal with limescale in the heat exchanger. Is there no chemical that will do so or is the heat exchanger irreparably damaged now? I hope we don't need another new boiler as it cost a small fortune last time.

5. I can't see any facility for locking the m.vs. in the manual position (Siemens ZA - V228C) or for setting the pump to a fixed speed, the lack of which certainly makes balancing difficult, esp. without an electronic balancing device, which our installer didn't use. The difference between flow and return seems to vary.

6. It occurs to me that it must be rather wasteful for the towel rail to be on all the time when the boiler is firing as this means the hot water going round a 28mm circuit from the basement to the first floor. If we have an auto-bypass installed, as you suggest, will this make any difference to the flow to the towel rail?

7. We have a mixture of old (1974) Danfoss and newer Drayton trvs. I know how to get the heads off the former and free the pins if they get stuck but not the Drayton ones, which seem to function OK so far but I don't know whethe4r they are responsible for any of the ticking noise.

Please excuse my ignorance. I am a 72 yr old female with an even older and more infirm husband who is not knowledgeable about these matters so I am groping in the dark and trying to inform myself so we can get a proper job done. Our installer's answer to the air in the towel rail was to add a lot of leak sealer to the system which clearly did not solve the problem.

Many thanks again for your help, which I am sure other readers will also find useful.

Patagonia

 

[patagonia]

Having just read another thread about boiler knocking and banging, I see someone says sludge is grey/black not rust coloured. The stuff in our expansion tank is more rust coloured. Does this make a difference to the treatment required?

 

[D_Hailsham]

1. I'm afraid I don't know how to take the covers of the m.vs. so all I can tell you is that the arm which is supposed to whizz over and go rigid when the zone stat is turned off no longer does so.

Can you hear the valve motor working when you turn the stat up and down? If you can then either the actuator is faulty or the complete valve.

Here are Siemens instructions for removing the motor and housing:


1. Before working on the synchronous motor housing replacement you must switch off the electrical supply.
2. Lift up fully the two coloured locking sliders.
3. Press in simultaneously on both plastic tongues and lift up the plastic cover.
4. Disconnect the electrical internal connector.
5. Now remake the electrical internal connector from the new motor housing unit.
6. Hold the coloured sliders up and locate the plastic tongues in their respective slots, push down firmly until the tongues are fully located then push down the coloured locking sliders.
7. Turn on electrical supply and test for operation

The pump doesn't have any numbered settings - just a knob with a pointer to a band which goes from thin to thick with a circule at one point which I presume is the half way mark. We have it pointing to about 2/8th inch from the starting point. If we turn it up higher we get a whooshing noise in the rads nearest the boiler. The boiler has no numbered settings either; we usually set it to about three quarters of the way from the start.

Does your pump look like this?

If so the fixed speeds are the one, two and three dashes on the red body of the pump.

None of the rads have air in them but one or two don't feel as hot at the bottom as at the top, particularly one in the sitting room where there is quite a difference between the flow and return pipes, even with the lockshield fully open, so may have sludge in them, unless it is that the underflow pipe sizes are not correct or the pump not high enough.

Certainly sounds like sludge. If this is the only radiator exhibiting this problem, it would be worthwhile removing the radiator and flushing it through with the garden hose. this is how you do it:

1. Turn off the heating
1. Close down the lockshield completely
2. If you have a Drayton TRV, remove the head (see later), put on the decorators cap (This is a blue or white cap rather like a very large bottle top) and do it up tight. I do not have any experience of Danfoss TRVs, so I don't know if its possible to shut them off completely.
3. Make sure you have plenty of dust sheets, towels etc under the rad connections. The muck which comes out will stain your carpets badly.
4. Put a container (I use an old meat dish) under one of the joints to catch the water. then loosen the connection between the valve and the rad to let the water out. This is a slow job and you will have to empty the container regularly. Do up the connection while you do this. You can control the flow by how much the connection is undone and by opening the bleed valve slightly.
5. When no more water comes out of one end of the rad, undo that connection completely so the rad is free to move.
6. Repeat 4 at the other rad connection, but lift up the free end of the rad to make the water flow to the other end.
7. Repeat 5 at the other end.
8. Do up the bleed valve, carefully lift the rad from the brackets and turn upside down. This prevents any water coming out when you carry it outside to flush through.
9. Flush the rad from both ends until you get no more much out.
10. Replace the rad (reverse of removing, but there is no water to drain)

Radiators are very heavy and I would not expect you to do this on your own

Since we have some sludge in the expansion tank (despite the fact that an inhibitor (Sentinel) was supposed to have been added when the new boiler was installed about 5 yrs ago (how long is it supposed to last?)as well as these other problems, we thought we had better have a power flush.

The fact that you have had hydrogen formation means that the inhibitor is too weak. Don't forget that, every time you bleed a radiator, you are letting out water with inhibitor and replacing it with plain water from the tank. If you have had a valve leaking and been bleeding a lot you might not have much inhibitor left!

If you do decide to have a power flush, get several written quotes and check what sort of guarantees they give.

However, I note your comments that this would no deal with limescale in the heat exchanger. Is there no chemical that will do so or is the heat exchanger irreparably damaged now?

I had a Kingfisher at my last house and it started kettling. Luckily this boiler has a large cast iron heat-exchanger, unlike modern ones which are usually aluminium or stainless steel. I added Sentinel X200 Noise Reducer to the system and the noise went away.

Details are Here

I can't see any facility for locking the m.vs. in the manual position (Siemens ZA - V228C) or for setting the pump to a fixed speed, the lack of which certainly makes balancing difficult, esp. without an electronic balancing device, which our installer didn't use. The difference between flow and return seems to vary.

Not familiar with the Siemens valve, so I don't know how to lock the valve open. The instruction on the Siemens web-site just says:

When draining/venting your system put the Manual lever in the ‘MAN’ open position.

If we have an auto-bypass installed, as you suggest, will this make any difference to the flow to the towel rail?

It shouldn't, but it might be worth including the towel rail in the balancing so it does not take more than its fair share of the water. As it is the first rad after the pump, the lockshield will be almost closed. The other valve can also be closed down the same amount as the flow is dictated by whichever valve is closed the most.

We have a mixture of old (1974) Danfoss and newer Drayton trvs. I know how to get the heads off the former and free the pins if they get stuck but not the Drayton ones

Set TRV4 to MAX then turn the large knurled nut under the white plastic top, see pic below.

Please excuse my ignorance. I am a 72 yr old female with an even older and more infirm husband who is not knowledgeable about these matters so I am groping in the dark and trying to inform myself so we can get a proper job done.

You certainly don't give the impression of being an ignorant 72 year old female. [/url]

 

[patagonia]

1. "Can you hear the valve motor working" - When the valves are working one can hear a slight ticking noise if one puts one's ear close to the valve when the zone stat is turned up and a whizzing noise as the metal bar moves to the fixed position when the stat is turned off. I put my ear to the faulty one while my husband turned up the stat and one could hear the background ticking noise but it was overwhelmed by the loud banging; the valve is of course stuck open and the hot water circulating. What I did notice this time, being so close to the valve, is that parallel to the slot the metal bar moves in there is another slot and in the valve which is working a piece of black plastic moves across the slot when the stat is turned on whereas in the faulty one it jerks as though trying to move but doesn't manage to do so; perhaps this is what is causing the loud banging noise. I noticed that when the boiler ignited in response to switching on the first floor stat, the ticking in the pipes (which then continues all round the upstairs) started.

2. "Does your pump look like this?" - Yes, except it is the other way up and it DOESN'T have the dashes, only the graduated curved marking.

3. Unfortunately, it is a very large double rad. and there is no way we could remove it on our own. Danfoss supply a green cap which one can fit to the pipe if the weather is v. cold as they wd otherwise come on even at the lowest setting. However, we will have to get someone in.

4. When I have bled the towel rail (which has 2 lockshield valves by the way) I always stopped as soon as the air/gas was replaced by water and the leak from the rad. valve must have been minimal as there was never any water on the floor, just a slight green stain on the pipe. My guess is that he didn't put enough in for our sized system. I also felt that the pump might be too powerful and might be sucking air into the system somehow. We once tied up the ballvalve in the expansion tank to see whether the water level reduced and it didn't. What should be done about the sludge in the expansion tank? Do I gather you don't think we really need a power flush? I am not in a hurry to spend around £700 or more if it is not necessary. Do you think the Sentinel noise reducer would help with the other noises in the system? I'll have a look at that link next.

5. What sort of guarantee can one expect after a power flush?

I certainly feel reasonably well informed now that I have read all your contributions to myself and others. You are doing a great service. Thanks again.



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