Quick central heating question

[bambam]

Hi

Having a small problem with our central heating system at the moment. We have it set on a timer so it comes on at say 6.30 and goes off at 9 etc. Last few days it seems that the timing function hasn't been working - as in the heating hasn't come on.

If I switch the heating off from the controller, I can hear a valve close or switch off on the heating system and if I then set the controller to 'on' as opposed to running the timer programme, it starts working.

I'm not sure if the problem is with the controller or something else on the system. The controller is a Drayton LP522. We've used these controllers for ages and they're pretty bullet proof. Any ideas what I could check or any tests I could run before I have to call someone in?

Cheers

[hops]

But it’s usually mechanical things that fail as opposed to electrical. The motorised valves tend to fail but it sounds like yours is kicking in. Depending on what type you have fitted there is normally a lever or knurled ring that can be moved manually if the motor fails. Try and have an assistant turn the thermostat up from a point where the boiler is not firing whilst you watch the valve. If the valve kicks in and the heating works then I would suspect the timer. Once the valve kicks in touch the pipes either side of it to ensure the water is passing through the valve. Needless to say be careful with hot pipes.

[thieuster]

Same here... Dutch brand boiler (Nefit). We're aware of the trouble: the boiler is on its last legs (18 y/o) A new one will be installed within a week. The boiler-settings override the clock signals. Perhaps it is good to check the boiler as well!

M

[Harry Smith]

If the controller is battery powered (remote) check the batteries are not low. Ours acted funny on depleted batteries.

[IAmATeaf]

It could just be a sticking valve, find the valve and on the side there should be lever for manually overriding, move the lever back and forth a few times to feel how it moves.

Then set the timer for a minutes later and then watch the valve to see what it does.

[demonloop]

I’ve replaced two controllers in recent times that were fried. They do go wrong eventually

[RitchieUK]

Are you able to demand on and off from the control unit?

Or are you manually moving the valve

If the control unit can 'manually' demand a start just not on the timer sounds like an issue with the timer unit

As others have suggested I'd check power to it (batteries)

Set the timer to come on and off at a time and be there

Where is the thermostat - has that been turned down so it's not 'demanding' a heating Signal

Might not be the answer but I upgraded my timer and thermostat to Hive just before as and it's great (really simple install as well)

Ritchie

Sent from my EML-L09 using Tapatalk

[bambam]

Thanks chaps.

Right, so I've bled all the radiators (just in case) and they were all fine - no air in the pipes.

I can get the CH to work if I select 'On' from the controller. When I do, I hear the motorised valve kick in, the boiler fire up etc.

If I then go to the wall thermostat, and turn it down the boiler and valve will turn off and close and when I turn it back up they will kick in again.

The heating is set to go on at 4.30 so I'll make sure I'm there to see what happens. In the meantime, I'll have a look at the motorised valve in case its sticking.

At the moment it all points to the controller. Its mains powered but I think it has a back-up battery.

[MCFastybloke]

What kind of valve? Spring return or MOMO?

[bambam]

Ok, so the heating actually came on at 4 and not 4.30 and after a while of messing about and checking various things, here's what I've found:

There are two motorised valves, one for CH and one for HW.

When I switch the CH off, the motorised valve returns on its own and you can feel the tension if you try to press it. If you do move it, it will return on its own.

When CH is set on 'on' (on the controller) with the room stat set to high, the valve lever can be moved freely (as in it doesn't return on its own). Pipes seem equally hot either side.

When CH is set to 'on' and the stat is set to a low temperature then the valve lever returns on its own and if pressed will return back again. Pipe seems hotter on the boiler side.

With the stat back to a higher temp, the lever moves freely again.

With CH on 'timer' and stat on high, lever returns on its own and will return if pressed. After a few mins, lever moves freely and pipes seem equally hot either side.

With CH on 'timer' and stat on low, lever returns on its own.

As the heating started at 4, I left it to run for about 40 mins and after about that time, it seemed to switch itself off. Only some of the radiators got warm - a couple downstairs and a couple upstairs, the rest were still quite cold.

In terms of system, we have a Megaflo so there is no pump for the CH and we have a Valiant condensing boiler. Room stat clicks when you turn the temp up or down accordingly.

Any ideas?

[RitchieUK]

Hmmmm

I'm not a plumber so thoughts are from an avid DIYer not an expert

Strange that it came on 30mins early

There seems to be something linked to the thermostat - as in when you demand a high temp it is allowing it and when low it's closing the boiler off

What room is the thermostat in? Does that room 'feel' warm

Is it a case that the thermostat is doing its job, ie it's detecting the desired temperature, but that's only being reached in that room

If so playing with TRVs on rads and balancing the rads might help

Sent from my EML-L09 using Tapatalk

[IAmATeaf]

So it’s working now? Even with a mega flow there must be a pump, no?

[MCFastybloke]

So it’s working now? Even with a mega flow there must be a pump, no?

Yes, inside the boiler casing,

Take casing off, put hand on pump when boiler dormant and set to call for heat, do pump come to life?

[blackal]

Ok, so the heating actually came on at 4 and not 4.30 and after a while of messing about and checking various things, here's what I've found:

There are two motorised valves, one for CH and one for HW.

When I switch the CH off, the motorised valve returns on its own and you can feel the tension if you try to press it. If you do move it, it will return on its own.

When CH is set on 'on' (on the controller) with the room stat set to high, the valve lever can be moved freely (as in it doesn't return on its own). Pipes seem equally hot either side.

When CH is set to 'on' and the stat is set to a low temperature then the valve lever returns on its own and if pressed will return back again. Pipe seems hotter on the boiler side.

With the stat back to a higher temp, the lever moves freely again.

With CH on 'timer' and stat on high, lever returns on its own and will return if pressed. After a few mins, lever moves freely and pipes seem equally hot either side.

With CH on 'timer' and stat on low, lever returns on its own.

As the heating started at 4, I left it to run for about 40 mins and after about that time, it seemed to switch itself off. Only some of the radiators got warm - a couple downstairs and a couple upstairs, the rest were still quite cold.

In terms of system, we have a Megaflo so there is no pump for the CH and we have a Valiant condensing boiler. Room stat clicks when you turn the temp up or down accordingly.

Any ideas?

Bloody hell! A cohesive bullet list of findings! (Usually you have to drag the info out)

The motor valves appear to be working on demand - correctly.
In manual - the controls appear to be driving the valves normally.

It would appear that it is your programmer at fault UNLESS - there is an intermittent faulty connection in the feedback switches on the motor valves. These allow a signal to go back to the boiler/pump - to tell them that the valve is open - “fire up and start pumping”

A loose connection or dodgy switch there - may be affected by the heat through the valve, such that once it works successfully - it continues to do so, until the system cools down again (say - overnight). Switches are atop the motor valve

Good luck, but I sense that you have the skill to work through the issue - logically. Do you have a multimeter to check for feedback signals?

[bambam]

Quick update - it didn't come on early - I just got the starting time wrong!

Anyway, after messing about with it yesterday, and setting the room stat to 35 degrees, the heating seemed to stay on and switch off at the correct time. This morning it did the same thing too (but I'd turned the stat back down to 25 - it never reaches that anyway).

Its been on now for 30 mins or so, so will have look at how its doing in a while. So far, the valve seems to be in the open position and letting the water through.

Back with more later....thanks for all the comments and suggestions to date.

[MCFastybloke]

New Stat time

[Craizeehair]

Could be the thermostat out of calibration or it needs turning up a few degrees as it’s got a bit colder, we get quite a few calls this time of year with people saying the heating isn’t staying on long enough to heat the house but the stat is turning off where it’s set to ie 19 or 20 degrees but that’s not giving sufficient heat in the colder weather? Sounds like the pump, motorised valves etc are working ok, probably done already but worth checking your on / off times on the timer... doesn’t sound like too much


Sent from my iPad using Tapatalk

[bambam]

Could be the thermostat out of calibration or it needs turning up a few degrees as it’s got a bit colder, we get quite a few calls this time of year with people saying the heating isn’t staying on long enough to heat the house but the stat is turning off where it’s set to ie 19 or 20 degrees but that’s not giving sufficient heat in the colder weather? Sounds like the pump, motorised valves etc are working ok, probably done already but worth checking your on / off times on the timer... doesn’t sound like too much


Sent from my iPad using Tapatalk

Thanks. All seems ok so far, fingers crossed it will stay that way. The boiler is due a service anyway so that should highlight any issues with the system. Will keep an eye on the stat - might well be giving a false reading as it seems to be on 21.5 or 22 most of the time and it feels a lot warmer than that in the house today. Sitting in the study in a t-shirt and thats the coldest room normally.

Reckon its worth taking it off the wall and giving it a clean/changing the battery?

[Craizeehair]

Thanks. All seems ok so far, fingers crossed it will stay that way. The boiler is due a service anyway so that should highlight any issues with the system. Will keep an eye on the stat - might well be giving a false reading as it seems to be on 21.5 or 22 most of the time and it feels a lot warmer than that in the house today. Sitting in the study in a t-shirt and thats the coldest room normally.

Reckon its worth taking it off the wall and giving it a clean/changing the battery?

Won’t do any harm, be careful and make sure is is battery operated though, you could expose 240v wiring if it’s a hard wired stat


Sent from my iPad using Tapatalk

[IAmATeaf]

Unless the stat is just a wireless sender unit then it will be connected to the boiler circuitry and will have 240v through it so be careful. If it’s just one of those analog rotary jobbies they are cheap enough to replace but from what you’ve posted it sound like it might have just been a stuck valve? Will probably happen again at some point so might be worth getting it replaced it it’s is fairly old.

[bambam]

Won’t do any harm, be careful and make sure is is battery operated though, you could expose 240v wiring if it’s a hard wired stat


Sent from my iPad using Tapatalk

Unless the stat is just a wireless sender unit then it will be connected to the boiler circuitry and will have 240v through it so be careful. If it’s just one of those analog rotary jobbies they are cheap enough to replace but from what you’ve posted it sound like it might have just been a stuck valve? Will probably happen again at some point so might be worth getting it replaced it it’s is fairly old.

Thanks. The stat is hardwired to the boiler but it has batteries in it as well - probably for the display. Anyway, took the module off and there wasn’t much that I could do other than clean the case.

Heating was fine for a bit and then woke up this morning and it either hadn’t come on or the it had started and then stopped as the rads were lukewarm.

Cycling through the options on the controller and it kicks in again. Before doing that I checked the valve and it was in the open position.

Seems to me that it might be the controller that is not communicating to the boiler? Or is there something in the boiler that could be at fault?

Cheers

[IAmATeaf]

So the water always comes on and works?

I had something similar but in my case nothing would come on and for me it turned out to be a problem with the boiler, replaced the logic board and all was fine. Does your boiler have a display or LEDs that might blink to indicate what it thinks might be the issue?

[Craizeehair]

Do you have two motorised valves, one for heating and one for water?

If the heating valve was in the open position then in theory that should prove the timer / thermostat, that should then power the pump and boiler, so could be a valve issue... possibly not switching correctly? Could also be a boiler component, sensor, pcb etc...


Sent from my iPhone using Tapatalk

[blackal]

Is your HW on at the same times as the CH?

Did the HW heat up successfully?

If they are both on at the same time periods, then a dodgy switch in the CH motor-valve would not shut down the boiler, as the switch in the HW valve would keep the boiler firing and pumping.

Separate the times of the CH and the HW completely. If you don’t get the boiler powering the CH after that - then it could be the feedback switch on the CH motor valve.
A quick check would be to swap over the motor heads between CH and HW.

[thegreatdogwood]

Sounds like the thermostat / timer to me. Assuming it is low voltage (bell wire sized cable connecting to boiler and battery operated) then it's cheap and quick to replace. As others have said best to leave mains voltage to an electrician.

[bambam]

Another update.

Got home and the CH wasn't on - although the programme lights were on for both CH and HW on the programmer and the stat was set to 28 degrees and the valves were open.

Cycled through the options as the family were complaining about of the cold and it came back on and then switched off automatically when the programmer reached the switch off point.

Woke up this morning and house was cold, although I had heard the heating start at 6 when its set to come on (you can hear knocking in the pipes). This time (having read this thread last night), I switched the HW off and ran the CH programme - all ok. Its now set to be on permanently as I'm at home today and is working fine.

So given the exhaustive testing and checking over the last week or so seems to have reinforced the initial assumption that the CH comes on when the programmer starts the programme and then switches back off for some reason, what do we think the fault might be?

I'll be honest and admit that I don't understand the way that these systems work fully so let me ask a question:

When the room stat sends a signal that the temp is lower than the setting, where does that signal go? To the boiler or the controller? Must be the controller I would have thought.
Does the controller then send a signal to the boiler to switch on (and then off again at the end of the programme)?

If the issue is with the programmer then its a simple swop out for a new one isn't it?

Thanks

[RobDad]

I had a crazy situation in our house shortly after we moved in. Basically, none of the heating would come on anywhere over 3 floors unless the underfloor heating in the conservatory was calling for heat. Electrician said it was impossible but after 5 hours he traced the fault to 2 wires which had been installed incorrectly. He didn’t even charge much to fix it, he got so frustrated finding the fault it became a bit of a mission for him I think! Worked perfectly after that, apparently it had been set up incorrectly for the whole time the previous owner had lived there and he’d basically heated the conservatory needlessly for years without realising what was wrong!


Sent from my iPhone using Tapatalk

[blackal]

Google-image “central heating s plan wiring diagram” - look at the very first image from Flameport.com

The S-plan diagram will show you the basics.

https://www.flameport.com/electric/c...ing_S_plan.cs4

You can see that the timer sends the signal to the Boiler and Pump via:

1. The Room thermostat,
2. The CH Zone valve.

Best test is using a voltmeter on the following points, while the heating is ‘in demand’

This will show you how far the signal is getting.

a. Input to the thermostat (4 on the connector strip )
b. Between thermostat and CH zone valve (5 on the connector strip)
c. Between the CH zone valve and the Boiler/pump (1 on the connector strip)

Hopefully yours will be wired up similar, but it isn’t difficult to figure out.

It could well be the thermostat, but - it is the zone valve that heats up fairly quickly when the CH comes on (after heat/flow are established), so may affect the switch in the valve motor head - causing it to open (if it is intermittent faulty)

Remember you are dealing with mains voltage (live to neutral)

[MCFastybloke]

When the room stat sends a signal that the temp is lower than the setting, where does that signal go? To the boiler or the controller? Must be the controller I would have thought.
Does the controller then send a signal to the boiler to switch on (and then off again at the end of the programme)?

If the issue is with the programmer then its a simple swop out for a new one isn't it?

Thanks

Stat goes to boiler, The internal PCB sorts it all out

[hogthrob]

(Sucks air through teeth) "You need a new boiler, mate."

/British Gas

[bambam]

(Sucks air through teeth) "You need a new boiler, mate."

/British Gas

NO!

[bambam]

Google-image “central heating s plan wiring diagram” - look at the very first image from Flameport.com

The S-plan diagram will show you the basics.

https://www.flameport.com/electric/c...ing_S_plan.cs4

You can see that the timer sends the signal to the Boiler and Pump via:

1. The Room thermostat,
2. The CH Zone valve.

Best test is using a voltmeter on the following points, while the heating is ‘in demand’

This will show you how far the signal is getting.

a. Input to the thermostat (4 on the connector strip )
b. Between thermostat and CH zone valve (5 on the connector strip)
c. Between the CH zone valve and the Boiler/pump (1 on the connector strip)

Hopefully yours will be wired up similar, but it isn’t difficult to figure out.

It could well be the thermostat, but - it is the zone valve that heats up fairly quickly when the CH comes on (after heat/flow are established), so may affect the switch in the valve motor head - causing it to open (if it is intermittent faulty)

Remember you are dealing with mains voltage (live to neutral)

Stat goes to boiler, The internal PCB sorts it all out

Thanks. From what I can work out, the valve is ok as it opens and closes as it should and the stat sends the signal to the boiler ok (you can hear the click as its calls on/off depending on the temp set). The main thing seems to be the controller that starts the programme as usual and then something happens and the boiler switches off and the valve closes. Cycle through the options on the programmer and it works, or you can leave it to 'On' and it stays on.

Hmm..

[MCFastybloke]

Check stat cuircuit with a meter to verify its sending power and not just clicking

Sent from my SM-G920F using Tapatalk

[blackal]

Thanks. From what I can work out, the valve is ok as it opens and closes as it should and the stat sends the signal to the boiler ok (you can hear the click as its calls on/off depending on the temp set). The main thing seems to be the controller that starts the programme as usual and then something happens and the boiler switches off and the valve closes. Cycle through the options on the programmer and it works, or you can leave it to 'On' and it stays on.

Hmm..

The valve opening and a ‘click’ does not guarantee that the signal is passing through the valve motor - to the boiler. The boiler needs to know that the motor valve (zone valve) has opened before firing up.

It may be that the switch is dodgy, and works sometimes when the circuit is cold, but when the pipe work, valve and motor heat up - the switch flutters open. By the time you realise there is no heating - the pipe work is cold again.

Room Stat sends signal to motor valve to boiler/pump

Cyl stat does similar in the HW circuit.

[blackal]

Any progress?

[R11]

Had similar a while ago. Replaced the relevant section of the motorised valve (not the pipework) and all was fine. They’re not exspensive.

In in our case we had zoned system for heating. Heating would only kick in in zone 1 when it was demanded in zone 2 as well. Could feel the valve pushing itself back manually and not sticking where it should.

Easy enough fix if you’re comptent/willing to have a go. Make sure you mark/note location of wiring when remove the old valve and isolate power before. Should be a fuse spur switch somewhere nearby.

Onviously may may not be the case with yours but sounds very similar.

[bambam]

Any progress?

Hi

Yes and no... I looked at the wiring diagram linked above and then printed off the one for the Megaflo we have. Then I called Drayton and spoke to their tech team - who were very helpful.
Then I used the multimeter to check the voltages as described earlier. This is what I found:

- Programmer to stat = shows voltage when on. Shows no voltage when off.
- Stat to valve = shows voltage when on and none when off.
- Valve to boiler = shows voltage when on and none when off.

The programmer only shows voltage when 'on' sometimes - so when the programme has kicked in and starts to run the HW and CH for example, it will show voltage but then the heating will suddenly stop and the voltage from the CH side of the programmer shows nothing.

The guy from Drayton said that if this happens then just replace the programmer with a like for like and it should be all good.

So yes, I think I've diagnosed the problem thanks to all the help and advice on here.

No because I haven't bought a new programmer yet and the CH didn't kick in this morning!

[blackal]

Glad it is on its way to getting sorted. You will recognise that you now understand a lot more about your system, and able to save time and money in the future.

[bambam]

Hi

Quick update:

Never got round to replacing the programmer and got sort of got used to switching the heating on manually, thinking that I'd get the programmer some time soon.
Anyway, the manual option didn't work so I called someone as I have some insurance cover and thought they'd come and replace the programmer. Turns out it was the motorised valve in the end! Apparently it was working but getting stuck so although the lever went up and down outside, inside it wasn't quite working. So one new valve later we're back up and running.
The acid test will be when we put it back on timer to see if it kicks in and switches off properly.

Thanks to all that tried to help on here. I definitely know more about the system now.

[blackal]

Bloody hell! A cohesive bullet list of findings! (Usually you have to drag the info out)

The motor valves appear to be working on demand - correctly.
In manual - the controls appear to be driving the valves normally.

It would appear that it is your programmer at fault UNLESS - there is an intermittent faulty connection in the feedback switches on the motor valves. These allow a signal to go back to the boiler/pump - to tell them that the valve is open - “fire up and start pumping”

A loose connection or dodgy switch there - may be affected by the heat through the valve, such that once it works successfully - it continues to do so, until the system cools down again (say - overnight). Switches are atop the motor valve

Good luck, but I sense that you have the skill to work through the issue - logically. Do you have a multimeter to check for feedback signals?

There ya go!

[bambam]

There ya go!

You did indeed call it right! Smugness fully deserved. The valve eventually gave up - that might have been what was causing banging in the pipes while it was opening up. Since the new valve has been put in there's no noise in the pipes and the whole system is a lot quieter.

I miss the banging in the pipes as it acted as a sort of alarm clock!

Thanks for all your help everyone.

[KavKav]

NO!

A shouty NO from me also! As far as a list of suppliers and installers go from a ‘value for money’ and reliability perspective, I would place British Gas somewhere south of ‘Grand Nigerian Best Boiler and Roofing Installers’, Offices Worldwide and advance Western Union cash transfer deposit payments accepted with all guarantees honoured thank you most much and have a great day.

[Pitfitter]

Nice to see you got it sorted, can I ask a quick question of our experts please, last year I flushed out the system and added a tub of rust inhibitor, all working fine, last week when decorating I removed a rad to paper behind it and the water from the system was coloured like Coca Cola, I stored some in a jar and nothing has settled, so, it is merely the inhibitor that has coloured the water or has more dirt been released from the system and I need a flush again? Ta guys.

[IAmATeaf]

Not a plumber or an expert but the inhibitor won’t clean the water, will just inhibit rust/sludge formation. What you are probs my seeing is sludge that was still in the system. Unless you Powerflush the system it will be difficult to remove with a normal drain of the system. Do have a magnet trap type device installed? If so then what does the water in that look like and how much crap had it trapped?

[CaptainSlow]

Nice to see you got it sorted, can I ask a quick question of our experts please, last year I flushed out the system and added a tub of rust inhibitor, all working fine, last week when decorating I removed a rad to paper behind it and the water from the system was coloured like Coca Cola, I stored some in a jar and nothing has settled, so, it is merely the inhibitor that has coloured the water or has more dirt been released from the system and I need a flush again? Ta guys.

What type of system is it?

[Pitfitter]

Cheers guys, a powerflush had been suggested by my BiL who’s a sparky but often works along side a plumber, the system is an ordinary? type boiler water is fed in by a high level tank, it does not have a magnetic trap, once the weather improves a powerflush will be the first thing on the agenda and then a filter. Ta.