Please can anyone help a DIY guy? ...CH problem....

[vintageaxeman]

Good morning!

I have a problem with my central heating system…..and am wondering if anyone can help.

The system:

1. 15 year old detached house, with a 15 yr old Honeywell Y Plan CH system, which to all extents and purposes works FINE.

2. Boiler is a traditional ‘IDEAL Classic’ boiler, fitted inside the garage, wall mounted. Balanced flue.

3, Standard steel radiators, microbore plumbing. They all get hot very quickly when the system works properly.

4. Honeywell Y System, with a 3 way valve V4073A (28mm pipe) and pump, and hot water cylinder with a Honeywell cylinder thermostat, and the junction box for all the wiring, is all in the airing cupboard upstairs.

5. Downstairs in the hall there is a standard Honeywell Room thermostat. Model 6360B

6. Standard programmer, was a Honeywell ST6400, is now a Honeywell ST9400C, which times the hot water and heating separately.



Everything has worked fine until this summer. Normally I can set the programmer to Hot Water, or Heating, or Both….and it can be all automatic or I can just press the Extra Hour button on either.

What SHOULD happen of course is that when the electronics calls for heat, either for the hot water cylinder, or for the central heating, it will switch the 3-way diverter valve to the appropriate pipe and simultaneously switch the boiler and the pump on.

When I ask the system to heat up the hot water, everything works. Also, when I set the system to deliver hot water AND central heating at the same time, everything works fine….radiators get hot, hot water gets to temperature, etc.

BUT….My problem is this: When I ask the system to heat up the radiators ON THEIR OWN, the pump does not switch on, regardless of the setting on the room stat in the hall.


So far, I have tried the following:

1. Turned the electricity off and checked the tightness of all the wires in ALL the components and in the wiring centre. All tight and sound.

2. Replaced the valve actuator with a new replacement. In the process I checked whether the valve in the 3 way 28mm valve body was seized and it seems fine…. it swings from side to side perfectly as far as I can see, diverting the water to wherever it needs to go.

3. I then thought I had better check out the room thermostat in the hall, so I replaced it with a new one. NO CHANGE.

4. I then decided it MUST be the programer, so I bought a new direct replacement, but the current model. Fitted it to the existing baseplate, and it works like a charm on most settings, but STILL no heating without the hot water being on.

5. It CAN’T be the cylinder thermostat.

6. There is only one live cable going to the pump from the wiring centre, and I know the pump works, so it can’t be that.

7. I can’t imagine that the boiler has anything to do with it….It’s just switched on and off when there is a demand for heat….Surely it’s nothing there….?

8. So that just takes me back to the 3-way diverter valve…..could it possibly be that the swing of the actuator is not going far enough to hit limit switches and turn the pump on? So this morning I took the actuator head off and let it dangle free, set the system to ask for heating, HOPING that I would hear the sound of the pump…..but nothing.


Other than partially draining the system and replacing the whole diverter valve, (£75), I just dont know what to try next.


Any ideas? And thank you in advance for them!

 

[telectrix]

folow the switched L from programmer through valves and stat. using a metr set on ac volts.

 

[tony mc]

You need to get someone in to sort the issue out as it could end up very expensive just changing parts.

If the system works on water and heating but not on CH only it sounds like the valve is not driving far enough across to activate the micro switch which should make the orange wire live on the mid position valve!

It really shouldnt take long for a good electrician to locate the fault !

 

[tony mc]

Thats the same as mine Tel but blown up and laminated so I can see the dam thing !

 

[telectrix]

Thats the same as mine Tel but blown up and laminated so I can see the dam thing !

mine is on my ipad. blown up to full screen.

 

[Sparkie30]

Had exatly the same problem some time ago. Plumber Replaced the 3 port valve and good.

 

[Leesparkykent]

With heating only selected on the programmer and the thermostat calling for heat the grey and white on the 3 port should both be live. White should be live as its connected to the thermostat which is calling for heat and programmer is on for heating. The grey should be live as the HW is selected to off on the programmer. If they are both live then the motor should turn the ball and arm within the valve body closing port B and making the orange live which then switches the boiler.

 

[vintageaxeman]

With heating only selected on the programmer and the thermostat calling for heat the grey and white on the 3 port should both be live. White should be live as its connected to the thermostat which is calling for heat and programmer is on for heating. The grey should be live as the HW is selected to off on the programmer. If they are both live then the motor should turn the ball and arm within the valve body closing port B and making the orange live which then switches the boiler.

Thank you guys, I will heed all this advice and check it out when there is a bi of natural light available for me, I am not a spark but I do know what to be careful of when using a voltmeter. I am confident I can check it out as you have all described. Thank you.

 

[vintageaxeman]

Orange wire shows around 60v, white wire shows 240v.
That's on a NEW head and valve, sitting on the carpet. I presume that when you say 'confirm the orange wire becomes Live, that you mean 240v? But this CAN't be a faulty valve or head. This is the 3rd head I've tried....
Help much appreciated on this one.
By the way, I am loath to rewire (partly because the tails are all so short), but the honeywell wiring box is not done according to the printed or online Y-system wiring diagram...things are in a different order so it's really hard for a skilled amateur like me to follow....

Where do I go next with this please?

Remember that the valve appears to respond properly, the main issue is that the pump does not come on when heating is called for.

 

[Leesparkykent]

Orange wire shows around 60v, white wire shows 240v.
That's on a NEW head and valve, sitting on the carpet. I presume that when you say 'confirm the orange wire becomes Live, that you mean 240v? But this CAN't be a faulty valve or head. This is the 3rd head I've tried....
Help much appreciated on this one.
By the way, I am loath to rewire (partly because the tails are all so short), but the honeywell wiring box is not done according to the printed or online Y-system wiring diagram...things are in a different order so it's really hard for a skilled amateur like me to follow....

Where do I go next with this please?

Remember that the valve appears to respond properly, the main issue is that the pump does not come on when heating is called for.

Select heating on and hot water off, turn room thermostat all the way up and check for voltage on the grey, white and orange.

 

[mattg4321]

I had something similar recently. All wired correctly, valve was opening fully with 230v to white and grey but wasn't getting 230v on orange. Changed the head on the valve - same problem.

Called Honeywell to see if they could shed any light. Explained the problem and fairly quickly they said you need a capacitor between N and orange which they'd send out to me. Said DON'T fit anymore new heads as you will damage them without said capacitor. Mumbled something about pump overrun which I didn't catch and put the phone down!

Part arrived a couple of days later, fitted along with a new head and it all worked fine. Anyone else had this too?

 

[vintageaxeman]

I had something similar recently. All wired correctly, valve was opening fully with 230v to white and grey but wasn't getting 230v on orange. Changed the head on the valve - same problem.

Called Honeywell to see if they could shed any light. Explained the problem and fairly quickly they said you need a capacitor between N and orange which they'd send out to me. Said DON'T fit anymore new heads as you will damage them without said capacitor. Mumbled something about pump overrun which I didn't catch and put the phone down!

Part arrived a couple of days later, fitted along with a new head and it all worked fine. Anyone else had this too?

That's interesting, MattG. Thank you. Might give them a ring. Could you give me the spec of the capacitor? Cheers.

 

[mattg4321]

I'm sorry I don't remember. If you call Honeywell and ask for technical they came up with it as the fix immediately. It's clearly a problem well known to them. Let us know how you get on.

 

[Last plumber]

Good morning!

I have a problem with my central heating system…..and am wondering if anyone can help.

The system:

1. 15 year old detached house, with a 15 yr old Honeywell Y Plan CH system, which to all extents and purposes works FINE.

2. Boiler is a traditional ‘IDEAL Classic’ boiler, fitted inside the garage, wall mounted. Balanced flue.

3, Standard steel radiators, microbore plumbing. They all get hot very quickly when the system works properly.

4. Honeywell Y System, with a 3 way valve V4073A (28mm pipe) and pump, and hot water cylinder with a Honeywell cylinder thermostat, and the junction box for all the wiring, is all in the airing cupboard upstairs.

5. Downstairs in the hall there is a standard Honeywell Room thermostat. Model 6360B

6. Standard programmer, was a Honeywell ST6400, is now a Honeywell ST9400C, which times the hot water and heating separately.



Everything has worked fine until this summer. Normally I can set the programmer to Hot Water, or Heating, or Both….and it can be all automatic or I can just press the Extra Hour button on either.

What SHOULD happen of course is that when the electronics calls for heat, either for the hot water cylinder, or for the central heating, it will switch the 3-way diverter valve to the appropriate pipe and simultaneously switch the boiler and the pump on.

When I ask the system to heat up the hot water, everything works. Also, when I set the system to deliver hot water AND central heating at the same time, everything works fine….radiators get hot, hot water gets to temperature, etc.

BUT….My problem is this: When I ask the system to heat up the radiators ON THEIR OWN, the pump does not switch on, regardless of the setting on the room stat in the hall.


So far, I have tried the following:

1. Turned the electricity off and checked the tightness of all the wires in ALL the components and in the wiring centre. All tight and sound.

2. Replaced the valve actuator with a new replacement. In the process I checked whether the valve in the 3 way 28mm valve body was seized and it seems fine…. it swings from side to side perfectly as far as I can see, diverting the water to wherever it needs to go.

3. I then thought I had better check out the room thermostat in the hall, so I replaced it with a new one. NO CHANGE.

4. I then decided it MUST be the programer, so I bought a new direct replacement, but the current model. Fitted it to the existing baseplate, and it works like a charm on most settings, but STILL no heating without the hot water being on.

5. It CAN’T be the cylinder thermostat.

6. There is only one live cable going to the pump from the wiring centre, and I know the pump works, so it can’t be that.

7. I can’t imagine that the boiler has anything to do with it….It’s just switched on and off when there is a demand for heat….Surely it’s nothing there….?

8. So that just takes me back to the 3-way diverter valve…..could it possibly be that the swing of the actuator is not going far enough to hit limit switches and turn the pump on? So this morning I took the actuator head off and let it dangle free, set the system to ask for heating, HOPING that I would hear the sound of the pump…..but nothing.


Other than partially draining the system and replacing the whole diverter valve, (£75), I just dont know what to try next.


Any ideas? And thank you in advance for them!

Take the programmer off and look at the back plate. There should be a wire on the 'HOT WATER OFF' terminal !

If that's has not been installed, there is your answer.

Additionally and for future ref without being patronising, there is never any need to swap and see with anything in Heating. Tha vast majority of things can be tested. You will waste a lot of time and money doing that and if you don't have a good knowledge of how things work, plumbing side included, you will draw the wrong conclusions.

Sorry to prattle on but I hate to see waste

 

[tony mc]

This is connected in mine between the orange and neutral!

 

[tony mc]

This is what is connected to my boiler and it connects the orange of the 3 port to Neutral.

Not sure why its connected but cant see how this would solve the above problem.

Are you 100% sure you have 230v on both the white and grey wires as you said that when calling for both HW and CH it works fine so the motor is working as it is driving to the centre position and being held!

 

[Lucien Nunes]

You said quite specficically that the PUMP does not run when demand is only for heating. Does the boiler fire up? Is the pump wired in parallel with the boiler or via an overrun thermostat in the boiler?

With the head disconnected from the system and the white and grey wires both fed with 230V (CH call, HW sat) the actuator should complete its travel and make the orange wire live. If this is not happening, the actuator appears to be faulty.

 

[mattg4321]

That looks similar to what Honeywell sent me Tony. Also fitted between Orange/Boiler SW and Neutral. It solved my problem but not sure why to be perfectly honest. Everything was wired correctly but every time you replaced the head on the valve it would damage it and you wouldn't get 230v on the Orange.

 

[tony mc]

I was hoping Lucien Nunes was going to inform us what it was and what it would do!

 

[Lucien Nunes]

Ah, OK. I've not seen this done before and I am not sure why it is done. The orange lead on a 3-port has two functions. When there is call for heating but not for water, the valve moves to the far position and a contact completes a circuit from white to orange to feed the boiler / pump. The only function the capacitor might have in relation to this is as a suppressor to reduce arcing at the microswitch when switching the boiler/pump load. I would be surprised if the microswitch would fail rapidly without it, unless they have started using very weedy microswitches or the present generation of mid-position valves actually use a solid-state switching alternative to a microswitch (It's years since I looked inside one, perhaps someone could confirm?) Personally I would use a snubber with built-in resistor for that purpose and the only reason to add it outside the valve would be if the one built into the valve was inadequate for certain loads. Mention of the pump overrun would suggest that the switching device in the valve is being damaged by the pump motor being dumped back on the orange lead and creating a transient after running from the boiler PL via the overrun thermostat.

There is another sneaky function for the orange lead, which is to backfeed the demagnetisation resistor in the valve when there is call for hot water via the normally-closed contact in the cylinder stat. The small resulting AC current in the winding is supposed to avoid the situation where, if the valve has been sat at the mid-position for a long time with DC flowing through the motor via the stall diode, the stator becomes slightly magnetised preventing the spring spinning the motor back to the rest position once the call for heat via the white lead is removed. There is a minor side-effect if the valve is in the far position when this happens: The valve stays put because grey is still live and current flows via the demagnetisation resistor back out of the orange lead. I can see a possibility that if this is used to control boiler electronics via an input that is unduly sensitive, the 1mA or so from the orange lead might cause unwanted triggering. The capacitor would provide a load to absorb that, however it would not damage the valve so I don't see that this is the reason.

If anyone can confirm or deny whether modern 3-ports have a triac or something controlling the orange lead, that might shed some light on it.