Hi, can anyone offer any advice as to why the heating would run when HW is called for?

[Andyd 112233]

Hi, can anyone offer any advice as to why the heating would run when HW is called for?

 

[Cbuk2k2]

Hi, can anyone offer any advice as to why the heating would run when HW is called for?View attachment 60012

More often than not its becuse the zone valve on your heating has failed open.

 

[Andyd 112233]

More often than not its becuse the zone valve on your heating has failed open.

Hi thanks for your message. There is not a valve on this system. It looks like it uses the double pole relay, It is a very old system. 1978 it was installed

 

[Cbuk2k2]

Hi thanks for your message. There is not a valve on this system. It looks like it uses the double pole relay, It is a very old system. 1978 it was installed

Based on the wiring center diagram you've posted you have a conventional system boiler.

You will have one, two (or even 3) zone valves as per the pictures bellow.

 

[Sintra]

Hi thanks for your message. There is not a valve on this system. It looks like it uses the double pole relay, It is a very old system. 1978 it was installed

Surely there still has to be some sort of a motorised valve to close the heating circuit. If not then you will always have heating when the boiler fires.

 

[Cbuk2k2]

Surely there still has to be some sort of a motorised valve to close the heating circuit. If not then you will always have heating when the boiler fires.

Plumbers have a habit of hiding these under floors/baths etc in the UK.

 

[davesparks]

Based on the wiring center diagram you've posted you have a conventional system boiler.

You will have one, two (or even 3) zone valves as per the pictures bellow.

No, the wiring diagram posted does not show a conventional system boiler with zone valves.

The wiring diagram posted shows a 2 pump system utilising a DPDT relay. The biggest clue to this is 'two pump system' written on it.
[automerge]1596964186[/automerge]

Surely there still has to be some sort of a motorised valve to close the heating circuit. If not then you will always have heating when the boiler fires.

According to the picture it is a two pump system, no motorised valves are used with this.
[automerge]1596964649[/automerge]

Hi, can anyone offer any advice as to why the heating would run when HW is called for?

It is impossible to say from just that diagram.

Haa it always worked this way or is it a fault which has developed recently?

Does the room thermostat have any effect when the CH has come on via the hot water controls?

Unfortunately the wiring diagram is incomplete, it doesn't show the internal links between the connections so we can only guess at what the full circuit is.

Without further information this needs to be tested by a good electrician.

 

[Cbuk2k2]

No, the wiring diagram posted does not show a conventional system boiler with zone valves.

The wiring diagram posted shows a 2 pump system utilising a DPDT relay. The biggest clue to this is 'two pump system' written on it.
[automerge]1596964186[/automerge]


According to the picture it is a two pump system, no motorised valves are used with this.

I apologies, your right, I didn't look closely enough at the diagram to see the second pump. I didn't even know such a system existed, I've seen gravity hot water but never a second pump.

Surely without a valve both systems will always heat up?
[automerge]1596964910[/automerge]

No, the wiring diagram posted does not show a conventional system boiler with zone valves.

The wiring diagram posted shows a 2 pump system utilising a DPDT relay. The biggest clue to this is 'two pump system' written on it.
[automerge]1596964186[/automerge]


According to the picture it is a two pump system, no motorised valves are used with this.
[automerge]1596964649[/automerge]


It is impossible to say from just that diagram.

Haa it always worked this way or is it a fault which has developed recently?

Does the room thermostat have any effect when the CH has come on via the hot water controls?

Unfortunately the wiring diagram is incomplete, it doesn't show the internal links between the connections so we can only guess at what the full circuit is.

Without further information this needs to be tested by a good electrician.

If there are no valves in the system a blockage in the hot water flow/return may well force flow through the heating circuit instead.

 

[davesparks]

I apologies, your right, I didn't look closely enough at the diagram to see the second pump. I didn't even know such a system existed, I've seen gravity hot water but never a second pump.

Surely without a valve both systems will always heat up?

No, or not to any significant extent. With one pump running and the other not the vast majority, if not all, of the hot water will be circulated by the running pump and not get through the stationary pump. This assumes the system is properly designed.

There is a possibility of heat creeping via the return pipe, but good pipework design should combat this, or a non return valve.
[automerge]1596965220[/automerge]

If there are no valves in the system a blockage in the hot water flow/return may well force flow through the heating circuit instead.

I doubt that this would cause enough flow through the heating to make it appear to be on, maybe slightly warm at best.

A blockage in the hot water pipework will cause the hot water pump to be pumping against the blockage, this won't normally cause any water to flow via the heating pump.

 

[Andyd 112233]

This is the old wiring centre, we assume it has always worked correctly. Please not that on the picture if there is a notch then the terminals have a link. We have rewired the property but kept the heating system as was just renewing the cabling. Could the frost stat cause an issue if set to call for heat?

 

[davesparks]

This is the old wiring centre, we assume it has always worked correctly. Please not that on the picture if there is a notch then the terminals have a link. We have rewired the property but kept the heating system as was just renewing the cabling. Could the frost stat cause an issue if set to call for heat?

Ah, so you are an electrician working on the system, your OP gave the impression of a fault finding situation on an existing installation, not that you'd interfered with the wiring and messed it up.

My first question has got to be why did you mess with a working system?

Did you not take the time to investigate and understand the control system before you took it apart?

Did you test the system before taking it apart to ensure you understand how it is supposed to work and whether or not it was working correctly?

You have the old wiring centre and the wiring diagram so you can work backwards from this to draw yourself a diagram of how it was connected previously. From this you can work out how the system is supposed to work and then start to fault find.
[automerge]1596969169[/automerge]
Do you have a diagram of exactly how you have connected the new wiring for this system?

Without that the most we could possibly do is draw a diagram of how it was originally wired, but that won't help explain why it is not working now.

 

[Andyd 112233]

Ah, so you are an electrician working on the system, your OP gave the impression of a fault finding situation on an existing installation, not that you'd interfered with the wiring and messed it up.

My first question has got to be why did you mess with a working system?

Did you not take the time to investigate and understand the control system before you took it apart?

Did you test the system before taking it apart to ensure you understand how it is supposed to work and whether or not it was working correctly?

You have the old wiring centre and the wiring diagram so you can work backwards from this to draw yourself a diagram of how it was connected previously. From this you can work out how the system is supposed to work and then start to fault find.

Thanks for your message.

My mistake was not confirming how the system worked and if it worked correctly. We had to rewire the system as all cabling did not have any cpc's and the original install was installed very poorly. I have done as you suggest and worked backwards and cannot see any immediate issue with the design of the system. Hence I am looking for another input from electricians. Thanks for taking time to reply to this thread. I assume you don't have any advice as requested ?

 

[Cbuk2k2]

Thanks for your message.

My mistake was not confirming how the system worked and if it worked correctly. We had to rewire the system as all cabling did not have any cpc's and the original install was installed very poorly. I have done as you suggest and worked backwards and cannot see any immediate issue with the design of the system. Hence I am looking for another input from electricians. Thanks for taking time to reply to this thread. I assume you don't have any advice as requested ?

Do the pumps stop and start in response to demand from the two thermostats/time clock?

If you connect a switched live to the boiler and temporarily connect power the pump bypassing the controls does the issue go away?

If you fire the boiler and run only one pump and the other circuit heats up that would imply its a piping design/plumbing fault rather then a an electrical issue.

Heating systems used to be entirely gravity fed using only the fact cold water is more dense than hot water. It may be your getting effects such as these.

 

[Andyd 112233]

Do the pumps stop and start in response to demand from the two thermostats/time clock?

If you connect a switched live to the boiler and temporarily connect power the pump bypassing the controls does the issue go away?

If you fire the boiler and run only one pump and the other circuit heats up that would imply its a piping design/plumbing fault rather then a an electrical issue.

Heating systems used to be entirely gravity fed using only the fact cold water is more dense than hot water. It may be your getting effects such as these.

Thanks for your message. I am back on the job tomorrow. I will what you have suggested ?

 

[davesparks]

Thanks for your message.

My mistake was not confirming how the system worked and if it worked correctly. We had to rewire the system as all cabling did not have any cpc's and the original install was installed very poorly. I have done as you suggest and worked backwards and cannot see any immediate issue with the design of the system. Hence I am looking for another input from electricians. Thanks for taking time to reply to this thread. I assume you don't have any advice as requested ?

So can you post the wiring diagram you have created of the old system? Or describe its operation?
Can you also post the wiring diagram of what you have installed?

You haven't given enough information to be able to offer any helpful advice as far as I can see.

A diagram of what you have installed will allow us to see how it is currently operating and suggest how to achieve the desired operation.

I have given all the advice I can confidently give without further information.
I could offer you a bunch of random guesses at what might be wrong, but that wouldn't help.

 

[Andyd 112233]

So can you post the wiring diagram you have created of the old system? Or describe its operation?
Can you also post the wiring diagram of what you have installed?

You haven't given enough information to be able to offer any helpful advice as far as I can see.

A diagram of what you have installed will allow us to see how it is currently operating and suggest how to achieve the desired operation.

I have given all the advice I can confidently give without further information.
I could offer you a bunch of random guesses at what might be wrong, but that wouldn't help.

I am back on site tomorrow Dave, I will see what is happening and if unable to resolve I will send a diagram of the installed system. Thanks for your message

 

[davesparks]

I've sketched what I would expect the basic control circuit to be for a standard (non overrun) boiler with a two pump system.



This would not be for a pump overrun boiler.

 

[Cbuk2k2]

I've sketched what I would expect the basic control circuit to be for a standard (non overrun) boiler with a two pump system.

View attachment 60036

This would not be for a pump overrun boiler.

Hi Dave,

Whats the purpose of the relay?

To create a common switched live without both pumps interacting?

 

[davesparks]

Hi Dave,

Whats the purpose of the relay?

To create a common switched live without both pumps interacting?

The relay is to seperate the pumps yes, without it they would backfeed

 

[Andyd 112233]

I was back on the job today. My mistake was that I had the pump switch wires mixed between the HW and HTG. Thank you for everyone's suggestions. First time using the forum and happy to say it was a good experience