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

[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

 

[Lucien Nunes]

I don't know why dual pumps are not more popular. Given how long the better pumps last and how unreliable zone valves tend to be, I've always thought it a good idea. I put a dual pump system in 20 years ago for someone who was fed up with valve failures, and AFAIK both original pumps are still going. And in the days before intelligent pumps you could set the HW pump low and avoid having a bypass regulator. Then there was the SMC controller 3-port pump. Anyone remember those?

 

[davesparks]

. Then there was the SMC controller 3-port pump. Anyone remember those?

I don't know the system you've mentioned but I have come across the grundfoss pump plan system, two pumps on a common base casting with a relay in a box for a wiring centre.

 

[Cbuk2k2]

I don't know why dual pumps are not more popular. Given how long the better pumps last and how unreliable zone valves tend to be, I've always thought it a good idea. I put a dual pump system in 20 years ago for someone who was fed up with valve failures, and AFAIK both original pumps are still going. And in the days before intelligent pumps you could set the HW pump low and avoid having a bypass regulator. Then there was the SMC controller 3-port pump. Anyone remember those?

The modern Grundfoss pump plan systems never really caught on I the UK because they were not marketed much apparently.

Pump plan relays on check valves which are just another mechanical device in the heating medium circuit.

Two other issues are that modern bookers generally provide a pump overrun feature, thus allows the heat exchanger to Bd cooled after burner shutdown. To do this with two pumps requires a specialist programmer which appear to be fairly hard to come by.

Thd biggest factor is probably the level of electrical competency in heating engineers. Manny struggle with the standard wiring centre sbd would be unseen to deviate from this.

 

[davesparks]

Two other issues are that modern bookers generally provide a pump overrun feature, thus allows the heat exchanger to Bd cooled after burner shutdown. To do this with two pumps requires a specialist programmer which appear to be fairly hard to come by.

Why on earth would you need a specialist programmer to allow a pump overrun? The programmer doesn't feature in the pump overrun at all.

All it needs is a relay to connect one of the pumps to the overrun terminal when there is no demand on the boiler switched live. The grundfoss pump plan included this in the simple, easy to connect wiring centre supplied with it.

 

[Cbuk2k2]

Why on earth would you need a specialist programmer to allow a pump overrun? The programmer doesn't feature in the pump overrun at all.

All it needs is a relay to connect one of the pumps to the overrun terminal when there is no demand on the boiler switched live. The grundfoss pump plan included this in the simple, easy to connect wiring centre supplied with it.

I don’t know, you’d have to ask why Grundfoss decided to do it that way. The fact a relay in a box with wiring would require CE certification in order for it to be legally sold probably puts it beyond the scope of your average domestic electrician/heating engineer.

 

[davesparks]

I don’t know, you’d have to ask why Grundfoss decided to do it that way. The fact a relay in a box with wiring would require CE certification in order for it to be legally sold probably puts it beyond the scope of your average domestic electrician/heating engineer.

The CE certification is the manufacturers problem, not the installer.

 

[nicebutdim]

The CE certification is the manufacturers problem, not the installer.

One difference is where goods are imported from outside the EU, on which occasion the importer becomes liable for ensuring that goods are compliant. Not an everyday issue for most electricians, but potentially worth keeping in mind when sourcing items for those more unusual jobs.

 

[davesparks]

One difference is where goods are imported from outside the EU, on which occasion the importer becomes liable for ensuring that goods are compliant. Not an everyday issue for most electricians, but potentially worth keeping in mind when sourcing items for those more unusual jobs.

What has that got to do with this?

I stated that grundfoss supplied a wiring centre which included the relay required for the pump plan system and now we are wandering off in the rhubarb talking about CE marking!

 

[nicebutdim]

What has that got to do with this?

I stated that grundfoss supplied a wiring centre which included the relay required for the pump plan system and now we are wandering off in the rhubarb talking about CE marking!

Reading the previous comments again, it would seem that I've added nothing of relevance to the thread as I'd misunderstood the post you were replying to.

As such, you could file my comment under miscellanious information or ignore it completely.

 

[Cbuk2k2]

The CE certification is the manufacturers problem, not the installer.

If you buy a number of electrical components and integrate them into an assembly or enclosure you are then classed as the manufacture of that assembly.

Irrespective of if the commoners used are CE marked the assembly as a whole must go through a product safety/conformance process.