Rewire heating relay box

[HRP123]

Hi there thanks for your time to look at this.


I've got a multi pump / circuit system which is connected via a relay box to the boiler and Honeywell timer programmers. Picture attached.
Right now any single circuit can turn the boiler on an off at any time (assuming the programmers allow it). There are central heating (two zones), towel rails (one zone), underfloor heating (two manifolds) and hot water cylinders (2 of them).


I'm trying to rewire the system to make it hot water priority. So basically if the hot water circuit calls for heat, then the other circuits should go off temporarily to allow it to reach temperature as quickly as possible. This should allow me to range rate the boiler down (40kw current) and ensure it doesn't burn crazy amounts of gas trying to satisfy all open circuits at once.

I cannot see any diagrams online for these kinds of relays - I cannot even see the name of the product (generic plastic box). Can anyone help?
Thanks!!

 

[bernardgreen]

That looks very much like a real DIY design and build.

Without an accurate wiring diagram it will be impossible to determine how to alter the wiring to provide hot water priority.

I assume this was in place when you moved into the house, Did the previous owner have any design notes for the system that may include a circuit diagram ?

Failing that a competent person is needed to create a wiring diagram by tracing and documenting each and every wire and each and every relay. connection

 

[Deleted member 267285]

I take it you know if the boiler is capable of being range rated? Orange wires are generally the switch live wires from motorised valves if that helps?

 

[HRP123]

That looks very much like a real DIY design and build.

Without an accurate wiring diagram it will be impossible to determine how to alter the wiring to provide hot water priority.

I assume this was in place when you moved into the house, Did the previous owner have any design notes for the system that may include a circuit diagram ?

Failing that a competent person is needed to create a wiring diagram by tracing and documenting each and every wire and each and every relay. connection

It was the plumber who I hired to install this originally... yes this is exactly why I haven't called him back. I'm just trying to understand the principle of how this works as I have a friend who is an electrician but just is not familiar with this relay box. Cannot work out how they operate as I don't know what brand they are !

 

[HRP123]

I take it you know if the boiler is capable of being range rated? Orange wires are generally the switch live wires from motorised valves if that helps?

Thanks, yes actually I have already range rated the boiler down - and generally when all the circuits are not on it works fine at half the output (20kw as opposed to 40kw) - in fact if the radiators and underfloor are on the flow temperature falls slightly because the boiler is working flat out which suits just fine actually for these two circuits. Thanks

 

[bernardgreen]

The relays and their sockets are manufactured by Finder

It is strange that in your picture there are no visible connections to the COM and/or NC contacts on the relay sockets. Only the NO contacts seem to be wired. Are there wires to the COM contacts that are not visible in the pictures, likely to be a daisy chain of short links or a bus bar

u

 

[RandomGrinch]

Cannot work out how they operate as I don't know what brand they are !

A bit of guess work, and I don't know the relays, but they appear to me to be SPST relays with a 240V AC coil and an internal link to provide live to the output.
The left hand terminals power the coil - the top terminal neutral, the bottom terminal the live to operate the coil.
The right hand terminals are the switched live outputs.

If you want to start tracing the wires, you could take the spare relays out to give yourself a bit more space.

Most of the blue wires appear to be neutral, so that simplifies things a bit, apart from this one...

Which seems to be a switched live.

This yellow/green wire also appears to be a live...

Both wires should have some brown sleeving on them to avoid confusion.

Again, these are only a guesses - a multimeter would be very useful for this problem!

EDIT:
I didn't see Bernards post, before I posted this. Yes, there are probably extra terminals on the relay out of sight on the image, but these are likely to be a simple link to the common terminal...

 

[Harry Bloomfield]

The basic idea should be, one of using the demand for HW, to interrupt the supply going to each zone valve.

So take the output of the cylinder stat to power the coile of an additional, multi-pole relay, and wire a pair of NC contact of the new relay, in series with each zone valve used central heating.

 

[polesapart]

I'm guessing that the relays are there to prevent backfeed from some commoned component .

As others have said you have a bespoke situation.

 

[bernardgreen]

So take the output of the cylinder stat to power the coile of an additional, multi-pole relay, and wire a pair of NC contact of the new relay, in series with each zone valve used central heating.

It may be possible to use a single NC contact to remove the supply from all the relays / circuits controlling the zone valves

 

[HRP123]

This is all SUPER helpful, thanks for this I am very grateful to each of you for your time.

I'm a novice myself trying to understand this before I get someone who knows how these things work to do the wiring. This way I can make sure it is done properly.

So if I understand the basics - on the left we have junction connectors - these are probably from the various diverter valves. As we have multiple diverter valves on each heating circuit, this probably joins the relevant valves together.

From here they go to the delay, so that when either one of the diverter valves on each circuit calls for heat, it starts the boiler + boiler pump.

Having relays makes sure that opening one circuit doesn't by mistake open another (i.e. backfeed)?

So the idea is that by fitting another multi-pole relay, when the HW diverters call for heat, it closes the connection to the other circuits. When the HW has reached temperature, it opens the connection again.

Can anyone possibly help me work out which kind of Finder multipole relay I would need to get for this application. I had a look on various websites but there are so many variations of relays that I don't really know which one I am looking for!

Again I really appreciate all your time and explanation, this forum is really helpful.

 

[HRP123]

The relays and their sockets are manufactured by Finder

View attachment 298378

It is strange that in your picture there are no visible connections to the COM and/or NC contacts on the relay sockets. Only the NO contacts seem to be wired. Are there wires to the COM contacts that are not visible in the pictures, likely to be a daisy chain of short links or a bus bar

View attachment 298381
u

Hmm, I'm not sure - will take another picture when I get home later from the other side - thanks

 

[bernardgreen]

Can anyone possibly help me work out which kind of Finder multipole relay I would need to get for this application.

Once we have an idea of how things are wired then one of the un-used relays already there could be wired up to remove power from the heating circuits when hot water is required.

Have you contacted the person who installed the system to ask if he can provide you with a circuit diagram.

 

[HRP123]

Once we have an idea of how things are wired then one of the un-used relays already there could be wired up to remove power from the heating circuits when hot water is required.

Have you contacted the person who installed the system to ask if he can provide you with a circuit diagram.

The plumber who originally wired it up did no circuit diagrams, this was something that had really pushed his capabilities as I remember he was phoning other people for help. I can see behind the board that there are some pencil notations UF, CH etc.

I've contacted him multiple times as I am trying to improve the efficiency of the design / reduce gas consumption - but he has not been forthcoming. Plus he did this about 9 years ago so I don't think he would remember if he did come and would be trying to work it out himself!