Protecting a boiler with a relay

[Harry Palmer]

I am fitting a Heat only boiler that just serves the radiator circuit, the boiler has its own dedicated block terminal connector on the PCB but I cannot connect the pump to it as we normally do, the pump is a commercial type and Worcester Bosch have stated it will damage the PCB because of the excessive load/current drawn by the pump.


W-B have advised fitting a relay to protect the boiler electronics. A work colleague has emailed me a picture (see link below) of one a sparky wired for him in similar circumstances but that's where the fun begins, can anyone please help me with a simple wiring schematic on how to install this particular relay to serve both pump/boiler and the other items listed below which may or not be relevant in relation to the relay


Other items fitted which may be relevant:


Honeywell RF2 Pack 1 RF Programmer and room stat

Honeywell T4360 Frost Thermostat

Honeywell L641B Pipe Thermostat

Relay image link: dav - https://ibb.co/nLwAUb

Thanks in advance for any help


Ps. I'm hoping it’s just a simple case of some knowledgeable soul identifying the Supply & Load side of the relay!

 

[Deleted member 26818]

The top is power in, the bottom is power out.
A1 and A2 are for your control wires the rest are for what you want switched.

 

[telectrix]

A1 and A2 are the coil. then 1 switches to 2, 3-4, 5-6, 7-8

 

[Harry Palmer]

The top is power in, the bottom is power out.
A1 and A2 are for your control wires the rest are for what you want switched.

Thank you both for the swift replies. As you are aware I am not a sparky, I do however have knowledge of heating controls, but both anwers are confusing me a little, can either of you chaps post me a visual link of a wiring diagram as I can understand this better, sorry to be a pain :/

 

[Deleted member 26818]

What type of pump do you have?
Single phase (230V) or 3phase (415V).

 

[Deleted member 26818]

Basically, the cable that you would normally take from the boiler control to the pump goes instead to contacts A1 and A2. Brown in A1 and Blue in A2.
You then take power to the the other terminals on the contactor.
It’s preferable to take this power from the same source as supplies the boiler, but that may be impractical?
Connect Brown to terminal 1 and Blue to terminal 3.
From the bottom of the contactor you take power to the pump. Brown in terminal 2 and Blue in terminal 4.
I would then connect all the Earth wires together using a terminal block.

 

[UKMeterman]

@spinlondon Please check your statement above, A1 A2 is the COIL controlling the contacts.

 

[Harry Palmer]

What type of pump do you have?
Single phase (230V) or 3phase (415V).

Its a normal single phase 230v

 

[Harry Palmer]

@spinlondon Please check your statement above, A1 A2 is the COIL controlling the contacts.

Has Spinlondon made an error in his statement?

 

[UKMeterman]

Slightly the connections are correct the discription is in error. What you have is an electricly controlled switch. When power is put onto terminals A1 A2 this causes a coil of wire inside to become a big magnet and thus the insides of the switch move. If A1 A2 were a CONTACT and not a COIL then it would short stuff out, big bang and a repair bill.

As stated above wire A1 A2 to the boiler in place of the pump and all should be good.

 

[Harry Palmer]

Basically, the cable that you would normally take from the boiler control to the pump goes instead to contacts A1 and A2. Brown in A1 and Blue in A2.
You then take power to the the other terminals on the contactor.
It’s preferable to take this power from the same source as supplies the boiler, but that may be impractical?
Connect Brown to terminal 1 and Blue to terminal 3.
From the bottom of the contactor you take power to the pump. Brown in terminal 2 and Blue in terminal 4.
I would then connect all the Earth wires together using a terminal block.

Apologies but can you just clarify, A1 & A2 are permant live & neutral from the breaker? I think i understand the rest of your guide

 

[UKMeterman]

Get the wiring diagram for the boiler, identify the pump on the diagram for the boiler, connect A1 A2 where the pump is shown the on the wiring diagram for the boiler. Connect the rest as stated above

 

[buzzlightyear]

not harry palmer, the spy impress files. where is a cylinder stat going ?

 

[Harry Palmer]

not harry palmer, the spy impress files. where is a cylinder stat going ?

Not the Harry Palmer but a Harry Palmer. BTW its The Ipcress File.

No hot water required, boiler only serving radiator circuit, all hand wash basins/sinks served by hot water heaters

 

[Harry Palmer]

Get the wiring diagram for the boiler, identify the pump on the diagram for the boiler, connect A1 A2 where the pump is shown the on the wiring diagram for the boiler. Connect the rest as stated above

By jove I think ive got it. Thank you UKMeterman for your time and expert advice

 

[UKMeterman]

The other important question is can we have a photo of the rating plate of the pump. It may need special proteciton.

 

[Harry Palmer]

The other important question is can we have a photo of the rating plate of the pump. It may need special proteciton.

As requested:

link: sdr - https://ibb.co/iiZE5G

 

[Harry Palmer]

Basically, the cable that you would normally take from the boiler control to the pump goes instead to contacts A1 and A2. Brown in A1 and Blue in A2.
You then take power to the the other terminals on the contactor.
It’s preferable to take this power from the same source as supplies the boiler, but that may be impractical?
Connect Brown to terminal 1 and Blue to terminal 3.
From the bottom of the contactor you take power to the pump. Brown in terminal 2 and Blue in terminal 4.
I would then connect all the Earth wires together using a terminal block.

Also thank you too Spinlondon for taking the time and trouble to help

 

[Deleted member 26818]

Yes I wrote contacts A1 and A2 when I should have written terminals A1 and A2.

 

[Harry Palmer]

Get the wiring diagram for the boiler, identify the pump on the diagram for the boiler, connect A1 A2 where the pump is shown the on the wiring diagram for the boiler. Connect the rest as stated above

Update

To UKMeterman and spinlondon repectively, I have attched a basic wiring diagram below that I created in Microsoft Paint, can either of you please tell me if I have interperated your wiring guide incorporatiing the 'Contactor' switch correctly?

Thanks

Link: PROPOSED PUMP WIRING DIAGRAM - https://ibb.co/jUGgpb

 

[Deleted member 26818]

No.
You got from ‘Boiler to external pump connections’ to terminals A1 and A2 correct.
You got terminals 4 and 2 to external pump correct.
The power to terminals 1 and 3 has to come from another source (preferably the same source as supplies the boiler).

 

[Deleted member 26818]

I hope this explains:

Top FCU has whatever fuse is recommended for the boiler (3A?).
Lower FCU (13A?).

 

[Harry Palmer]

I hope this explains:
View attachment 39611
Top FCU has whatever fuse is recommended for the boiler (3A?).
Lower FCU (13A?).

I undertand where i went wrong, again thank you spinlondon for the wiring diagram and of course taking the much appreciated time to reply