Wireless Replacement for Randal 103

[thomooseg]

I have just moved house and the central heating system is a bit ancient and looking to change it. The boiler is a Glow Worm Fuel Saver MKII with a Randal 103 and wired thermostat on the landing.

Can the Randall 103 that currently runs the system be replaced with a Honeywell CM927? In my old house I had a Combi Boiler and fitted a Honeywell CM927 myself which was very straight forward. I have been told that the Honeywell CM927 can be used as a replacement as the Randal 103 as they are both single channel units that control heating and hot water together.

The wires going into Randal 103 looks very different to my old Combi setup and I can’t figure them out despite reading loads about it. I think I may need a junction box to do the job and disconnect the old wired thermostat but any help with wiring would be much appreciated.

Many thanks in advance. View media item 54123 View media item 54124 View media item 54125

 

[doitall]

Should be easy but it looks like you have a few extra wires.

Old first, showing volts free switching, It looks like you have a link between 3-6 so you need to link L-A in the receiver. but post the make and model of the boiler before you do.

ON(1)-B
COM(3)-A
L(6)-L
N(5)-N

 

[thomooseg]

Hi doitall,

Thanks for the quick reply. The boiler is a The boiler is a Glow Worm Fuel Saver MKII.

 

[doitall]

Can you tell where is the extra wires in 1 & N go.

Put simply.

The boiler SL goes to B.
The boiler 9 goes to A.

Plus you need the L & N

The pump should be wired to the boiler direct for the over-run to work.

 

[scatmanjohn]

A Honeywell CM927 is a programmable wireless room thermostat.

You can't replace a Randal 103 with that.

 

[thomooseg]

Hi,

Sorry for not coming back sooner but have been out for the day.

In reply to your question, I have no idea what the extra wires are for but I have a plan. I have had a look at the Boiler Control Box Wiring and currently it goes like this:

Boiler to Pump:
Live from 7
Neutral from N
Earth from E

Boiler to Randal 103:
Live from L (Brown)
Neutral from N (Blue)
Earth from E (Yellow/Green)
Switch Live from SL (Black)

What I am going to do is start from scratch at the boiler and wire it as follows:

Boiler to Pump:
Live from 7
Neutral from 8
Earth from E

Boiler to Honeywell BDR91 Relay Box:
Live from L – Into L
Neutral from N – Into N
Earth from E – Into single terminal strip.
The boiler SL - Into B
The boiler 9 - Into A

I will remove the Randal 103, add a FCU before the Honeywell BRD91 Relay Box as there is currently no isolator switch for the boiler and hopefully job done.

I hope this makes sense and any comments welcome.

Thanks again,

 

[thomooseg]

A Honeywell CM927 is a programmable wireless room thermostat.

You can't replace a Randal 103 with that.

Why not?

 

[mickyg]

A Honeywell CM927 is a programmable wireless room thermostat.

You can't replace a Randal 103 with that.

Why not?

because unless the heating is on you will get no hot water.

 

[scatmanjohn]

^^^ What micky said.

I have a plan

Sorry!!! couldn't resist

 

[doitall]

A Honeywell CM927 is a programmable wireless room thermostat.

You can't replace a Randal 103 with that.

When you guys have finished taking the ****.

A. The Randall 103 is a 24 hour time switch.

B. The Honeywell cm927 is a programmable room stat.

C. They are perfect as a replacement.

What is not clear and what I was trying to find out is how a time clock can do DHW and HTG.

Unfortunately I shall be partying for the next few days and wont be online.

Going on the above replies I suggest the OP waits for D Halsham or me to return in the new year.

 

[scatmanjohn]

looking forward to the solution

 

[doitall]

looking forward to the solution

Could be interesting

I can only think the DHW is gravity and the timer just brings the pump on.

Needs lots more information.

Untitled

• doitall
• 26 Dec 2012
• 1

Had a good look at the 103 and boiler connections and have to agree with the others if the boiler is doing DHW and HTG then a programmer and RF stat would be a better buy.

Still can't see how the 103 can satisfy both when wired into the pump over-run stat in the boiler.

 

[thomooseg]

The Randal 103 controls the DHW & HTG at the same time so unless the heating is on I get no hot water. There is no setting to turn on DHW only like you get on the Randal 102. If I want hot water when the heating is off I have to turn on the immersion and the hot water tank is in the loft.

The reason why I want to use the Honeywell BDR91/CM927 is because I already have one so saves me buying something else. If I have to buy something else then suggestions welcome. The Randal 103 only has a Timed; Off & Constant function and the Honeywell should do the same job.

Please excuse my ignorance but how do I tell if the DHW is gravity and the timer just brings the pump on? I am not a heating engineer (as you can probably tell) and electrical engineering is more my thing, which is why I understand the electrical side.

To also add it is my plan to have the boiler changed (by a heating engineer) to a more modern/efficient one (possible combi) in the summer when we figure out what changes we want to make to the house as we have only just moved in. The reason for wanting the Honeywell installed is because I have a young child (this is why I am awake so early) and it is important to keep their room at a constant temperature at night and the CM927 allows me to do this.

I have used this Forum before when I renovated my old house but have not been on for about 3 years so couldn’t remember my user name etc so have had to start again.

Thanks.

 

[gas112]

DIA its a feulsaver so HW cannot be gravity got to be pumped

 

[doitall]

DIA its a feulsaver so HW cannot be gravity got to be pumped

Yes I know gas112.

Clearly the existing timer is unsuitable and replacing with a proper programmer is the way forward.

But it may also need a motorized valve added to control the heating.

More system information is clearly wanted first.

I'm partying now till the new year, so if thomooseg wants to wait till then I'll run through the boiler connections with him when I get back.

On the other hand if the OP wanted to use the 927 as the existing, temporarily, then the same control could be used with a combi boiler when it's installed.