Glow Worm 18R mind of its own

[DAVEJPPL]

Glow Worm 18R was fitted 6 months by a plumber to replace the old faulty Glow Worm.

Had ongoing issues with central heating coming on randomly but cannot control it using programmable timer or room stat.

Initially the plumber sent me out to pick up a hot water cylinder stat then a programmable timer which he said were also giving intermittent faults.

eventually it seemed to only occur occasionally so we left it but now it is constantly on and has been since yesterday and the house is roasting

the only way I can stop it is by turning off the main switch that seems to cut power to the whole system

that then means no heating at all

I do not want the plumber back as it has become embarrassing (and he is a neighbor) making it awkward

everything I’m reading online points to either faulty frost stat in boiler or incorrect boiler wiring.

Any advice (before I can get another heating engineer out next week) appreciated

 

[picasso]

What type of zone valves do you have ?

 

[Harry Bloomfield]

I do not want the plumber back as it has become embarrassing (and he is a neighbor) making it awkward

everything I’m reading online points to either faulty frost stat in boiler or incorrect boiler wiring.

It reads as if plumber friend has made a terrific mess of the wiring. Was the plumber friend gas qualified to be able to do the work at all?

You will get more help, if you are able to describe more about the rest of your system - type of timers, stats, 3-port valves, water cylinder. Include some photos too.

All we know at the moment, is that the boiler is an heat only boiler, possibly supplying an open-vented system.

Rather vaguely - You need to begin by working out what type of system you system was designed to be (likely Y-plan), then (if you feel competent) mark up all the cables as to where they go at the joint box (probably in the airing cupboard). Then there are plenty of diagrams on the internet, explaining how it should be wired.

 

[DAVEJPPL]

System is Y plan
Mid position Valve - Drayton MA1
Pump - Grundfos UPS3
Room Stat - Honeywell T6360
Timer - Drayton LP722

there are no other room / zone stats

photos attached and with their associated image of wiring

at the junction box in airing cupboard

black cable is the Mid position valve

White cable entering box at top of photo is hot water tank stat

white cable entering box at left of photo is Grundfos pump

the fitter (neighbor, not friend ) is gas safe certified as had to get a certificate for it as house is currently up for sale

I’m happy to fault find the wiring with some guidance to avoid putting up with the choice of 26c or freezing

 

[picasso]

Ask your neighbour/plumber if he has removed the 24v link on the pcb, very common for it to be left in and the boiler will run 24/7 ignoring programmer and stat.

 

[CBW]

Ask your neighbour/plumber if he has removed the 24v link on the pcb, very common for it to be left in and the boiler will run 24/7 ignoring programmer and stat.

Was my first thought.

 

[DAVEJPPL]

Ask your neighbour/plumber if he has removed the 24v link on the pcb, very common for it to be left in and the boiler will run 24/7 ignoring programmer and stat.

Just checked and there is a link between RT & Live which is obviously not a factory link

there is also a link across “burner off”

 

[picasso]

No wonder your boiler is running constantly, you have a link between live and switched live (rt) the switched live is supposed to come from the controls.

 

[DAVEJPPL]

No wonder your boiler is running constantly, you have a link between live and switched live (rt) the switched live is supposed to come from the controls.

So is it a case of just removing that link or is there some wiring to be changed inside the birds nest junction box ?

 

[picasso]

The red and yellow cable marked should be the pump and switched live to the boiler, you need to find out which one is the boiler switched live and connect it to the RT slot on the boiler (after you remove the link) do not connect any thing to the 24v part. just noticed there is also a brown and black cable on that connector, either of these could be the boiler switched live.

 

[DAVEJPPL]

OK thanks Picasso

appreciate the advice

I’ll do some tracing tomorrow morning in daylight rather than having to switch all power off and have her indoors freezing

I’ll report back

cheers

 

[ianmcd]

you need to trace the yellow wire that is connected to the orange wire from the mid position valve, and this is connected to the RF terminal on the boiler, that link must be removed , seen some misguided idiot wiring but that is school boy error

 

[DAVEJPPL]

you need to trace the yellow wire that is connected to the orange wire from the mid position valve, and this is connected to the RF terminal on the boiler, that link must be removed , seen some misguided idiot wiring but that is school boy error

Could this be some attempt at overcoming the issue that there are only 3 wires arriving (L, N & E) at the boiler meaning there is no switched live wire going from junction box to boiler?

If it is some form of hash job does it mean I need somehow to get a wire for this purpose installed?

if so I see a bit of a do coming with my neighbor for the hash job and then a mega job of having carpet and flooring removed as boiler is in the garage and jcn box in airing cupboard

 

[picasso]

Could this be some attempt at overcoming the issue that there are only 3 wires arriving (L, N & E) at the boiler meaning there is no switched live wire going from junction box to boiler?

Yes

If it is some form of hash job does it mean I need somehow to get a wire for this purpose installed?

Yes

if so I see a bit of a do coming with my neighbor for the hash job and then a mega job of having carpet and flooring removed as boiler is in the garage and jcn box in airing cupboard

Dont hold back

 

[DAVEJPPL]

Yes

Argh ! Bugger

that’s not good

I have now (apart from 1 cable) traced all wiring

apart from the local cabling - pump / tank stat / 3 port valve

there are 6 cables entering jcn box

Supply
Timer
Room Stat
Boiler
Frost Stat

I need to identify the last of the 6 BUT would there be any problem in removing the frost stat (fitted next to boiler) and using one of those wires as the switched live to boiler?




Yes



Dont hold back