Installing a froststat for boiler - identifying wires first

Makhaira

Makhaira

Makhaira

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Joined
23 Nov 2007
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Location
Lancashire, UK
One of my summer jobs is to fit a frost thermostat to my boiler ahead of winter, since in the past it just had a room thermostat attached, set at 5C as its lowest in the garage, which fired up the boiler way too much!

Background

I asked the plumber when he was last round to fit a froststat for me (pipestat variant). He disconnected the existing room thermostat in the garage before announcing that my boiler had an integral froststat and so all was fine...

Having since had issues with said plumber, I contacted the manufacturer of my boiler this week, who has confirmed that my boiler does NOT have a froststat!

Current Situation

- The boiler fires up from the timing control in the house just fine at the moment, so no issue there.
- I have two mains-type cables entering the thermostat enclosure in the garage, and a single cable exiting the thermostat and entering the boiler.
- The thermostat is an ancient Landis and Gyr rotary design, with no obvious part number on it.

Where to go next?

I'm loathe to ask a plumber to do this. At the end of the day it should just be a simple wiring job, I just need to know what I'm going to be dealing with, and then I can identify the various parts.

So, any suggestions on what this menagerie represents?

Cheers!
 
Cheers Darren. Could well be a winner for the £40 mark.

Any views on the wiring? I'm assuming it's a mains supply, a feed from the controller in the kitchen, and then obviously the switched output to the boiler, but that's just educated guesswork on my part.
 
What boiler is it? I thought frost protection was standard for boiler design now?
 
Main 15 HE.

Just got the front off a thermostat in my house and this one conveniently has a label on the inside. Unfortunately their ability to draw circuit schematics leaves something to be desired... Pretty sure though that it's just a simple switch thermostat, with 3 connections so that the output can switch off/on or on/off at the desired threshold, with a live input.

I'm therefore totally baffled what the other mains cable is, since if it's not a mains powered stat, I'll have to trace it and see what it's there for....
 
You may have a feed to a junction box to supply your zone or mid position valves,cylinder stat,pipe stat could be a number of things to be honest.
 
Taken apart the thermostat above the boiler, still none the wiser really! Picture below.

https://dl.dropboxusercontent.com/u/2793861/2013-08-15 17.42.40.jpg

I've traced both cables and they both just disappear back into the wall of my house, so short of randomly continuity testing or ripping up floorboards, I'm a bit stuffed for tracing anything.

Any suggestions so I don't have to start from scratch?

Cheers for any help.
 
This is my best guess at how it's all set up.

- Important fact first, it's all 230v.
- The live currently connected to the live input of the boiler must be the switched live from the control unit to the boiler.
- The live currently clipped out of the way on the right must be a permanent live, which would be connected to a thermostat, and the output of that thermostat bridged to the boiler Live input. Therefore giving you the ability to be turned on by EITHER the control unit or the thermostat itself.

Make sense to any plumbers or sparkies in the room? System is a domestic tanked, single room thermostat in the house, cylinder stat in place. I believe it's a Y plan system (I have a combined pump and valve mounted below the hot water cylinder that can give CH/CH+HW/HW).
 
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