Replacing room thermostat with programmer / thermostat

Discussion in 'Plumbers' Talk' started by Ceedub, Nov 7, 2017.

  1. Ceedub

    Ceedub New Member

    Hi all.

    I have a Glow Worm 30CXI installed in boiler cupboard upstairs. Since I've moved in I havent been able to get the timer to work properly on the boiler itself. The timer works - the clock is moving and you can hear it - but it doesn't work on the program timer. The boiler does function correctly for heating when set to permanently on. My conclusion is that the timer is knackered - confirmed by the glow worm support line who wanted over £300 to replace it. I spoke to a local parts supplier who could sell me the timer unit for approx 160 inc VAT (cant remember exactly it was over 6 months ago that I enquired).

    I'm content that I can install a programmer / thermostat in place of my current installation in downstairs hallway. The current stat has 3 wires - Live, Neutral and Earth. I've been looking through some of the old forum posts that talk about 2 wire installations, switched lives etc. I'm just a bit confused as to what to go for. In my head I just want a mains powered programmer and simply replace it. But I'm not a plumber so could be wrong.

    Finally - upon installing the programmer downstairs - would I need to remove the mechanical timer from the boiler (happy to do this myself - it seems to be easily removable).

    Many thanks for your advice.
  2. sam spade

    sam spade Active Member

    The simplest solution is to install a battery powered programmable thermostat where the current thermostat is currently located. Wiring is simple as only two wires are used - Live and Switched Live. If the existing stat has a neutral connected, this can be connected to a small terminal block and hidden behind the back plate.

    You say the existing stat has Live, Neutral and Earth (presumably going by the wire colours). This can be confusing as the "earth" wire may actually be the switched live. If you post info about the thermostat (make/model) and say which terminal each wire connects to we can tell you how to wire the new prog-stat.

    There is no need to remove the exiting timer; just set it to permanently on.

    The battery life is normally over a year, sometimes two or more - depends on the product.
    Deleted member 33931 likes this.
  3. Hellooooo fellow 30CXi-er.

    What a shame - mine came with a clock, but I threw it away... (or sold it for a fiver on ebay...)

    Because, yes, you are better off with a prog stat for this.

    First, are you SURE you have only TWO wires and an earth going to your room stat? What make and model of stat is it?

    Most 'old' stats needed three wires, so you have to watch out for the 'earth' not being an earth, but a switched live.

    In any case, what you have is NOT a live and neutral, but at the very least a 'live' and 'switched live'.

    Once you have told us the model of stat you have, and where each wire goes, we can advise further.

    To make your new prog stat work, you either need to remove your old clock, by-pass it, or simply keep it there running on 'ON' 24 hours.
  4. Ceedub

    Ceedub New Member

    Thanks very much for your replies. Most definitely 3 wires going into the current stat. Brown, Blue and earth hence my assumptions. Its a Honeywell - believe it to be a 4360 or 6360. It has Brown to pin 1, Blue to pin 3. Pins 5 and 6 are missing - there are no screws present.

    I'd be happy to remove the old clock (would mean finding a blanking plate somewhere but sure they cant be that rare or expensive) or simply leave it in. Bypassing would probably be more tricky.

    I've attached a few photos of the stat.

    Many thanks for your help - it was actually some of your older posts I was reading earlier. Small world.

    Attached Files:

  5. Ceedub

    Ceedub New Member

    It wouldn't work having 2 attachments for some reason. Stat with cover off shown below.

    Attached Files:

  6. Cool, if these are the connections, then it is a 2-wire jobbie and the earth is an earth.

    Ok, the BROWN is the 'live and that goes to pin 1. BLUE is not a neutral but a 'Switched Live' - ie it becomes 'live' when the stat calls for heat. Really, this wire should have a circle of brown tape wrapped around it.

    Any 2-wire stat will work. This usually means a battery-operated device. Yes, go for a Prog Stat (check out the IQE from our hosts) or whichever one you prefer.

    Wiring it will be a doddle - it'll likely have an A and B, or COM and NO. When you chose one, we'll tell you.

    Yes, the old clock needs switching to 'always on'.
  7. Ceedub

    Ceedub New Member

    Thanks for your advice. I looked into the IQE but they seem to be unavailable here so checked Amazon and they're unavailable there too. Can only assume its a product recall. Next on the list is Flowmasta 22199SX - though the blurb for this says 3 wire install. Having read the guide I'll assume that one of these is not an earth so is unsuitable.

    Second option is the Horstmann Centaurstat 7 room thermostat. States its 2 wires but I'm not sure on whether it will function well.

    Last choice (typically most expensive) Danfoss TP5000Si. The TP4000 seems to be unavailable so the slightly more expensive cousin is probably the best bet. I'm probably going to go for this one - it seems like it can do a lot.

    In your opinion which would be better? I think that the Danfoss seems like it would be easier to install but at the end of the day they'd both still work the same - all be it with different front end interfaces and amount of programmes per day.
  8. Can you point me to the Flowmasta 22199SX blurb? Almost certainly that is a 2-wire jobbie. I cannot see how it needs three wires.

    Personally, I think I would look on a well-known auction site for the Danfoss or similar - fair chance you'll pick one up for the price of a normal cheapy.
  9. Ceedub

    Ceedub New Member

    Flowmasta link here

    I shall look into the well known auction site. Thanks very much for your help.
  10. Ah, I thought you meant the actual instructions.

    Almost certainly Screwfix are mistaken there. I cannot see how it needs three wires - it doesn't make sense.
  11. Ceedub

    Ceedub New Member

    the manual says about 4 wire cable - but this might not be for the install as it does say 4 way cable provided.

    Wiring: Warning: Turn off the electrical devices and receiver before wiring. There is 4-wire cable provided
    Color Connection
    Brown 230Vac Live
    Blue 230Vac Neutral
    Black Common
    Grey Control (Call for Heat)

    I've gone for one of the Danfoss ones now anyway - the price seemed decent so will now just wait out for delivery.

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