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Urgent call to Plumbers/Heating Engineers.

Mullardman

Mullardman

Moderately extreme...
Right. Digistat 2 programmer/switch for my Combi 105 HE boiler has died. So.. I can get hot water on demand but the boiler will not kick in.

I have been recommended, and purchased a Neomitis Wireless digital 7 Day programmer/thermostat with a wireless controller thingy. (RT7RFPlus)

Old stat has just a live and a neutral to it, like a lightswitch.

New stat has provision for live and neutral but has a third conector described as 'common' but it's not clear whether it is commoned inside the unit via the contact pins, or whether I need to common it 'externally.'

Anyone?
 
Yep. But it turns out I bought the wrong one.
I only have a switch wire to the location of the old unit. So.. it seems the simplest replacement is just a programmable room stat.

As a temporary measure I've connected a light switch so the c/h can be switched on and off from living room. I'll get a suitable device on Monday.
 
Wilky said:
Hi Col.

As you say the old stat will have 2 wires (not necessarily mains either).
This would be a suitable replacement.

https://www.screwfix.com/p/drayton-22083sx-room-thermostat/75750

Just wire between common and ON.

Regards
Dave.
Click to expand...

Hi Dave,
Good to hear from you. I'll look into various options on Monday. At the moment we at least have heat, but no thermostatic control. I've turned down the temp control on the boiler C/H section so the rads aren't blasting out and if it gets too warm I can just switch off with my temporary light switch/manual control.

The local heating engineer who originally worked with the bloke who fitted the boiler and old stat, seems very keen on these Neomitis units. I shelled out 70 odd quid for the wrong one. I'm sure with a bit of effort I could fit the receiver close to the boiler and then stick the control section somewhere.. but it all seems a bit OTT for what I need so I think I'll return it.
Anyway..he recommended the Neomitis RTE 7C, which isn't a 'remote' type but none of the locals seem to stock it. If I get one, it seems to have three terminals... labelled in order l-r NC, COM and NO. https://all-guidesbox.com/manual/13...nstallation-instructions-manual-8.html?page=1 I think I'd have to wire to 1 and 3. but none of this is very clear to an incompetent like me.

The wires I have are old black and red in an FTE with the Earth cut short. (I think the old controller was double earthed). The black shows live on a neon screwdriver, but I don't think colour means anything as it's just a switch wire.

s1h1 said:
The receiver can be placed next to the combi, where power is available.
Click to expand...

Yes. Thanks for that, but it seems a bit OTT as the controller bit would almost certainly still end up where the old wired stat was.... so little point.
 
Morning Col.

I've never heard of Neomitis TBH - no local stockists down our way, but if you go for that unit you would wire to COM and NC (heating demand).
It doesn't matter which way around you put those conductors and the unit is double insulated - best to sleeve the earth conductor so it is safely terminated.
As S1H1 suggested, you could use the existing unit, but understand you want to keep it simple.
An alternative unit would be https://www.screwfix.com/p/honeywell-home-t4-wired-programmable-thermostat/8672v
Wires to A and B.

Dave.
 
Hi Dave, someone on another forum recommended that Honeywell too... and the reviews are good.

If I decided to fit the two part Neomitis I bought, it would have to be fitted via some sort of flex outlet box, as the boiler is fed from a socket, via heat resistant flex.. in an airing cupboard.
 
Wilky said:
Morning Col.

I've never heard of Neomitis TBH - no local stockists down our way, but if you go for that unit you would wire to COM and NC (heating demand).
It doesn't matter which way around you put those conductors and the unit is double insulated - best to sleeve the earth conductor so it is safely terminated.
As S1H1 suggested, you could use the existing unit, but understand you want to keep it simple.
An alternative unit would be https://www.screwfix.com/p/honeywell-home-t4-wired-programmable-thermostat/8672v
Wires to A and B.

Dave.
Click to expand...

had a neomitis fitted last year in a place , absolute PITB as the dial is so shiny you cant get a grip on it !!!! i actually sanded it down a bit to get some grip
 
Wilky said:
Morning Col.

I've never heard of Neomitis TBH - no local stockists down our way, but if you go for that unit you would wire to COM and NC (heating demand).
It doesn't matter which way around you put those conductors and the unit is double insulated - best to sleeve the earth conductor so it is safely terminated.
As S1H1 suggested, you could use the existing unit, but understand you want to keep it simple.
An alternative unit would be https://www.screwfix.com/p/honeywell-home-t4-wired-programmable-thermostat/8672v
Wires to A and B.

Dave.
Click to expand...

Hi Dave,
I've been having a bit of a think and a closer look at the existing boiler installation. I think I'd like to fit the Neomitis receiver in the airing cupboard on the landing..next to the boiler. I'm sort of convinced by the claimed benefits of this unit and its 'Boiler Plus Compliant' benefits and 'future proofing'. The boiler is fed via a flex from a power socket, and although I haven't opened things up yet the flex must run to the connector block in the boiler.
I've also spotted a twin and earth running up from the floor into the area of the boiler where the connector block is. I assume that to be the 'switch wire' from the existing room thermostat..coming up from the lounge.

So, if I open up that section of the boiler.. none of which is sealed AFAICS, I'd assume I can just redirect the switch wire to the new receiver. I think from the below image, I need that to go to 3 and 4 on the receiver.

https://photos.app.goo.gl/P383h73aoZokgEd68

However..I'm still unsure about the difference between 230 v connection and 'voltage free connections', but I assume I need the former. If so.. that is the 'switch' wire sorted, but I still have the N and L on the left of the wallplate, which I assume need connecting to similar on the boiler conector block below.

https://photos.app.goo.gl/f4XQwUFHCFrBqCLv5

Am I close? It's all a bit confusing and to me..contradictory.. but I don't like to be beaten.


hifinutt said:
had a neomitis fitted last year in a place , absolute PITB as the dial is so shiny you cant get a grip on it !!!! i actually sanded it down a bit to get some grip
Click to expand...

I checked that on mine. It's not easy to grip the rim of the dial, but there is a depression intended for a thumb/finger and it is very easy to turn if that is employed.
 
Hi Col.

You could get some heat resistant 5 core flex (0.75mm2 conductor CSA).
Using 5 core on the boiler, connect to LNE with the remaining 'switching pair' to terminals 1 & 2.
Other end will go to receiver backplate, connect to LNE and 'switching pair' to terminals 3 & 4.
Then take a mains supply into the receiver backplate to LNE.
Make sure that the plug or fused connection unit has a 3A fuse fitted.

Hope that's clear enough.

Dave.
 
Hi Dave, I used to think I was indecisive but now I'm not so sure...:)

Thanks for your advice which pretty much confirms what I'd worked out.. but.. When I looked at the actual practicalities of getting into the boiler.. then wiring to the receiver..I could forsee issues, such as the need for a back box on the receiver, or belting a hole in the plasterboard. Also shelving in the way and Mrs Mull's insistence, despite my frequent admonitions.. in piling mountains of bedding and towels etc.. all around the airing cupboard and rather too close to the boiler casing for my liking.

Also, the 'Boiler Plus Compliance' of the Neomitis unit seems to be of no use until I get a new boiler and that will be when it happens...

So.. returned the Neomitis and ordered a simple three wire programmable room stat...

Apologies for the hassles and thanks again for the advice.
 
All sorted. Fitted a Honeywell CM 901 which cost me about £60.. as opposed to the £140 being asked on eBay...
 
Keep an eye on the clock on that. We have a Honeywell timer and it loses about a minute every couple of months, which is a bit odd for a digital clock...
 
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