What thermostat can I get to replace this ancient one?

[kiltedcamel]

Hi I have this really old honeywell thermostat and I'm pretty sure it doesn't work. Even if I set it quite low the boiler never turns off, if I turn it completely off the boiler does turn off. See Pic below, it says 4200 3879-001 on inside cover.

View media item 60624
It has 3 wires connected to pins 1, 2, and 3. pins 4 and 5 are unused.

My question is can I upgrade to a more modern one like the 2 below?

http://www.ebay.co.uk/itm/Honeywell...DIY_Materials_Plumbing_MJ&hash=item231bf5f8a9

http://www.ebay.co.uk/itm/Honeywell...DIY_Materials_Plumbing_MJ&hash=item460ce8f963

Which would be easiest to fit and accurate on temperature?

 

[Dan Robinson]

Depending on your control system, a DT90e or a CM907.

 

[kiltedcamel]

Hi my programmer is a Landis and staefa rwb9

View media item 60625

 

[Dan Robinson]

Valves?

 

[kiltedcamel]

honeywell 3 port valve, conventional gloworm fuelsaver 35F boiler, indirect hot water cylinder, fully pumped system.

 

[Dan Robinson]

Cm907 then. Leave the timer on constant for heating.

 

[kiltedcamel]

Ok thanks, I did like the look of that one.
Can I ask why not a DT90e based on my set up?
and would a t6360 be rubbish?

Thanks very much

 

[Dan Robinson]

The 6360 is based on technology Noah was using.

The DT90e is just a dumb thermostat, although more accurate than your old one.

The CM907 beings in TPi and intelligent control of the boiler (once you enable the right settings.

The extra cost will be recouped in a year or so and transferrable to a new boiler when the time comes.

 

[mfarrow]

I'm pretty sure it doesn't work.

How do you know this? Does it not click on/off?

These were still made in the 1990's, so not as ancient as you might imagine.

 

[Dan Robinson]

The 6360 is the same but a bit prettier.

One in the 1990s is going to be as accurate as a Starbuck's Statement of accounts.

Even worse if T3 isn't connected to neutral like so many were.

 

[Charnwood]

Can I ask why not a DT90e based on my set up?
and would a t6360 be rubbish?

The Honeywell CM907 will act as a programmer and thermostat. The DT90 will just do what the stat you have now does.

The CM907 offers 6 time periods, all of which can be set with a diffferent temperature. It also 'learns' how to heat the house i.e. it learns how long it takes your system to heat the house to the required temperature and switches the heating on at the time neded to get the house to temperature at the required time. You set the time you want the temperature, not guess what time to start the boiler, as on a standard programmer. Well worth the extra cost.

In answer to part 2 above - yes.

 

[kiltedcamel]

I have gone with a Honeywell CM707 as I couldn't turn down a bargain price of £10 !

I will look at cm907 if and when we upgrade our boiler.

Now I just have to worry about installing it. I take it that it doesn't use the neutral wire. Instead of terminating this in a block to make safe, can I just disconnect it at the other end from the junction box?

Thanks

 

[kiltedcamel]

Now I just have to worry about installing it. I take it that it doesn't use the neutral wire. Instead of terminating this in a block to make safe, can I just disconnect it at the other end from the junction box?

Thanks

Is this safe anyone?
Thanks!

 

[Charnwood]

I have gone with a Honeywell CM707 as I couldn't turn down a bargain price of £10 !

I will look at cm907 if and when we upgrade our boiler.

A TENNER? I'll take 20.

If the 707 works then keep it. I'm sure the only difference is that the 707 has a service interval reminder type thing.

 

[kiltedcamel]

Yeah 2nd hand though and no instructions but available online. Can you advise on my question regarding the neutral wire?
thanks