Adding a room stat

[Nick98]

The CM901 is a 24 hour timer. The CM907 is a 7-day timer, which has more flexibility, e.g. each day of the week can be individually set.

You would need a 3-core (plus earth) cable from the stat back to your wiring centre (junction box).

Thank you for your excellent advice. I will go down the Honeywell route now on your recommendation. My last question is that some of the replies suggested going wireless. The CM907 though is wired so the best/easiest I could do with that is get it into the hall. If I really need it in the lounge then than is about 60 feet away from the wiring center (and 3 rooms away) so in this situation wireless would be much easier. In this situation what model would you suggest. I like the idea of the 7 day programmable option.

Regards

Nick

 

[D_Hailsham]

My last question is that some of the replies suggested going wireless. The CM907 though is wired so the best/easiest I could do with that is get it into the hall. If I really need it in the lounge then than is about 60 feet away from the wiring center (and 3 rooms away) so in this situation wireless would be much easier. In this situation what model would you suggest. I like the idea of the 7 day programmable option.

Wireless will give you the flexibility of being able to try out various locations for the control unit, but you have to remember that the signal between the two units degrades with distance and obstructions. So, if there is 60ft from wiring centre to the control unit and three or four walls between, you may not get a very good signal. However I think you still will get good results with a wired stat located in the hall. But if you want to go down the wireless route the Honeywell CM927 is the one to go for.

As the hall/landing rad(s) are obviously too small you will have to experiment with the correct temperature setting to make sure the boiler does not run continuously in a vain attempt to reach the set temperature. So you may find that setting the stat to 19 or 20°C will still mean a living room temperature of 21°C. The important thing is that the room stat keeps the boiler going until the other rooms have reached temperature.

Slightly off-topic. Do you know if your radiators have been balanced? If they haven't that could possibly explain the difficulty heating the hall/landing.

 

[Nick98]

Wireless will give you the flexibility of being able to try out various locations for the control unit, but you have to remember that the signal between the two units degrades with distance and obstructions. So, if there is 60ft from wiring centre to the control unit and three or four walls between, you may not get a very good signal. However I think you still will get good results with a wired stat located in the hall. But if you want to go down the wireless route the Honeywell CM927 is the one to go for.

Many thanks. Will go for the wired version in the hall as I agree with the issue around signal strength. If the sender was in the garage and the receiver in the lounge then the signal would have to pass through 4 walls to get there. Will try not to bother you for wiring advice (note use of the word try!)

Slightly off-topic. Do you know if your radiators have been balanced? If they haven't that could possibly explain the difficulty heating the hall/landing.

The honest answer is I have no idea! When we moved in the house had been empty for about 18 months so I took the precaution of getting a local firm to service the boiler, aga and a couple of gas fires. They also replaced a couple of TRVs and weeping valves on the CH pump etc. Since then they have been back to fit a small rad in the coat/shoe cupboard but thats about all. Is there any way of checking or should I just ask them to come and do it?

Off topic for me but I also have an issue with underfloor heating in our ensuite - but will post that seperately under a new heading. Any help with that little problem would be very much appreciated as going round in ever decreasing circles!!

 

[DP]

My wife was given the quote verbally when the boiler was being serviced but I thought it sounded very expensive, hence doing it myself.

Can see you fitting a wireless unit based on your understanding (or lack of) being out of balance when to what the service guy would have suggested. Skipping the post, it seems he was not hard selling but suggesting a roomstat might improve running cost. With this comes his expertism which will be missing when you start opening the the wiring centers and gaze upon 10 terminals (if you are lucky) and know not if the system is wired as Y plan, S plan or for HW gravity.

 

[Nick98]

Can see you fitting a wireless unit based on your understanding (or lack of) being out of balance when to what the service guy would have suggested. Skipping the post, it seems he was not hard selling but suggesting a roomstat might improve running cost. With this comes his expertism which will be missing when you start opening the the wiring centers and gaze upon 10 terminals (if you are lucky) and know not if the system is wired as Y plan, S plan or for HW gravity.

Sorry - but I thought this was a DIY forum where people like me came for advice. Am I mistaken? But as you asked it happens it is a Y plan system with an unvented HW cylinder.

No I am not an electrician, and dont profess to be, not am I a gas or plumbing engineer. What I am though is a a competent DIY homeowner who knows his own limitations. I also happen to be a chartered engineer having served a 5 year apprenticeship, 4 years at college and 28 years experience in the defence industry. Yes - if I cant do it I will of course pay the money and get it done but surely to take a 3 wire feed that is simply a live, a neutral and a demand feed isn't beyond my skills is it?

 

[DP]

But as you asked it happens it is a Y plan system with an unvented HW cylinder.

You cannot have have Y plan with unvented cylinder.

 

[Nick98]

You cannot have have Y plan with unvented cylinder.

Sorry but that is what I have got according to the plumber we use! A three way valve in the garage where the CH and HW split and a seperate 2 way on the flow to the cylinder in the airing cupboard.

 

[stardanny]

You cannot have have Y plan with unvented cylinder.

Yes, you can.

Please explain why not?

Dan

 

[DP]

Check out your G3 notes if you have UV qualifications.

Let us say the boiler does not shut down down due to a defect and 3 way valve (if no 2 port valve fitted as well) is HW mode. Where do you think the heat from the boiler will end up?

 

[stardanny]

Check out your G3 notes if you have UV qualifications.

Let us say the boiler does not shut down down due to a defect and 3 way valve (if no 2 port valve fitted as well) is HW mode. Where do you think the heat from the boiler will end up?

It will end up in cylinder. You make a point. But without a 2 port valve is a design fault and if cylinder overheat, primary ECO will cut out, failing that ERV and T+PRV will open.

I had a look in my note, yes you can have 3 port valve as long a 2 port valve is fitted on HW side.

Dan.

 

[DP]

(if no 2 port valve fitted as well)

I did qualify that

Early Vaillant UVs, coupled to VC242 type heat only boiler only had three port valvw and no 2 port. But that setup was assembled that way according to MIs