Would a room stat be beneficial?

[number49]

Just wondering if having a room stat in the living area would be give any benefits in terms of energy savings or boiler life? Have heard stuff mentioned but not sure if it applies to my system though.

System is as follows (think it's called Y-Plan but not sure):

Traditional boiler
DHW cylinder
TRV's on all rads
Mid-position valve controlled by 7-day programmable timer with separate heating & hot water programmes.

Downstairs is open plan lounge straight into dining area.

Am assuming if a stat was beneficial it'd be in the lounge and would mean removing the TRV's from lounge and dining room.

Any advice?

 

[JohnD]

if you mean that there is currently no room stat then yes, one would be very advisable.

It used to be thought that you should have the wall stat in the room which was slowest to heat up, this was usually the hall, but now it is thought that it should be in the room you use most, probably the living room. The stat should be in a room without sources of heat other than the CH (open fire, cookers, big sunny windows) and should have at least one rad with no TRV (if it is a large room with two rads, have the room stat nearer the rad with no TRV)

You still need to adjust the rads so that the room with the room stat is the slowest to heat up, otherwise it will turn off the heating when the other rooms are still cold.

 

[number49]

Cheers JohnD.

At the moment when the programmer is set to 'heating on' the boiler fires up until the rooms are up to temp then turns off, and then refires when they start to cool which seems to be the same control that a room stat offers.

As there's def no room stat fitted, what is telling the boiler to turn on/off when heating is needed/not needed? is it the return temperature from the heating circuit as the TRV's close when the room's get up to temp?

 

[doitall]

The boiler is just cycling on it's own stat, not a good idea.

 

[bengasman]

Easiest question this week; yes.
Any roomstat will be an improvement, a programmable even more so.
Look in FAQ for more info.

 

[number49]

Thanks gents.

next question, what type is best to use with my system and how easy is it to fit one?

The boiler is a Saunier Duval Xeon (think it's a 50ff)
Controlled by Drayton Tempus 7 controller like this http://www.diy.com/diy/jsp/bq/nav.jsp?isSearch=true&fh_search=tempus+7&x=0&y=0.
Mid Port Valve
Cylinder stat

Have tried finding the boiler manual online but the SD website is down.

Is it really a job for a spark/plumber?

Not bothered about wired/wireless. Have a concealed route to where it'd be fitted.

 

[JohnD]

I have always been happy with Drayton/ACL controls, and they provide good circuit diagrams. Honeywell also seems fine. The hard-wired ones are very reliable and easy to fit. As you have a Drayton controller they will doubtless be compatible. Drayton and their other brands are part of the Invensys group. See http://www.invensyscontrolseurope.com/home/ and http://www.draytoncontrols.co.uk/content.aspx?id=2591

They make wireless and programmable ones which I am sure are very good but more complex and not so easy to understand. Some people find it difficult to operate sophisticated devices. I like the simple ones as
I am very simple. http://www.draytoncontrols.co.uk/product.aspx?id=1367
I bet the RTS1 is the most common.


I am not a pro.

 

[D_Hailsham]

Next question, what type is best to use with my system and how easy is it to fit one?

I would go for the Honeywell CM907 (wired) or CM927 (wireless). These are programmable stats. If you don't want a programmable one get the Honeywell DT90E or DT92E

They are very easy to fit.

Can you follow the wiring from the Tempus 7 and from the mid-pos valve?

The Tempus 7 should have a wire from terminal 1 to the cylinder stat SAT and from terminal 3 to cylinder stat common.

The mid pos valve will probably be wired as follows:
White connected to Tempus 7 terminal 4
Grey to cylinder stat SAT (same terminal as Tempus 7 terminal 1
Orange to boiler (same terminal as cylinder stat call)

If this is correct. Here's what you do:

If you go for the CM9XX versions they replace the connection between the Tempus 7 and the valve white wire. So the CH side of the Tempus 7 is redundant.

If you go for the DT9XX versions they go between the Tempus 7 and the white wire. The CH side of the Tempus 7 still works.

Wired CM907
Remove the wire between Tempus 7 terminal 4 and the valve white wire.
Connect CM907 A to Permanent Live
Connect CM907 B to the valve white wire

Wireless CM927
Remove the wire between Tempus 7 terminal 4 and the valve white wire.
Connect CM927 L to a permanent Live
Connect CM927 N to a permanent Neutral
Link CM927 A to CM927 L
Connect CM927 B to the valve white wire

Wired DT90E
Disconnect the wire between Tempus 7 terminal 4 and the valve white wire at the Valve end.
Connect this wire to DT90E terminal A
Connect DT90E B to the valve white wire

Wireless DT92E
Connect DT92E L to permanent Live
Connect DT92E N to permanent Neutral
Disconnect the wire between Tempus 7 terminal 4 and the valve white wire at the Valve end.
Connect this wire to DT92E terminal A
Connect DT90E B to the valve white wire

Post if you are unclear on anything.

 

[bengasman]

(Programmable) roomstats are fairly easy to fit if you are competent working on 230V.
The siemens rev24 (rf) is the best, closely followed by the honeywell cm927