Adding a room stat

[Nick98]

Hi all - looking for some guidance and advice please. I live in a large detached property built in 2000 to the then current regs by a very reputable local builder.

We have lived here for 4 years however I noticed that I dont have a room stat fitted in the house, just TRVs throughout. This is costing me fortune to heat (I think its a fortune anyway) as my annual gas bill is over £2k (but I do have a gas Aga which eats gas!).

Anyway basic spec is:

Ideal Standard Mexico RS125 floor mounted boiler
Drayton Lifestyle LP722 Programmer
Honeywell 3 port zone valve
Grundfoss pump

All of which is in the garage

This set up feeds 25 radiators all fitted with Drayton Lifestyle TRVs except 4 heated towel rails which have standard valves (there are 5 in total but one has a TRV).

For completeness the HW cylinder is an Ariston unvented one with a Grundfoss gold pump supplying hot water. This is controlled via a separate Drayton Lifestyle LP111 Programmer along with a two port Honeywell zone valve (cant remember what this does!). All of this part of the system being in the airing cupboard.

Anyway I would like to fit a room stat and have a simple Drayton RTS1 to fit. The wiring for it seems quite straightforward but I would like to know where I should take the mains voltage from and the call for heat signal?

Also I assume that it is good practice to use a three core and earth cable to run to the stat and just not connect the earth (rather than use the earth as the call for heat?)

Finally is this stat good enough for the job/system I have or should I invest in something more advanced (programmable/digital maybe?).

Thanks in advance

Nick

 

[kpmhw13]

nick,ditch the hard wired stat you have and fit a rf stat,cost more for part but basically zero wiring so you can experment where it works best in the colder months.
rf stats are ok now days but i have had problems with drayton rf sets.
saw a honeywell in my neighbours place,looks good.

 

[miggy]

Yep go wireless plenty after market stuff out there.

 

[bengasman]

Hi all - looking for some guidance and advice please. I live in a large detached property built in 2000 to the then current regs by a very reputable local builder.

We have lived here for 4 years however I noticed that I dont have a room stat fitted in the house...

That is a contradiction, unless you have one of the very rare models that is exempt from having a roomstat; afaik a Mexico is not exempt.
Not uncommon when builders install heating systems.

 

[screech]

get a honeywell wireless stat, it's a lot less hassle than running cable from your room stat to the programmer and from the room stat to the valve.

 

[D_Hailsham]

Drayton Lifestyle LP722 Programmer
Honeywell 3 port zone valve
25 radiators all fitted with Drayton Lifestyle TRVs
HW cylinder is an Ariston unvented one with a Grundfoss gold pump supplying hot water. This is controlled via a separate Drayton Lifestyle LP111 Programmer along with a two port Honeywell zone valve (cant remember what this does!).

I agree on using a wireless programmable thermostat, but first a question.

You have a two channel programmer (LP722) and a single channel one (LP111). Why? Is the second (HW) channel on the LP722 used for anything or do you control the HW exclusively from the LP111.

The two port zone valve is a required safety mechanism for the unvented cylinder. The 3-port valve is the main control sending the water to rads and/or HW cylinder.

If you install a wall thermostat you will have to set the TRV in the same room to Max, otherwise they will conflict.

With a (very?) large house (25rads) it probably should have been zoned - normally upstairs and downstairs - with separate time and temperature controls in each zone. Current regulations require zoning if the total floor area is over 150m². However the presence of a three-port valve shows that it has not been zoned.

Converting to two zones will only be possible if the pipework for the two zones is completely separate immediately after the pump.

 

[Nick98]

Drayton Lifestyle LP722 Programmer
Honeywell 3 port zone valve
25 radiators all fitted with Drayton Lifestyle TRVs
HW cylinder is an Ariston unvented one with a Grundfoss gold pump supplying hot water. This is controlled via a separate Drayton Lifestyle LP111 Programmer along with a two port Honeywell zone valve (cant remember what this does!).

I agree on using a wireless programmable thermostat, but first a question.

You have a two channel programmer (LP722) and a single channel one (LP111). Why? Is the second (HW) channel on the LP722 used for anything or do you control the HW exclusively from the LP111.

The two port zone valve is a required safety mechanism for the unvented cylinder. The 3-port valve is the main control sending the water to rads and/or HW cylinder.

If you install a wall thermostat you will have to set the TRV in the same room to Max, otherwise they will conflict.

With a (very?) large house (25rads) it probably should have been zoned - normally upstairs and downstairs - with separate time and temperature controls in each zone. Current regulations require zoning if the total floor area is over 150m². However the presence of a three-port valve shows that it has not been zoned.

Converting to two zones will only be possible if the pipework for the two zones is completely separate immediately after the pump.

Hi - thanks for the response. Just to clarify the LP722 controls the central heating and the hot water, the LP111 just controls the gold pump that supplies pumped hot water to all the taps (upstairs and downstairs).

I can quite easily put the room stat in the hall (as we have an integral double garage that has access from the hall) running the wiring from the boiler, along the garage wall and into the hall. The hall currently has two rads fitted - both with TRVs on max (as they are in every room downstairs as we tend to only turn the TRVs down upstairs as it is just too hot otherwise!)

The house is larger that average as we have 5 double bedrooms (4 en-suite) lounge, dining room, sitting room, kitchen/breakfast room, study, family bathroom etc plus rads in the airing cupboard, coat cupboard and one in the garage.

I must admit I was suprised when I counted up 25 (not something I have done before!) and in fact have recounted to find there are actually 27!! - the 27 being split up as 18 downstairs and 9 upstairs.

As for splitting it into two zones then what benefit will this give me? (excuse my ignorance on this matter)

I will have a go a posting a picture of the pipework at the bolier and pump if it would help?

Thanks once again

Nick

p.s. total floor area is way in excess of 150sq m

 

[D_Hailsham]

Hi - thanks for the response. Just to clarify the LP722 controls the central heating and the hot water, the LP111 just controls the gold pump that supplies pumped hot water to all the taps (upstairs and downstairs).

Can't see the point of the LP111. Why you you want to control when the hot water is allowed to come out of the taps?

I can quite easily put the room stat in the hall (as we have an integral double garage that has access from the hall) running the wiring from the boiler, along the garage wall and into the hall.

Some "experts" say that the room stat should be in the living room as that is where you spend most of your time; the rest of the house is then controlled by TRVs. The thinking behind that seems to be that the living room will be hotter than all the others. I'm not convinced as it assumes you keep all the doors shut - except when you go in and out of a room.

The hall currently has two rads fitted - both with TRVs on max (as they are in every room downstairs as we tend to only turn the TRVs down upstairs as it is just too hot otherwise!)

If you have TRVs set to max they are not doing anything as they will only start to operate when the room temperature reaches about 28°C. If you find that the room does not reach the required temperature (say 21°C) with the TRV set to max, then the radiators are undersized.

Bedrooms would normally be set to a lower temperature, say 18°C.

As for splitting it into two zones then what benefit will this give me?

Better control as you would not have to heat the upstairs rooms all day long. You could heat them up just before you went to bed. Again this seems to assume that you keep the bedroom doors closed all the time.

I doubt if a pic of the pipework will help.

The bottom pic shows how the pipework would need to be configured to enable two zones.

Untitled

• D_Hailsham
• 20 Jan 2011
• 2

 

[Charnwood]

Fit timers to the TRVs to create zones: Pegler Terrier I-Temp or ETRVs

 

[Nick98]

Thanks for the response - it is much appreciated and sorry for the delay in responding but I work away a lot. Anyway in answer to your questions:

Can't see the point of the LP111. Why you you want to control when the hot water is allowed to come out of the taps?)

I don't think I am explaining myself properly! The LP111 only controls the gold pump, and can be set to come and and off at different times to the HW and CH. If the LP111 is off then I still get hot water - it it has to run through the pipework from the cylinder first and takes a while to run hot - so if I put the shower on say it would take 15 seconds or so to run at normal temp. If however the LP111 is on, and the gold pump is running, then hot water is delivered instantly.

I understand this is the same sort of set up as used in hotels to give 'on demand' hot water without having to run the hot tap first?

I guess the only real benefit is saving water (and a few seconds of time) but I have never worked out whether the savings are outweighed by the cost of the gold pump running?

Some "experts" say that the room stat should be in the living room as that is where you spend most of your time; the rest of the house is then controlled by TRVs. The thinking behind that seems to be that the living room will be hotter than all the others. I'm not convinced as it assumes you keep all the doors shut - except when you go in and out of a room.

I must admit I thought it worked the other way around!! In that the stat should be in the hall (out of direct sunlight and not above a radiator) and it would be this stat that tried to control the heating. By then setting the TRVs to other temps the rads in other rooms would shut off when they reached the temp set on the TRV.

If you have TRVs set to max they are not doing anything as they will only start to operate when the room temperature reaches about 28°C. If you find that the room does not reach the required temperature (say 21°C) with the TRV set to max, then the radiators are undersized.

Agreed - I in most rooms they are set at half way on the dial but in the hall they tend to be on flat out. I think this is because of the size of the hall way (circa 12' x 12') along with a galleried landing where my office is. The bedrooms are set to around 18°C as suggested.

Better control as you would not have to heat the upstairs rooms all day long. You could heat them up just before you went to bed. Again this seems to assume that you keep the bedroom doors closed all the time.

A good point and one worth considering, especially as it would cut down on my heating bills!!

By the sounds of it the Drayton stat I have needs chucking in the nearest bin and replacing with an RF stat. Either way when the stat is in what sort of saving would you think I would realistically see? The BG fitter who serviced the boiler in the winter suggested 30% but I cant see that - mind you he might have been trying to justify the £400 quote he gave me!!

Thanks again for all your help - it is much appreciated.

 

[screech]

bg supply and fit a wireless stat for about £170, £200 for programmable (give or take a few quid). was £400 for a wired version?

 

[Nick98]

bg supply and fit a wireless stat for about £170, £200 for programmable (give or take a few quid). was £400 for a wired version?

No - it was for an RF unit as far as I recall. My wife was given the quote verbally when the boiler was being serviced but I thought it sounded very expensive, hence doing it myself.

 

[D_Hailsham]

I guess the only real benefit is saving water (and a few seconds of time) but I have never worked out whether the savings are outweighed by the cost of the gold pump running?

I doubt if you save any money.

I must admit I thought it worked the other way around!! In that the stat should be in the hall (out of direct sunlight and not above a radiator) and it would be this stat that tried to control the heating. By then setting the TRVs to other temps the rads in other rooms would shut off when they reached the temp set on the TRV.

A modern room stat is more accurate than a TRV and controls the temperature within closer limits.

In most rooms they are set at half way on the dial but in the hall they tend to be on flat out. I think this is because of the size of the hall way (circa 12' x 12') along with a galleried landing where my office is.

That means the hall/landing rad(s) are undersized. Turning a TRV to max will not make it give out more heat.

By the sounds of it the Drayton stat I have needs chucking in the nearest bin and replacing with an RF stat.

The RTS1 is OK, but it does not have the controllability of a modern programmable stat such as the Honeywell CM900 series.

What sort of saving would you think I would realistically see? The BG fitter who serviced the boiler in the winter suggested 30% but I cant see that - mind you he might have been trying to justify the £400 quote he gave me!!

A competent DIYer familiar with electrics should be able to install a programmable stat (with our help ). The CM900 series can be obtained for between £50 and £100, so you should be able to recover the cost within one to two years.

 

[Nick98]

The RTS1 is OK, but it does not have the controllability of a modern programmable stat such as the Honeywell CM900 series.

Thanks - I can pick up a CM901 locally for just over £60. I think I was only favouring Drayton as the current programers and TRVs are all Drayton hence just searched for the same! Having said that the valves are Honeywell and the pumps Grunfoss so I guess it makes no difference?!

A competent DIYer familiar with electrics should be able to install a programmable stat (with our help ). The CM900 series can be obtained for between £50 and £100, so you should be able to recover the cost within one to two years.

Again thank you for your help. Out of interest what sort of saving would a Room Stat offer on my heating bills? By the sound of it around £5 a month?

Final question from me is the TRVs have proved 'troublesome' since we moved in and I have replaced 12 heads so far out of the 25 we have fitted. The fault is always the same in that the TRVs wont turn down as the plastic insert (bad description but all I can think of!) that pushes on the pin seems to be loose and the sensing head rattles. Thus rad is on flat out all the time.

I assumed that this was because the pin was stuck but when I check (just pushing on them with a coin or similar) they operate fine. It only seems to be the original heads that are failing in that I have not yet had to replace a head I have previously replaced.

This was getting expensive so I wrote to Drayton Customer services enquiring whether this was a known issue but never received a reply. Any thoughts?

 

[D_Hailsham]

Thanks - I can pick up a CM901 locally for just over £60. I think I was only favouring Drayton as the current programers and TRVs are all Drayton hence just searched for the same! Having said that the valves are Honeywell and the pumps Grunfoss so I guess it makes no difference?!

Makes don't matter, though Grundfos make the best pumps and Honeywell valves seem to last longer than other makes.

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).

Out of interest what sort of saving would a Room Stat offer on my heating bills? By the sound of it around £5 a month?

That's the $64k question. I would hope that you would save more than £5 a week.

Savings come from better control. With the traditional mechanical stat there is a large (3-4°C) difference between the stat opening and closing. They also keep the boiler running flat out until the required temperature is reached. You then get this sequence of events:

a) The house temperature rises above the set temperature due to the continued emission of heat after the boiler turns off.

b) Because of (a) the thermostat is turned down.

c) Because of the wide differential, the house cools down too much

d) Because the house is too cold the stats is turned up; and the cycle start again.

The Honeywell stat overcomes this in two ways:

a) Using an electronic sensor which has a differential of 0.5°C

b) Automatically reducing the boiler output as the room temperature is approached so you do not get the overshoot.

Final question from me is the TRVs have proved 'troublesome' since we moved in and I have replaced 12 heads so far out of the 25 we have fitted.

You say they are Drayton Lifestyle valves. This brand name has not been used for a long time now and suggests they are probably from the time when ACL owned Drayton. The products have improved since Invensys took them over. Modern Drayton TRVs are very reliable.

If the heads are not working correctly, then the only thing to do is replace them.