Upgrading Drayton RTS1 room thermostat

[rjm67]

Hi all,

I would like to put in a programmable room thermostat, but I'm not sure what the easiest upgrade option would be. I'm fairly certain that the Digistat 3 would be an easy replacement, but does anybody have any cheaper ones that would be an easy swap? We have a gravity system with potterton profile e50 boiler.

Would this one work for example? http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102632&ts=96922&id=12157

Cheers in advance for any advice.

R.

 

[D_Hailsham]

We have a gravity system with potterton profile e50 boiler.

What makes you think it is a gravity system?

 

[rjm67]

Just when I think I get to grips with this stuff, I get thrown a curve ball

I feel like I'm sitting an exam.

Definitely not a combination boiler, and we have header / expansion tanks. How did I do?

R.

 

[D_Hailsham]

Definitely not a combination boiler, and we have header / expansion tanks. How did I do?

5 for effort, 0 for content.

There are two correct answers: because I have no pump or because the CH is pumped but the HW is not.

The fact that you have a header expansion tank is no guarantee that you have a gravity system. It's the presence of a pump which determines if a system is gravity or not. If there is a pump, the water is circulated by the pump. If there is no pump then the water is circulated under the effects of gravity (hot water rises and cold water falls)

So you can have a full gravity, where there is no pump at all; or a part gravity, where the pump is in the CH circuit but not the HW circuit. This is called a pumped CH gravity HW system.

The reason for asking the "exam" question is that the type of programmer will depend on what sort of system you have.

One clue to the type of system you have is the options available on your existing time switch. If your only options are HW only or HW and CH, then you probably have a gravity or pumped/gravity system. But the only way of confirming this is to look at the pipework and see if there is a pump and one or more motorised valves.

As to the programmable thermostat, you should also take a look at the Honeywell range, CM901 and CM907 (wired) or the CM921 and CM927 (wireless). You must bear in mind that all most room stats are single channel switches; this means that they only control the central heating. You will need either to retain your existing time switch to control HW times or install a separate single channel time switch to do this.

There are Application Notes on this at Honeywell's web site:

http://content.honeywell.com/uk/homes/applicat.htm

See guide nos: 109 and 110

 

[rjm67]

Coorrrr learning more with every post

I see now, I should have put more information in to start with
Potterton e50 Boiler
Grundfos pump
Drayton tempus three Control panel
Cylinder tank with thermostat
Drayton RTS1 room thermostat
Three way motorised valve
Header / Expension tank.

I was going to take a second guess at my setup now, but I'm not sure.

The control panel allows separate CH / Water. I wanted to upgrade the room thermostat just so that I can set different temps at diferent times of the day / week.

Does your honeywell recommendations still stand then based upon the further information provided?

Finally, thank you so much for your detailed reply. I love to understand more about how things work, and how to explain myself properly.

Cheers
R.

 

[ChrisR]

It doesn't matter a flying fig, if you're replacing a thermostat with a programmable one you can have different temps at different times of the day regardless of how your HW works!

As it happens, with a 3 way valve, you'll almost certainly find you have fully pumped, albeit "open vented" Ch and HW.

SO you program your Tempus to 24hrs CH and use the stat to turn the CH on and off.

 

[D_Hailsham]

Does your honeywell recommendations still stand then based upon the further information provided?

Yes.


You have a Y-plan system. There is a Honeywell Application note explaining how to install a Programmable Thermostat at:

http://content.honeywell.com/uk/homes/files/pag109.pdf

Although this shows a different timer to control the HW, ChrisR is quite correct; you can set the CH side of the Tempus to Continuous and use it just to control the HW. This means that you can have the HW and CH on times completely independent of each other.

It doesn't matter a flying fig, if you're replacing a thermostat with a programmable one you can have different temps at different times of the day regardless of how your HW works!

Agreed, but it may not always be possible to have the CH on without the HW on. This will depend on the type of controls. My original dig was aimed at those who assume that, just because they have a F and E tank, they have a gravity system.