Honeywell Rondostat - Type of Radiator Valve Required?

[Fionn]

Hi all,
        I recently picked up a number of Honeywell Rondostat HR20 timed thermostatic radiator valves from ebay.
Now from looking at them, it seems that the actuator goes in and out.
When I remove the knob from my radiator valves I'm left with a piece inside that rotates with the knob causing it to move in and out.
Now i'm wondering if my valves are suitable for the Rondostat and if perhaps I just have to wind out the existing rotating piece
fully?
It comes to a stop when I back it off completely and I'm loathe to force it off in case I'm wrong!
Thanks in advance,
Fionn.

[tony.]

That looks like the lockshield valve, used to balance the flows.

If you dont have a trv,generally has numbers or I II III etc to indicate temperature, you wont be able to fit them.

Regards

Tony

[Fionn]

Hi Tony,
           Thanks for the reply!
That doesnt sound too great, I had to do a google to find out what a lockshield valve was.
Would it be possible for me to replace the valves with something compatible without too much fuss?
All my rads seem to have the same type of valve.
The CH loop is unvented if that's of any significance.
Thanks,
Fionn.

[tony.]

Fionn,

You would have to drain down the central heating pipework and remove 1 of the lockshield valves and replace it with a trv.

It can be a diy job depending on your experience, or it may be best to get a heating engineer in to do it.

The rondostats only fit certain trvs so if you still want to fit them make sure you get the appropriate trv

Regards

Tony

[wookey]

Yes it's easy to replace the lockshield valve on one end with a TRV. You will have to drain the system to do it. If you buy the right sort of TRVs they come with _two_ valves in so that you can separate the radiator and the pipies withouthaving to drain in the future. These are really nifty and all of a quid of so more than the standard ones. I can't find a link to such a thing now, but I know they exist :-)

http://www.bes.co.uk/ (page 120) even sell danfoss valves without the header so you don't need to throw it away when fitting the HR20.

Oh one thing I did discover when researching actuators is that there are valves with 2.5mm travel and valves with 5mm travel. I don't know which the HR20 expects or whether all UK TRVs are the same.

[Fionn]

Hi Tony / Wookey,
                           Thanks for the info, thats a pain that I will need to drain the system but I guess I'll just have to do it.
Wookey, it's great that the valves are available without the TRV header. I will have to check out the dimensions of the double valve type to see if they will fit
between my rads and pipes.
I did a bit of testing with my calipers and it looks like the movement on the HR20is is on the order of 2.5 to 3mm, certainly not near 5mm anyway so that may prove useful later.
I will check out BES on the valves anyway,
Cheers,
Fionn.

[Fionn]

Had a look at BES p120 but the TRV valve bodies that they sell are only suitable for commercial applications with large pipes.
I think I might just remove one of my existing valve bodies and take that and the HR20 to a plumbing supplier and see what they can do for me.
Might be a while until I can do without the heating though!

[Fionn]

Just wanted to pull this one back up to add some info.
Myson do valves that are compatible with the Rondostat.
2TRV 15AN (vertical head) and 2TRV 15IN (horizontal head) are the part numbers for 1/2in rads in case anyone else is replacing manual valves.