Radiators with flow from the top

[goaty_man]

Hi everyone,

I'm thinking of chancing the valves on my radiators to TRVs, however I have a few concerns.

At the moment each radiator only appears to have one valve. Water enters the radiator from the top and leaves at the bottom (or is it the other way around????). The pipe entering the top of the radiator has what appears to be a manual valve, whereas the pipe into the radiator at the bottom has no valve at all, instead it just appears to be an elbow which joins the rad to the pipe.

I want to add TRVs to each rad as well as lockshield valves. Am I able to do this???? If so can I change it so that each pipe enters the radiator at the bottom with an air vent at the top at one side and a blacking cap at the other side?


One other question I have relates to the pipes themselves. They appear to be made of either iron or steel, I rubbed them with wire wool and they very polished, I thought it may be chrome but gently filed a small section of this, it did not reveal any copper!!!!! Is this usual, the system is about 25-30 years old. Can I use standard compression fittings on this pipework.


Any advice would be appreciated.


Graham

 

[oilman]

The system was probably gravity originally if it's not now. The pipes going into the top of the radiator is the right place as this assists circulation. I suggest you leave it, and leave the valves in place. You can probably just remove the elbow and connect a thermostatic valve in its place. The return side of the radiator is the better place to put them anyway. You can use the old valves as the lockshield valve, though this is not so necessary if you have thermostatic valves.

 

[corgiman]

Except lockshields are very necessary of you wish to balance your system properly

(sorry Oilman)

 

[oilman]

Lockshields may be useful, but this system has the radiators connected correctly from a thermodynamics point of view.
Thermostatic valves shut off and so allow flow to the rest of the system.
Thermostatic valves have small passages compared to manual valves.
Most (almost all) systems I see haven't been balanced anyway.

 

[goaty_man]

Guys,

Thanks for the advice. Can I ask a couple more questions???? How would I know if it was a gravity system? You mention not playing with the pipework, would the TRVs go at the pipework leading into top of the radiator or into the bottom? If it's the top one, do you recommend that I leave the elbow from the bottom without changing it, or is it advisable to replace it with a manual valve?

Many thanks,

Graham

 

[oilman]

If you have a pump, it's not gravity.

Leave the top valves on, they will be the lockshield valves. Put the thermostatic valves on the bottom in place of the elbow. Er...see my first post.

 

[DP]

Better option would be to instal a programmable room stat. Unless you are confident, leave the installation as is well alone. It is working fine at present.

You will have to drain the system, which will disturb the system sediment. Upon refilling, if you are unlucky, you could end up with air locks which will have you going round in circles.

 

[PTH]

~If you do go for TRV's, and you do have a gravity system, I would strongly suggest that you get valves with low loss characteristics - they are usually sold as for single pipe systems and most are made by Samson but are marketed by many people including Ellis Miller, Oventrop and, I think Danfoss. Drayton and Hattersley also make them. I'd be inclined to leave it alone and do as DP suggests if you want some temperature control without manually turning valves on and off.

 

[goaty_man]

Thanks Guys,

The info you have provided is great. I'm gonna give it a bash and change the elbows to (low loss) TRVs.

I have two final questions if I may. I want to add a heated towel rail in the bathroom, I have removed the radiator (with a pipe into the top and one in the bottom) and want to attach it to the same pipe work. Are you able to advise me as to:

* If it's a gravity system do I need to follow the same set up (i.e. pipe into top and one from bottom).

* If it's pumped can I just have two pipes from the bottom.

I noticed that prior to taking the rad off it needed bleeding on a regular basis. It's the only one in the system that did. Any suggestions?

Once again thanks

Graham.