Imperial TRV to metric radiator

[Farooko]

Hi All
I am replacing an old radiator and TRV has a male thread of 3/4 and ofcourse the new radiator is 15mm.

-Could you please tell me what connectors I need as I dont want to change the TRV?

-Also, since the new radiator is replacing the old imperial one, the gap is 90mm on each side. Which extension do I need to use in this case.

I have also tried to do a highly technical drawing to explain what I am trying to do.

 

[Madrab]

That's not the way it works, the tails, that are fitted into the rad, would be the mate for the current valve whatever size it may be, normally you would remove the tail from the old rad and use it in the new if you weren't changing the valve.

The issue you have here is you will need to use tail extension, they only come in metric @ 15mm. You would need a couple of 100mm tail extensions and then cut them to size. That's an awful lot of gap though and you should be able to get a metric rad closer to the width than that TBH.

 

[Farooko]

Thanks Rob. I have looked in metric sizes and 1fter 1600 its the 1800mm one. And my current one is around 1770mm. So, I was assuming htat I have to choose the smaller one as I dont want to move the pipe work. Do you think I can fit 1800?

 

[Madrab]

Ah ok, you're in the middle for sizes. 1700mm wide rads seem to be an uncommon size, 1300mm too for some strange reason that's never been explained and there's not a lot of them about and those that are, are at a premium.

If you are happy with those size of tails either end then you are probably going to have to change the valves. Can you post a pic of the current valves?

 

[Farooko]

Please see the pics attached. The second picture is with the nut thats used for a 15mm thread and its small (just to show that the threads are bigger than 15mm)

 

[Farooko]

Thats the valve on old radiator

 

[Madrab]

The pictured lockshield uses a 3/4" union, rather than a 15mm/1/2" compression joint.

You do get adapters but not sure how good they are as I've never used them, I usually just change the valve

 

[Farooko]

Thanks Rob for your help. I have now decided to bleed the system and replace the valves itself. One more question:

I believe i got lock shield on both sides (please see the pics attached of the valves from both sides). Can I replace one of them with a TRV? And where should it go? I cant find any arrows on the valves currently on and I got a gravity feed system boiler

thanks

 

[Madrab]

Yes you are correct, you have lockshields on both sides. Yes you can fit a TRV. Most TRV's these days are bi directional so just check that when you purchase.

If you can, buy bungs and bung the feed and expansion tank. That creates a vacuum in the system are reduces the amount of water lost when changing the valves and avoids a full drain down. It will also minimise the chance of getting airlocks, which can be a nightmare for DIYers.