New rad slow to heat up

[ZACCCC]

Number 1. I teed off the 22mm flow at a point about 6 inches before the manifold for all the other rads, but for some reason the new rad is slower to heat up and even after an hour the top corner of the rad, above the exit valve, is still not fully hot whereas all the other rads are red hot. Both the inlet and outlet pipes to the rad are red hot.

The rad inlet valve is less than 4 foot from the tee. The tee is a 22 to 15mm reducing tee, then I've got about 3 inches of 15mm copper pipe and then a 15 x 8mm reducer and then the 8mm pipe to the rad.

Number 2. I've got a slight leak at the outlet port of the rad where the valve screws into it. I made the mistake (I think) of not undoing this part of the valve and screwing it into the port before I put the rad on the wall so, once the rad was on the wall I was turning the whole of the valve to get it screwed into the outlet port. I did put ptfe on the valve connection but when everything was connected up there was a slight leak. I kept tightening it up a quarter turn at a time but it wasn't doing any good and I've now 'rounded' a couple of corners of the nut and think I might have stripped the thread. Could I have knackered the thread on the rad or would the thread on the valve end go first?

 

[ZACCCC]

I've just put a new rad in my bathroom and I've got a couple of problems.

Number 1. I teed off the 22mm flow at a point about 6 inches before the manifold for all the other rads, but for some reason the new rad is slower to heat up and even after an hour the top corner of the rad, above the exit valve, is still not fully hot whereas all the other rads are red hot. Both the inlet and outlet pipes to the rad are red hot.

The rad inlet valve is less than 4 foot from the tee. The tee is a 22 to 15mm reducing tee, then I've got about 3 inches of 15mm copper pipe and then a 15 x 8mm reducer and then the 8mm pipe to the rad.

Number 2. I've got a slight leak at the outlet port of the rad where the valve screws into it. I made the mistake (I think) of not undoing this part of the valve and screwing it into the port before I put the rad on the wall so, once the rad was on the wall I was turning the whole of the valve to get it screwed into the outlet port. I did put ptfe on the valve connection but when everything was connected up there was a slight leak. I kept tightening it up a quarter turn at a time but it wasn't doing any good and I've now 'rounded' a couple of corners of the nut and think I might have stripped the thread. Could I have knackered the thread on the rad or would the thread on the valve end go first?

 

[kbdiy]

Where is the return (outlet as your call it) connected to? You don't mention that in your post.

The reason the rad is cold at the top is probably trapped air so has not been bled properly, BUT it could be due to incorrect pipework, hence my question above.

As for the valve tail - maybe stripped thread on the tail as it's brass and therefore softer that the steel rad, but you will need to remove it to find out. I would be inclined to buy a new one, remove the tail from the valve, wrap with PTFE and screw into the rad until tight. Then attach the valve and pipe.

 

[ZACCCC]

Hi kb and thanks for getting back to me, your answer's very helpful. The return on the rad goes to the main 22mm return on the system via the same arrangement of reducer and reducing tee as on the flow.

When I repressurized the combi boiler I bled all the rads then repressurized again and then bled all again so I hadn't thought about bleeding the new rad again but I'll definitely give it a try.

I was glad to learn that although I might have stripped the valve tail the thread on the rad would probably still be ok. But I will do as you suggest and take the valve out and possibly get a new one.

Thanks again.