New radiator issues

[Dylan T]

Hi all -

My wife had an old radiator in her upstairs office that ran off 10mm pipe which needed replacing, so I purchased a new radiator and moved it to the next wall as it was colder. As I moved the radiator a good 3 meters in the direction of the joists, I didn't want to have to pull up a lot of floorboards, so opted to ran copper along the wall. I've done it and all working fine, but a couple of problems I was hoping for some feedback on:

1) A downstairs radiator is now cold on the flow pipe and cold at the bottom. Am I right that this indicates sludge in the system and maybe what I did has unsettled some of the sludge down to the next radiator? I thought it might be an air lock at first but unless I'm mistaken that would result in the top being cold.

2) Is running 15mm copper around the wall like this bad practice in terms of kids due to the heat? We don't have any young ones around the house now but hopefully soon we will; I hadn't considered how far away from the wall 15mm pipe sticks out, especially once on the clips, and am now thinking keeping it at 10mm microbore would have been much neater, especially in trunking. I have heard people say that 15mm is better, but I can't really see how it would make much difference; some thoughts on this would be GREATLY appreciated, as if I'm going to switch I may as well do it now while all my tools are out!

Many thanks

 

[Hugh Jaleak]

Downstairs may be a balancing issue, if the office rad was throttled down, either by use of the lockshield valve or even the fact it was piped in microbore, it may now be stealing flow from the downstairs rad. Water will always take the path of least resistance, so try closing down the lockshield valve on the new rad, and see if the downstairs heats up better.

You'd be surprised how much extra surface area, (and flow), a slight increase in pipe size (diameter) achieves.

 

[Dylan T]

Interesting, many thanks. Will give it a go! Was it unwise to step up to 15mm?

 

[Hugh Jaleak]

Nothing wrong with using 15mm, its common practice now anyway. Balancing instructions can be found in the FAQ's if you need them, but assuming you haven't touched anything else, if it is a balancing issue, throttling back the new rad should be sufficient.

 

[Dylan T]

Thanks Hugh. I've now had the time to follow your advice and a several how to guides regarding balancing radiators, and unfortunately it hasn't worked. I also tried replacing this problem downstairs radiator as I had a brand new double of the same size (was currently a single) that I couldn't get rid of, so figured when in Rome. However the issue is still there; although weirdly when I first put it on it worked a treat and was roasting but since then it has cooled down. The actual feed pipe is cold, which is the weird thing to me. Every radiator before it is hot but the pipe by the time it gets to the radiator is cool to touch. Any google search suggests that only the return pipe should get cold due to imbalancing. I've also bled all the radiators both with the boiler on and off; is it possible there is some sort of air lock in that pipe somewhere? That's all I can think of but I'm not sure how I would even fix that.

 

[Hugh Jaleak]

Could well be an air lock, what I'd suggest you try is turn all the other radiators off, (only need shut the valve off one end, ideally the handwheel or TRV so you dont upset the balancing of the rest of the system), this should force all the flow from the pump into the problem rad. Once flow has been restored, turn the other back on and see if it remains hot.

Always make sure system is off when bleeding, Trying to bleed with the pump circulating could have the reverse effect and draw air in.