Radiator Valves reverse plumbed

digitaldr

We got gas fired central heating installed about 6 years ago and got a few designer radiators installed. They've all worked very well except for the two in the kitchen - have never really got that warm. Despite several opinions from various plumbers (not the guy that installed them - he wasn't the best although was recommended by the builder!) no one has been able to figure out the cause of the problem.

Anyway to cut a long story short I've noticed that the valves on the two poorly performing radiators are plumbed backwards i.e. return is plumbed to thermostatic valve and flow to lock shield side (I figured this out just by feeling the temp of the pipes as the heating came on - lockshield side heated up first). I've opened the lockshield and TRV up full with no major improvement.

Could this be the cause of the problem?

Valves are these ones:



I've emailed the manufacturer but haven't got a reply yet. Also couldn't find any manual for valves online.

boatbuilder

First two things to check would be:
1. If its a pressurised system, that the pressure gauge reads around 2bar.
2. have the radiators been balanced?

digitaldr

Thanks for the instant reply! It's a pressurised system and boiler has just been serviced and rads have been balanced by a plumber in the past few weeks.

boatbuilder

I thought I read somewhere recently that if the valves are on the wrong sides, it can trap air bubbles in one of the valves, causing a blockage of sorts, so it would be no harm to swap them around so they are in the correct positions.

Plombier

If you turn off all other radiators in your house will they then work.

Sparkpea

if they are not 2 way valves then it may make a bit of a difference

digitaldr

Thanks for all the help. I tried turning off all the other rads as suggested by Plombier and lo and behold the two rads worked. Figured then that it was a balancing problem after all - turns out that the plumber hadn't bothered to turn down the lockshields on our other designer valves - they're non-standard - recessed and need to be adjusted with an allen key.

Good job I didn't need to correct the flow and return as the valves are a monoblock design i.e flow and return in one unit so would need to have the copper pipes going into them swapped so plaster board would have to be cut into etc.

Thanks again

Sparkpea

what is your pressure set to? you never answered that question. some designer tall radiators need more pressure in the system to heat effectively

digitaldr

Pressure is at about .75 bar cold and 1.5 (sometimes a little more) bar hot. They are tall rads.

Sparkpea

normally I would set pressure 1 bar cold for normal systems, systems with tall fancy rads should be about 1.5 cold, which will rise when hot

digitaldr

I think expansion vessel (it's an internal one in boiler) might be a bit small for the number of rads we have. When I tried running at a higher pressure it went above 3 bar (after being on for a good few hours) and the PRV opened. Unfortunately it didn't reset properly and had to be replaced. I know I could get an external expansion vessel but things are running ok now and I've spend enough money on boiler recently. It was outside (at wife's insistence) but had to be moved inside due to pipe freeze/burst. Cost €390 (€300 labour + €90 for longer flu).