CH Problem

[John]

My Sister rang today and asked me to 'pop in' as two of her radiators are not heating up (at all). I went round and had a look. It is a sealed system combi boiler set up. Water pressure OK (just under 2 Bar), rads full of water, TRV's and check valves all open and correct. I took the TRV head off and I could push the pin down but only by about 4 to 5mm, is this a normal amount of travel? I presume so as both rads were the same. I went round the house and turned all other rads off (TRV end only) and waited... The two rads in question remained cold even after 10 mins although the boiler was lit. We then turned off the check valves on the 'good' rads and after a few minutes the boiler started a slight vibrating noise (main case) so we went round and turned the check valves back on and the vibrating stopped.

Whilst waiting for the rads to heat up, which they didn't! I had a thought, the two rads concerned are downstairs and are the only ones in the house that are piped from underneath the floor, it is and old stone built terrraced house. My thoughts went to thinking that maybe we have a frozen pipe scenario somewhere. I asked my sister about the pipes under the floor and she said the last time her partner was under the floor she doesn't remember seeing any of "that grey foamy tube stuff around the pipes" (sic). The system was installed approx 7 years ago and in Feb this year she had to have a new "pressure thingy" (sic) installed and the guy drained, flushed, refilled and put inhibitor in it, so I cannot see there being a sludge blockage.

Are my thoughts in any way feasible and if so what is the best course of action to locate the frozen bit and if necessary to defrost it? I haven't actually looked under the floor yet as she has just had new carpets fitted and didn't want them taking up unless absolutely necessary!!!

Cheers

John

[cj]

Hi could be a number of things but before ripping up floors try this. turn off lock-shield end of rad' (not the thermostatic valve) make sure the thermostatic valve is fully open then open the bleed valve at the top of the rad. you should get a strong flow of water if not the trv may be stuck closed. if ok reverse procedure i.e. shut trv open lock-shield. this is only a start as if the pipes are frozen or worse still blocked you will get similar results but its a start especially if you get warm water from the bleed point. Don't forget that as it's a sealed system you will have to top up the boiler after each test.

[RonOB]

I had a similar problem to this after fitting TVRs a couple of months ago. I filled the sytem up and bled the rads but one (upstairs) radiator was stone cold. It turned out that it just needed about 2 pints of water bled out of it - messy job but did the trick, why can't they put bleed nipples on the bleed vales so you can attach a small section of hose to make life so much easier, cleaner, nicer when bleeding?

Ron

[John]

The bleed valve is to bleed air out. Not sure what you achieved by draining water out. Must have been a coincidence that it started working. Any air in the pipes would have found its way into the radiators anyway.