Water flows into rad from both sides, but doesn't flow when heating on

[jonshutt2]

Our central heating system has a few problems: one of which is a downstairs radiator that's been completely cold since we moved in.

We took it off, cleaned it (a bit dirty), and put it back.
We refilled it by opening the tap on the left.
Ran heating system - heat.

We then opened the bleed valve and let the water run out into a bucket - when we did this it filled up with hot water from the right. Shut bleed valve - it stayed warmish, but the pipe leading out of the rad remained cold.

I'm not experienced with out it's set out - but we know now that hot water can enter from right, we could refill with water from the left, but it's not flowing through.

Any thoughts?


In addition, none of the upstairs works. There is a magnaclean on the return from the upstairs but while the upstairs isn't flowing this is basically doing nothing. We took a towel rail off upstairs and that was full of black sludge, cleaned and put it back, but there must be other issues somewhere

Cheers

 

[EAST61]

Please upload a pic of this radiator and its valves and give us more information about what type of central heating system you have

 

[jonshutt2]

Hi - cheers - will add a photo tonight. The system is powered by an old (1995ish) ideal mexico 2 (non-combi) boiler with a hot water tank, pressurized system. The radiator is fairly standard, less then 1m wide double skinned, bleed valve top left opened with key, shut off valves both sides had to be opened with spanner - water flows after about 1/2 turn. It's in an old house (1850s) so figuring out what goes where is tricky!

 

[dilalio]

Blocked return

 

[JohnD]

turn off all the hot radiators. Do one or more of the cold ones now heat up? Balancing.

 

[jonshutt2]

haven't tried turning all hot ones off. will try...

If the return is blocked, is it normal that I can fill up the rad from this pipe?

 

[ericmark]

turn off all the hot radiators. Do one or more of the cold ones now heat up? Balancing.

That would also be my first thought, I thought when you got a new central heating system installed the installer would trim the lock shield valves to some where near what is required and the system would actually work. However from mothers house I find this is not the case, all her lock shield valves were wide open, with TRV's on most radiators the system once hot did to some extent work, however instead of as heating was switched on all rooms warming together, what happened is the rooms took it in turns, closest to boiler got hot first then as that rooms TRV closed the other rooms would slowly follow.

However there was a point where the hall started to heat up, and the wall thermostat was in the hall, so once hall got warm the whole house turned off. The problem is to balance the system it has to be running, and I found when I got to the house all rooms were warm and the TRV's were working, so old idea of recording the incoming and out going temperatures and setting the difference the same on every radiator may seem good on paper, but in practice it did not work.

I tried at first closing the lock shield valve completely, on the radiator nearest to the boiler, and slowly 1/4 turn at a time opening it again, with around 1/2 an hour between tests checking of course the boiler was running, as soon as I felt hot water I stopped, seemed to be around 1½ turns to get it to flow, once done first radiator at 1½ turns I turned every radiator off and back on again at 1½ turns I found now every radiator working, but some rooms a little cold, these rooms the valve got 2 turns open. I am sure there is a better more professional method to balance but it did work.

While setting the balance all TRV's were turned wide open, once all radiators were warm, then it was time to set the TRV for each room, this I found odd, as it seemed unlike the lock shield setting all rooms the same did not work, most upstairs rooms seemed to end up 1.5 to 2 using numbers on the valve, and down stairs 3 to 4 I would guess this is because heat raises and so upstairs is heated from the room below.

It took me a long time to trim everything in, so I can in some ways understand why not done by the people installing the system, but one would have expected at least some effort even if only turning every lock shield valve open 2 turns, but no they were all left wide open.

I tried to repeat this in my sisters house, she had a different make of lock shield valve, with her house it was ¾ turn open only, but she had micro bore pipe, and I found some blocked pipes, I ended up with a battery and a car tyre compressor trying to blow out the pipes, the result was a surprise, found copper slivers which seemed to be from inside of pipe, once cleared no more problems, suspect poor quality pipes used. Both my sisters house and mine have the black sludge in the radiators, wanting to fit a new TRV in mother house I was dreading the black sludge does not matter how hard I try always spill water, had carpet cleaner at the ready to suck up any spill, but the water was crystal clear, an additive put in where first installed had clearly done a good job, so I bought another bottle and poured it into radiator before refilling.

Living in a house it is easier, hot radiators get turned down, it seems odd to be aiming for the radiators that work, rather than those which don't, but water takes easiest route.

 

[dilalio]

haven't tried turning all hot ones off. will try...

If the return is blocked, is it normal that I can fill up the rad from this pipe?

You said pipe leading out of rad remained cold... that's the return!

 

[jonshutt2]

Hi all. Thanks for the info folks. I think it's a balancing issue that's exacerbated by sludge build up in the slower flowing sections.

I tried closing off all the other radiators in the house - and the downstairs rad in question did actually get warm - it took an hour or so - which is the best I've ever seen it.
The return pipe never really got warm. Dilalio - I know it's the return, but surely it shouldn't stay cold - the hot water should flow through? I filled the rad from the return so I know water can get through from somewhere - but I admit to being no expert!

I then tried shutting off all the downstairs rads and turning one of the 3 upstairs rads on - as with the problem downstairs rad - it got hot in about an hour, but the return never got warm.

The pump kept running so i'm guessing that the pump was happy that something was flowing. I'm hoping that leaving it on and running through the 'bad' sections may start to flush it out?

 

[JohnD]

if it is getting warm, then there is at least some flow.

As you suspect sludge, you may as well add some X400. It will only cost you about £15. Bale out all the mud from the F&E first, and sponge it clean, using bleach if there is any fungus or bacteria, with the float tied up, then drain a bucket of water before you tip in the chemical and mix in well as the tank refills.

X400 is very mild. You can leave it circulating for up to four weeks before it starts to lose its power and the sludge settles again. You will know it is working when the water goes jet-black with loosened sludge (or brown, which is worse)

Drain it out and rinse to remove the loosened sludge.

If you have a system filter empty it daily as it will fill up with loosened sediment.

Verify that your cylinder is not getting heated when you put CH on and HW off.

Turn up the speed of your pump but check this does not cause pumping-over into your F&E tank. If it does, turn the speed back down.

If you have no F&E tank, use the "injection" cartridge of X400, unless you have some open pipe and you can use a funnel.

 

[jonshutt2]

Thanks JohnD. I'm not sure if we have F&E tank as it's a pressurised system. I'll try the pump speed thing, and I can put some x400 in the magnaclean - although there is very little flow going through that return it may start to dissipate through the system - as you say - if it's getting warm there must be some flow

 

[jonshutt2]

Right - just for peoples info - here's an update.

I checked the pump, it was set to full. We'd made some improvements but decided another shot at asking a professional. The guy came and pretty quickly noticed the pump wasn't doing much. So that's replaced now, and the magnaclean moved to the correct return pipe, and every radiator downstairs is now fully working. Within 4 hours the magnaclean had about 2-3mm of sludge on it. The upstairs works better but still not flowing through - the tops of the radiators get hot but not the bottom or the out flow pipes.

So I think we now either wait to see if it cleans up by way of the magnaclean, take 2 upstairs radiators off and flush manually, or get the guy back to do a powerflush.
Maybe closing off all the downstairs and forcing more upstairs may be enough to start getting flow though.

 

[JohnD]

if you're thinking about paying £hundreds for a powerflush, it's certainly worth investing in some X400 first.

Best case, it fixes your problem. Worst case, you're £15 down.

Keep emptying the magnaclean until it stays clean. You can scrape the sludge into a jamjar if you like, see how much you get. It will dry hard.

After adding the chemical, turn one radiator on and all the others off, to maximise flow. Do each of them in turn. Some people like to vibrate the rads or bang them with a rubber mallet to help loosen the sludge. This may make your magnaclean fill up quickly.

 

[jonshutt2]

Just a follow up - we received plenty of good advice on here and this is how we finally have heat in all our rooms:

• manually removed, took outside and cleaned smaller radiators
• replaced pump - this got downstairs working but upstairs still not really working
• tried x400 - didn't do much
• got a plumber to flush with one of them big magaclense - didn't do much
• drew up plans of where we thought pipes went - identified where pipes went upstairs and split to the 3 radiators
• got the plumber round - they remove some tiles to expose pipes and discovered some of the pipes connecting the upstairs radiators connected wrong - so water couldn't flow back down. They replaced a few pipes, now works perfectly.
• added extra radiators to rooms with no existing ones
• now have a warm house!

So basically - a few issues - sludged radiators, week pump, and a badly installed system.
My guess is that a few years ago, the bathroom was renovated, and the bathroom installer replaced/added a towel rail, and connected the pipes in wrong - so no amount of x400 / flushing would ever have solved it until the plumbers took some tiles off and looked at the pipe work.

next step - insulation to try and keep this hard earned heat inside!