Problem Radiator

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Problem Radiator

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Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Tue Dec 03, 19 2:53 pm Post subject: Problem Radiator

One upstairs rad won`t warm,and won`t bleed the normal way to rectify the problem.
Its the bathroom rad,and pipes come up into the room and travel 8ft to connect to rad,under normal practice when bleeding one feels the heat rise in the rad as the air is released,not with this one,
Before starting the rad and the 8ft length of pipe is cold,start bleeding and the pipe slowly starts to warm till it reaches the rad,the panel doesn't warm from the bottom up as normal,but as I carry on bleeding,i`m pulling warm water out of the bleed nipple and the top of the rad warms but does not warm the rad lower down.
All other rads in the house work,i`ve even turned the other upstairs rads off thinking the pressure will force through.

Its oil central heating from a Worcester boiler,after pulling out a few buckets of water from this rad over a few nights,firstly I thought it may have a blockage in the lower part of the rad,not I`m starting to think its possibly the pump as this is the furthest rad from the boiler and pump which is alongside the boiler.

Any thoughts?

dpack

Joined: 02 Jul 2005
Posts: 46207
Location: yes

Posted: Tue Dec 03, 19 5:06 pm Post subject:
drain, flush and refill it, if it is an airlock it should clear, even a lump or sludge might clear. a CH pump should run quiet and vibration free, pop a screwdriver tip on it and an ear the blunt end. any irregular noises or grating is probably new pump time. i would go for is it the pump first, but it is worth flushing regularly anyway

derbyshiredowser

Joined: 11 Feb 2007
Posts: 980
Location: derbyshire

Posted: Tue Dec 03, 19 5:20 pm Post subject:

if you get this kit you can connect your radiator directly to a 1/2 hose I was told on a plumbing forum last september and then fill/ flush the rad. I'd got a blocked 1.8m x 60cm rad with an 10 mm microbore feed and it freed off before I had to flush it . I freed it by turning the pump up to max but you obviously have to be aware of the safety valves and seals in the boiler.

https://www.screwfix.com/p/flomasta-universal-filling-kit-5-pcs/8145k

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Tue Dec 03, 19 8:09 pm Post subject:
When you say ,Drain and flush,do you mean the whole system? As here,downstairs,the pipes go up either side the front door and each side has a drain off cock,i`ve only ever drained it off once when the hallway rad didn't warm up,as the drain off cock is near it.

derbyshiredowser

Joined: 11 Feb 2007
Posts: 980
Location: derbyshire

Posted: Tue Dec 03, 19 10:17 pm Post subject:

I ended up flushing the entire system 3 times before the pipes were running clear, all 7 radiators had been changed for new ones. However its a 10mm microbore system. When the radiators were left on the front for the scrapman the amount of silt sediment running out was phenominal and we had had all types of non heating patterns in individual radiators. Bearing in mind in the last 38 years to my knowledge we had had inhibitors in the system I was very surprised. You can also get varying degrees of flushing addative that you leave in for a week or so I used a fernox one.

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Wed Dec 04, 19 12:19 am Post subject:

Its just this one bathroom rad here,all the other 7 rads work fine,on low settings and high,i`ve tried all different settings.

Its just odd that eventually only the top of the rad warms unlike the others that warm from the bottom up,that`s what`s making me think the lower part of the rad is blocked,

I think I`ll try draining the system out and let it refill and most likely have to bleed the other rads then and see if it works before I take this problem rad off and rinse it out,orther wise I`ll have to get a plumber in as this time of year the stock take up most of my day.

Shane

Joined: 31 Oct 2005
Posts: 3467
Location: Doha. Is hot.

Posted: Wed Dec 04, 19 3:38 am Post subject:
Does the problem radiator have a thermostatic valve? Could be that the valve is malfunctioning if it's just the one rad that's having an issue.

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Wed Dec 04, 19 11:13 am Post subject:
Yes Shane it does have a thermostatic valve, but would that being faulty cause the 8ft of pipe before the rad to be cold until I start bleeding,then it slowly warms through its length till reaching the rad.

dpack

Joined: 02 Jul 2005
Posts: 46207
Location: yes

Posted: Wed Dec 04, 19 11:14 am Post subject:

it could be a thermostatic valve but the bathroom rad is often the one that is permanently on with two normal valves.

if i suspect a blockage i drain by turning off the feed to the expansion tank opening all the drain cocks and then start with the highest/furthest rad from the boiler and work down and closer letting in air from the top

to refill close all air cocks and refill uphill and away from the boiler one rad at a time.
run at full power, bleed air/refill rads

split systems do complicate matters and need refilling as best you can from below.

it is possible to flush with mains pressure but drain and refill will cure many airlocks and sludge issues.

i just realized i assumed this system has a header tank rather than being a sealed system, slightly different drain and fill is required for sealed systems.

derbyshiredowser

Joined: 11 Feb 2007
Posts: 980
Location: derbyshire

Posted: Wed Dec 04, 19 1:09 pm Post subject:
If you google the problem there are some great plumbing and electrical problem pages for central heating all with some great things to try and some not what to do. Totally agree with all of dpacks tips above , when I initially drained the system I didn't open the bleed valves and so didn't drain it completely the first time , when I realised it then took 2 hours to drain the whole system.

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Wed Dec 04, 19 2:22 pm Post subject:

The downstairs hallway is the permanent on rad,it made more sense to me as the heat rises and warms the stairs and landing,i had the plumber change it from the bathroom as I couldn't dry myself after bathing,it was like a sauna,
Yes header tank in attic,i presume filling the system,as when I did drain off at the cock in the hallway ,over 12 yrs ago,i just let it fill up on its own and everything worked till now.

Just to clarify,the central heating system here is separate from the hot water system,heating by Worcester boiler,hot water by Rayburn

derbyshiredowser

Joined: 11 Feb 2007
Posts: 980
Location: derbyshire

Posted: Wed Dec 04, 19 6:38 pm Post subject:

Ty Gwyn wrote:

You don't say whether or not you put an inhibitor in when you filled it 12 years ago but you are going to get a build up of silt within the system in 12 years. However a systematic bleeding as per dpack seems a good place to start. Yes filling the system it will do on its own but you still need the bleeding.

Ty Gwyn

Joined: 22 Sep 2010
Posts: 4613
Location: Lampeter

Posted: Wed Dec 04, 19 6:57 pm Post subject:
I presume by Inhibitor you mean an additive chemical? I didn't put anything in,just let it fill up on its own after the air lock had cleared.

derbyshiredowser

Joined: 11 Feb 2007
Posts: 980
Location: derbyshire

Posted: Wed Dec 04, 19 8:43 pm Post subject:

Ty Gwyn wrote:

I presume by Inhibitor you mean an additive chemical?

I didn't put anything in,just let it fill up on its own after the air lock had cleared.

I use this one we are in a very hard water area so it helps and the radiators were here when we moved in 38 years ago and they were old then and we only had them out last year

https://www.screwfix.com/p/fernox-f1-central-heating-protector-500ml/77218

dpack

Joined: 02 Jul 2005
Posts: 46207
Location: yes

Posted: Thu Dec 05, 19 2:07 pm Post subject:

try this first
if the affected rad has a thermostatic valve you can remove the top bit by unscrewing it and then try operating the valve by pressing the little plunger thing
iirc no top=fully open if the stick has full and free movement .fully shut if the stick is pushed in
the extra movement of a topless thermostatic poked up and down can shift lumps or release a stuck piston

descaler is a good place to start with a system that has not been fettled in 12 yrs.

the stuff has instructions as to how that version works best

it may show up a few leaks and weeps but leak sealer in the final refill will usually sort those

it will help remove sludge but it also exposes new metal to corrosion so corrosion inhibitor in the final refill is a very good idea.

there is a pump machine thing that pulse washes a system with a hot chemical enema but it costs a lot to have it done and it can be a bit too robust for old systems

if i was going to fettle what you seem to have i would give it a very good clean through and replace the pump (standard pumps are pretty cheap and usually easy to fit, if it is an odd one don't bother so long as it turns enough)

if in dought it is a few quid and 5 mins with a pair of wrenches to replace a thermostatic or simple valve if the system is already drained

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