Central Heating/Radiator question

lawrie29

lawrie29

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Lawrie
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So, I have a double radiator in the hall which was only getting hot at the top. A little google later and I find out that it is probably because the rad is sludged and need flushing.

So, I drain the rad, take it off the wall and flush it through with the hose. i turned it every which way but loose and ran the water through it till it ran clear.

After reconnecting it, and expecting the whole rad to get hot, still the same problem. I also now have discovered that whilst the inlet pipe gets nice and hot, the outlet stays cool.

Convieniently the is on the side of the radiator with a drain point, so I turned off the radiator, open the drain valve and then gently open the outley valve. Out came a load of brown liquid, but it ran clear pretty quickly.

So that stopped my plan of it mayba being a bloackage int a pipe somewhere on the outlet side.

Any thooughts?
 
Wouldn't the flooded hallway have made for a better photo op? :naughty:
 
Yes, he inlet is opening fine. I know this as when I opened the drain initially, loads of water came out, and I realised I had left the inlet open, so it was draining the system. Turned it off quick and then had to open the bleed valve to drain it.
 
Frantic_Inc said:
Wood and matches?
Click to expand...

It woudl take a while to heat the radiator with wood and matches, and make the house smell of smoke. though would gladly swap it for a wood burner.
 
photon said:
Wouldn't the flooded hallway have made for a better photo op? :naughty:
Click to expand...

You flood your hallway and take shot and let me know:lol::lol:
 
You may still have sludge as it can be hard to shift, hitting with a rubber mallet helps whilst flushing.

But did you count how many turns, or fraction of a turn, that you had to make when shutting off the return valve?
And did you then only open it by the same amount when you put the rad back?

If you have just opened the return valve fully then you can get a hot top & a cold bottom :). The rad then needs balancing but for a quick solution shut the return valve completely and then open by between half a turn and a whole turn.
Lots of advice on balancing online but basically you need a temp. difference of 12 degC (or 20 degF) between the flow pipe and the return pipe.
http://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php
 
We had the same problem recently and I cleaned the system out out, it now heats as it should, in fact I was able to turn the thermostat on the boiler down a bit and get the same if not better heat.
If there was a lot of sludge we're now at the time of year where you could drain and flush the whole system, if you get a can of flushing agent and add it to the header tank you can run the system for about a fortnight, then drain the system when hot out through the outside drain valve until it runs clear, during this time I usually shut the rad valves and open one at a time to ensure the full head of water is moving through the rads individually to help shift the gunge, then when refilling the system add the can of inhibitor(bought at the same time as the flush), bleed system and bob's yer auntie's man.
 
You could try bleeding it. As it sounds like you have got an air lock in it. Yoy will need a bleeding key.
 
pampers said:
You could try bleeding it. As it sounds like you have got an air lock in it. Yoy will need a bleeding key.
Click to expand...

An air lock gives a hot bottom & a cold top due to the air at the top of the radiator.
Sludge gives a cold bottom and a hot top due to the sludge at the bottom of the radiator preventing the flow of hot water along the bottom channel.
A fully open lockshield, or return, valve can give a cold bottom and a hot top as the hot water passes through the radiator too quickly and does not give much of its heat up.
 
Suvv said:
An air lock gives a hot bottom & a cold top due to the air at the top of the radiator.
Sludge gives a cold bottom and a hot top due to the sludge at the bottom of the radiator preventing the flow of hot water along the bottom channel.
A fully open lockshield, or return, valve can give a cold bottom and a hot top as the hot water passes through the radiator too quickly and does not give much of its heat up.
Click to expand...

I have bled the radiator to let it fill up after I drained it, so know it is not this.

However I have opened the return valve to full whack, which may explain it. I will try it with the return valve only open a turn or two to see how that affects things.

Thanks for your help.
 
pampers said:
You could try bleeding it. As it sounds like you have got an air lock in it. Yoy will need a bleeding key.
Click to expand...

Oi! ....Watch the language ;)

Sent from my X10i using TP Forums
 
is it a new system or an old system, is it pressurisedor do you have a tank in the loft???
 
It is an old system. I don't have a tank in the loft. I don't think it is pressurised, it automatically tops itself up with water.

I have just had a play with the return valve and it made no difference. If the hot water was going through so fast it was not heating the whole radiator, the return valve+ pipe would be hot and they are not.

The drain for this radiator is at the return end, so I turned off both valves, opened the drain valve and then slowly opened the inlet. It then took a while for hot water to come out of the drain, and has heated up the majority of the radiator.

My thought is that if the return valve was open, then water should be flowing through the system so the rad would heat up, as it will flow through when the drain is open. So I don't think I have a problem with the rad, but with the pipes further along the network which are not allowing the water to flow properly. Does this sound right, or am I making this up as I go along?
 
it does sound like its choked, try shutting down the rest of them apart from one and this one. and see if it heats up. also you might have a short bit of pipe connecting the flow and return pipes check if this is fully open or slighty open or shut.
Check all your rads to see if the return valves are fully open? if so shutting them a bit nearer the boiler will help flow reach the end of the system.
check what speed your pump is set at it might have selector 1,2 or 3.
if you can take a few photos of boiler,pump, and the link pipe if it has one.
To be honest there could be a few different things going on. defo get a cleaner in it for a week.
 
Where would the flow and return pipes be? Near the boiler? Near the tank?
Pump is on 3.
 
Last edited:
Hi Lawrie

a few questions

Is this something that has just happened or been like this for a long while ?

Are any of your other radiators getting hot ?

Are the inlet / outlet pipes a nearer temp match on other radiators ?

You may have an air lock in the return pipe ?

If this is the rad furthest away, your pump maybe goosed and not able to push the water round everywhere

The outlet pipe should always be cooler (although not cold) than the inlet, otherwise the hot water is runing straight through the rad without warming it up - this is part of balancing the system.

Bit of a long process, but turn all the rads off upstairs, turn the rads off downstairs except the hall one (normally you start with the furthest rad), switch the heating on and see if this now gets hot - this will purge any air from the return pipe from that radiator.

You then need to open up another rad downstairs - again working from furthest away to nearest and allow that one to get hot, before you open the next - so you are opening more rads up.

Make sure you open both valves on each rad to maximum for this process.

If you find this then clears it, it was probably air or a bit of gunge that has been moved.

If you find when you start opening more rads up the hall one starts to go cold then I would be looking at either a blockage in a pipe or your pump is goosed as water will take the easiest route and if there is a blockage it will simply go through the other rads, if the pump is on it's way, as you open more rads up, it's easier fot the water to go through the nearer ones and those further away - a typical symptom can be all up stairs get hot, hilst downstairs are luke warm.

If you listed to the pump, does it sound to be running smoothly or does it sound to be sloshing the water round - this could indicate a blockage and the pump is struggling to push the water round the system....


Hope this is of some help and you solve the problem......
 
I have a similar problem with one of my rads. The middle section was stone cold and the top only luke warm. I've been meaning to flush it or replace it for 3 years, thats 3 very cold winters. After reading this i went and had a feel at the pipes on it and looking at how much the valves are open.The output pipe was too hot to touch and the input was cold. Get this... the dozzy monkey who put the plumbing in when they modernised our house put the thermovalve on the exit side which i assumed was the input. The input valve which i thought was the output was screwed almost all the way closed.

So, opening up the "output" and hey prestoe the rad gets hot all the way down and what i thought was teh input but turns out to be teh return is now hot and the rad works fine.
Thanks to this thread i have saved alot of money and hassel. TP to the rescue again.
 
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