Central Heating Conundrum - odd goings-on

[uptoyou]

Hi all,

Wonder if someone can advise on a plumbing problem on a new rad?

Background:
4 x rads upstairs fine
1 x rad downstairs - works, but takes a while to heat up.
There was 2nd rad downstairs on the dividing wall between kitchen and dining room, but took the wall out and removed the rad a couple of years ago.
Due to the one rad downstairs taking so long to heat up, I thought I would fit another one to get me through this winter.

The guys who took the wall out a couple of years ago re-routed the pipework over the dividing area between kitchen and dining room and left the pipes capped off at low level ready for when a new rad was to go in.

So, drained down the central heating, put the new rad in, re-filled the central heating. Bled the four rads upstairs, then the two downstairs. The four rads upstairs are working fine, but neither of the two downstairs are heating up.

After lots of head scratching, I have open up the plasterboard when the guys who took the wall down and boxed in the new pipework for the new rad.

In the pic below I have circled two sections which I believe is what they fitted.

The two areas circled in RED were hot to the touch, but within a foot further along to the left were cold.



Bleeding the radiator out of the tiny bleed hole for about 20 minutes, pulled the hot water through the feed pipe and eventually the downstairs rad started to heat up, around the edges, but an hour later, no additional heat, and the water coming from the bleed hole was hot.
Nothing ever seemed to go back to the return as this pip remained cold.

Closing the bleed hole on the rad, caused it to cool down again, and eventually the feed pipe in the ceiling cooled also.

In summary:

1. The feed and return in the ceiling both start to cool after the angled sections (I have determined which is feed/return purely from how the pipe heated up when bleeding)
2. Bleeding the rad pulls hot water through the feed
3. How the rad is plumbed in below - I didn't know which was the feed/return at the time, but the valves are bi-directional so don't think this should be an issue
4. When bleed is closed, rads and pipes cool down
5. Pic below shows area on rad which heats up when bleeding



6. Other rad which used to work isn't coming on at all now

Any advice appreciated!

 

[terryplumb]

Is your system pressurised or fed from a feed and expansion tank ?
You could try turning off all upstairs radiators by their trv or wheel head valve ( but dont touch the lockshield valves) and see if the two downstairs rads heat up. From what you said there are only 6 rads in total ,is that so ?

 

[uptoyou]

Hi, I think Feed & Expansion tank!
Turned off all rads upstairs by the TRV, nothing downstairs still.
Six rad total, pump is newish (4 or 5 years old maybe).

There are two things throwing me:

1. Why are both the feed and return hot at the the angled join in the ceiling, and then cool down after the join?
2. When I open the bleed on the rad, the feed pipe gets hot as the water has an escape through the air release hole. When I close the bleed valve, the hot water stops. So the water is unable to return through the return pipe - couls this be a faulty blocked TRV, a blockage (physical or air in the rad). How can I test this?

 

[uptoyou]

Just to add:

Circled in the pic below, are the two pipe ends I was left with by the previous plumbers, not knowing which was the flow and which was the return I have ended up plumbing the longer one (which I now believe is the feed), in to the lockshield valve, and the shorter one (which I now believe is the return), into the TRV.
I believe they are both bi-directional so this should not be a problem?!?

I have loosened the nut at the bottom of the TRV and it leaks, so water is either passing through it, or going in to it.

Q. Once the system was drained down, both feed and return were empty. As there is now water on the underside of the TRV, can this only happen by water passing through it from the rad, or does the feed naturally also fill with water when the system is re-filled?

 

[terryplumb]

For any radiator to heat up ,hot water from the boiler has to flow through it ,and out the other side, where it makes its way back to the boiler. It wont matter which pipe has the trv/ lockshield fitted ,if bi directional.
There are a number of reasons that will prevent yours from heating.
1. Valve closed
2. Blockage in pipework
3. Air locked pipework
Always assuming the pump is working ,and the two pipes to radiator are actually connected to flow / return.

Yes water is present in both pipes going to a rad ,to answer your question when filling up

 

[uptoyou]

Thanks terryplumb!

I am assuming they are both connected to feed and return as that is what the plumbers left to use. Am certain feed is correct, and can only assume they didn't make an error and that the return is the remaining one.

I will unplumb what I have done and loop the feed directly into the return to try and eliminate the rad, valves and pipework done yesterday from being faulty.

 

[terryplumb]

That will tell you nothing. Turn both valves off and remove the rad. Open one valve at a time ,to ensure full flowing water runs out for a minute, this will also purge any air from pipelines.
From info you have provided so far ,the down stairs rad that used to get warm ,should be getting to full temp ,when all upstairs rads were closed by their trv, as you have made no alterations to its pipework. It appears to me that there is air present in your system / lack of water ,or a pump issue.

 

[uptoyou]

I'll try that now, thanks.

FYI, just looked in the header tank and there is some mossy/sludge sitting on the bottom inch or two of the tank, could this be contributing to anything?

 

[terryplumb]

Could do with a clean out , crud in your pipework will never do any good ,and will cause problems. Fit a bung into the outlet at the bottom of the tank to prevent any crud going down into pipework and clean the tank. Make sure you use long rubber gloves to protect hands and arms. Dont forget to isolate the incoming water supply first ,and when your done make sure you take the bung out !!
Is there something tied to the float arm of the ballcock ???

 

[uptoyou]

I've drained the system so I can fit a couple of ball valves to the feed and return - thats some cord to close the ballcock so the header tank doesn't fill.

 

[uptoyou]

Update (not a positive one) -
I've added a drawing below to clarify the issues:

Pic1 - This is part of what I believe is new pipework going up and over the old kitchen doorway, then back down to where it terminates in Pic3

Pic2 - a bit difficult to explain this section, but I'll try. The orange marked pipes I think have always been there - these are very hot to the touch. The blue marked pipes I think have been added (sames pipes as in Pic1), as there are char marks on the wood around these extensions - these blue marked pipes feel hot at the point where they are connected to the orange marked pipes, by then cool rapidly the further along the pipe you go.

When I bleed the new Rad6 of water, the top pipe in Pic1 heats up, all the way until there is hot water coming of of the bleed hole of Rad6 - I have highlighted the area of Rad6 which heats up - it never gets REALLY hot (only warm), and the return pipe stays cold (maybe as the all the hot water is coming out of the bleed valve?). When I then close the bleed valve, eventually the radiator and all pipework cools back down.

Pic3 - I then fitted the ball valves and closed Rad6 of completely and turned all the rads upstairs off to try and get Rad5 working again (Pic4) - the green marked pipe barely gets warm to the touch, no other part of the radiator heats up at all (this rad used to take a long time to heat up, but never got REALLY hot).

And that's where I am. I've drained the system a couple more times and re-filled top/bottom, bottom/top. I've also added cleaner to the last fill - no change.

Closing off completely Rad6 to bring the system back to what it was originally doesn't seem to be working either.

Grateful for any further advice?!?

 

[MeldrewsMate]

You have been given good advice.

Turn both valves off and remove the rad. Open one valve at a time, to ensure full flowing water runs out for a minute, this will also purge any air from pipelines...
...It appears to me that there is air present in your system / lack of water, or a pump issue.

I will only add that you should clean out the loft tank first, then clean the pump. A new pump can get blocked in less than a minute by a dirty system.
The pipework installed by your builders will encourage airlocks, so

Turn both valves off and remove the rad. Open one valve at a time , to ensure full flowing water runs out for a minute, this will also purge any air from pipelines...
...It appears to me that there is air present in your system / lack of water, or a pump issue.

 

[uptoyou]

oops, got so involved draining and filling, I forgot this! :/
Thanks MeldrewsMate (and terryplumb again), will do this now.

 

[uptoyou]

OK, update:

So, closed the valves, drained the rad, took it off the wall.

Open the valve on the top pipe (which I had assumed was the feed) - ran for about a minute, hot water runs out at pressure, gurgling, then cleans up, could be air.

Open the valve on the bottom pipe (which I has assumed was the return) - ran for about 30 seconds, again, hot water runs out at pressure, more gurgling and bubbly. Cleans up a bit, bit more air.

I then consider that I haven't turned the bolier off and I could be emptying it quicker than the header tank can fill it, so have stopped for a while to let the system re-fill.

Q1. Does this sound like air locks?
Q2. is it normal for a return to push hot water out at pressure?
Q3. Should the bolier be on (pumping), when I run the valves through?

 

[uptoyou]

Early signs are that this has fixed it...thank you ever so much!

More air came out of the bottom pipe when I ran it through again, then cleaned up. Put the rad back on, bled it with just one pipe open, then opened the other.

Rad has come on and appears to have stayed on!

I will leave it for a few days then do the same procedure to the original rad which has always taken ages to barely heat up as this one is still doing barely anything.

Thanks again!