Radiator hot at top, cold bottom - why?

[Tony_Park]

Hi, we have 1 rad (double)which is affected as above.

All other rads are fine, system has only been filled since Aug, when a couple of new rads were installed.

Cold rad has been drained today, no sludge present - water is nice and clean.
Rad has a new feed valve, but looks like plumber re-used an old one on return. Thermostats show water entering at 50+ oC, and return shows room temp. Temp seems hot across top, and warm centrally hightwise, and warm down side of rad on return.

Anyone any thoughts on why this is happening?

Thanks
Tony

What could be causing this problem? I'm wondering if the return valve is faulty.

[AlBags]

There's a similar question in Motoring I added to!
Helps prevent corrosion of system structure by chemical means .. like coolant in a car engine will prevent the cast iron, steel and aluminium content from corroding and sludging the system.

[AlBags]

(Inhibitor often has an oilyness content that can help lubricate wet internal running parts)

[The Builder]

........... sounds like you have the same problem as Tony, Emerald.
Tony ......as Al was saying, there must be a bung-up in the rad or a bit of debris blocking a valve. Maybe take the rad off, powerflush it through, replace the other valve.
Inhibitor simply prevents the inside of the rads from rusting and corroding from the inside. I think it lubricates the pump as well.

[The Builder]

............ ^^^ ............. sorry Al, didn't know you were around :o))

[AlBags]

No worries mate ..
Around a lot at the moment with this cold. Good time to do all the customer's inside jobs.

[emeraldblue]

Thanks.My cold rad is the one used to drain the system, but he just attached a rubber tube to the tap at the bottom.It sounds like all the crap from the system has settled in this rad.

[Tony_Park]

Thanks, I'll try flushing the rad tomorrow, and while it's off check the flow from each valve

I believe that system cleanser may help, and if I recall correctly, that it should stay in the system for a period of time, and then drained. I'll give this a try too.
Thx
Tony

[Tony_Park]

Hi

Well here's the latest update:

Took rad off the wall, flushed through some water, some black particles did come out, but suspect not enough to have caused a problem.

While rad was being flushed, banged it with rubber mallet to see if that would help- no additional deposits came out.

Also checked the flow from both feed and return valves.
Both had water flowing, but looked TP me like there was a greater vol from the return for the same no of turns on the valve. Replaced feed valve.

Reconnected rad and introduced some x400 to circulate for a few weeks.

Current situation is that pretty much the same situation is in place - return valve is still just warm to touch. Wondering whether the return flow pressure is too much for the flow, and therefore stopping the water circulating all the way round the rad? Is this feasible? If so, does this potentially mean that there is an obstruction prior to the feed valve, since that's been replaced with a new valve?

Thx
Tony

[The Builder]

Well Tony ............. not much left to try is there? :o(
The valves are pretty simple, as long as they're not bunged, they just do what they're supposed to. I can't remember if you told us if you have microbore/minibore pipework or 15mm.
8mm microbore can bung up quite easily.......... creased pipework somewhere??

[Tony_Park]

Hi

15mm copper :(

Think I may need to call our plumber :(

Thanks
Tony

[The Builder]

Sorry we haven't been able to help Tony. Could you let us know when you've sorted it? It would be a great help to others ............ er ............ and me!

[peetee]

Hi there builder.air in rad is problem. System needs bleeding. you need a radiater key Each rad has a square type key at bottom end of rad.You need to start at furthest rad and work back to first rad Hope it cures problem. All the best from peetee.

[peetee]

Sorry Tony, thought user name was builder. Im new here. peetee.

[Tony_Park]

Hi,

Air in the system is not the problem, all rads have been bled before, and the one with the problem has been bled this pm, when the rad was rehung

When we get to the bottom of it, I'll be sure to let u know



Thx
Tony

[woodchopper]

I had the same problem when a plumber fitted a new radiator in the upstairs bedroom - was hot nat top and cold at bottom - was caused by an airlock in the system. To cure it there was a valve at the hot tank which he closed down a bit to divert more water through the radiators insteda of the heating coils for the hot water.
As soon as he did this there was a sudden gush of water and air through the radiators and the air was bled off. Result one piping hot new radiator.

[Tony_Park]

Hi guys,

well, not sure what the solution was here - our usual plumber hasn't even had time to get in touch.

Today, I decided to test the 2 refitted rads in our dining room - both seemed to be showing the same problem - so I left the heating on a high temp, and just sat and waited. About an hour later, there was a loud gurgling noise, and suddenly the rads heated up very quickly. Suspect there was an airlock somewhere in the system - no idea where, however all 3 rads that seemed to exhibit the problem now seem to be roasting hot. The wifes now happy, as things are warming up, and best of all, didn't cost us for a plumber!!!

In a couple of weeks time, I'll drain the system to get rid of the x400 and put in the required inhibitor. Suspect that the previous owner of the house did very little to maintain the heating, as they spent most of their time in the kitchen in front of the coal fire.

Thanks for all help and advice throughout this journey - lets hope it doesn't happen again.

Thanks
Tony

[Tony_Park]

Hi,

Well the problem returned the following day.

Is it possible that its the pump failing? Thinking about the design of the house, the 3 affected rads could be the only ones serviced by the pump, as the other rooms with rads downstairs, may be gravity fed from the rooms above.

Also, if it could be the pump, is a Grundfos Super Selectric UPS 15-60 a special or non standard model?

Thx
Tony

[Tony_Park]

Ok, we have a solution, in our case, it was an airlock in the feed pipe, so what our plumber did, was to attach a hosepipe to the airvent (removed) and backfilled with a small amount of water, to push the airlock back up into the FE tank - now the 3 radiators are nice and toasty warm :-D

Hope this helps someone if they see the same problem...

Tony