Continued Central Heating Problem

[reiver]

Just wondering what sort of pipe work you have to the Rads ? Just some of the plastic push fit pipe is known to degrade and clog up the pipe work ( especially the grey plastic ) through time .

 

[BSAvale]

Just wondering what sort of pipe work you have to the Rads ? Just some of the plastic push fit pipe is known to degrade and clog up the pipe work ( especially the grey plastic ) through time .

The rad In question has plastic push fit pipes to it, as do the other two at the front of the house (they work properly). Another thing I’ll check.

 

[mudman]

Had the same problem, took two geriatric plumbers, my Dad and his pal, both 70+, to fix the problem.

it was black gunk / residues in the rads and pipes, not helped by the pipe work being that micro bore stuff. Flushed and cleaned the lines and Rads, refilled and repressurised etc. all good but not a quick job, those two guys drank a lot of tea!

 

[kennyc]

I haven't looked more than a few posts in (lifes too short) but your radiator should start off hot at the bottom, then cooler towards the top. That's if it has been done properly, i.e. flow into the bottom, return should be at the top, meaning a long pipe. Lockvalve on inlet (flow, at the bottom), TRV on outlet at the top, where it is conveniently positioned to adjust without stooping down.

This gets the best out of any radiator.

Sure, far too many installations have both valves at the bottom, thereby wasting a lot of their capability.

Installing them with the outlet at the top and inlet at the bottom is best, but some don't like to look at the exposed vertical pipe leading to the top.

Hot water rises. Pump it in at the bottom, suck it out at the top.

An infrared thermometer waved over the thing will show you the temperature distribution, whether the flow and return are connected backwards, whether there is air in the top (so cold) and it's time to bleed, etc.

Of course your pump has to be up to the job, and is unlikely to be able to move the water around sufficiently if the balancing valves are open too far.

Depending on the lay of the pipework, and its sizing, it may be that there is far more black crud blocking up the pipes than the rads. By the time you find loads inside the rads, having taken them off and flushed them, your pipework could be far more badly clagged up. TBH flushing the pipework through properly is best left to a professional, it's not as easy as just connecting a hosepipe to one end and letting it run.

As I said, I don't have time to read this all the way through, so if these basic principles have not already been discussed, that's my pennyworth.

got to be honest, its been a decade or 4 since I did my apprenticeship, and things may have changed, but, the rad should be hottest at the top not the bottom , TBOE connections as you describe were common when rads were fed from a single pipe system or a gravity fed system, it allowed the natural tendency of cooling water to drop through the radiator and back into the circulation loop, helping the relatively slow circulation of those systems the only time the return was at the top was when someone got the pipes the wrong way around !
TBOE allows slightly more heat output from any given radiator (I was always told it was in the region of 5-10% depending on radiator) than the almost universal BBOE method the vast majority of people are familier with, the pump drives the water into the rad and sucks it out the opposite end, the beauty of the two pipe system at work, gravity has very little to do with the circulation in a modern system.

 

[starr shot]

Just a thought but when the extension rad was connected up the flow is going the right way

 

[muddy42]

I hope you get this fixed, i’ve had similar intermittent issues. By the way a stalking Thermal is ok for seeing how a radiator heats up. Turn heating on and watch the radiator from the other side of the room. Also you can see where the heat escapes from your house.

 

[Sharpie]

got to be honest, its been a decade or 4 since I did my apprenticeship, and things may have changed, but, the rad should be hottest at the top not the bottom , TBOE connections as you describe were common when rads were fed from a single pipe system or a gravity fed system, it allowed the natural tendency of cooling water to drop through the radiator and back into the circulation loop, helping the relatively slow circulation of those systems the only time the return was at the top was when someone got the pipes the wrong way around !
TBOE allows slightly more heat output from any given radiator (I was always told it was in the region of 5-10% depending on radiator) than the almost universal BBOE method the vast majority of people are familier with, the pump drives the water into the rad and sucks it out the opposite end, the beauty of the two pipe system at work, gravity has very little to do with the circulation in a modern system.

I defer to you.

I am no plumber. But my big experience was sorting out my parent's house, a four storey Edwardian pile, the heating having been put in before they bought it, prior to 1961, powered by a huge open coal fired hearth with back boiler, gravity fed. At least 150 tonnes of chimney stack above it. Together with the other six chimney stacks for the other open fires in other rooms.

We've looked into taking out that chimney stack to free up room above, not that that would make a great difference to the large grand rooms with very high ceilings. (Not very ECO to have to heat up all that, mostly above our heads, but hey ho.

Some rooms still had their gas lights operational, it was quite a period piece.

Together with an electric heater inline to keep the whole lot from freezing up whilst they were away for a month or two over the Winter. It's still there under the floor and still works, about 3kW. Now redundant thank goodness, the modern (Worcester Bosch) boiler periodically circulates, measures the temperature and fires up when required to keep it from freezing. Assuming it has not tripped out, which it sometimes does inexplicably, even puzzling the technician with the diagnostic tools.

Subsequently in the '70s that was replaced with a gas boiler, initially still gravity, But soon enough a pump was fitted. Next upgrade was to redo the pipes to a flow and return system.

Other boiler upgrades since of course.

But for this rather grand house, gravity I think is still a large part of what keeps it going, none of the pipework is insulated.

So probably totally irrelevant to the OP. But my experiments with my IR thermometer do suggest that letting the hot water in the bottom, then the cooler out of the top seems to work, though now I see that is not supposed to be how it should work. Anyway, that's how it was done, back in the day.

 

[bobthedug]

Another ex heating engineer but I still keep my hand in. Not sure if I’ve missed it but did the radiator ever perform satisfactory?
Very difficult to diagnose and as you have discovered, it’s a process of elimination.
From reading through the previous posts, I’m inclined to think 1) The trv is possibly on the return pipe and it may the type that should be fitted to the flow. One of your earlier posts indicated the lock shield valve was heating up first. Some trv’s also must be fitted a certain way and have a small arrow on the body to indicate
2) The pipe run going to and from the issue radiator is too small a bore for the length of run.
Something to try is to isolate the radiator and draw water through the return and then close the return and draw water through the flow.
Use an old valve and hose or a washing machine hose which will fit some valves and run it into a bucket. That should give an indication of either of the pipes being blocked.
Some others have suggested what I would do as well. As far as balancing the system, on all the working rads, turn the lock shield valve all the way down until it’s closed and then open it 3/4 turn.

 

[kennyc]

I defer to you.

I am no plumber. But my big experience was sorting out my parent's house, a four storey Edwardian pile, the heating having been put in before they bought it, prior to 1961, powered by a huge open coal fired hearth with back boiler, gravity fed. At least 150 tonnes of chimney stack above it. Together with the other six chimney stacks for the other open fires in other rooms.

We've looked into taking out that chimney stack to free up room above, not that that would make a great difference to the large grand rooms with very high ceilings. (Not very ECO to have to heat up all that, mostly above our heads, but hey ho.

Some rooms still had their gas lights operational, it was quite a period piece.

Together with an electric heater inline to keep the whole lot from freezing up whilst they were away for a month or two over the Winter. It's still there under the floor and still works, about 3kW. Now redundant thank goodness, the modern (Worcester Bosch) boiler periodically circulates, measures the temperature and fires up when required to keep it from freezing. Assuming it has not tripped out, which it sometimes does inexplicably, even puzzling the technician with the diagnostic tools.

Subsequently in the '70s that was replaced with a gas boiler, initially still gravity, But soon enough a pump was fitted. Next upgrade was to redo the pipes to a flow and return system.

Other boiler upgrades since of course.

But for this rather grand house, gravity I think is still a large part of what keeps it going, none of the pipework is insulated.

So probably totally irrelevant to the OP. But my experiments with my IR thermometer do suggest that letting the hot water in the bottom, then the cooler out of the top seems to work, though now I see that is not supposed to be how it should work. Anyway, that's how it was done, back in the day.

I suspect your system has had the flow and return replaced back to front, gravity circulation always took the flow to the top pipe if fitted TBOE, if its been converted to a twin pipe system with a pump it will probably work just fine in reverse, it won't be the only one I have ever seen work happily for years back to front

 

[kes]

I would ask the same question as Starshot above - is the outflow valve working I am fairly sure its not opening fully? I am assuming its at the bottom of the rad ?
If you know the rad is connected properly, I would change the inflow and outflow connections for new ones, after tapping them with a rather large piece of wood !

 

[johndeere]

As already stated look at the pump, i had similar issues some radiators were hot some only tepid turned out the pump was working but was not moving the water around the system efficiently £114 later new pump from screwfix every radiator was nice and hot.

 

[Sharpie]

I suspect your system has had the flow and return replaced back to front, gravity circulation always took the flow to the top pipe if fitted TBOE, if its been converted to a twin pipe system with a pump it will probably work just fine in reverse, it won't be the only one I have ever seen work happily for years back to front

You are almost certainly correct. My part in "sorting it out" was simply to replace several radiators with more efficient finned ones in two rooms that struggled to warm up the rooms in chilly weather. Same dimensions, so no actual plumbing required. They were using electric oil filled radiators to supplement them. Together with fitting TRVs all round (they had none), then re-balancing the whole system. It's an open system with a header tank in the roof, and a massive hot water cylinder so bleeding it was no problem.

I did use Drayton TRVs, not the cheapest, but I was told that they were the best. They were the major expense, we needed rather a lot of them. When I visit I make sure to turn them up and down a few times, just in case they stick. I think that's important, particularly with the cheaper ones. Balancing it took several days of trial and error until I began to get a feel for how things interacted, not sure a professional would have the time to be able to do that. The IR thermometer was extremely useful, not sure I could have done it without it.

Fitting the TRVs was a great success, before then my parents had been struggling twiddling the manual valves, altering the boiler thermostat above optimal for condensing operation etc. Also had to explain that leaving every internal door open, as they liked to, was not making the control any easier, basically trying to heat the entire house, even when they were only using two floors most of the time. Drastic reduction in gas bills.

But it does seem that when it was converted to flow and return, it was done "backwards". Or maybe the boiler pump is fitted the wrong way around, I don't know. Still it seems to work well enough now.

Sorry, that has been an unhelpful digression from the OP's problem.

 

[375 mag]

I would say you need a full system flush you've either got gunk or air trapped in your system. I've just done mine twice to fix it, I should have hired the proper machine to do it. But all good now took a couple of days to get all the trapped air out.