cold rad

[nick/matt1]

could be scaled up. boilwer only fires for few minutes therefore heat is lost before radiator. it seems that as the return is hot and the flow is not, the valves could be the wrong way round... and causing restriction. either that or the pressure on the return is greater than the flow so it cant push round.

 

[PaulRB]

Ok guys.
I can't believe so many people are willing to think this thru and offer advice!!
Just to be clear; all rads have new valves, some are TRVs and others wheelhead.
I have fitted a brand new pump.
I have drained down twice in 48 hours and the water coming out of the system is lovely and clean.
Before fitting the new rad I fixed a hose from the o/side tap ( off the mains ) to both valves + blasted thru to try and clear air or blockages.
The pipework to + from the rad is in the 1st floor void between ceiling + floor.
It is a long horizontal run I'm sure + it could be an air lock. It doesn't "feel" like air though, because it doesn't splutter when I drain some water from the return pipe + air doesn't collect in the rad, which I would expect if it was being shifted by the hot coming thru.
It could be a blockage but I'm puzzled as to how the hot water can get thru + continue to work for 2/3 days.
I have taken a board up to reveal the pipework + turned the heating on, in the hope of feeling hot water in the flow pipe and establishing where, exactly, there may be an air lock or blockage.
However, I can only access about 4 feet of pipe, then it goes over a wall. The pipe is cold for as far as I can feel.
I'm convinced that the problem is
a) a long pipe run including having to go over the wall,
b) a tee joint that the hot water is by-passing ( but which I can't get access to without taking up carpets + floorboards + which I'm trying to avoid.
c) a lack of circulation caused by a + b

Now my plan is to drain the system and fit an automatic air vent in the horizontal pipework, hopefully solving the problem of air in the pipe.
At the same time, I was going to fit 2 full-bore iso valves in the vertical section of both flow + return pipes so I can later fit a towel rad with a heating element in, without having to drain the whole system and losing all the inhibitor.
I also thought it might be a cheap alternative to fit 2 tees in the vertical return pipe, connect a drill-driven pump between them and use it every 2/3 days to assist the circulation in the system.
I know that seems extreme but it might be enough to get us thru winter and the rad may work more continuously when the weather turns cold and we have the heating on longer.

Thanks again everyone and the more I discuss this, the more common this fault seems to be. It's nice to know we're not alone!

 

[PlumbBobBob]

is there a rad on the other side of the wall you could tee into doing away with the up and over pipe

 

[fuzzy]

im confused by what you mean 'return pipe'. i thought you said you dragged water through the flow pipe, which is it?

if its an air lock you need to drag water through the flow and then the return, they are both seperate pipes. this is how you get rid of an air lock, no need to auto air vent mate

it is either an air lock - if so fix as i advise
pump underpower - new pump
bi passing - new tee as i suggest or re pipe closer boiler for reverse return to 'even' pressures

 

[PaulRB]

im confused by what you mean 'return pipe'. i thought you said you dragged water through the flow pipe, which is it?

if its an air lock you need to drag water through the flow and then the return, they are both seperate pipes. this is how you get rid of an air lock, no need to auto air vent mate

it is either an air lock - if so fix as i advise
pump underpower - new pump
bi passing - new tee as i suggest or re pipe closer boiler for reverse return to 'even' pressures

ok rad has 2 pipes - 1 bringing hot water, other returning water to boiler. I think of them as the flow and return pipes.
There is a drain valve on the return pipe which I can use to drain about 2/3 pints.
This is replaced by hot water thru the flow pipe and, once I have some circulation, the rad will work for 2/3 days, until the water in the system cools. Then I have to drain again. ( obviously I can't keep draining so I'm looking into why the rad works for 2/3 days then stops )
I think you're right about the hot water by-passing the flow pipe but I can't get at the joint to put in a swept tee.
Not the pump - it's new + working fine.
Thanks

 

[nick/matt1]

reduce the flow toradiator which comes off the tee to allow flow through this rad

 

[Halesowen1]

YOU NEED TO GET A PLUMBER/HEATING ENGINEER OUT NOW AS THIS IS WORTHLESS.
Its down to something you have done whether you believe that or not. This cannot just happen for nothing, Fitting air vent wont do nothing, fitting tees and a drill pump is pointless.
It needs draining, putting drain off on this problem rad pipework, fit higher powered pump, fill back up, then turn every other rad off completely, if no heat still leave running and start draining from rad with hose, this will draw water around.

 

[dontknowitall]

I'm beginning to wonder if the flow and return to/from the radiator have both been plumbed into the flow (or return) on the heating circuit.

 

[Halesowen1]

Plus this tee wont do anything, if no water will get round with others all off it aint gonna do anything.
If it all worked OK before then the system needs getting back to how it was.
You do not know if pump is working OK, just because its new means nowt.
Get a more powerfull pump. If you cannot draw heat to this rad with others off its circulation problem, be that air (no), This tee you have been told (no as it was fine before), Maybe faulty rad or pump causing obstruction of flow or not enough power to feed rad.

 

[Halesowen1]

When you have eventually been getting heat from this rad after removing and putting a link between, have you then gone to all other rads and just opened them up??
As I feel it is pump and when you open them back up again it is just easier for the water to flow around these other rads that are piped closer. balance the system correctly after getting heat to it.

 

[fuzzy]

ok rad has 2 pipes - 1 bringing hot water, other returning water to boiler. I think of them as the flow and return pipes.
There is a drain valve on the return pipe which I can use to drain about 2/3 pints.
This is replaced by hot water thru the flow pipe and, once I have some circulation, the rad will work for 2/3 days, until the water in the system cools. Then I have to drain again. ( obviously I can't keep draining so I'm looking into why the rad works for 2/3 days then stops )
I think you're right about the hot water by-passing the flow pipe but I can't get at the joint to put in a swept tee.
Not the pump - it's new + working fine.
Thanks

you could be drawing air from the flow yes, and this may heat up the rad yes, but if theres an aitr lock on the return it wont work or will partially work. shut the flow valve and draw the water through, that will drag water from the return pipe

is the pump the same size and power? what setting is it on?

 

[PaulRB]

Reply to Halesowen 1

Ok Ok I hear you!
Trouble is, I phoned around to get a plumber in.
Regular guy said he was just too busy, 3 others didn't even get back to me.
I've spoken to about a dozen plumbers down at the local plumbers merchants and they've all said the same thing ie; air lock, sludge, long pipe run, by-passing tee etc.
When I tell them what I've done they all scratch their heads and say they would've done the same.
If I could find 1 plumber who said " I know what that is. I've come across it before. Do this." I'd jump at it.
The only thing I want to avoid is taking up the carpet/floorboards in the other room to access the pipe joint.
However, that may be the only way.

Can you tell me why I can get hot water into the rad AND it will carry on working fine for 2/3 days before stopping.
If the new pump can circulate the water ok for 2/3 days why do you think its the pump?
Appreciate your help, thanks.

 

[fuzzy]

well its certainly something causing it, im still not convinced you have all the air out of it, until you isolate the return and draw it from the flow pipe then do the same with the flow you will never be sure all the air is out

air can be trapped at the top of pipes but not the full bore, therefore restricting flow but not stopping it. if thi sis a long run when it fires from cold it may bi pass. you have to keep trying these things or you may never find out

once you have eliminated this check the pump power, the speed you have it on.

then if all this is fine and you say valves are fine and pipework fine you only have option of putting swept tee in and/or re pipe if you want a proper solution

 

[PaulRB]

Thanks.
When I drain down the system to fit an air vent and iso valves I suppose I could also fit a drain valve in the flow pipe and try shutting off the return valve + drawing water thru the flow pipe.
I've tried running the pump on all 3 settings but no joy.
I really think it needs a swept tee but I didn't want the hassle of gaining access.
Might have to swallow it and take up the carpet.

Thanks again

 

[Halesowen1]

Why are you fitting iso valves and air vent??
All the system worked fine before with nonw of this. This will not solve your problem.
Have you balanced the system correctly once you have had heat to the rad??
Did you buy the identical pump??
Why would it need a swept tee?? it has never had one before.
Think logically, none of these things on system when it was working fine so why would you put one in now??
Where abouts are you?

 

[jase158]

are the pipes level, bit of a long shot but if they have air in a bit of pipe which isnt straight, the air will stay there, with using for a few days steam (or something similar as wont be steam as has to be 100 degrees to get steam) could buid up and cause it to completely block, when draining slightly it is removing a little bit of air and then building up over a few days?

told you it was a long shot, but to find out if this is even remotely possible, check the pipes in loft to see if they are level. if not, try to lower them.

 

[fuzzy]

have you altered the height of the peipes when you swapped the rad? that may have put a air lock situation in the pipes?

dont worry about aav's just draw the water from each pipe seperately, that will clear the air if there is any

if its dragging air in it will be poor vent inlet position or a leak on the negative side of the system

 

[PaulRB]

Ok.
Fitting air vent in pipe in case it is an air lock.
To do this, I will have to drain the system so I might as well fit iso valves in 2 pipes feeding the rad so that, at a later date, if I can't solve the problem, I can fit a towel rad with heating element without having to drain the whole system.

Yes I bought the identical pump.
I'm in Dorset and around here plumbers are like gold-dust. It does P me off though, when they don't even return a call.
Haven't altered height of pipes. Already thought of that and I took up floorboard in wardrobe to access pipework in the hope that I could lower the pipework and reduce chance of air lock.
Not possible because pipes travel over 2 walls.
I will try dragging hot water into rad with all others turned off and leave the system like that for 3/4 days to seee if rad continues to work.
If it does, that would point to balancing of system.
If it stops working after 3/4 days I don't know what could be the cause.
I suppose I find it so frustrating because it does work properly for those 2/3 days.
Thanks

 

[JimField]

If all else fails pressurise it, with a Expansion vessel , filling loop and Prv valve you can buy them as a kit. Not too expensive that would be my next move,bit of a strange one, .Good to hear all the idea's though.

 

[fuzzy]

Ok.
Fitting air vent in pipe in case it is an air lock.
To do this, I will have to drain the system so I might as well fit iso valves in 2 pipes feeding the rad so that, at a later date, if I can't solve the problem, I can fit a towel rad with heating element without having to drain the whole system.

Yes I bought the identical pump.
I'm in Dorset and around here plumbers are like gold-dust. It does P me off though, when they don't even return a call.
Haven't altered height of pipes. Already thought of that and I took up floorboard in wardrobe to access pipework in the hope that I could lower the pipework and reduce chance of air lock.
Not possible because pipes travel over 2 walls.
I will try dragging hot water into rad with all others turned off and leave the system like that for 3/4 days to seee if rad continues to work.
If it does, that would point to balancing of system.
If it stops working after 3/4 days I don't know what could be the cause.
I suppose I find it so frustrating because it does work properly for those 2/3 days.
Thanks

may work for 3/4 days if a partial air lock, thats why i asked if the pipes had moved, ive had it before, long shot i know but we are running out of options. dont put aav iin, its a waste of time, drawing water out of each pipe will solve air problem if it is. shut of both valevs and take off rad, connect hose to each outlet and drag through

 

[PaulRB]

Thanks Fuzzy.
Haven't moved any pipes.
I'll have to fit a drain valve on the flow pipe in order to drag water thru.
Already have one on the return pipe.
Are you saying that, once I draw water thru both pipes, any air should be gone and the system should work as normal?
What worries me is that after working for 3/4 days air may be getting back into the system, or do you think I'm not actually purging the system of air and its the same air gradually returning to the pipe, causing a blockage?
Wouldn't an air vent cover that possibility?
When you talk about a poor vent inlet position, do you mean the pipe that hooks over the expansion tank in the roof?
If so, couldn't I extend that pipe to end underwater, so it couldn't suck in any air?
Thanks

 

[fuzzy]

i cannot ensure you that it will fix the problem but it will eliminate the problem being air.

fitting a aav could cause issues, if air is entering the system theres a problem, if you try to fix this by aav you will keep bringing in fresh water which is untreated and has fresh oxygen, therefore it will cause corrosion, not a good idea. aavs are only there to help initial filling

dont extend the pipe, it shouldnt suck in air, were is the vent (hooked pipe) inlet, cold feed to sysem and pump in conjunction with each other?

 

[PaulRB]

There is a vent pipe hooked over the expansion tank in the attic.
Directly below the expansion tank is the airing cupboard with a copper hot water tank, pump and 3-way valve.
The boiler is in the garage.
I think I need to shut the wheelhead valve on the flow side and then drain some water from the system, clearing it of air in the return pipe.
Then shut the lockshield valve on the return side and drain some water from the system, clearing it of air in the flow pipe.
Then I shouldn't have any air in those pipes.
You may be right that air is trapped in the return pipe which is stopping the circulation, and I thought it was in the flow pipe.
Thanks.

 

[067256]

Hey PaulRB....let me know how it goes. I am trailing you trying to work this out.
I eventually got my rad to warm up by turning all other rads off but it took a loonnnngggg time and it didnt even get hot....just warm to the touch!!
Put the rads back on and kitchen rad still does not work.

 

[fuzzy]

whats the output of the new rad compared to the old rad?

im guessing that restriction in a towel rad is greater than normal rad which may restrict flow more than previous and contribute to it not/struggling to circulate