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Gas Central Heating System


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13 replies to this topic

#1 ShirleyGibson

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Posted 03 August 2006 - 05:30 AM

Hi,

I'm in London so hopefully someone knows something about central heating!  My central heating isn't working properly.  There are five radiators in total - the first and second get hot, but the other three do not.  We have tried bleeding the radiators, which had no effect.

We called in a plumbing company and they say there is a blockage, and they wanted to flush the system - but quoting £500 to do the job!!

The plumber even said that we could do it ourselves - but does anyone know exactly how to do it?  What does it involve?

I haven't got the details with me of what heating system etc it is, but can provide that if required.

Thank you!

Shirley.


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#2 Lurker_ahammer48_*

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Posted 05 August 2006 - 08:27 AM

Hi Shirley

I have to ask this question. Is it a hot water heating system or steam heat? 2 very different animals.

Is the piping to the radiators exposed? can U get to them?

Let us know


#3 ShirleyGibson

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Posted 14 August 2006 - 03:40 AM

Hi!  Sorry it's taken me a while to reply, I've been away on holiday.

The central heating system is hot water based, not steam.

Shirley.


#4 ShirleyGibson

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Posted 14 August 2006 - 03:40 AM

Sorry, forgot to add that yes we can get to the pipes on the radiators, they are exposed.

Shirley.


#5 Rrey199

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Posted 14 August 2006 - 02:15 PM

:dude: Are your radiators the cast-iron standing variety, or is it baseboard radiation running along the wall?

Is the home and oldie, or newer.

Does the system use a circulator pump, or is it a gravity system?

If you had heat last season, but not this year, It's most likely not a blockage.

Are the radiators that won't get hot upstairs by chance?

My vote is that either your circulator isn't working, or that the system is airbound.

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#6 ShirleyGibson

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Posted 15 August 2006 - 12:38 AM

:yikes: Ooh, lots of technical questions!  :D  Ok.

Are your radiators the cast-iron standing variety, or is it baseboard radiation running along the wall?  They are attached to the wall - like in this picture http://www.uktvstyle...x/aid/125.shtml
however mine has one pipe going in on end and another coming out the other.  I'm not sure which type that is, sorry!

Is the home and oldie, or newer.  The home is 1960's - but I think the heating system is about 10 years old, no older. 

Does the system use a circulator pump, or is it a gravity system?  Ooh not sure on this one.  We have a feeder tank in the loft which is where the heating system gets more water from should it need it.  This has to be filled by hand, it is not automatic - so if a radiator is drained, then we need to fill this tank up again.  There is a pump as well, on the main boiler which I think pumps the water around the system.

If you had heat last season, but not this year, It's most likely not a blockage. 
Are the radiators that won't get hot upstairs by chance?  There are five radiators, and they are all on one level.  What happened was the second to last radiator in the loop stopped getting hot.  We tried bleeding it, and it seemed to get better.  Then the last radiator in the loop stopped getting hot too, and finally the third radiator is not hot at all now either.  This happened over a period of time (say 2 months).  We have two radiators that are blisteringly hot, and the third radiator is warm to touch but the other two are cold.  We have tried bleeding the radiators but this doesn't seem to have made any difference.

Hope that helps!

Shirley.



#7 ShirleyGibson

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Posted 21 August 2006 - 03:31 AM

:? So does no one know how to help me??

Shirley


#8 Mad Mac

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Posted 21 August 2006 - 06:05 PM

When you say "bleeding", are you opening the radiators at the top and letting the built-up air out until water starts running? That's the way to get things moving again.

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#9 ShirleyGibson

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Posted 22 August 2006 - 01:38 AM

Yes, I do mean letting air out until the water starts coming out again.  This didn't have any affect though...:(:(:(

#10 dgs

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Posted 22 August 2006 - 01:12 PM

Before you start flushing I would suggest you check the system is balanced  - that is the most likely culprit (and the least messy and easiest to try first). If you get heat in some radiators and not others the most likely cause is that the flow of hot water through the system is not balanced.  You are aiming to have water flow through all the radiators at a rate which distributes heat across the house.  Each radiator has a valve on each side at the bottom - one is covered with a cap you can turn (which you use to temporarily turn off heat to a room for instance)  - the other is covered with a round cap which you cannot turn.  That second cap is the key - pop it off and underneath is a valve (hearafter referred to as the balance valve) you can turn this up or down with a spanner (wrench for the non-UKers ) to restrict or increase the rate at which water flows into that radiator - you try not to mess with this unless you have the problem you have.

To balance the system - go round every radiator and shut down the balance valve to stop hot water flowing into it - now start the system up and turn up your thermostat so the boiler fires up - go to the first radiator on the system after the boiler and open the balance valve a bit - feel the radiator  - give it a few minutes for hot water to spread across the radiator - open the valve until you are getting a good heat output but try to keep it clamped down as much as possible - that hot water has to be shared out right? Go to the second radiator and repeat - you might have to go round the system a few times to get it balanced- remember if you restrict the flow on radiators closer to the boiler, radiators further down the line will get more heat.  My guess is you had this problem before - bleeding the radiators may have just showed it up.

Now if that fails you could flush the system but it will be a real pain to do because your system does not refill automatically from what you say. Here's how..

Flushing the system means using a chemical cleaner to flush out any contaminants/sludge from the radiators and pipe work.  You should be able to buy the necessary chemical from a hardware store - ask in the plumbing section and they will know what you need.  While you are there look for another chemical which acts as a preservative - reduces corrosion in the system - you will want to do this after you have flushed.   The chemical bottle should give you more exact details but you usually want to circulate the cleaner stuff in your system for a while before you let it out to let it do its work. 

Go up in the loft and pour your chemical into the header tank you referred to earlier - read the instructions on the bottle to see how long you need to run the system with that in.  Once you have run for however long is required turn it off and  let all the water out of the system - find the  radiator  which is the lowest in the house - it should have a drain valve on it at the bottom which you can open to drain the system into a bucket (you said your system wont auto fill - normally you would disable the ball valve in the loft while you were doing this - you should be ok however ) .When no more water comes out go round the house and open the bleed valves on all the radiators to make sure you have drained the system fully. Close all the bleed valves and start filling the system from the loft.  Now work from the lowest radiator to the highest bleeding each radiator  - this whole process is going to be a real pain if you dont have a system which automatically tops up of course!  You will probably want to circ that water for a little while than drain again to get the remnants of cleaner out (follow the chemical instructions to be sure) - now you can fill again with the preservative added.

If this still does not cure your problem you can remove individual radiators by shutting down the valves at each end and then undoing the nuts at each end - - do one end first and have a bucket or similar under it to catch the water that will come out - (when you do all this be careful to support the stem coming out of the floor with a wrench when you are turning the nut on the radiator - you dont want to damage that copper pipe).  Undo the other end then lift the radiator to take it off the wall brackets.  You might find a clogged up radiator or valve somewhere through this process and you could give the radiator a good flush with a hose outside if you like. 

One last thing - the water that comes out of the system will be black ! Make sure you protect your carpets if you are flushing the system or taking out radiators.  Good luck


#11 ShirleyGibson

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Posted 22 August 2006 - 11:48 PM

:) Thank you thank you thank you!!!!

I will try balancing the radiators first - although I'm not sure why one day everything was working fine, and then the next 3 out of 5 radiators weren't working at all! 

I had to laugh when you said that the water inside radiators was black - I know that only too well!  We took one off the wall once (forgetting to close off the valves first!) and I got covered in black sludge, so did the walls, and carpet!  The damn things are really heavy too and I couldn't help my husband much staggering to our bath to let the water out...  I was totally amazed when my CREAM trousers actually came out clean after soaking and washing them!  My walls have never been the same, neither has our carpet but fortunately we have to redecorate anyway and will be getting new carpets eventually.  Oh well at least I can laugh about it now.

Good thing it's a long weekend this weekend in the UK, guess I know what I will be doing!

I'll let you know how I get on.

Shirley.


#12 ShirleyGibson

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Posted 29 August 2006 - 02:47 AM

Hi,

Well we spent most of yesterday working on our central heating system.  Balancing didn't work - it did get one of the three radiators that wasn't working to work so it was somewhat a success.

So we set about flushing the system (which is 10 years old by the way!).  Followed all your instructions, and got excited when on bleeding the system after flushing, draining and refilling radiator 3 got hot, and radiator 4 got luke warm.  Radiator 5 was having none of it, and did not get hot.  Bizarely radiator 3 after getting hot when being bled is now stone cold.  In fact the pipe that runs to the radiator is hot at the top and cold at the bottom.  Confused!!

I was suprised that not very much gunk came out of the system when we drained it - is that right??  We also discovered that in the header tank the pipe leading down to the system is about an inch off the bottom of the tank, so we are now thinking that the chemical didn't actually go into the system.  So we are going to do it all again this weekend...

Can you tell me why radiator 3 got hot when it was bled, but then didn't get hot afterwards (and we didn't touch anything, I swear!).  Why is radiator 5 (the last in the system) not getting hot?  We can hear it filling with water and it bleeds without any problem...  Does this mean there is still a blockage between radiator 3 and 4 (which gets lukewarm but not hot)?

Finally, does having an immersion tank (what I would call a geyser) have anything to do with our heating not working?  I do know that when the heating is off we don't have any hot water, so use a timer on our immersion tank to provide hot water when heating is off.

Thanks again.

Shirley.


#13 dgs

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Posted 31 August 2006 - 08:02 AM

The radiators are normally connected like this:

   __     __    __     __    __
  |_1|  |2_|  |_3|  |_4|  |5_|
  |    |  |    |  |    |  |    |  |    |
_|__|_|__|_|__|_|__|_|__| __

water flows--->

If you have a blockage in the exit pipe off 3 it will get hot as you let water into it as you bleed it but then once the radiator is full no more water is going to circulate through that rad because of the blockage- it will instead flow through the pipe beneath to the next radiator.  Alternatively - did you leave the valve at the exit for rad 3 clamped down by mistake?

That alone would not explain why the last 2 radiators were not getting heat however unless there is some serious crud blocking the system beyond rad 3.. 

Btw - dont expect to see lumps of gunk coming out - the chemical you used to flush is supposed to dissolve it so it will flow out. Maybe it might be worth trying another flush- this time partially drain the system then top up with chemical and water so you know the chemical is getting into circulation.  Did you circulate the chemical for the recommended time?  It looks like your blockage is likely to be beyond rads 1 and 2 - I would suggest you clamp those down (ie screw the valves on them right down) for a while when you are circulating the flushing chemical to force it as much as possible to make its way through the last 3 radiators.  Its probably worth forcing the chemical through each radiator in turn by adjusting the valves on the radiators to make sure you are pushing the solution through every pipe if at all possible.

If all this fails I would start to  wonder if there is something more fundamental like a failing water pump. ie insufficient pressure moving water around the system.  But I would try the relatively cheap flushing approach at present.




#14 ShirleyGibson

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Posted 05 September 2006 - 02:03 AM

IT WORKED!!!

We left the chemical in far longer than it said to (overnight instead of 4 hours!) but the next morning when we switched the heating on all the radiators were blasting the heat out.

Thank you very very VERY much for your help!!!!!!!!

:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D

Shirley.





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