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Radiator problems


billytheghillie
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Power flush out and give the rads a vibrate at the same time. but be prepared to find some pin holes if the rads are getting on a bit.

Is your heating system open vent or sealed?

Feed and expansion tank in loft = open vent. 

Sealed should have a pressure gauge and expansion vessel. 

if its open vent, you might have a problem with pumping over and thats why its sludged up. 

Edited by seph234
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Try turning them all off and opening one let it run until bottom gets warm. Close it go to next one and do same all around the system. If that don't work you could backflush with hose pipe and drain cock. 

Sometimes you just have to take the rad off and empty the black sludge outside and wash out with hose pipe. Don't get it on your carpets.

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sounds sludged up to me ,  if old rads change them  and use an inhibitor  will be cheaper in the long run     if a header tank system you may have a leak which is being topped up hence introducing fresh water  oxygen  generating rust and sludge    have found this in combi systems as when having to top up the pressure every couple of weeks fresh water and leaks cause the problem 

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This might sound silly - but I'll say it anyway .......... then explain why.

Are you sure that the thermostat (not radiator valves, but the main room/hall electrical thermostat) is turned up enough?

Explanation:  When the system starts, two things happen. 

  • First hot water flows from the boiler and starts at the top of the radiators, gradually working its way down from the top of each radiator.
  • Second, a very small electric 'accelerator' heater inside the thermostat starts to locally heat the thermostat.  The purpose of this is to speed the operation of the thermostat and reduce 'overshoot' where the room goes well over the set-point temperature before the thermostat switches the heating off.  This also saves fuel.
  • What can happen if the room is almost at the temperature that the thermostat is set to, the thermostat shuts the system off before the radiators have fully filled with hot water all the way down.  When shut off, the small electric 'accelerator' heater inside the thermostat also shuts off - and after a period, the heating restarts ........ and the whole cycle begins again.   Result - radiators only really get hot at the top.

There are two 'clues';  First - all radiators are doing the same.  Sludge tends to affect some more than others.  Second, at this time of year the room being almost at the set-point is very feasible.

It is an easy and 'free' thing to try to set the thermostat higher and try again.  Flushing is time consuming and dirty and may be needed, but you don't want to do it unnecessarily.

Edited by JohnfromUK
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8 hours ago, JohnfromUK said:

This might sound silly - but I'll say it anyway .......... then explain why.

Are you sure that the thermostat (not radiator valves, but the main room/hall electrical thermostat) is turned up enough?

Explanation:  When the system starts, two things happen. 

  • First hot water flows from the boiler and starts at the top of the radiators, gradually working its way down from the top of each radiator.
  • Second, a very small electric 'accelerator' heater inside the thermostat starts to locally heat the thermostat.  The purpose of this is to speed the operation of the thermostat and reduce 'overshoot' where the room goes well over the set-point temperature before the thermostat switches the heating off.  This also saves fuel.
  • What can happen if the room is almost at the temperature that the thermostat is set to, the thermostat shuts the system off before the radiators have fully filled with hot water all the way down.  When shut off, the small electric 'accelerator' heater inside the thermostat also shuts off - and after a period, the heating restarts ........ and the whole cycle begins again.   Result - radiators only really get hot at the top.

There are two 'clues';  First - all radiators are doing the same.  Sludge tends to affect some more than others.  Second, at this time of year the room being almost at the set-point is very feasible.

It is an easy and 'free' thing to try to set the thermostat higher and try again.  Flushing is time consuming and dirty and may be needed, but you don't want to do it unnecessarily.

They say that every day is a school day. I’ve certainly learnt something and that’s after spending my working life in the commercial heating industry.

Thanks for that John. That sounds like a very plausible explanation.

OB

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A lot depends on the system design, radiator output and what you are asking your boiler to do. Manufactures calculations for the output of radiators are by using top and bottom opposite end's for the rad valve's. Ultimately you can turn the room stat up to a zillion degrees but if the waterways in the radiator are becoming blocked it will never work correctly. If you base the thermal drop across the rad at around 10 degrees your hand will not really notice it. One very effective way at looking at temperature on a rad is by using a thermal camera. The heavy deposits usually start in the bottom centre of the rad and slowly build up in a curve untill it vertually stops all flow. The most cost effective and long term solution is to power wash the whole system it would only take around 4 hours. 

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9 hours ago, JohnfromUK said:

This might sound silly - but I'll say it anyway .......... then explain why.

Are you sure that the thermostat (not radiator valves, but the main room/hall electrical thermostat) is turned up enough?

Explanation:  When the system starts, two things happen. 

  • First hot water flows from the boiler and starts at the top of the radiators, gradually working its way down from the top of each radiator.
  • Second, a very small electric 'accelerator' heater inside the thermostat starts to locally heat the thermostat.  The purpose of this is to speed the operation of the thermostat and reduce 'overshoot' where the room goes well over the set-point temperature before the thermostat switches the heating off.  This also saves fuel.
  • What can happen if the room is almost at the temperature that the thermostat is set to, the thermostat shuts the system off before the radiators have fully filled with hot water all the way down.  When shut off, the small electric 'accelerator' heater inside the thermostat also shuts off - and after a period, the heating restarts ........ and the whole cycle begins again.   Result - radiators only really get hot at the top.

There are two 'clues';  First - all radiators are doing the same.  Sludge tends to affect some more than others.  Second, at this time of year the room being almost at the set-point is very feasible.

It is an easy and 'free' thing to try to set the thermostat higher and try again.  Flushing is time consuming and dirty and may be needed, but you don't want to do it unnecessarily.

This is the reason many of the "BMS boys" suggest not supplying a neutral wire to themostats and just using it as a switch.  No N wire no heater, less to go wrong.

 

2 minutes ago, B725 said:

A lot depends on the system design, radiator output and what you are asking your boiler to do. Manufactures calculations for the output of radiators are by using top and bottom opposite end's for the rad valve's. Ultimately you can turn the room stat up to a zillion degrees but if the waterways in the radiator are becoming blocked it will never work correctly. If you base the thermal drop across the rad at around 10 degrees your hand will not really notice it. One very effective way at looking at temperature on a rad is by using a thermal camera. The heavy deposits usually start in the bottom centre of the rad and slowly build up in a curve untill it vertually stops all flow. The most cost effective and long term solution is to power wash the whole system it would only take around 4 hours. 

This was why I suggested checking a single rad to ***** the sludge content as it may remove unwarranted expense if  no blocked.

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6 minutes ago, B725 said:

Not having a neutral wire can give quite a descrepancy between the on and off of the stat,

Quite correct but at lease the heating does not keep switching :lol:.  for this reason I to have a

8 minutes ago, B725 said:

digital and works on +or - . 5 of a degree

It also has 6 different time periods set a differing temperatures

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They key things with just turning the thermostat up to check is that it costs nothing and takes almost no time.

I tend to use my thermostat as a 'seasonal' thing that turns the heating off early on a warm day - and use thermostatic radiator valves for getting the room to the right temperature, but I have a quite large system with 4 separate heating zones (each with it's own thermostat and separate timer/programmer channel).

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What we don't know is how the system is piped up. My niece recently bought their first house, after moving in they complained it wasn't very warm, after pulling a couple of board's up I found it was a single pipe system and done in 15mm. So the old bbu went along with all the rads and pipe work, a new Ideal Logic +combi new rads and 22mm to each pair of rads a RF stat and the house has a nice even comfortable temperature. 

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30 minutes ago, vampire said:

Its now good practice to drain heating system every ?2 or 5 years cant remember (without checking the book) and add new inhibitor.

Is that advice backed up by actual data (rather than just a way for heating engineers to drum up business), and are modern CH systems more problematic than older ones?  

We never drained or added inhibitor at our previous house, the only repairs during our 35 year occupancy were two replacement motorised valves and one thermostat for the gas boiler, and everything was still working perfectly when we left.   Very simple system, 15mm piping, old-fashioned Ideal Standard boiler (non-condensing) that was little more than a lump of cast iron -- presumably illegal to fit a boiler like that nowadays..  

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On 22/10/2019 at 07:35, JohnfromUK said:

This might sound silly - but I'll say it anyway .......... then explain why.

Are you sure that the thermostat (not radiator valves, but the main room/hall electrical thermostat) is turned up enough?

Explanation:  When the system starts, two things happen. 

  • First hot water flows from the boiler and starts at the top of the radiators, gradually working its way down from the top of each radiator.
  • Second, a very small electric 'accelerator' heater inside the thermostat starts to locally heat the thermostat.  The purpose of this is to speed the operation of the thermostat and reduce 'overshoot' where the room goes well over the set-point temperature before the thermostat switches the heating off.  This also saves fuel.
  • What can happen if the room is almost at the temperature that the thermostat is set to, the thermostat shuts the system off before the radiators have fully filled with hot water all the way down.  When shut off, the small electric 'accelerator' heater inside the thermostat also shuts off - and after a period, the heating restarts ........ and the whole cycle begins again.   Result - radiators only really get hot at the top.

There are two 'clues';  First - all radiators are doing the same.  Sludge tends to affect some more than others.  Second, at this time of year the room being almost at the set-point is very feasible.

It is an easy and 'free' thing to try to set the thermostat higher and try again.  Flushing is time consuming and dirty and may be needed, but you don't want to do it unnecessarily.

John, your a star, I did the above and Hey Presto all rads are now hot from top to bottom. Thank you very much.

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