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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Bleeding radiator question
I have a radiator that doesnt appear to bleed properly.
I open the bleed valve and it will hiss maybe a couple of seconds then stops, but no water comes out. I have removed a nearby rad in the bathroom for refurbishment if that is relevant. How come? is there an issue here? |
#2
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Bleeding radiator question
On Monday, 6 May 2019 23:57:14 UTC+1, ss wrote:
I have a radiator that doesnt appear to bleed properly. I open the bleed valve and it will hiss maybe a couple of seconds then stops, but no water comes out. I have removed a nearby rad in the bathroom for refurbishment if that is relevant. How come? is there an issue here? Is it a sealed system? Presumably it is. NT |
#3
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Bleeding radiator question
On 06/05/2019 23:57, ss wrote:
I have a radiator that doesnt appear to bleed properly. I open the bleed valve and it will hiss maybe a couple of seconds then stops, but no water comes out. I have removed a nearby rad in the bathroom for refurbishment if that is relevant. How come? is there an issue here? Air lock in the pipe feeding it? Shut down all other radiators to try and force the flow through the problem radiator. -- mailto : news {at} admac {dot} myzen {dot} co {dot} uk |
#4
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Bleeding radiator question
r.
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#5
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Bleeding radiator question
DerbyBorn wrote :
So - air comes out and then no water? There must be some presure pushing out the air - but the presure goes when the water level get to the valve? Very odd. Is the system pressurised properly? Water should **** out.Are both valves open (not necessarily fully)? That air is probably the gas resulting from the products of oxidation (rust) inside the rad. There is obviously a blockage to both sides of the rad, or the water pressure is inadequate. |
#6
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Bleeding radiator question
On 06/05/2019 23:57, ss wrote:
I have a radiator that doesnt appear to bleed properly. I open the bleed valve and it will hiss maybe a couple of seconds then stops, but no water comes out. I have removed a nearby rad in the bathroom for refurbishment if that is relevant. How come? is there an issue here? If you have a leak you can get negative pressure in the top of the house. So a hiss as a bit of air goes _in_ then no water comes out. TW |
#7
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Bleeding radiator question
On 06/05/2019 23:57, ss wrote:
I have a radiator that doesnt appear to bleed properly. I open the bleed valve and it will hiss maybe a couple of seconds then stops, but no water comes out. I have removed a nearby rad in the bathroom for refurbishment if that is relevant. How come? is there an issue here? Sealed system or vented? Are you sure that is not air being sucked in you can hear? -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#8
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Bleeding radiator question
On 07/05/2019 10:38, John Rumm wrote:
Sealed system or vented? Are you sure that is not air being sucked in you can hear? Sealed. The sytem is pressurised and heating all radiators, however, I increased the bar pressure and that appears to have sorted it. The bar pressure is now half bar more than it normally is. |
#9
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Bleeding radiator question
ss wrote in :
On 07/05/2019 10:38, John Rumm wrote: Sealed system or vented? Are you sure that is not air being sucked in you can hear? Sealed. The sytem is pressurised and heating all radiators, however, I increased the bar pressure and that appears to have sorted it. The bar pressure is now half bar more than it normally is. surprised the boiler didn't shut down due to low pressure. |
#10
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Bleeding radiator question
On 07/05/2019 15:05, DerbyBorn wrote:
surprised the boiler didn't shut down due to low pressure. Thats what baffled me as the boiler always run at a lower pressure so didnt feel the need to explore that avenue. Possibly the higher pressure has dislodged something or cured an airlock. The only time the boiler has shut off was about 3 years back when it was almost at zero, had been away on hols and it wouldnt fire up on return, it will run ok at .25 bar and I generally take it up to 1 bar when necessary, on this ocassion I took it to 1.25 and it appeared to sort the issue. Of course bar indications assume the dial is not faulty. |
#11
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Bleeding radiator question
On 07/05/2019 15:05, DerbyBorn wrote:
ss wrote in : On 07/05/2019 10:38, John Rumm wrote: Sealed system or vented? Are you sure that is not air being sucked in you can hear? Sealed. The sytem is pressurised and heating all radiators, however, I increased the bar pressure and that appears to have sorted it. The bar pressure is now half bar more than it normally is. surprised the boiler didn't shut down due to low pressure. Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#12
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Bleeding radiator question
On 07/05/2019 16:06, John Rumm wrote:
Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. |
#13
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Bleeding radiator question
In article , ss
wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
#14
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Bleeding radiator question
On 07/05/2019 17:11, charles wrote:
In article , ss wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. If the pressure gauge is low down in the system it will "see" the weight of all the water in the system above it added to whatever pressure you have as a result of the compression of the gas in the expansion vessel. 1 bar is ~30' of water. For boilers installed in lofts, you get the opposite effect - the pressure shown on the gauge there will actually be lower than what you would measure on the ground floor. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#15
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Bleeding radiator question
In article ,
John Rumm wrote: On 07/05/2019 17:11, charles wrote: In article , ss wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. If the pressure gauge is low down in the system it will "see" the weight of all the water in the system above it added to whatever pressure you have as a result of the compression of the gas in the expansion vessel. 1 bar is ~30' of water. 32ft when I was at university, but so much has changed in the intervening 57 years, that has probably, too. For boilers installed in lofts, you get the opposite effect - the pressure shown on the gauge there will actually be lower than what you would measure on the ground floor. -- from KT24 in Surrey, England "I'd rather die of exhaustion than die of boredom" Thomas Carlyle |
#16
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Bleeding radiator question
ss wrote:
On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. You definitely need to keep it at a pressure where the highest point in the system is comfortably above atmospheric (comfortably, to allow for when completely cold or a slight leak) or air can get in and cause corrosion. As well as some radiators not using all their area. -- Roger Hayter |
#17
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Bleeding radiator question
On 07/05/2019 20:14, charles wrote:
In article , John Rumm wrote: On 07/05/2019 17:11, charles wrote: In article , ss wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. If the pressure gauge is low down in the system it will "see" the weight of all the water in the system above it added to whatever pressure you have as a result of the compression of the gas in the expansion vessel. 1 bar is ~30' of water. 32ft when I was at university, but so much has changed in the intervening 57 years, that has probably, too. :-) Yup that's inflation for you, I think the accurate conversion is 33.46' now, but I was allowing for some wiggle room with my "~" -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#18
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Bleeding radiator question
On 07/05/2019 17:11, charles wrote:
surely on a sealed system, the pressure will be the same throughout the system. Thats what I thought after JR's reply but googling does say height gives a drop in pressure. |
#19
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Bleeding radiator question
On 07/05/2019 21:45, ss wrote:
On 07/05/2019 17:11, charles wrote: surely on a sealed system, the pressure will be the same throughout the system. Thats what I thought after JR's reply but googling does say height gives a drop in pressure. A non-pressurised system will be at atmospheric pressure at the highest point (header tank) and at atmospheric pressure plus the head of water at the lowest point. A pressurised system is no different, except that its "atmospheric" pressure is higher. SteveW |
#20
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Bleeding radiator question
On 07/05/2019 20:26, John Rumm wrote:
llowing for some wiggle room with my "~" Well thast wot it meens innit - a wiggle symbol -- "If you dont read the news paper, you are un-informed. If you read the news paper, you are mis-informed." Mark Twain |
#22
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Bleeding radiator question
On 07/05/2019 20:26, John Rumm wrote:
On 07/05/2019 20:14, charles wrote: In article , Â*Â*Â* John Rumm wrote: On 07/05/2019 17:11, charles wrote: In article , ss wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. If the pressure gauge is low down in the system it will "see" the weight of all the water in the system above it added to whatever pressure you have as a result of the compression of the gas in the expansion vessel. 1 bar is ~30' of water. 32ft when I was at university, but so much has changed in the intervening 57 years, that has probably, too. :-) Yup that's inflation for you, I think the accurate conversion is 33.46' now, but I was allowing for some wiggle room with my "~" Although this is a bit academic, it might be of general interest to someone. The International Standard Atmosphere defines sea level pressure as 1013.25 hPa; in the bottom part of the atmosphere, this decreases by approximately 1 hPa every 30 feet. The real-world sea-level pressure varies daily between (very roughly) min and max of 980 and 1040 hPa, so that's between about 32.8 and 34.8 feet of water. Here endeth the lesson ;-) |
#23
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Bleeding radiator question
John Rumm wrote:
On 07/05/2019 20:14, charles wrote: In article , John Rumm wrote: On 07/05/2019 17:11, charles wrote: In article , ss wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. If the pressure gauge is low down in the system it will "see" the weight of all the water in the system above it added to whatever pressure you have as a result of the compression of the gas in the expansion vessel. 1 bar is ~30' of water. 32ft when I was at university, but so much has changed in the intervening 57 years, that has probably, too. :-) Yup that's inflation for you, I think the accurate conversion is 33.46' now, but I was allowing for some wiggle room with my "~" Is that using metric water? -- Roger Hayter |
#24
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Bleeding radiator question
On 08/05/2019 22:21, Roger Hayter wrote:
John Rumm wrote: On 07/05/2019 20:14, charles wrote: In article , John Rumm wrote: On 07/05/2019 17:11, charles wrote: In article , ss wrote: On 07/05/2019 16:06, John Rumm wrote: Remember that if its an upstairs rad, then the pressure at the RAD could easily be half a bar (i.e. 15' of head) lower than that seen at the boiler. Many boilers will work down to 0.5 bar, which could equate to no nett pressure at all on the first floor. That could be it, the rad in question was on 1st floor. surely on a sealed system, the pressure will be the same throughout the system. If the pressure gauge is low down in the system it will "see" the weight of all the water in the system above it added to whatever pressure you have as a result of the compression of the gas in the expansion vessel. 1 bar is ~30' of water. 32ft when I was at university, but so much has changed in the intervening 57 years, that has probably, too. :-) Yup that's inflation for you, I think the accurate conversion is 33.46' now, but I was allowing for some wiggle room with my "~" Is that using metric water? Yup ;-) (now recompute for heavy water!) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#26
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Bleeding radiator question
On 09/05/2019 21:14, Vir Campestris wrote:
On 08/05/2019 12:04, wrote: Although this is a bit academic, it might be of general interest to someone. The International Standard Atmosphere defines sea level pressure as 1013.25 hPa; in the bottom part of the atmosphere, this decreases by approximately 1 hPa every 30 feet. The real-world sea-level pressure varies daily between (very roughly) min and max of 980 and 1040 hPa, so that's between about 32.8 and 34.8 feet of water. Here endeth the lesson ;-) Hectopascals? really? This is the first time I've ever seen them used. Andy Yup! It used to be millibars, but that became too familiar so it changed to hPa - even units get rebranded :-) |
#27
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Bleeding radiator question
On 09/05/2019 21:23, wrote:
On 09/05/2019 21:14, Vir Campestris wrote: On 08/05/2019 12:04, wrote: Although this is a bit academic, it might be of general interest to someone. The International Standard Atmosphere defines sea level pressure as 1013.25 hPa; in the bottom part of the atmosphere, this decreases by approximately 1 hPa every 30 feet. The real-world sea-level pressure varies daily between (very roughly) min and max of 980 and 1040 hPa, so that's between about 32.8 and 34.8 feet of water. Here endeth the lesson ;-) Hectopascals? really? This is the first time I've ever seen them used. Andy Yup! It used to be millibars, but that became too familiar so it changed to hPa - even units get rebranded :-) I've seen Pascals and kPa many times. It's the hecto that surprised me. Andy |
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