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?

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

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

r.

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.

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

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 |
\================================================= ================/

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.

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.

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.

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 |
\================================================= ================/

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.

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

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 |
\================================================= ================/

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

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

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 |
\================================================= ================/

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.

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

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

In article
,
says...


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 "~"

I've never seen a precise figure but 34'[1] is the figure that
springs to mind, so not a bad approximation.

[1]Another approxomation I recall is the height of the ridge
of the roof of a two storey house - no idea how accurate (or
otherwise) that is, though.

--

Terry

---
This email has been checked for viruses by AVG.
https://www.avg.com

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 ;-)

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

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 |
\================================================= ================/

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

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 :-)

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