Hello,
This is my first post - and I'm looking for some help on a Central Heating System that's sending me mad!

I've got the following system:
- Sealed CH system in 3 storey house + Cellar (i.e. 4 floors)
- Expansion vessel in Cellar with Pressure Gauge
- Boiler on Ground Floor
- 20 radiators across all floors

Problem is I get air in the (top) 2nd floor radiator and hence a cold radiator eventually. I'm having to bleed it about every 2 days to keep it from going cold. I understand this is air getting into the system somewhere, so I've increased the pressure to 2.0bar to try to identify leaks. I've found a few dodgy radiator tails and so sorted those out. There's no sign of water in the air side of the expansion vessel. Since I have the pressure gauge in the cellar and then 3 floors above that, then I also believe I need a higher intial cold pressure - so I've ended up with about 1.8bar. When warm the pressure only increases to about 1.9bar, so I've assumed the pressure vessel is doing its job. I've thought about adding some leak sealer but was trying to avoid that by fixing the leaks 'properly'.

I can't see how the air is getting in if the system is pressurised (i.e. if I put a needle in a water balloon to make a leak then surely only water would come out - and no air would get in).

So I'm out of ideas and wondered if anyone could help before I got a plumber in.

I've read the (excellent) Sealed CH FAQs at
http://www​.makewrite​.demon.co.​uk/SealedC​H.html
but still none the wiser.

Thanks in advance,
Rob.

You might be having trouble with your expansion tank, or your make up valve.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"AmateurRob" wrote in message
...

Hello,
This is my first post - and I'm looking for some help on a Central
Heating System that's sending me mad!

I've got the following system:
- Sealed CH system in 3 storey house + Cellar (i.e. 4 floors)
- Expansion vessel in Cellar with Pressure Gauge
- Boiler on Ground Floor
- 20 radiators across all floors

Problem is I get air in the (top) 2nd floor radiator and hence a cold
radiator eventually. I'm having to bleed it about every 2 days to keep
it from going cold. I understand this is air getting into the system
somewhere, so I've increased the pressure to 2.0bar to try to identify
leaks. I've found a few dodgy radiator tails and so sorted those out.
There's no sign of water in the air side of the expansion vessel. Since
I have the pressure gauge in the cellar and then 3 floors above that,
then I also believe I need a higher intial cold pressure - so I've ended
up with about 1.8bar. When warm the pressure only increases to about
1.9bar, so I've assumed the pressure vessel is doing its job. I've
thought about adding some leak sealer but was trying to avoid that by
fixing the leaks 'properly'.

I can't see how the air is getting in if the system is pressurised (i.e.
if I put a needle in a water balloon to make a leak then surely only
water would come out - and no air would get in).

So I'm out of ideas and wondered if anyone could help before I got a
plumber in.

I've read the (excellent) Sealed CH FAQs at
http://tinyurl.com/4xxj27s
but still none the wiser.

Thanks in advance,
Rob.




--
AmateurRob

On Wed, 18 Jan 2012 20:59:06 +0000, AmateurRob
wrote:


Hello,
This is my first post - and I'm looking for some help on a Central
Heating System that's sending me mad!

I've got the following system:
- Sealed CH system in 3 storey house + Cellar (i.e. 4 floors)
- Expansion vessel in Cellar with Pressure Gauge
- Boiler on Ground Floor
- 20 radiators across all floors

Problem is I get air in the (top) 2nd floor radiator and hence a cold
radiator eventually. I'm having to bleed it about every 2 days to keep
it from going cold. I understand this is air getting into the system
somewhere, so I've increased the pressure to 2.0bar to try to identify
leaks. I've found a few dodgy radiator tails and so sorted those out.
There's no sign of water in the air side of the expansion vessel. Since
I have the pressure gauge in the cellar and then 3 floors above that,
then I also believe I need a higher intial cold pressure - so I've ended
up with about 1.8bar. When warm the pressure only increases to about
1.9bar, so I've assumed the pressure vessel is doing its job. I've
thought about adding some leak sealer but was trying to avoid that by
fixing the leaks 'properly'.

I can't see how the air is getting in if the system is pressurised (i.e.
if I put a needle in a water balloon to make a leak then surely only
water would come out - and no air would get in).

So I'm out of ideas and wondered if anyone could help before I got a
plumber in.

I've read the (excellent) Sealed CH FAQs at
http://tinyurl.com/4xxj27s
but still none the wiser.

Thanks in advance,
Rob.

If it's a steam system, ignore this.
Never had steam radiators.
I've had a couple hot water systems.
You don't say if the system was recently emptied, then refilled
If so, when refilling the radiators should be vented from the bottom
up as they fill.
If this wasn't done, there may be air trapped in them that migrates
upward.
With 29 psi on the system you would be aware of leaks.
From what you've said, the only possibility is the radiators weren't
properly vented upon refilling.
If not, it's new to me.

--Vic

On Jan 18, 8:59*pm, AmateurRob
wrote:
Hello,
This is my first post - and I'm looking for some help on a Central
Heating System that's sending me mad!

I've got the following system:
- Sealed CH system in 3 storey house + Cellar (i.e. 4 floors)
- Expansion vessel in Cellar with Pressure Gauge
- Boiler on Ground Floor
- 20 radiators across all floors

Problem is I get air in the (top) 2nd floor radiator and hence a cold
radiator eventually. *I'm having to bleed it about every 2 days to keep
it from going cold. *I understand this is air getting into the system
somewhere, so I've increased the pressure to 2.0bar to try to identify
leaks. *I've found a few dodgy radiator tails and so sorted those out.
There's no sign of water in the air side of the expansion vessel. *Since
I have the pressure gauge in the cellar and then 3 floors above that,
then I also believe I need a higher intial cold pressure - so I've ended
up with about 1.8bar. *When warm the pressure only increases to about
1.9bar, so I've assumed the pressure vessel is doing its job. *I've
thought about adding some leak sealer but was trying to avoid that by
fixing the leaks 'properly'.

I can't see how the air is getting in if the system is pressurised (i.e.
if I put a needle in a water balloon to make a leak then surely only
water would come out - and no air would get in).

So I'm out of ideas and wondered if anyone could help before I got a
plumber in.

I've read the (excellent) Sealed CH FAQs athttp://tinyurl.com/4xxj27s
but still none the wiser.

Thanks in advance,
Rob.

--
AmateurRob

For air to get in, water must be getting out.
First check that no water is escaping from the safety valve. (Tape a
plastic bag over the outlet & leave for a while.)
If there is, the problem usually lies with the expansion vessel losing
its air charge. You need to depressurise the system to replace the
air, pressure needs to be set as manufacturer recommends, usually
around 1 to 1.5bar

If this fixes it but the problem recurrs after a while. you need a new
expansion vessel, the diaphragm inside is ruptured/leaking.
This can be checkedby removing itand trying to charge it with air. If
it won't hold a charge it is buggered.

Also search for other leaks.

Question. Does the sytem hold pressure when not used, ie cold?

There is another option, it may not be air but hydrogen, the by
product of anerobic oxidation.
Metals in the system take oxygen out of the water leaving hydrogen.
This can be resolved by adding corrosion inhibitors to the water.
This is more likely if you live in a hard water area.

You can test for this by seeing if the "air" you get out of the system
burns by applying a light to it. Obviously becareful, it burns with a
very hot colourless flame.

One place where it's hard to find leaks is inside the boiler. With a
small leak, the water can just be evaporated away.

On Jan 19, 4:00*am, harry wrote:
On Jan 18, 8:59*pm, AmateurRob
wrote:









Hello,
This is my first post - and I'm looking for some help on a Central
Heating System that's sending me mad!

I've got the following system:
- Sealed CH system in 3 storey house + Cellar (i.e. 4 floors)
- Expansion vessel in Cellar with Pressure Gauge
- Boiler on Ground Floor
- 20 radiators across all floors

Problem is I get air in the (top) 2nd floor radiator and hence a cold
radiator eventually. *I'm having to bleed it about every 2 days to keep
it from going cold. *I understand this is air getting into the system
somewhere, so I've increased the pressure to 2.0bar to try to identify
leaks. *I've found a few dodgy radiator tails and so sorted those out..
There's no sign of water in the air side of the expansion vessel. *Since
I have the pressure gauge in the cellar and then 3 floors above that,
then I also believe I need a higher intial cold pressure - so I've ended
up with about 1.8bar. *When warm the pressure only increases to about
1.9bar, so I've assumed the pressure vessel is doing its job. *I've
thought about adding some leak sealer but was trying to avoid that by
fixing the leaks 'properly'.

I can't see how the air is getting in if the system is pressurised (i.e..
if I put a needle in a water balloon to make a leak then surely only
water would come out - and no air would get in).

So I'm out of ideas and wondered if anyone could help before I got a
plumber in.

I've read the (excellent) Sealed CH FAQs athttp://tinyurl.com/4xxj27s
but still none the wiser.

Thanks in advance,
Rob.

--
AmateurRob

For air to get in, water must be getting out.
First check that no water is escaping from the *safety valve. (Tape a
plastic bag over the outlet & leave for a while.)
If there is, the problem usually lies with the expansion vessel losing
its air charge. *You need to depressurise the system to replace the
air, pressure needs to be set as manufacturer recommends, usually
around 1 to 1.5bar

If this fixes it but the problem recurrs after a while. you need a new
expansion vessel, the diaphragm inside is ruptured/leaking.
This can be checkedby removing itand trying to charge it with air. If
it won't hold a charge it is buggered.

Also search for other leaks.

Question. Does the sytem hold pressure when not used, ie cold?

There is another option, it may not be air but hydrogen, the by
product of anerobic oxidation.
Metals in the system take oxygen out of the water leaving hydrogen.
This can be resolved by adding corrosion inhibitors to the water.
This is more likely if you live in a hard water area.

You can test for this by seeing if the "air" you get out of the system
burns by applying a light to it. Obviously becareful, it burns with a
very hot colourless flame.

It sounds a lot more like there were pockets of air in some of the
radiators which were never properly bled out that are now migrating
on their own to new places in the system...

~~ Evan

On Jan 18, 3:59*pm, AmateurRob
wrote:
Hello,
This is my first post - and I'm looking for some help on a Central
Heating System that's sending me mad!

I've got the following system:
- Sealed CH system in 3 storey house + Cellar (i.e. 4 floors)
- Expansion vessel in Cellar with Pressure Gauge
- Boiler on Ground Floor
- 20 radiators across all floors

Problem is I get air in the (top) 2nd floor radiator and hence a cold
radiator eventually. *I'm having to bleed it about every 2 days to keep
it from going cold. *I understand this is air getting into the system
somewhere, so I've increased the pressure to 2.0bar to try to identify
leaks. *I've found a few dodgy radiator tails and so sorted those out.
There's no sign of water in the air side of the expansion vessel. *Since
I have the pressure gauge in the cellar and then 3 floors above that,
then I also believe I need a higher intial cold pressure - so I've ended
up with about 1.8bar. *When warm the pressure only increases to about
1.9bar, so I've assumed the pressure vessel is doing its job. *I've
thought about adding some leak sealer but was trying to avoid that by
fixing the leaks 'properly'.

I can't see how the air is getting in if the system is pressurised (i.e.
if I put a needle in a water balloon to make a leak then surely only
water would come out - and no air would get in).

So I'm out of ideas and wondered if anyone could help before I got a
plumber in.

I've read the (excellent) Sealed CH FAQs athttp://tinyurl.com/4xxj27s
but still none the wiser.

Thanks in advance,
Rob.

--
AmateurRob

Vic has it right. Any air in the system will be picked up by passing
water. The water will then release this air at the point of least
pressure. This is usually at the highest/farthest radiator. Rich
Trethewey gave a great explanation of this on one episode of TOH. A
simple explanation is that water will boil more vigorously in a pot
with the lid removed than a pot with a lid on.

You need to bleed every radiator in the system until all air is gone.
I usually do this first with the system off then run the pump(s) for a
while then shut down and bleed again. In a big system like you have
it can take a long time but you will eventually get all of the air
out. Then you just have to keep the pressure high enough to prevent
the new water from releasing air again.

Many boilers have an air eliminator on top of the boiler. Years ago, I saw a
demo of a "Spirovent" which I thought was totally fascinating. Perhaps the
OP air eliminator isn't working properly.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"Limp Arbor" wrote in message
...

Vic has it right. Any air in the system will be picked up by passing
water. The water will then release this air at the point of least
pressure. This is usually at the highest/farthest radiator. Rich
Trethewey gave a great explanation of this on one episode of TOH. A
simple explanation is that water will boil more vigorously in a pot
with the lid removed than a pot with a lid on.

You need to bleed every radiator in the system until all air is gone.
I usually do this first with the system off then run the pump(s) for a
while then shut down and bleed again. In a big system like you have
it can take a long time but you will eventually get all of the air
out. Then you just have to keep the pressure high enough to prevent
the new water from releasing air again.

On Wed, 18 Jan 2012 20:59:06 +0000, AmateurRob wrote:
Problem is I get air in the (top) 2nd floor radiator and hence a cold
radiator eventually. I'm having to bleed it about every 2 days to keep
it from going cold. I understand this is air getting into the system
somewhere, so I've increased the pressure to 2.0bar to try to identify
leaks. I've found a few dodgy radiator tails and so sorted those out.

It might be a problem with the fill loop or the pressure relief valve -
have you checked for leaks there? Your setup might also have an automatic
air bleed valve as part of the system, and apparently these can sometimes
fail and start letting air in.

cheers

Jules

Thanks for all the replies - I'll try to address most of them with this reply:

- System has not been emptied recently (other than a isolating a couple of radiators when I've re-PTFE'd the rad tails) and I've been getting rid of air for a few months now - can't believe there's that much air in there!

- No leaks from pressure relief valve near expansion vessel - there's a pipe that goes to a drain that's been dry the whole time.

- I've assumed expansion vessel is fine since (a) no water from air inlet (b) only a small rise in cold-hot pressure change (0.1bar).

- Pressure holds all the time - it only loses pressure when I bleed the air out.

- Got some inhibitor to add, but I wanted to make sure I'd sorted the leaks before I added it (and then diluted it with refills). Might add that to eliminate the 'hydrogen' gas possibility.

- I suppose boiler leak is a possibility - I'm going to get it serviced and will find out then.

- I'll re-bleed all the rads again to eliminate as much as possible.

- Can someone tell me what gauge pressure (in the cellar) I should set so that my ground floor, 1st floor and 2nd floor rads are at the right pressure (plus it's a Victorian house so the ceiling/height of each floor is 9 or 10feet)


Thanks,
Rob.

On Jan 19, 3:30*pm, AmateurRob
wrote:
Thanks for all the replies - I'll try to address most of them with this
reply:

- System has not been emptied recently (other than a isolating a couple
of radiators when I've re-PTFE'd the rad tails) and I've been getting
rid of air for a few months now - can't believe there's that much air in
there!

- No leaks from pressure relief valve near expansion vessel - there's a
pipe that goes to a drain that's been dry the whole time.

- I've assumed expansion vessel is fine since (a) no water from air
inlet (b) only a small rise in cold-hot pressure change (0.1bar).

- Pressure holds all the time - it only loses pressure when I bleed the
air out.

- Got some inhibitor to add, but I wanted to make sure I'd sorted the
leaks before I added it (and then diluted it with refills). *Might add
that to eliminate the 'hydrogen' gas possibility.

- I suppose boiler leak is a possibility - I'm going to get it serviced
and will find out then.

- I'll re-bleed all the rads again to eliminate as much as possible.

- Can someone tell me what gauge pressure (in the cellar) I should set
so that my ground floor, 1st floor and 2nd floor rads are at the right
pressure (plus it's a Victorian house so the ceiling/height of each
floor is 9 or 10feet)

Thanks,
Rob.

--
AmateurRob

question....is the system ALWAYS under pressure?...even when idle?

it's hard to understand how new air could enter the system if all of
it is under positive pressure all the time?

Mark

On Thu, 19 Jan 2012 20:30:29 +0000, AmateurRob
wrote:


Thanks for all the replies - I'll try to address most of them with this
reply:

- System has not been emptied recently (other than a isolating a couple
of radiators when I've re-PTFE'd the rad tails) and I've been getting
rid of air for a few months now - can't believe there's that much air in
there!

- No leaks from pressure relief valve near expansion vessel - there's a
pipe that goes to a drain that's been dry the whole time.

- I've assumed expansion vessel is fine since (a) no water from air
inlet (b) only a small rise in cold-hot pressure change (0.1bar).

- Pressure holds all the time - it only loses pressure when I bleed the
air out.

- Got some inhibitor to add, but I wanted to make sure I'd sorted the
leaks before I added it (and then diluted it with refills). Might add
that to eliminate the 'hydrogen' gas possibility.

- I suppose boiler leak is a possibility - I'm going to get it serviced
and will find out then.

- I'll re-bleed all the rads again to eliminate as much as possible.

- Can someone tell me what gauge pressure (in the cellar) I should set
so that my ground floor, 1st floor and 2nd floor rads are at the right
pressure (plus it's a Victorian house so the ceiling/height of each
floor is 9 or 10feet)



You may need a local expert's help if thorough bleeding doesn't work.
A pressurized system can't let air in unless it comes from a make-up
water supply. Never saw that in a water supply.
I've had expansion tanks on top floor and basement, and they were
never an issue.
They had no "air inlet."
Their purpose is to absorb system hydraulic shock.
They can get water-bound, but I think that's from years of oxygen
dissolving into the water.
The one I had in the basement could be isolated and drained.
I never got significant water from it when I drained it as a check.

As far as pressure to maintain, that's something that's specced for
the system.
One of mine had a straight city water connection.
The other had a reducing regulator between city water and system.
But no gauges at all, so I never knew if it worked.
I drained that system a couple times, and had no problem refilling.
City water pressure was about 40 psi in both cases.
I expect any hot water system can easily handle that.
I always shut off the water supply after completely bleeding.
No need for make-up water in these systems.
And if you did spring a leak, you'd have a continuous one.
Once full, the only pressure of meaning is head pressure.
And pump capacity as measured by pressure if not naturally
circulating.
Mine had no gauges, but the circ pump working was evident by a slight
flow noise.
That circ pump system is still running fine after maybe 50 years.

The other system I had was even older, and entirely natural
convection.
Both were 2-story houses.
These are really simple systems, and I suspect your problem is
incomplete bleeding.
Could be wrong though.
Please let us know how it gets resolved.

--Vic

On Jan 19, 8:30*pm, AmateurRob
wrote:
Thanks for all the replies - I'll try to address most of them with this
reply:

- System has not been emptied recently (other than a isolating a couple
of radiators when I've re-PTFE'd the rad tails) and I've been getting
rid of air for a few months now - can't believe there's that much air in
there!

- No leaks from pressure relief valve near expansion vessel - there's a
pipe that goes to a drain that's been dry the whole time.

- I've assumed expansion vessel is fine since (a) no water from air
inlet (b) only a small rise in cold-hot pressure change (0.1bar).

- Pressure holds all the time - it only loses pressure when I bleed the
air out.

- Got some inhibitor to add, but I wanted to make sure I'd sorted the
leaks before I added it (and then diluted it with refills). *Might add
that to eliminate the 'hydrogen' gas possibility.

- I suppose boiler leak is a possibility - I'm going to get it serviced
and will find out then.

- I'll re-bleed all the rads again to eliminate as much as possible.

- Can someone tell me what gauge pressure (in the cellar) I should set
so that my ground floor, 1st floor and 2nd floor rads are at the right
pressure (plus it's a Victorian house so the ceiling/height of each
floor is 9 or 10feet)

Thanks,
Rob.

--
AmateurRob

The purpose of the expansion vessel is to take up the expansion of
water when the system warms up.
You should see a rise in pressure as the system warms.
When it cools to it's initial temperature, it should return to the
initial pressure.
If the pressure is less after every heat cycle, you are losing water
somewhere.
If this is happening, eventually after a few cycles it will get to
zero and then below zero and you will get air sucked into the system.
This is the classic sign of pressure vessel problems.

Have your tied a plastic bag ove rthe safety valve outlet to check if
it's coming from there?
This is where the water escapes in 99%of cases (due to expansion
vessel problems)
You can't tell by just looking, the water comes out in drips and may
evaporate especially as it's warm.

For every foot head of water you get 0.4436 psi of pressure.
So, you will get a pressure difference in you case of around 12 psi
between the highest and lowest parts of you system (when the pump is
not running).

15psi = 1bar approx.

On Jan 19, 3:30*pm, AmateurRob
wrote:
...
- Can someone tell me what gauge pressure (in the cellar) I should set
so that my ground floor, 1st floor and 2nd floor rads are at the right
pressure (plus it's a Victorian house so the ceiling/height of each
floor is 9 or 10feet)


Never been to HVAC school but I've heard "10 pounds per floor" is
standard. So in a slab house 10 pounds is enough, 20 pounds in a
ranch with the boiler in the basement...

Using that 'rule' you would need 40lbs. My mother's house is two
floors (10 feet) with a basement and has always been set to 35lbs.

If it were me I would check the specs on the boiler and go just shy
(5lbs) of the max when cold. Run it up to temp and make sure the
pressure doesn't get too high.

Well, at .434 psi per foot of height, that 10 psi per floor might be a bit
much.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"Limp Arbor" wrote in message
...

Never been to HVAC school but I've heard "10 pounds per floor" is
standard. So in a slab house 10 pounds is enough, 20 pounds in a
ranch with the boiler in the basement...

Using that 'rule' you would need 40lbs. My mother's house is two
floors (10 feet) with a basement and has always been set to 35lbs.

If it were me I would check the specs on the boiler and go just shy
(5lbs) of the max when cold. Run it up to temp and make sure the
pressure doesn't get too high.