Hi

I've been helping a friend get her canal boat 'ship shape' and the heating
sytem is most odd, there's a log burner with some sort of back boiler and
pipes that run from one end of the boat to the other, via the radiatoirs.
The pump (a small 12v affair) is at the rear in the engine bay and there is
a loop of pipe that goes up and over before going to the inlet of the pump.
This loop seems to alway get air in it, it does have a bleed valve but it's
a pain to keep having to bleed it. Also you have to bleed it with the pump
off otherwise the pump just sucks more air in.
My question is this, can I put an autmatic vent valve onto this loop,
bearing in mind it's on the inlet side of the pump and only 6in away from
it, or will it just result in more air being sucked into the system. If it's
not a problem then it will make life easier in keeping air out of the
system.

many thanks

STeve

"stevet" wrote in message
...
Hi

I've been helping a friend get her canal boat 'ship shape' and the heating
sytem is most odd, there's a log burner with some sort of back boiler and
pipes that run from one end of the boat to the other, via the radiatoirs.
The pump (a small 12v affair) is at the rear in the engine bay and there is
a loop of pipe that goes up and over before going to the inlet of the pump.
This loop seems to alway get air in it, it does have a bleed valve but it's
a pain to keep having to bleed it. Also you have to bleed it with the pump
off otherwise the pump just sucks more air in.
My question is this, can I put an autmatic vent valve onto this loop,
bearing in mind it's on the inlet side of the pump and only 6in away from
it, or will it just result in more air being sucked into the system. If it's
not a problem then it will make life easier in keeping air out of the
system.

many thanks

STeve



The little rise in the pipe is actually there to catch the air bubbles, before
they get to the pump, and bleed them off. It might actually help to extend the
pipe, that the bleed nipple is on, further up. The extension will catch more
bubbles at a time, and should make it easier to bleed the system of all the
bubbles at one time.

Why does it actually need to be bled frequently anyway?

"BigWallop" wrote in message
k...

"stevet" wrote in message
...
Hi

I've been helping a friend get her canal boat 'ship shape' and the
heating
sytem is most odd, there's a log burner with some sort of back boiler
and
pipes that run from one end of the boat to the other, via the
radiatoirs.
The pump (a small 12v affair) is at the rear in the engine bay and there
is
a loop of pipe that goes up and over before going to the inlet of the
pump.
This loop seems to alway get air in it, it does have a bleed valve but
it's
a pain to keep having to bleed it. Also you have to bleed it with the
pump
off otherwise the pump just sucks more air in.
My question is this, can I put an autmatic vent valve onto this loop,
bearing in mind it's on the inlet side of the pump and only 6in away
from
it, or will it just result in more air being sucked into the system. If
it's
not a problem then it will make life easier in keeping air out of the
system.

many thanks

STeve



The little rise in the pipe is actually there to catch the air bubbles,
before
they get to the pump, and bleed them off. It might actually help to
extend the
pipe, that the bleed nipple is on, further up. The extension will catch
more
bubbles at a time, and should make it easier to bleed the system of all
the
bubbles at one time.

Why does it actually need to be bled frequently anyway?

A stupid suggestion?
A canal boat is probably rarely in rough water?
So why does the system have to be a closed loop? Could it not be an open
system with a small 'header' tank at the high point in the system? Any air
in the system would circulate to the high point and 'bubble off' to be
replaced by water through gravity?

On Mon, 10 Jan 2005 00:38:52 -0330, Terry wrote:

So why does the system have to be a closed loop?

For the same reason that domestic systems are closed loops, to keep
oxygen out of the water. Even open vented systems the the water does
not circulate through the header tank (or shouldn't).

Got to admit I don't like the idea of a woodburner with boiler that
doesn't have gravity as the means of circulating the water. If the
pump fails or auxillary battery goes flat the water in the boiler will
boil PDQ and the resultant steam has no where to go...

--
Cheers
Dave. pam is missing e-mail

I've cross posted this to uk.rec.waterways, where the pros and cons of
gravity versus pumped hot water from stoves is a perennial topic of
conversation. Well, it's a change from toilets.

On Sun, 9 Jan 2005 22:53:23 -0000, "stevet"
wrote:

Hi

I've been helping a friend get her canal boat 'ship shape' and the heating
sytem is most odd, there's a log burner with some sort of back boiler and
pipes that run from one end of the boat to the other, via the radiatoirs.
The pump (a small 12v affair) is at the rear in the engine bay and there is
a loop of pipe that goes up and over before going to the inlet of the pump.
This loop seems to alway get air in it, it does have a bleed valve but it's
a pain to keep having to bleed it. Also you have to bleed it with the pump
off otherwise the pump just sucks more air in.
My question is this, can I put an autmatic vent valve onto this loop,
bearing in mind it's on the inlet side of the pump and only 6in away from
it, or will it just result in more air being sucked into the system. If it's
not a problem then it will make life easier in keeping air out of the
system.

many thanks

STeve


--
On-line canal route planner: http://www.canalplan.org.uk

(Waterways World site of the month, April 2001)

"Nick Atty" wrote in message
...
I've cross posted this to uk.rec.waterways, where the pros and cons of
gravity versus pumped hot water from stoves is a perennial topic of
conversation. Well, it's a change from toilets.

I saw a rather "well used" Hudson boat last year in Braunston with a can on
the roof and a bit of plastic pipe going into the beam across the roof at
the front of the cabin, so I asked the owner about it and the explanation
was as follows.

He was going to make the roof beam into a header tank for his heating
system as it was the highest point of the boat and fully welded on all
seams. From this he had run a large diameter copper pipe the length of the
boat just below the ceiling inside the accommodation and another along the
floor. These were the flow and return for his heating system. He had spaced
radiators down the length of the boat just below gunwale level connected
between the high and low level pipes flow and return. His back boiler on his
stove which was in the front corner of the cabin was also connected to
these pipes.
He now has a gravity feed central heating system that requires no
electricity/pumps etc no danger of an air lock getting in the boiler, in the
absence of a leak no chance of the boiler running dry when hot. It all just
works

--
Brian
From Sunny Suffolk

I've been helping a friend get her canal boat 'ship shape' and the heating
sytem is most odd, there's a log burner with some sort of back boiler and
pipes that run from one end of the boat to the other, via the radiatoirs.
The pump (a small 12v affair) is at the rear in the engine bay and there is
a loop of pipe that goes up and over before going to the inlet of the pump.
This loop seems to alway get air in it, it does have a bleed valve but it's
a pain to keep having to bleed it. Also you have to bleed it with the pump
off otherwise the pump just sucks more air in.
My question is this, can I put an autmatic vent valve onto this loop,
bearing in mind it's on the inlet side of the pump and only 6in away from
it, or will it just result in more air being sucked into the system. If it's
not a problem then it will make life easier in keeping air out of the

An automatic vent has to be on outlet side, ie positive pressure. You
need to find where the air is getting into the system and cure that,
and, or move the pump down-stream to a position where it wont suck air.
Air, or rather oxygen in the system on a continuous basis is a
'very-bad-thing' it'll rot your radiators in no time. There is some
mechanism in the system to allow expansion of the heated water I hope,
is air entering thru that, as when the system cools.
g

Geoff wrote:


and, or move the pump down-stream to a position where it wont suck air.


I lied, move the pump UPstream, sorry

Geoff

A bit more info about the system, it's an open system with a header tank
that's inside the boat, it can only hold about 5 litres. It's not at the
highest point in the system though as the pipe from the burner goes up and
right over the top of the cabin and is probably a couple of inches higher
that the tank. There's also a vent outlet that goes out through the roof
that is permamently vented, it has a fitting with some fibre washers in it
that seem to allow air through. The other heath robinson bit is that the
rads are connected in series so you can't turn any one of them off or down
as it would stop the flow completely.
As to getting air in the sytem, If you let the burner get too hot without
the pump running then it vents steam out through the vent valve and the
system looses a lot of water and air 'gets in', it then takes ages to bleed
everything again, hence the desire for an automatic valve.
My plan is to put a pipe thermostat on the outlet pipe from the burner and
get it to turn the pump on if the water gets too hot.
The other suggestion I like from BigWallop is to extend the bleed valve near
the pump up higher so that it can accomodate more air before it affects the
pump operation.
Or I could reposition the pump so that it's before the loop and use an
automatic valve.

thanks for all your help.

STeve




"Geoff" wrote in message
...

I've been helping a friend get her canal boat 'ship shape' and the
heating sytem is most odd, there's a log burner with some sort of back
boiler and pipes that run from one end of the boat to the other, via the
radiatoirs. The pump (a small 12v affair) is at the rear in the engine
bay and there is a loop of pipe that goes up and over before going to the
inlet of the pump. This loop seems to alway get air in it, it does have a
bleed valve but it's a pain to keep having to bleed it. Also you have to
bleed it with the pump off otherwise the pump just sucks more air in.
My question is this, can I put an autmatic vent valve onto this loop,
bearing in mind it's on the inlet side of the pump and only 6in away from
it, or will it just result in more air being sucked into the system. If
it's not a problem then it will make life easier in keeping air out of
the
An automatic vent has to be on outlet side, ie positive pressure. You need
to find where the air is getting into the system and cure that, and, or
move the pump down-stream to a position where it wont suck air. Air, or
rather oxygen in the system on a continuous basis is a 'very-bad-thing'
it'll rot your radiators in no time. There is some mechanism in the system
to allow expansion of the heated water I hope, is air entering thru that,
as when the system cools.
g

stevet wrote:
Geoff

A bit more info about the system, it's an open system with a header tank
that's inside the boat, it can only hold about 5 litres. It's not at the
highest point in the system though as the pipe from the burner goes up and
right over the top of the cabin and is probably a couple of inches higher
that the tank. There's also a vent outlet that goes out through the roof
that is permamently vented, it has a fitting with some fibre washers in it
that seem to allow air through. The other heath robinson bit is that the
rads are connected in series so you can't turn any one of them off or down
as it would stop the flow completely.
As to getting air in the sytem, If you let the burner get too hot without
the pump running then it vents steam out through the vent valve and the
system looses a lot of water and air 'gets in', it then takes ages to bleed
everything again, hence the desire for an automatic valve.
My plan is to put a pipe thermostat on the outlet pipe from the burner and
get it to turn the pump on if the water gets too hot.
The other suggestion I like from BigWallop is to extend the bleed valve near
the pump up higher so that it can accomodate more air before it affects the
pump operation.
Or I could reposition the pump so that it's before the loop and use an
automatic valve.

thanks for all your help.

STeve



Hi Steve, I'll need to spend time pondering your post, but, I do feel
your going about this all wrong.
In my opinion you 'must' prevent air from entering the system. If your
getting boiling up into the header then you must take steps to prevent
this, bloody dangerous if nothing else, can you not have the pump
running whenever the stove is alight?

stevet wrote:
Geoff

A bit more info about the system, it's an open system with a header
tank
that's inside the boat, it can only hold about 5 litres. It's not at
the
highest point in the system though as the pipe from the burner goes
up and
right over the top of the cabin and is probably a couple of inches
higher
that the tank. There's also a vent outlet that goes out through the
roof
that is permamently vented, it has a fitting with some fibre washers
in it
that seem to allow air through. The other heath robinson bit is that
the
rads are connected in series so you can't turn any one of them off or
down
as it would stop the flow completely.
As to getting air in the sytem, If you let the burner get too hot
without
the pump running then it vents steam out through the vent valve and
the
system looses a lot of water and air 'gets in', it then takes ages to
bleed
everything again, hence the desire for an automatic valve.
My plan is to put a pipe thermostat on the outlet pipe from the
burner and
get it to turn the pump on if the water gets too hot.
The other suggestion I like from BigWallop is to extend the bleed
valve near
the pump up higher so that it can accomodate more air before it
affects the
pump operation.
Or I could reposition the pump so that it's before the loop and use
an
automatic valve.

thanks for all your help.

STeve




"Geoff" wrote in message
...

I've been helping a friend get her canal boat 'ship shape' and the

heating sytem is most odd, there's a log burner with some sort of
back
boiler and pipes that run from one end of the boat to the other,
via the
radiatoirs. The pump (a small 12v affair) is at the rear in the
engine
bay and there is a loop of pipe that goes up and over before going
to the
inlet of the pump. This loop seems to alway get air in it, it does
have a
bleed valve but it's a pain to keep having to bleed it. Also you
have to
bleed it with the pump off otherwise the pump just sucks more air
in.
My question is this, can I put an autmatic vent valve onto this
loop,
bearing in mind it's on the inlet side of the pump and only 6in
away from
it, or will it just result in more air being sucked into the
system. If
it's not a problem then it will make life easier in keeping air
out of
the
An automatic vent has to be on outlet side, ie positive pressure.
You need
to find where the air is getting into the system and cure that,
and, or
move the pump down-stream to a position where it wont suck air.
Air, or
rather oxygen in the system on a continuous basis is a
'very-bad-thing'
it'll rot your radiators in no time. There is some mechanism in the
system
to allow expansion of the heated water I hope, is air entering thru
that,
as when the system cools.

Re-plumb it correctly. It'll also be quite inefficient with rads
connected in series.... and the open header tank SHOULD be the highest
point. I doubt you'll ever get it sorted the way it is.
Tony
ex-plumber on the Basy

Geoff

Your right, I plan to put a pipe thermostat on the outlet pipe of the log
burner and have this switch the pump on, it'll probably need a relay near
the pump as there's about a 50 foot run to the back of the boat and at 12v
there would probably be a lot of loss unless I used thick cable. I though of
using a timer delay relay that keeps the pump running for a time after the
stat has gone open to stop the pump from cycling on and off. That should
stop any more air getting in and then once it's all bled it will hopefully
stay that way.

many thanks

Steve

"Geoff" wrote in message
...
stevet wrote:
Geoff

A bit more info about the system, it's an open system with a header tank
that's inside the boat, it can only hold about 5 litres. It's not at the
highest point in the system though as the pipe from the burner goes up
and right over the top of the cabin and is probably a couple of inches
higher that the tank. There's also a vent outlet that goes out through
the roof that is permamently vented, it has a fitting with some fibre
washers in it that seem to allow air through. The other heath robinson
bit is that the rads are connected in series so you can't turn any one of
them off or down as it would stop the flow completely.
As to getting air in the sytem, If you let the burner get too hot without
the pump running then it vents steam out through the vent valve and the
system looses a lot of water and air 'gets in', it then takes ages to
bleed everything again, hence the desire for an automatic valve.
My plan is to put a pipe thermostat on the outlet pipe from the burner
and get it to turn the pump on if the water gets too hot.
The other suggestion I like from BigWallop is to extend the bleed valve
near the pump up higher so that it can accomodate more air before it
affects the pump operation.
Or I could reposition the pump so that it's before the loop and use an
automatic valve.

thanks for all your help.

STeve



Hi Steve, I'll need to spend time pondering your post, but, I do feel your
going about this all wrong.
In my opinion you 'must' prevent air from entering the system. If your
getting boiling up into the header then you must take steps to prevent
this, bloody dangerous if nothing else, can you not have the pump running
whenever the stove is alight?

stevet wrote:
Geoff

Your right, I plan to put a pipe thermostat on the outlet pipe of the log
burner and have this switch the pump on, it'll probably need a relay near
the pump as there's about a 50 foot run to the back of the boat and at 12v
there would probably be a lot of loss unless I used thick cable. I though of
using a timer delay relay that keeps the pump running for a time after the
stat has gone open to stop the pump from cycling on and off. That should
stop any more air getting in and then once it's all bled it will hopefully
stay that way.
Remember the pipe stat will probable switch the wrong way, ie. switch
off at high temp so you'll need the relay to correct this.
I agree with Drifter, I dont think the system as descibed is ever going
to be much good, in fact it sounds a bit unsafe, rip it out and start
over. B'ain't big dollar
g

"stevet" wrote in message
...
Geoff

Your right, I plan to put a pipe thermostat on the outlet pipe of the log
burner and have this switch the pump on, it'll probably need a relay near
the pump as there's about a 50 foot run to the back of the boat and at 12v
there would probably be a lot of loss unless I used thick cable. I though
of
using a timer delay relay that keeps the pump running for a time after the
stat has gone open to stop the pump from cycling on and off. That should
stop any more air getting in and then once it's all bled it will hopefully
stay that way.

If you are going to do that I would suggest that you have a short vertical
pipe run at the back of the boiler so the hot water in the boiler can rise
and heat the switch. If the pipe is horizontal out of the boiler, the boiler
will probably boil before the heat gets to the switch.
RS use to do switches that switched the way you want that you strapped on
pipes. Also the timer is a very good idea, otherwise the boiler heats up,
the pump starts, pulls cold water from the rads and pump cuts out, water
stops flowing and heats up, pump starts, more cold water , pump stops.
You can get a plug in timed relay that they use for heated car back windows
that would do the job nicely.

What makes you think I've been there.

--
Brian
From Sunny Suffolk

Brian

The pipe up from the boiler is vertical up to the ceiling of the boat, I'll
put the pipe stat on that run. I did phone a local auto electrical shop for
the relay and I think I've found one that will do the trick. It's a job
lined up for this weekend so I'll keep you all posted.
The 'rip it out and start again' option is definitely the best long term but
with a boat that needs to be lived in pretty soon and lots of other work
needing to be done it may have to wait until the summer.

cheers

STeve

"brian" wrote in message
...
"stevet" wrote in message
...
Geoff

Your right, I plan to put a pipe thermostat on the outlet pipe of the log
burner and have this switch the pump on, it'll probably need a relay near
the pump as there's about a 50 foot run to the back of the boat and at
12v
there would probably be a lot of loss unless I used thick cable. I though
of
using a timer delay relay that keeps the pump running for a time after
the
stat has gone open to stop the pump from cycling on and off. That should
stop any more air getting in and then once it's all bled it will
hopefully
stay that way.

If you are going to do that I would suggest that you have a short vertical
pipe run at the back of the boiler so the hot water in the boiler can rise
and heat the switch. If the pipe is horizontal out of the boiler, the
boiler
will probably boil before the heat gets to the switch.
RS use to do switches that switched the way you want that you strapped on
pipes. Also the timer is a very good idea, otherwise the boiler heats up,
the pump starts, pulls cold water from the rads and pump cuts out, water
stops flowing and heats up, pump starts, more cold water , pump stops.
You can get a plug in timed relay that they use for heated car back
windows
that would do the job nicely.

What makes you think I've been there.

--
Brian
From Sunny Suffolk