My CH system and Immersion hot water system uses two tanks. One tank is
directly above a solid fuel stove that feeds the indirect heating coil. This
tank does NOT have an immersion heater fitted. The base height of this tank
is about 2.5 meters above the ground. My seconf hot water tank is under the
stairs and at ground level. This tank IS fitted with an immesion. The
distance between the two tanks is about 30 foot as the pipe flies.

These two tanks are connected together by two pipes and I've fitted a
transfer pump in the loop so that in the winter when I have the fire going
full blast I can have one bath from the water provided by the immersion
heater and then turn the pump on for ten minutes to transfer the water from
the FIRE tank to the IMMERSION tank and let others have a bath quicker.

A slight problem occurs in the summer when the fire is let to go out and
there is only cold water in the upper FIRE tank. The hot water from the
lower IMMERSION tank now percolates its way to the higher, colder tank.
Heating it aswell.

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Any ideas Guys?


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On Sat, 30 Jul 2005 15:28:24 -0500, "Chris
wrote:

My CH system and Immersion hot water system uses two tanks. One tank is
directly above a solid fuel stove that feeds the indirect heating coil. This
tank does NOT have an immersion heater fitted. The base height of this tank
is about 2.5 meters above the ground. My seconf hot water tank is under the
stairs and at ground level. This tank IS fitted with an immesion. The
distance between the two tanks is about 30 foot as the pipe flies.

These two tanks are connected together by two pipes and I've fitted a
transfer pump in the loop so that in the winter when I have the fire going
full blast I can have one bath from the water provided by the immersion
heater and then turn the pump on for ten minutes to transfer the water from
the FIRE tank to the IMMERSION tank and let others have a bath quicker.

A slight problem occurs in the summer when the fire is let to go out and
there is only cold water in the upper FIRE tank. The hot water from the
lower IMMERSION tank now percolates its way to the higher, colder tank.
Heating it aswell.

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Any ideas Guys?



First of all, with this somewhat unusual arrangement, hopefully you
have made sure that there is a clear vent path from both cylinders to
the feed/expansion tank. This should be an individual one from each
and anything else that you add should not block this in any way.

I can think of two solutions:

- A zone valve arranged in series with the pump and powered by the
same supply. When you turn on the pump, the valve opens as well.

- A swing check valve in series with the pump. It remains closed
unless the flow from the pump opens it. Convection would not be
enough.

http://www.bes.ltd.uk/products/098.asp




--

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On Sat, 30 Jul 2005 15:28:24 -0500, "Chris
wrote:

My CH system and Immersion hot water system uses two tanks. One tank is
directly above a solid fuel stove that feeds the indirect heating coil. This
tank does NOT have an immersion heater fitted. The base height of this tank
is about 2.5 meters above the ground. My seconf hot water tank is under the
stairs and at ground level. This tank IS fitted with an immesion. The
distance between the two tanks is about 30 foot as the pipe flies.

These two tanks are connected together by two pipes and I've fitted a
transfer pump in the loop so that in the winter when I have the fire going
full blast I can have one bath from the water provided by the immersion
heater and then turn the pump on for ten minutes to transfer the water from
the FIRE tank to the IMMERSION tank and let others have a bath quicker.

A slight problem occurs in the summer when the fire is let to go out and
there is only cold water in the upper FIRE tank. The hot water from the
lower IMMERSION tank now percolates its way to the higher, colder tank.
Heating it aswell.

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Any ideas Guys?


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x-- 30+ Days Binary Retention with High Completion
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One tank, with both coil and imersion. A possible problem with this is
overheating of the water ?

Rick

Chris McBrien wrote:
My CH system and Immersion hot water system uses two tanks. One tank is
directly above a solid fuel stove that feeds the indirect heating coil. This
tank does NOT have an immersion heater fitted. The base height of this tank
is about 2.5 meters above the ground. My seconf hot water tank is under the
stairs and at ground level. This tank IS fitted with an immesion. The
distance between the two tanks is about 30 foot as the pipe flies.

These two tanks are connected together by two pipes and I've fitted a
transfer pump in the loop so that in the winter when I have the fire going
full blast I can have one bath from the water provided by the immersion
heater and then turn the pump on for ten minutes to transfer the water from
the FIRE tank to the IMMERSION tank and let others have a bath quicker.

A slight problem occurs in the summer when the fire is let to go out and
there is only cold water in the upper FIRE tank. The hot water from the
lower IMMERSION tank now percolates its way to the higher, colder tank.
Heating it aswell.

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Any ideas Guys?


The two hot water storage tanks should be connected in series, i.e.,

i) the cold feed from the cold water storage tank goes into the lowest
cylinder at the base.
ii) The hot water outlet goes from the top of the lower cylinder and
connects to the cold feed at the base of the higher cylinder.
iii) The hot water outlet from the top of the higher cylinder connects
to the HW distribution system.

For all practical purposes you could regard this as one cylinder. Put
the immersion heater into the upper cylinder.

The DHW pump should have a bronze impeller, NOT a standard CH pump.
I'd consider connecting a CH pump to a pair of closely-spaced tees on
the return from the upper cylinder, and connect this to the indirect
coil of the lower cylinder to heat it.

Andy Hall wrote:

I can think of two solutions:

- A swing check valve in series with the pump. It remains closed
unless the flow from the pump opens it. Convection would not be
enough.

http://www.bes.ltd.uk/products/098.asp

I recently did exactly that, fitting a BES swing-check valve to stop
gravity circulation between a thermal store and a hot water storage
cylinder on the floor above. It didn't work. Gravity
circulation/convection exerts sufficient differential pressure to keep
the swing-check valve open; in fact, it made no discernible difference.

A spring-check valve may have worked. I'm going to amend it to plan B,
a NC zone valve.

- A zone valve arranged in series with the pump and powered by the
same supply. When you turn on the pump, the valve opens as well.

Yes, I'd recommend that. Fitting the immersion heater to the upper tank
is the best plan, IMHO.

First, regarding the dual venting of both tanks.

In all fairness I did this system 22 years ago and first time I only
properly vented the one tank. I ASS-U-ME'd that the two connecting/transfer
pipes would allow the air back into the unvented tank... WRONG ! The first
time I drained the system (during the installation) I popped my head into
the loft and 14.7 psi on the outside and 0psi on the inside of the tank had
done its job and crushed the tank. We/I learned from that and put a hole
through 23 inches of Granite to get a vent pipe through and back to the cold
water source tank. Problem solved.

The motorized zone valve, switched with the pump, seems to be the logigal
answer. Beleive it or not I did buy one some seven years ago but.....

If I put the immersion into the upper FIRE tank I would not have any hot
water in the lower IMMERSION tank unless I used the transfer pump. The idea
was to get a second load of hot water into the IMMERSION tank from the FIRE
tank quickly, rather than switch the immersion on again.
The whole problem is caused by this 23 inch Granite wall that virtually
splits the house and the distance between the two tanks. I have to have the
FIRE tank right above the fire so that the pipe run to the indirect heating
loop is fairly short.

Thanks for the "Swing Valve" pointer, never knew they existed. Why only BSP
fitting? Are they more of an industrial device.

Thanks again guys. This is a great board.


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"Chris McBrien" wrote in message
. ..
First, regarding the dual venting of both tanks.

In all fairness I did this system 22 years ago and first time I only
properly vented the one tank. I ASS-U-ME'd that the two
connecting/transfer
pipes would allow the air back into the unvented tank... WRONG ! The
first
time I drained the system (during the installation) I popped my head into
the loft and 14.7 psi on the outside and 0psi on the inside of the tank
had
done its job and crushed the tank. We/I learned from that and put a hole
through 23 inches of Granite to get a vent pipe through and back to the
cold
water source tank. Problem solved.

The motorized zone valve, switched with the pump, seems to be the logigal
answer. Beleive it or not I did buy one some seven years ago but.....

If I put the immersion into the upper FIRE tank I would not have any hot
water in the lower IMMERSION tank unless I used the transfer pump. The
idea
was to get a second load of hot water into the IMMERSION tank from the
FIRE
tank quickly, rather than switch the immersion on again.
The whole problem is caused by this 23 inch Granite wall that virtually
splits the house and the distance between the two tanks. I have to have
the
FIRE tank right above the fire so that the pipe run to the indirect
heating
loop is fairly short.

Thanks for the "Swing Valve" pointer, never knew they existed. Why only
BSP
fitting? Are they more of an industrial device.

Thanks again guys. This is a great board.

Firstly terminology:
tank = cold water storage tank
cylinder = hot water storage cylinder

Do don't mention where the hot water draw-off comes from and how the two
cylinders are vented.

I would do this:

1. Have the FIRE cylinder as a "pre-heat" for the IMMERSION cylinder
2. No pump between.
3. Take the cold feed of the cold water storage tank into the bottom of the
FIRE cylinder.
4. From the top of the FIRE cylinder, DHW draw-off, take an open vent over
the cold tank
5. Take a pipe from the top of the FIRE cylinder, DHW draw-off connection,
to the cold feed of the IMMERSION cylinder.
6. From the top of the IMMERSION cylinder have a vent pipe over the cold
water storage tank, and from pipe take the hot draw off to the taps. So,
eaxch cylinder has a vent pipe each.
7. Remove the two cyldiners connection pipes.
8. Remove the pump.

- Both cylinders will be vented, so no implosions.
- No natural circulation between the cylinders
- One cylinder feeds the other. This acts as preheat in winter and pre-heat
in summer too as the water in the FIRE cylinder will be warmer than the
water in the cold water storage tank

Simple no need for pumps.

On Sat, 30 Jul 2005 15:28:24 -0500, "Chris
wrote:

My CH system and Immersion hot water system uses two tanks. One tank is
directly above a solid fuel stove that feeds the indirect heating coil. This
tank does NOT have an immersion heater fitted. The base height of this tank
is about 2.5 meters above the ground. My seconf hot water tank is under the
stairs and at ground level. This tank IS fitted with an immesion. The
distance between the two tanks is about 30 foot as the pipe flies.

These two tanks are connected together by two pipes and I've fitted a
transfer pump in the loop so that in the winter when I have the fire going
full blast I can have one bath from the water provided by the immersion
heater and then turn the pump on for ten minutes to transfer the water from
the FIRE tank to the IMMERSION tank and let others have a bath quicker.

A slight problem occurs in the summer when the fire is let to go out and
there is only cold water in the upper FIRE tank. The hot water from the
lower IMMERSION tank now percolates its way to the higher, colder tank.
Heating it aswell.

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Any ideas Guys?

Hi,

I'd have thought a sprung single check valve is enough to stop
convection, if not try a differential bypass valve as used in CH:

http://www.screwfix.com/app/sfd/cat/pro.jsp?id=67854#

cheers,
Pete.

The two pipes used to transfer the water between the two CYLINDERS were already insta=
lled when the house was modernised back in 1981. Only one cylinder was installed then=
and that was the IMMERSION cylinder. The house heating system then was electric stor=
age radiators... =C2=A3=C2=A3=C2=A3. I then installed a big cast iron Bont ESSE IV (=
12kWatts) solid fuel room heater with a water jacket. This had to fit into the 23 inch t=
hick Granite wall. The cylinder for the FIRE had to be right above it. I then "Teed" the=
two existing pipes into the new tank so that I could transfer the FIRE cylinder water t=
o the IMMERSION cylinder. There is no need to transfer hot water in the other directio=
n. OK the cold water from the IMMERSION gets transferred to the FIRE cylinder.

I will go ahead with the zone valve as I do have one. There are a pair of free contacts in t=
he zone valve that can be used to switch the pump on when the valve is open

Thanks again guys.


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On Sun, 31 Jul 2005 07:09:08 -0500, "Chris
wrote:

I will go ahead with the zone valve as I do have one. There are a pair of free contacts in the zone valve that can be used to switch the pump on when the valve is open


Good point on using the aux contacts - that is the right way and in a
more conventional design they are used to give the demand signal to
the boiler and indirectly the pump; this all happening once the valve
has opened.

Another thing that you could perhaps do is to fit a cylinder
thermostat on the FIRE cylinder and use that to open the valve....




--

..andy

To email, substitute .nospam with .gl

On Sat, 30 Jul 2005 15:28:24 -0500, "Chris
wrote:

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Can you mount the immersion tank _above_ the fire tank ?

With my experience of solid fuel waterheating, I've never been short of
heating capacity when the fire was lit and I've often been short of HW
storage after the fire had gone out. I'd have no problem with the fire
always heating both tanks, with thermosyphon circulation between both.
Obviously having the immersion in the upper tank and discouraging
circulation would be an improvement from that point too.

Another solution might be to rename the upper tank "single", the lower
tank "extra" and fit an immersion into the upper tank. Use the pump when
you want extra HW storage, otherwise just use the upper tank for
everything.

"Andy Dingley" wrote in message
...
On Sat, 30 Jul 2005 15:28:24 -0500, "Chris
wrote:

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Can you mount the immersion tank _above_ the fire tank ?

He said he can't do that.

Andy Dingley wrote:

On Sat, 30 Jul 2005 15:28:24 -0500, "Chris
wrote:

It is impossible to set the two tanks at the same hydrostatic height in
order to stop this natural transfer.

Can you mount the immersion tank _above_ the fire tank ?

With my experience of solid fuel waterheating, I've never been short of
heating capacity when the fire was lit and I've often been short of HW
storage after the fire had gone out. I'd have no problem with the fire
always heating both tanks, with thermosyphon circulation between both.
Obviously having the immersion in the upper tank and discouraging
circulation would be an improvement from that point too.

Another solution might be to rename the upper tank "single", the lower
tank "extra" and fit an immersion into the upper tank. Use the pump when
you want extra HW storage, otherwise just use the upper tank for
everything.

On a similar note I wish to add 2 solar panels to heat dhw. These have been
rescued from a swimming pool dismantling. I have been discussing it with
people on uk.environment and posted some pictures of what I think Ishould
do to make use of the panels and take the opportunity to plumb in a wood
stove back boiler.

Currently I use gas to heat a 60ltre cyclinder in summer. Some concerns have
been expressed that this will be causing waseful short cycling of the
boiler. I wonder what evidence there is for this. It has been suggested
that the short cycling would make the boiler less efficient than an offpeak
immersion, with a given daily loss from the tank of ~2kWhrs(t).

To make any sensible use of the solar I will need increased cylinder
capacity and this can only easily be fitted one floor below the current
cylinder, this makes a direct connection to the wood boiler more practical.

I have put a shematic at www.wokingnursery.co.uk/temp/solarpanel.html and
the main picture of the panels is followed by the proposed schematic and
the possible roof site for the panels, this is overdue for repair already.

AJH

I can put an immersion into the FIRE cylinder but my bathroom and shower are
right next to and above the IMMERSION cylinder so that's where the main hot
water usage is. The kitchen sink is at the other end of the house and tends
to use the hot/warm water from the FIRE cylinder as it is closer. The FIRE
cylinder only gets really hot when I turn off the CH pump so that all
12kWatts of the solid fuel stove goes into the indirect heating loop of the
FIRE cylinder. Then the water is worth transferring to the IMMERSION
cylinder to get a saving on its use.

I've looked at the BES website mentioned above and because the sring valve
is so cheap I'm going to give that a try first. If it fails I'll go back to
plan (a) and fit the zone valve.

Great to bounce these ideas around... Chris.


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Chris McBrien wrote:
I my bathroom and shower are
right next to and above the IMMERSION cylinder so that's where the main hot
water usage is. The kitchen sink is at the other end of the house and tends
to use the hot/warm water from the FIRE cylinder as it is closer.

If this is so, it suggests that you have the two cylinders connected in
parrallel. If so, when you turn on a hot tap, you will get some water
from both cylinders simultaneously. If one is hot and the other cold,
this will be a problem.


The DHWS pipework from the 2 cylinders should be connected in series,
see above. All the hot water supplied should be coming out of the top
outlet of the FIRE cylinder

I've looked at the BES website mentioned above and because the sring valve
is so cheap I'm going to give that a try first. If it fails I'll go back to
plan (a) and fit the zone valve.

You shouldn't have any valves in the open vent pipe from the top of the
cylinders, zone valves and check valves included.

Hi,

I'm aware the convection is in the same direction that the water is
pumped. The pump will be able to overcome the resistance of the check
valve or bypass valve, whereas the convection currents won't.

Another way to do it would be take the hot output from the top of the
immersion tank to the same level as the bottom of the tank or below,
before going to the other tank.

If you want to fit a zone valve, by all means do so

cheers,
Pete.

There are NO valves, check or zone, in the vent pipes of either the FIRE
cylinder or the IMMERSION cylinder.

My very initial mistake, 22 years ago was to omit the vent pipe on the FIRE
cylinder as I ASS-U-ME'd that the transfer pipework would allow the vent on
the IMMERSION cylinder to take care of matters. As I said earlier, I did
learn from that mistake.

Must go for a Pint. Its been a long day.

Chris.


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"Chris McBrien" wrote in message
. ..
I can put an immersion into the FIRE cylinder but my bathroom and shower
are
right next to and above the IMMERSION cylinder so that's where the main
hot
water usage is. The kitchen sink is at the other end of the house and
tends
to use the hot/warm water from the FIRE cylinder as it is closer. The FIRE
cylinder only gets really hot when I turn off the CH pump so that all
12kWatts of the solid fuel stove goes into the indirect heating loop of
the
FIRE cylinder. Then the water is worth transferring to the IMMERSION
cylinder to get a saving on its use.

I've looked at the BES website mentioned above and because the sring valve
is so cheap I'm going to give that a try first. If it fails I'll go back
to
plan (a) and fit the zone valve.

Great to bounce these ideas around... Chris.

I still don't know how the cylinders are vented and how the hot draw-offs
are configured.

"Aidan" wrote in message
oups.com...

Chris McBrien wrote:
I my bathroom and shower are
right next to and above the IMMERSION cylinder so that's where the main
hot
water usage is. The kitchen sink is at the other end of the house and
tends
to use the hot/warm water from the FIRE cylinder as it is closer.

If this is so, it suggests that you have the two cylinders connected in
parrallel. If so, when you turn on a hot tap, you will get some water
from both cylinders simultaneously. If one is hot and the other cold,
this will be a problem.

That is why it is a silly idea