On Mon, 07 Aug 2006 00:09:05 +0100, Doctor Drivel wrote:


"John Stumbles" wrote in message
news

This works and provides excellent recovery but you do need a gravity
(not sealed/unvented) primary.

???

What do you mean '???' ?

If the primary is unvented you have an unvented hot water cylinder of 15l
requiring all the appropriate safety controls. This rapidly gets outside
DIY.

"John Stumbles" wrote in message
news
On Mon, 07 Aug 2006 00:09:05 +0100, Doctor Drivel wrote:


"John Stumbles" wrote in message
news

This works and provides excellent recovery but you do need a gravity
(not sealed/unvented) primary.

???

What do you mean '???' ?

If the primary is unvented you have an unvented hot water cylinder of 15l
requiring all the appropriate safety controls. This rapidly gets outside
DIY.

You missed it.

Some quick recovery cylinders can be quite expensive. I gave a solution
which would outperform a quick recovery vented cylinder using a bronze pump,
plate heat exchanger and cheap direct cylinder. The flow and return to the
coil would just go into the plate heat exchanger. The plate and pump
replaces the quick recovery coil. The bronze pump is switched in at the
same time DHW is called. This will take all the output of a 40,50,60kW
boiler outperforming a quick recovery coil and cheaper in many cases.

Then I said if the mains pressure is good, using a flow switch and a cheaper
pump a heat bank can be made from the same components. The cylinder will be
vented at atmospheric pressure. The only high pressure is in one side of
the plate. All cheap and works a treat.

On Tue, 08 Aug 2006 12:58:35 +0100, Doctor Drivel wrote:


"John Stumbles" wrote in message
news
On Mon, 07 Aug 2006 00:09:05 +0100, Doctor Drivel wrote:


"John Stumbles" wrote in message
news

This works and provides excellent recovery but you do need a gravity
(not sealed/unvented) primary.

???

What do you mean '???' ?

If the primary is unvented you have an unvented hot water cylinder of 15l
requiring all the appropriate safety controls. This rapidly gets outside
DIY.

You missed it.

I don't think so ...

Some quick recovery cylinders can be quite expensive. I gave a solution
which would outperform a quick recovery vented cylinder using a bronze pump,
plate heat exchanger and cheap direct cylinder. The flow and return to the
coil would just go into the plate heat exchanger. The plate and pump
replaces the quick recovery coil. The bronze pump is switched in at the
same time DHW is called. This will take all the output of a 40,50,60kW
boiler outperforming a quick recovery coil and cheaper in many cases.

Yes I got that but that wasn't what I was talking about.

Then I said if the mains pressure is good, using a flow switch and a cheaper
pump a heat bank can be made from the same components. The cylinder will be
vented at atmospheric pressure. The only high pressure is in one side of
the plate. All cheap and works a treat.

Yes, that was what I was responding to. I said that it gives excellent
recovery (which mine certainly does) but I pointed out that the primary
must be vented (which you didn't specifically mention in your earlier post
though you do above).

So are we agreed?
Vented primary + direct cylinder + pump + flow switch + PHE = DIY heat
bank/thermal store.

My only reservation is that with my cheap standard direct cylinder
("Screwfix Direct direct cylinder") the amount of hot water you get from
it off the electric immersion is probably only enough for a shower. I
think it really needs a larger cylinder, and/or maybe an immersion heater
mounted at the bottom of the cylinder to _reduce_ stratification when
heated electrically. Probably something like a large off-peak storage
cylinder would be more suitable.

On 2006-08-12 14:04:13 +0100, John Stumbles said:

My only reservation is that with my cheap standard direct cylinder
("Screwfix Direct direct cylinder") the amount of hot water you get from
it off the electric immersion is probably only enough for a shower. I
think it really needs a larger cylinder, and/or maybe an immersion heater
mounted at the bottom of the cylinder to _reduce_ stratification when
heated electrically. Probably something like a large off-peak storage
cylinder would be more suitable.

I suspect that this will generally be a problem with immersion heaters anyway.

If you dump heat into an indirect cylinder from a boiler at 25-30kW,
there will be considerable convection currents inside the cylinder.
Obviously a direct cylinder is something else.

With an immersion running at 3kW, there is much less convection, as
witness the stratification that occurs anyway.

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

"John Stumbles" wrote in message
news
On Tue, 08 Aug 2006 12:58:35 +0100, Doctor Drivel wrote:


"John Stumbles" wrote in message
news
On Mon, 07 Aug 2006 00:09:05 +0100, Doctor Drivel wrote:


"John Stumbles" wrote in message
news
This works and provides excellent recovery but you do need a gravity
(not sealed/unvented) primary.

???

What do you mean '???' ?

If the primary is unvented you have an unvented hot water cylinder of
15l
requiring all the appropriate safety controls. This rapidly gets outside
DIY.

You missed it.

I don't think so ...

No, you never. We shall see.

Some quick recovery cylinders can be quite expensive. I gave a solution
which would outperform a quick recovery vented cylinder using a bronze
pump,
plate heat exchanger and cheap direct cylinder. The flow and return to
the
coil would just go into the plate heat exchanger. The plate and pump
replaces the quick recovery coil. The bronze pump is switched in at the
same time DHW is called. This will take all the output of a 40,50,60kW
boiler outperforming a quick recovery coil and cheaper in many cases.

Yes I got that but that wasn't what I was talking about.

Then I said if the mains pressure is good, using a flow switch and a
cheaper
pump a heat bank can be made from the same components. The cylinder will
be
vented at atmospheric pressure. The only high pressure is in one side of
the plate. All cheap and works a treat.

Yes, that was what I was responding to. I said that it gives excellent
recovery (which mine certainly does) but I pointed out that the primary
must be vented (which you didn't specifically mention in your earlier post
though you do above).

The primary does not have to be vented at all. The cylinder can be heated
via a coil and the primaries a part of a sealed unvented system. The only
time they require venting, is if the cylinder is being heated directly.

So are we agreed?

You never got it.

Vented primary + direct cylinder + pump + flow switch + PHE = DIY heat
bank/thermal store.

It doesn't have to be heated directly.

My only reservation is that with my cheap standard direct cylinder
("Screwfix Direct direct cylinder") the amount of hot water you get from
it off the electric immersion is probably only enough for a shower. I
think it really needs a larger cylinder, and/or maybe an immersion heater
mounted at the bottom of the cylinder to _reduce_ stratification when
heated electrically. Probably something like a large off-peak storage
cylinder would be more suitable.

A large thermal store is an advantage if electric only. But an eletric
boiler and pump will heat it up reasonably fast.

"Andy Hall" wrote in message
...
On 2006-08-12 14:04:13 +0100, John Stumbles
said:

My only reservation is that with my cheap standard direct cylinder
("Screwfix Direct direct cylinder") the amount of hot water you get from
it off the electric immersion is probably only enough for a shower. I
think it really needs a larger cylinder, and/or maybe an immersion heater
mounted at the bottom of the cylinder to _reduce_ stratification when
heated electrically. Probably something like a large off-peak storage
cylinder would be more suitable.

I suspect that this will generally be a problem with immersion heaters
anyway.

If you dump heat into an indirect cylinder from a boiler at 25-30kW, there
will be considerable convection currents inside the cylinder.

Nope. Having a TMV (UFH type) on the boiler flow/return ensures only up to
temp water enters the cylinder. From heat from cold of 20C the cylinder
will heat from top down. You can feel the line of say 75C working its way
down the cylinder, while just below the line it is 20C. Stratification is
maintained

On 2006-08-12 16:48:12 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2006-08-12 14:04:13 +0100, John Stumbles said:

My only reservation is that with my cheap standard direct cylinder
("Screwfix Direct direct cylinder") the amount of hot water you get from
it off the electric immersion is probably only enough for a shower. I
think it really needs a larger cylinder, and/or maybe an immersion heater
mounted at the bottom of the cylinder to _reduce_ stratification when
heated electrically. Probably something like a large off-peak storage
cylinder would be more suitable.

I suspect that this will generally be a problem with immersion heaters anyway.

If you dump heat into an indirect cylinder from a boiler at 25-30kW,
there will be considerable convection currents inside the cylinder.

Nope.

Yes.

Having a TMV (UFH type) on the boiler flow/return ensures only up to
temp water enters the cylinder.

Additional component.

From heat from cold of 20C the cylinder will heat from top down. You
can feel the line of say 75C working its way down the cylinder, while
just below the line it is 20C. Stratification is maintained

I was talking about heating with a coil. In that case, it certainly isn't

"Andy Hall" wrote in message
...
On 2006-08-12 16:48:12 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2006-08-12 14:04:13 +0100, John Stumbles
said:

My only reservation is that with my cheap standard direct cylinder
("Screwfix Direct direct cylinder") the amount of hot water you get
from
it off the electric immersion is probably only enough for a shower. I
think it really needs a larger cylinder, and/or maybe an immersion
heater
mounted at the bottom of the cylinder to _reduce_ stratification when
heated electrically. Probably something like a large off-peak storage
cylinder would be more suitable.

I suspect that this will generally be a problem with immersion heaters
anyway.

If you dump heat into an indirect cylinder from a boiler at 25-30kW,
there will be considerable convection currents inside the cylinder.

Nope.

Yes.

snip stupidity

Matt, you are stupid and should not comment on things you know sweet FA
about. Post about Makitas, that is your level.

On Sat, 12 Aug 2006 16:43:53 +0100, Doctor Drivel wrote:

The primary does not have to be vented at all. The cylinder can be
heated via a coil and the primaries a part of a sealed unvented system.
The only time they require venting, is if the cylinder is being heated
directly.

The primary _does_ have to be vented if you are using an ordinary
direct cylinder which is what we were talking about. Or actually what
_you_ were talking about and what I followed up on.

I know, you know, you know that I know and I know that you know that
thermal stores can be heated indirectly, but this is not what we were
talking about.

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of your hot water capacity through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on the
output of the PHE.

On 2006-08-15 00:48:54 +0100, John Stumbles said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of your hot water capacity through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on the
output of the PHE.

Starting to get complicated, though, isn't it....

"John Stumbles" wrote in message
news
On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set
to 75 degrees or more, the energy
storage will be more limited vs.
running at boiler flow temperatures.

If the cylinder has German insulation standards they heat loss is minimal.
Levels in the UK are dire.

This is exacerbated in systems
using external (plate) heat exchangers
because the pump circulating water
round the PHE runs at full bore
regardless of the demand,
so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of
your hot water capacity through
mixing within the cylinder long before you
would have done

With adequate speading pipes in the cylinder this is not a big issue.

if you were
drawing only enough to provide the amount
of DHW demanded. It should be
easy enough to fix this either cleverly
by modulating the pump

Yep, as Gledhill do.

or brute-force by restricting the flow with
a TRV type affair.

Yep, put a 2-port valve on the primaries from the cylinder that serve the
PHE and have a remote sensor on the DHW flow to the taps. Works well.
Danfoss do a good one. You may need a pressure by-pass valve around the
thermostat 2-port valve to cope when the valve is fully closed. There is
also the Grundfoss Alpha auto variable speed pump too. Setting up is a bit
tricky as it may fight with the DHW thermostat. I have seen a few work very
well and no pressure by-pass valve needed.

Either way would have the added
benefit of doing away with the need
for a TMV on the
output of the PHE.

Yep, and another valve eliminated that reduces flow. Another is the PRV
too.

"Andy Hall" wrote in message
...
On 2006-08-15 00:48:54 +0100, John Stumbles
said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of your hot water capacity
through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on the
output of the PHE.

Starting to get complicated, though, isn't it....

No.

On 2006-08-17 22:22:52 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2006-08-15 00:48:54 +0100, John Stumbles said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of your hot water capacity through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on the
output of the PHE.

Starting to get complicated, though, isn't it....

No.

Would you be willing to subsidise the extra cost??

"Andy Hall" wrote in message
...
On 2006-08-17 22:22:52 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2006-08-15 00:48:54 +0100, John Stumbles
said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot
tap
at part flow you're liable to lose most of your hot water capacity
through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on
the
output of the PHE.

Starting to get complicated, though, isn't it....

No.

Would you be willing to subsidise the extra cost??

Matt, what are you on about.

On 2006-08-18 00:25:40 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2006-08-17 22:22:52 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2006-08-15 00:48:54 +0100, John Stumbles said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of your hot water capacity through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on the
output of the PHE.

Starting to get complicated, though, isn't it....

No.

Would you be willing to subsidise the extra cost??

Matt, what are you on about.

Meaning if you think it's not such a big deal, would you be willing to
subsidise the installer for the additional cost of the components? Do
you know what the additional cost, including the cost of diagnosing and
replacing them as a result of failures during the system lifetime?

"Andy Hall" wrote in message
...
On 2006-08-18 00:25:40 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2006-08-17 22:22:52 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message
...
On 2006-08-15 00:48:54 +0100, John Stumbles
said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow
temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot
tap
at part flow you're liable to lose most of your hot water capacity
through
mixing within the cylinder long before you would have done if you
were
drawing only enough to provide the amount of DHW demanded. It should
be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either
way
would have the added benefit of doing away with the need for a TMV on
the
output of the PHE.

Starting to get complicated, though, isn't it....

No.

Would you be willing to subsidise the extra cost??

Matt, what are you on about.

Meaning if you think it's not such a big deal, would you be willing to
subsidise the installer for the additional cost of the components? Do you
know what the additional cost, including the cost of diagnosing and
replacing them as a result of failures during the system lifetime?

Matt, you have to stop prattling ********. A 2-port remote sensor
thermostat valve is not super expensive and it eliminates a TMV too.

"Doctor Drivel" wrote in message
reenews.net...

"John Stumbles" wrote in message
news
On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set
to 75 degrees or more, the energy
storage will be more limited vs.
running at boiler flow temperatures.

If the cylinder has German insulation standards they heat loss is minimal.
Levels in the UK are dire.

This is exacerbated in systems
using external (plate) heat exchangers
because the pump circulating water
round the PHE runs at full bore
regardless of the demand,
so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of
your hot water capacity through
mixing within the cylinder long before you
would have done

With adequate speading pipes in the cylinder this is not a big issue.

if you were
drawing only enough to provide the amount
of DHW demanded. It should be
easy enough to fix this either cleverly
by modulating the pump

Yep, as Gledhill do.

or brute-force by restricting the flow with
a TRV type affair.

Yep, put a 2-port valve on the primaries from the cylinder that serve the
PHE and have a remote sensor on the DHW flow to the taps. Works well.
Danfoss do a good one. You may need a pressure by-pass valve around the
thermostat 2-port valve to cope when the valve is fully closed. There is
also the Grundfoss Alpha auto variable speed pump too. Setting up is a
bit tricky as it may fight with the DHW thermostat. I have seen a few
work very well and no pressure by-pass valve needed.

Either way would have the added
benefit of doing away with the need
for a TMV on the
output of the PHE.

Yep, and another valve eliminated that reduces flow. Another is the PRV
too.

Another way is switch speeds of the DHW plate heat ex pump - Keston do this
with a Grundfoss. Using two flow switches set at different flows can switch
in the pump's speed. Low DHW flows and low speed, higher flows and the high
switching flow switch cuts in and a faster speed. Simple and effective.