I'm looking into a new heating/hot water installation based upon a heat pump
(~14kW) and ancillary input from a woodburner backboiler (~5kW). Heating
will be underfloor throughout. I'll be pumping the woodburner circuit
(vented with dump rad) since the cylinder/buffer will be on the ground
floor. There seem to be a few common configurations up for consideration;

A) Heat pump and woodburner both direct to a sealed buffer vessel (~150l)
connected to the UFH. A separate cylinder (~250l) for DHW which is fed
indirect from only the heat pump (if unvented) or also the woodburner (if
vented?). Diverter valves to switch heat input from buffer to cylinder.

B) Heat pump and woodburner direct to a vented store (~600l). UFH connected
to lower half of store. Mains pressure DHW from large bottom to top internal
coil (~9sqm). Diverter valves used to direct the heat pump and woodburner
circuits to the top or bottom of the store as required for DHW or UFH.

C) Like B but with pumped loop through plate heat exchanger for DHW.

D) Combination of A and B. The DHW unvented cylinder is a tank (~300l)
inside the top half of the sealed 'buffer' (~450l) and is heated by the
buffer. The buffer is fed direct by both the heat pump and woodburner and
their inputs can be diverted as for B. The UFH is connected direct to the
buffer.

E) woodburner connected direct to its own vented store (~200l). Heat pump
connected indirect to DHW cylinder (~300l) and also direct to UFH with
diverter valves to switch input. The store is connected to the heat pump
return via a plate heat exchanger.

My initial assessement is the two tank solution probably requires more
utility room space, unless I can stack
the pair. I'm attracted to the single tank solutions because I can get
mains pressure hot water and still easily have the woodburner input to the
DHW. Solution E) satisfies this requirement but I have reservations about
passing hot (70degC) water through the heat pump, perhaps this is not an
issue? Also there is no UFH buffer in this configuration. I'd rather a
vented storage system, which B) satisfies, but if the tank-in-tank solution
is technicaly superior then I'd be prepared to forgo this for D). I would
appreciate any comments on the relative merits of these
configurations to help make up my mind

Martin

On May 22, 5:55*pm, "MartC" noone@here wrote:
I'm looking into a new heating/hot water installation based upon a heat pump
(~14kW) and ancillary input from a woodburner backboiler (~5kW). Heating
will be underfloor throughout. I'll be pumping the woodburner circuit
(vented with dump rad) since the cylinder/buffer will be on the ground
floor. There seem to be a few common configurations up for consideration;

A) Heat pump and woodburner both direct to a sealed buffer vessel (~150l)
connected to the UFH. *A separate cylinder (~250l) for DHW which is fed
indirect from only the heat pump (if unvented) or also the woodburner (if
vented?). Diverter valves to switch heat input from buffer to cylinder.

B) Heat pump and woodburner direct to a vented store (~600l). UFH connected
to lower half of store. Mains pressure DHW from large bottom to top internal
coil (~9sqm). Diverter valves used to direct the heat pump and woodburner
circuits to the top or bottom of the store as required for DHW or UFH.

C) Like B but with pumped loop through plate heat exchanger for DHW.

D) Combination of A and B. The DHW unvented cylinder is a tank (~300l)
inside the top half of the sealed 'buffer' (~450l) and is heated by the
buffer. The buffer is fed direct by both the heat pump and woodburner and
their inputs can be diverted as for B. The UFH is connected direct to the
buffer.

E) woodburner connected direct to its own vented store (~200l). Heat pump
connected indirect to DHW cylinder (~300l) and also direct to UFH with
diverter valves to switch input. The store is connected to the heat pump
return via a plate heat exchanger.

My initial assessement is the two tank solution probably requires more
utility room space, unless I can stack
the pair. *I'm attracted to the single tank solutions because I can get
mains pressure hot water and still easily have the woodburner input to the
DHW. *Solution E) satisfies this requirement but I have reservations about
passing hot (70degC) water through the heat pump, perhaps this is not an
issue? *Also there is no UFH buffer in this configuration. *I'd rather a
vented storage system, which B) satisfies, but if the tank-in-tank solution
is technicaly superior then I'd be prepared to forgo this for D). I would
appreciate any comments on the relative merits of these
configurations to help make up my mind

Martin

Some principles:

Heat pumps are efficient at low output temp, but efficiency drops off
badly as output temp rises. With solid fuel there is only a slight
efficiency penalty for high output temps. So whatever you do, you want
2 water holding zones, with the heatpump and solid fuel outputs
separate. The hottest top layer from the heatpump can feed the solid
fuel heated water zone.

Gravity circulation si considered essential with solid fuel, as the
burner keeps going when power quits. A ground level hot tank will kill
gravity circulation. In theory you might get this to work if you have
some passive way to handle the excess heat, but thats not normally the
case.


NT

Tabby wrote:
On May 22, 5:55 pm, "MartC" noone@here wrote:
I'm looking into a new heating/hot water installation based upon a heat pump
(~14kW) and ancillary input from a woodburner backboiler (~5kW). Heating
will be underfloor throughout. I'll be pumping the woodburner circuit
(vented with dump rad) since the cylinder/buffer will be on the ground
floor. There seem to be a few common configurations up for consideration;

A) Heat pump and woodburner both direct to a sealed buffer vessel (~150l)
connected to the UFH. A separate cylinder (~250l) for DHW which is fed
indirect from only the heat pump (if unvented) or also the woodburner (if
vented?). Diverter valves to switch heat input from buffer to cylinder.

B) Heat pump and woodburner direct to a vented store (~600l). UFH connected
to lower half of store. Mains pressure DHW from large bottom to top internal
coil (~9sqm). Diverter valves used to direct the heat pump and woodburner
circuits to the top or bottom of the store as required for DHW or UFH.

C) Like B but with pumped loop through plate heat exchanger for DHW.

D) Combination of A and B. The DHW unvented cylinder is a tank (~300l)
inside the top half of the sealed 'buffer' (~450l) and is heated by the
buffer. The buffer is fed direct by both the heat pump and woodburner and
their inputs can be diverted as for B. The UFH is connected direct to the
buffer.

E) woodburner connected direct to its own vented store (~200l). Heat pump
connected indirect to DHW cylinder (~300l) and also direct to UFH with
diverter valves to switch input. The store is connected to the heat pump
return via a plate heat exchanger.

My initial assessement is the two tank solution probably requires more
utility room space, unless I can stack
the pair. I'm attracted to the single tank solutions because I can get
mains pressure hot water and still easily have the woodburner input to the
DHW. Solution E) satisfies this requirement but I have reservations about
passing hot (70degC) water through the heat pump, perhaps this is not an
issue? Also there is no UFH buffer in this configuration. I'd rather a
vented storage system, which B) satisfies, but if the tank-in-tank solution
is technicaly superior then I'd be prepared to forgo this for D). I would
appreciate any comments on the relative merits of these
configurations to help make up my mind

Martin

Some principles:

Heat pumps are efficient at low output temp, but efficiency drops off
badly as output temp rises. With solid fuel there is only a slight
efficiency penalty for high output temps. So whatever you do, you want
2 water holding zones, with the heatpump and solid fuel outputs
separate. The hottest top layer from the heatpump can feed the solid
fuel heated water zone.

Gravity circulation si considered essential with solid fuel, as the
burner keeps going when power quits. A ground level hot tank will kill
gravity circulation. In theory you might get this to work if you have
some passive way to handle the excess heat, but thats not normally the
case.


NT
+1 on this.

I would NOT feet 70C + water through a heat pump for sure.

Best use of heatpump is very closely spaced UFH. probably 6" spacing.
That way you can really use the modest water temps efficiently. You will
need DHW immersion anyway to top up the heatpump as it wont otherwise
get hot enough.

You will need a step down mixer to reduce solid fuel temps to UFH
ones..or a store..hmm

I'd avoid stores as much as possible.

What might work is to have a thermal store OR the DHW fed from solid
fuel, and use that to preheat the heatpump. If switched to the DHW you
can go up to 65C or so, but the store shouldn't go above 50C. If that is
enough for the UFH the heatpump simply wont cut in.

But I would imagine your normal working practice will be heatpump and
immersion for DHW *only* in summer, heatpump UFH/DHW alone in
spring/autumn, and only when its bloody freezing light the stove. And
that means your heatpump outflow will have to be well below freezing to
get soil heat out. So its unlikely running it through a heat-ex post
that will get it that hot !

On May 22, 8:16*pm, The Natural Philosopher
wrote:
Tabby wrote:
On May 22, 5:55 pm, "MartC" noone@here wrote:
I'm looking into a new heating/hot water installation based upon a heat pump
(~14kW) and ancillary input from a woodburner backboiler (~5kW). Heating
will be underfloor throughout. I'll be pumping the woodburner circuit
(vented with dump rad) since the cylinder/buffer will be on the ground
floor. There seem to be a few common configurations up for consideration;

A) Heat pump and woodburner both direct to a sealed buffer vessel (~150l)
connected to the UFH. *A separate cylinder (~250l) for DHW which is fed
indirect from only the heat pump (if unvented) or also the woodburner (if
vented?). Diverter valves to switch heat input from buffer to cylinder..

B) Heat pump and woodburner direct to a vented store (~600l). UFH connected
to lower half of store. Mains pressure DHW from large bottom to top internal
coil (~9sqm). Diverter valves used to direct the heat pump and woodburner
circuits to the top or bottom of the store as required for DHW or UFH.

C) Like B but with pumped loop through plate heat exchanger for DHW.

D) Combination of A and B. The DHW unvented cylinder is a tank (~300l)
inside the top half of the sealed 'buffer' (~450l) and is heated by the
buffer. The buffer is fed direct by both the heat pump and woodburner and
their inputs can be diverted as for B. The UFH is connected direct to the
buffer.

E) woodburner connected direct to its own vented store (~200l). Heat pump
connected indirect to DHW cylinder (~300l) and also direct to UFH with
diverter valves to switch input. The store is connected to the heat pump
return via a plate heat exchanger.

My initial assessement is the two tank solution probably requires more
utility room space, unless I can stack
the pair. *I'm attracted to the single tank solutions because I can get
mains pressure hot water and still easily have the woodburner input to the
DHW. *Solution E) satisfies this requirement but I have reservations about
passing hot (70degC) water through the heat pump, perhaps this is not an
issue? *Also there is no UFH buffer in this configuration. *I'd rather a
vented storage system, which B) satisfies, but if the tank-in-tank solution
is technicaly superior then I'd be prepared to forgo this for D). I would
appreciate any comments on the relative merits of these
configurations to help make up my mind

Martin

Some principles:

Heat pumps are efficient at low output temp, but efficiency drops off
badly as output temp rises. With solid fuel there is only a slight
efficiency penalty for high output temps. So whatever you do, you want
2 water holding zones, with the heatpump and solid fuel outputs
separate. The hottest top layer from the heatpump can feed the solid
fuel heated water zone.

Gravity circulation si considered essential with solid fuel, as the
burner keeps going when power quits. A ground level hot tank will kill
gravity circulation. In theory you might get this to work if you have
some passive way to handle the excess heat, but thats not normally the
case.

NT

+1 on this.

I would NOT feet 70C + water through a heat pump for sure.

Best use of heatpump is very closely spaced UFH. probably 6" spacing.
That way you can really use the modest water temps efficiently. You will
need DHW immersion anyway to top up the heatpump as it wont otherwise
get hot enough.

You will need a step down mixer to reduce solid fuel temps to UFH
ones..or a store..hmm

I'd avoid stores as much as possible.

What might work is to have a thermal store OR the DHW fed from solid
fuel, and use that to preheat the heatpump. If switched to the DHW you
can go up to 65C or so, but the store shouldn't go above 50C. If that is
enough for the UFH the heatpump simply wont cut in.

But I would imagine your normal working practice will be heatpump and
immersion for DHW *only* in summer, heatpump UFH/DHW alone in
spring/autumn, and only when its bloody freezing light the stove. And
that means your heatpump outflow will have to be well below freezing to
get soil heat out. So its unlikely running it through a heat-ex post
that will get it that hot !


You a want the heatpump to work on the coldest water in the cylinder,
so as to maximise the return per watt and per pound. So the feed to
the heatpump wants to go from the very bottom of the store. Since it
will deliver middling temp water, its output can return to the middle
of the cylinder, and from there find its own stratified level.

The solid fuel heat exchanger will produce primarily hot water out, so
its output can go to the top of the tank, or near. It will largely
heat the medium warmth water from teh heat exchanger, or if that isnt
being used, cold water, so its input can be from the middle of the
tank.

This is going to be the bset setup for most of the time. Perhaps in
future the feed and return points can be cpu controlled and the heat
sources prioritised according to what's wanted, but we're not there
today.

UFH would be fed from the middle of the tank or a bit lower.

You'd best include an immersion heater too, on occasion you'll be
grateful for it, such as when unwell.


NT

On May 22, 5:55*pm, "MartC" noone@here wrote:

Strange; when you budgeted for all this kit, did you consider paying
someone with the necessary expertise to design the system for you?
Did you think you'd get expert advise on a DIY forum?
I'm not concerned about what you do, but I can't follow the thought
processes involved.

Are you employing a HETAS bloke to install the wood-burner and the
flue? They generate scarey concentrations of CO.

"Tabby" wrote in message
...
On May 22, 5:55 pm, "MartC" noone@here wrote:

Gravity circulation si considered essential with solid fuel, as the
burner keeps going when power quits. A ground level hot tank will kill
gravity circulation. In theory you might get this to work if you have
some passive way to handle the excess heat, but thats not normally the
case.

There will be a gravity fed dump rad on a valve that opens when the power
fails.

"The Natural Philosopher" wrote in message
...
+1 on this.

I would NOT feet 70C + water through a heat pump for sure.

Best use of heatpump is very closely spaced UFH. probably 6" spacing. That
way you can really use the modest water temps efficiently. You will need
DHW immersion anyway to top up the heatpump as it wont otherwise get hot
enough.

DHW - I'm considering a Delonghi that gets to 65degC at a COP of 2, still
better than using an immersion (I'll still have one of course), otherwise
the Ecodan gets to 55degC at a similar COP. For UFH a spacing of 100 or 150
should keep it running much more efficiently when DHW is satisfied, I just
need to tap into that lower temp water.



You will need a step down mixer to reduce solid fuel temps to UFH ones..or
a store..hmm

I'd avoid stores as much as possible.

What's your reason for saying this?


What might work is to have a thermal store OR the DHW fed from solid fuel,
and use that to preheat the heatpump. If switched to the DHW you can go up
to 65C or so, but the store shouldn't go above 50C. If that is enough for
the UFH the heatpump simply wont cut in.

But I would imagine your normal working practice will be heatpump and
immersion for DHW *only* in summer, heatpump UFH/DHW alone in
spring/autumn, and only when its bloody freezing light the stove. And that
means your heatpump outflow will have to be well below freezing to get
soil heat out. So its unlikely running it through a heat-ex post that will
get it that hot !

It's going to be air source, but the running pattern is likely to be similar
to as you describe. The stove is an extra 5kW when needed in the depths of
winter, but when on in autumn/spring reduces the demand on the heat pump.
What I have found is that using a stove for space heating just overheats the
one room, I'm trying to tie it into heating the rest of the house too by
putting it into the UFH, the split will be say 1kW into room and 4into
water.

In message , MartC
writes


snip..

It's going to be air source, but the running pattern is likely to be similar
to as you describe. The stove is an extra 5kW when needed in the depths of
winter, but when on in autumn/spring reduces the demand on the heat pump.
What I have found is that using a stove for space heating just overheats the
one room, I'm trying to tie it into heating the rest of the house too by
putting it into the UFH, the split will be say 1kW into room and 4into
water.

Have you considered the impact of trying to get 4kW water and 1kW
convection on smoke eater performance?

When your firebox is surrounded by water at something under 100deg.C
claims to meet smoke regulations may be suspect.

Glossy brochures do not rush to give this information.

regards




--
Tim Lamb

On May 22, 9:58*pm, "MartC" noone@here wrote:
"The Natural Philosopher" wrote in ...

+1 on this.

I would NOT feet 70C + water through a heat pump for sure.

Best use of heatpump is very closely spaced UFH. probably 6" spacing. That
way you can really use the modest water temps efficiently. You will need
DHW immersion anyway to top up the heatpump as it wont otherwise get hot
enough.

DHW - I'm considering a Delonghi that gets to 65degC at a COP of 2, still
better than using an immersion (I'll still have one of course), otherwise
the Ecodan gets to 55degC at a similar COP. *For UFH a spacing of 100 or 150
should keep it running much more efficiently when DHW is satisfied, I just
need to tap into that lower temp water.



You will need a step down mixer to reduce solid fuel temps to UFH ones...or
a store..hmm

I'd avoid stores as much as possible.

What's your reason for saying this?



What might work is to have a thermal store OR the DHW fed from solid fuel,
and use that to preheat the heatpump. If switched to the DHW you can go up
to 65C or so, but the store shouldn't go above 50C. If that is enough for
the UFH the heatpump simply wont cut in.

But I would imagine your normal working practice will be heatpump and
immersion for DHW *only* in summer, heatpump UFH/DHW alone in
spring/autumn, and only when its bloody freezing light the stove. And that
means your heatpump outflow will have to be well below freezing to get
soil heat out. So its unlikely running it through a heat-ex post that will
get it that hot !

It's going to be air source, but the running pattern is likely to be similar
to as you describe. *The stove is an extra 5kW when needed in the depths of
winter, but when on in autumn/spring reduces the demand on the heat pump.
What I have found is that using a stove for space heating just overheats the
one room, I'm trying to tie it into heating the rest of the house too by
putting it into the UFH, the split will be say 1kW into room and 4into
water.

I wonder how you propose to extract such a high percentage of the heat
to the water. To achieve that you'd need a fine heat exchanger in the
flue gases. The exchanger would quickly crud up with soot, and its
output fall heavily. Also extracting so much heat would remove most of
the updraught, another problem to solve. Do you have a cunning plan?

PS, just wondering if it might be possible with a direct contact
exchanger tank mounted in the loft, ie the fumes travel over the top
of the water. The water would then need ongoing filtering.


NT

On Sun, 22 May 2011 21:43:53 +0100, MartC wrote:

There will be a gravity fed dump rad ...

If you can have a gravity dump rad why can't you have a gravity tank?

... on a valve that opens when the power fails.

If it hasn't jammed shut due to lack of use... IMHO the cooling of a
solid fuel boiler need to be totally passive and fail safe.

--
Cheers
Dave.

On May 22, 10:51*pm, Tabby wrote:

My previous question came to mind when I saw the considerable capital
expenditure that will go/had gone into this project, but you have come
to a DIY forum to solicit the opinions of NT.
NT's enthusiasm gets the better of him, IHHO he is an expert on
everything. On the frequent occasions that he strays into my area of
expertise, I can vouch for the fact that he spouts some awful bollox.
Worse than Drivel, but everyone knows to beware of Drivel's
misinformation.

PS, just wondering if it might be possible with a direct contact
exchanger tank mounted in the loft, ie the fumes travel over the top
of the water. The water would then need ongoing filtering.

NT-

Utter bolleaux. Have you ever seen such a heat exchanger? No, you
haven't. Why are you wasting everyone's time suggesting such clap-
trap?
A clue; flue gases from burning carbo-hydrates (all fossil & wood
fuels) contain water vapour and carbon dioxide and monoxide. The gases
also contain sulphur dioxide from the traces of sulphur in the fuel.
Dissolve this in water, you get sulphurous acid. This is why the
condense from condensing boilers is acidic and why non-condensing
boilers run at condensing temperatures will suffer from rapid
corrosion.

You're suggesting passing the flue gas over water? Can you
anticipate a problem with that?


I wonder how you propose to extract such a high percentage of the heat
to the water. To achieve that you'd need a fine heat exchanger in the
flue gases. The exchanger would quickly crud up with soot, and its
output fall heavily. Also extracting so much heat would remove most of
the updraught, another problem to solve. Do you have a cunning plan?

You'd need a gasifier for any high efficiency; the heat exchanger
would otherwise suffer from tars condensing and solidifying on the
heat exchange surface. Conventional stoves have the air flow upwards,
i.e., the wrong way around, for maximum efficiency. Lots of info on
gasifier combustion on the net.

"Onetap" wrote in message
...
On May 22, 10:51 pm, Tabby wrote:

My previous question came to mind when I saw the considerable capital
expenditure that will go/had gone into this project, but you have come
to a DIY forum to solicit the opinions of NT.
NT's enthusiasm gets the better of him, IHHO he is an expert on
everything. On the frequent occasions that he strays into my area of
expertise, I can vouch for the fact that he spouts some awful bollox.
Worse than Drivel, but everyone knows to beware of Drivel's
misinformation.

PS, just wondering if it might be possible with a direct contact
exchanger tank mounted in the loft, ie the fumes travel over the top
of the water. The water would then need ongoing filtering.

NT-


I've spent nothing yet, but the property is gutted so it's a blank slate as
far as heating is concerned. We're off mains gas hence the heat pump is a
contender, there is an LPG tank already installed, no oil tank. I get free
wood, and have been using the woodburner I inherited with the property (I
did have a new liner installed by a HETAS guy who also sweeps it once a year
as a requirement of my buildings insurance). This stove is too big and
overheats the one room, I cannot get its heat to other parts of the house
(except straight up the stairs!) with open door combinations. It's getting
old and will be downsized when replaced so I was exploring the idea of the
new one having a boiler and putting heat into the underfloor heating.

However, Tim and NT have both brought to my attention that I had clearly
overestimated the water/room heat split, I've checked a few today and at
best seen 3kW to each claimed for a 6kW stove, and less than this in most,
so the idea is less attractive given that it adds such complexity to the wet
installation. Do you have any other suggestions, ducting in this house
would be difficult to conceal but is it an option worth considering?

Martin

In message , MartC
writes

However, Tim and NT have both brought to my attention that I had clearly
overestimated the water/room heat split, I've checked a few today and at
best seen 3kW to each claimed for a 6kW stove, and less than this in most,
so the idea is less attractive given that it adds such complexity to the wet
installation. Do you have any other suggestions, ducting in this house
would be difficult to conceal but is it an option worth considering?

Sorry:-)

Given you have a free source of firewood, why not skip the direct heat
to the room and have a fully enclosed *furnace* heating a thermal store
by convection? Is there no opportunity for a cistern upstairs or in a
cupboard to the side? You can pump water to your under floor system.

regards

--
Tim Lamb

On May 23, 11:23*am, Onetap wrote:
On May 22, 10:51*pm, Tabby wrote:

*My previous question came to mind when I saw the considerable capital
expenditure that will go/had gone into this project, but you have come
to a DIY forum to solicit the opinions of NT.
NT's enthusiasm gets the better of him, IHHO he is an expert on
everything. On the frequent occasions that he strays into my area of
expertise, I can vouch for the fact that he spouts some awful bollox.
Worse than Drivel, but everyone knows to beware of Drivel's
misinformation.

yawn. again.


PS, just wondering if it might be possible with a direct contact
exchanger tank mounted in the loft, ie the fumes travel over the top
of the water. The water would then need ongoing filtering.

NT-

Utter bolleaux. Have you ever seen such a heat exchanger? No, you
haven't.

Direct contact exchangers are common in industrial equipment, and can
achieve higher efficiency than indirect types at lower cost.


Why are you wasting everyone's time suggesting such clap-
trap?

Just curious as to whether it might be possible to make such
technology functional at domestic use at low cost.


A clue; flue gases from burning carbo-hydrates (all fossil & wood
fuels) contain water vapour and carbon dioxide and monoxide. The gases
also contain sulphur dioxide from the traces of sulphur in the fuel.
Dissolve this in water, you get sulphurous acid. This is why the
condense from condensing boilers is acidic and why non-condensing
boilers run at condensing temperatures will suffer from rapid
corrosion.

Thank you for stating the fairly obvious.


* You're suggesting passing the flue gas over water? Can you
anticipate a problem with that?

Issues, of course. Problems, depends how its done. I was wondering if
perhaps acidity can be handled with either lime chips or by using only
plastic, and an occasional flush. That would imply a plastic heat
exchanger, which has its issues. Or occasional flushing might be
enough on its own.


I wonder how you propose to extract such a high percentage of the heat
to the water. To achieve that you'd need a fine heat exchanger in the
flue gases. The exchanger would quickly crud up with soot, and its
output fall heavily. Also extracting so much heat would remove most of
the updraught, another problem to solve. Do you have a cunning plan?

You'd need a gasifier for any high efficiency; the heat exchanger
would otherwise suffer from tars condensing and solidifying on the
heat exchange surface. Conventional stoves have the air flow upwards,
i.e., the wrong way around, for maximum efficiency. Lots of info on
gasifier combustion on the net.

Yup. I asume of course the OP will stick with more conventional
domestic haeting technology.


NT

On May 23, 7:49*pm, Tabby wrote:

Utter bolleaux. Have you ever seen such a heat exchanger? No, you
haven't.

Direct contact exchangers are common in industrial equipment, and can
achieve higher efficiency than indirect types at lower cost.

You didn't answer the question. You haven't seen one, ever, anywhere.
Why might that be?
They're not called heat exchangers, they're more usually called flue
gas scrubbers.

http://en.wikipedia.org/wiki/Flue-gas_desulfurization
Why might that be?

Issues, of course. Problems, depends how its done. I was wondering if
perhaps acidity can be handled with either lime chips or by using only
plastic, and an occasional flush. That would imply a plastic heat
exchanger, which has its issues. Or occasional flushing might be
enough on its own.

Give over; you were bull-****ting. Don't post drivel.

On May 23, 9:22*pm, Onetap wrote:
On May 23, 7:49*pm, Tabby wrote:

Utter bolleaux. Have you ever seen such a heat exchanger? No, you
haven't.

Direct contact exchangers are common in industrial equipment, and can
achieve higher efficiency than indirect types at lower cost.

You didn't answer the question. You haven't seen one, ever, anywhere.
Why might that be?
They're not called heat exchangers, they're more usually called flue
gas scrubbers.

http://en.wikipedia.org/wiki/Flue-gas_desulfurization
Why might that be?

Issues, of course. Problems, depends how its done. I was wondering if
perhaps acidity can be handled with either lime chips or by using only
plastic, and an occasional flush. That would imply a plastic heat
exchanger, which has its issues. Or occasional flushing might be
enough on its own.

Give over; you were bull-****ting. Don't post drivel.

snore

In message , MartC
writes

"Tim Lamb" wrote in message
.. .
In message , MartC
writes

However, Tim and NT have both brought to my attention that I had clearly
overestimated the water/room heat split, I've checked a few today and at
best seen 3kW to each claimed for a 6kW stove, and less than this in most,
so the idea is less attractive given that it adds such complexity to the
wet
installation. Do you have any other suggestions, ducting in this house
would be difficult to conceal but is it an option worth considering?

Sorry:-)

Given you have a free source of firewood, why not skip the direct heat to
the room and have a fully enclosed *furnace* heating a thermal store by
convection? Is there no opportunity for a cistern upstairs or in a
cupboard to the side? You can pump water to your under floor system.

regards

--
Tim Lamb

Couldn't find much on these, just an american site, but it sounds a bit
industrial to put in SWMBO's inglenook! The house layout is difficult, it
would be a serious compromise to put the store upstairs. I'm coming to the
conclusion that it's going to continue to be a dry stove in the living room
and a heat pump direct to UFH and indirect to DHW cylinder. Currently
investigating if I need a buffer for the UFH, it may be possible to skip
this if I use a heat pump that can modulate it's output power.

Umm... These things are always going to look industrial. They are also
very expensive!

A flick through the adverts in a CLA magazine found
www.dunsterheat.co.uk

I suppose you could cheat! Much of the *heat to the room* comes from
convection as air circulates over the steel or cast iron exterior
surface. Insulation? There must be log burners with boiler functions
which can be inset. Inglenook and SWMBO's ambitions may not help:-)

On the cistern location... my mother had a Rayburn solid fuel cooker in
a bungalow. The hot cistern was in a cupboard to the side.

A log burner with no thermal store is not going to quickly warm up your
house on a cold winter morning.

regards

--
Tim Lamb

On May 23, 6:15*pm, "MartC" noone@here wrote:
*Do you have any other suggestions, ducting in this house
would be difficult to conceal but is it an option worth considering?


I haven't read all the above, no time. You should start estimating the
size of the store from the heat storage required by running the heat
pump (GS or ASHP?) overnight on cheap rate electricity.
I would not connect the wood burner directly to this store, it would
take hours to reach a temperature at which there was some useful heat,
during which time you'd get problems with tar deposits and acid
condensation. You want to get it hot, as fast as possible, and then
maybe extract some heat to the UFH and/or the thermal store.

You should stick with a conventional set-up for the woodburner, with
a metal F&E cistern, heat dump radiator and gravity circulation to the
HWS cylinder. This is achievable, even with the cylinder a short
height above the boiler, if the installer can size gravity pipework.

The recommended volumes of wood storage is something that prospective
users tend to under-estimate (think open-sided shed; huge shed) and
your planned use may change after experience of using it.
Flexible (?) flue liners are not regarded as a permanent solution
(see HETAS guide on-line) and are only suitable for thoroughly
seasoned wood. Damper wood will produce more condensation, shorten the
life and invalidate the guarantee.

A batch wood-burner is an uncontrolled heat source and the
manufacturers' recommendations are that they should NOT be used to
heat an unvented water cylinder. It can be done, if the installer
knows how, but the cylinder cannot then be used as part of the thermal
store for the wood burner since the obligatory 2-port zone valve shuts
when the cylinder gets hot.

I think I'd go for a 2 coil cylinder and keep the two primary
systems separate.The wood burner will boil in service and there will
be a lot of corrosion particles in the water, compared to a sealed &
inhibited system.

You could extract heat from the woodburner into the UFH or the
thermal store, through a neutralizer cylinder or low loss header, but
the cost of the controls will be large compared to the 3-5 kW heat
available. I'd do this at a later date, once you've used the system,
if you still think it worthwhile. You need a device to monitor and
control the return temperature to prevent it falling too low whilst
doing so.

On May 24, 9:03*am, Tim Lamb wrote:

Umm... These things are always going to look industrial. They are also
very expensive!

Yes, but they're gasifiers, efficient and some types are designed for
use with a sealed system. If you have room for an separate plantroom,
they are practical.
There were plans for Renewable Heat Incentives, to pay the owner per
kW hr of wood-heat produced; I don't know what the state of these are
now, whether they were scrapped with the cut-backs. However, the
payback was such that people were buying them as a more attractive
investment, given that there's minimal interest available elsewhere
for their money.

On May 25, 10:43*am, Onetap wrote:

There were plans for Renewable Heat Incentives, to pay the owner per
kW hr of wood-heat produced; I don't know what the state of these are
now, whether they were scrapped with the cut-backs. However, the
payback was such that people were buying them as a more attractive
investment, given that there's minimal interest available elsewhere
for their money.

PS Forgot. RHIs should also be available for the heat pump
installation, providing you use an accredited installer and approved
equipment and providing George hasn't scrapped them.
You'll probably find the installers will want to sell you a wood
burner as well.

On May 25, 5:29*pm, Onetap wrote:

RHIs should also be available for the heat pump
installation, providing you use an accredited installer and approved
equipment and providing George hasn't scrapped them.

Still going, it seems.


http://www.bbc.co.uk/news/science-environment-12695877

On May 25, 5:34*pm, Onetap wrote:

Still going, it seems.

http://www.bbc.co.uk/news/science-environment-12695877

But not yet......

http://www.racplus.com/news/heat-pum...612382.article

There are heat pumps with a higher output temperature (75 degC &
Mitsubishi spring to mind).

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Dave Liquorice"
saying something like:

... on a valve that opens when the power fails.

If it hasn't jammed shut due to lack of use...

Ding.

IMHO the cooling of a
solid fuel boiler need to be totally passive and fail safe.

Exactly. Nothing in the gravity lines that might block them.

However... a few years ago I was in a large bungalow where the back
boiler fed a hot cylinder on the same floor level. The pipes went up to
the attic space, 5 metres along the floor there, down to the hot press
and into the hot cylinder. It was horribly inefficient compared to a
short run, but it did work, though gawd knows how.