Hi,

After much dewiberating, I decided to build my own heatbank and today
ordered a copper cylinder with extra tappings and lots of hopefully
sensibly placed sensor taps, plus a solar coil, for future proofing.

I'm sorted in principle for heat exchanger (thanks to John Stumbles' wiki
article), flow switch and pumps (Wilo Smart modulating is quite cheap and
featureful). I'm including 3 immersion heater bosses for 9kW of electrical
backup in case of boiler failure (or initially no boiler!).

But I'm confused by mixers. I need 3 high flow 22mm 3-port mixer/blender
valves with an adjustable temperature range of about 30-70C (or several
ranges - one for tap water, one for rads[1], one for UFH).

I'd like them not to be mentally expensive.

Many valves seem to be aimed at blending tap water down to non-burn levels
and the flow may be questionable as well as the temperature range.

The other class are often sold as solar valves.

Is there anywhere else I can look or are solar suppliers likely to be the
best bet?

Ta

Tim

"Tim S" wrote in message
...
Hi,

After much dewiberating, I decided to build my own heatbank and today
ordered a copper cylinder with extra tappings and lots of hopefully
sensibly placed sensor taps, plus a solar coil, for future proofing.

I'm sorted in principle for heat exchanger (thanks to John Stumbles' wiki
article), flow switch and pumps (Wilo Smart modulating is quite cheap and
featureful). I'm including 3 immersion heater bosses for 9kW of electrical
backup in case of boiler failure (or initially no boiler!).

But I'm confused by mixers. I need 3 high flow 22mm 3-port mixer/blender
valves with an adjustable temperature range of about 30-70C (or several
ranges - one for tap water, one for rads[1], one for UFH).

I'd like them not to be mentally expensive.

Many valves seem to be aimed at blending tap water down to non-burn levels
and the flow may be questionable as well as the temperature range.

The other class are often sold as solar valves.

Is there anywhere else I can look or are solar suppliers likely to be the
best bet?

Ta

Tim

DPS use Reliance Heatguard UHF valves as the heat exchanger mixer

PeterK

"Tim S" wrote in message
...
Hi,

After much dewiberating, I decided to build my own heatbank and today
ordered a copper cylinder with extra tappings and lots of hopefully
sensibly placed sensor taps, plus a solar coil, for future proofing.

I'm sorted in principle for heat exchanger (thanks to John Stumbles' wiki
article), flow switch and pumps (Wilo Smart modulating is quite cheap and
featureful). I'm including 3 immersion heater bosses for 9kW of electrical
backup in case of boiler failure (or initially no boiler!).

But I'm confused by mixers. I need 3 high flow 22mm 3-port mixer/blender
valves with an adjustable temperature range of about 30-70C (or several
ranges - one for tap water, one for rads[1], one for UFH).

One for rads? Take the rads F&R at centre or bottom of cylinder. Have TRVs
all around and a Wilo Smart pump. UFH below rads and solar coil at the
bottom.

I'd like them not to be mentally expensive.

Many valves seem to be aimed at blending tap water down to non-burn levels
and the flow may be questionable as well as the temperature range.

The other class are often sold as solar valves.

Is there anywhere else I can look or are solar suppliers likely to be the
best bet?

Navitron. Reliance for blending valves.

http://www.thermaflowheating.co.uk/f...s_27_03_09.pdf

Looking at their instructions the DHW pumps acts as a shunt pump as well -
mixing the temperature of the water right down the cylinder. It is always on
with no flow switch to switch the DHW pump in and out. So an added cost of
running a pump maybe 24/7. What would that cost per year?

It is an electric heat bank using a pressurised thermal store cylinder. It
uses an external DHW plate heat exchanger and thus outside of G3. The makers
say in the instructions it is within G3, it is not, from what I saw. Nu-Heat
do one similar and specify no G3 is required.

There is no T&P valve just a normal pressure discharge valve. I would have a
second valve fitted near the cylinder just in case. They specify a tundish
when one is not legally required, however, good to put one in, as drips will
not ice up in winter and block the discharge pipe with a potential
explosion.

Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a mixer
to achieve a practical balance between heat output and lack of 1st degree
burns

Take the rads F&R at centre or bottom of cylinder. Have
TRVs all around and a Wilo Smart pump. UFH below rads and solar coil at
the bottom.

I'd like them not to be mentally expensive.

Many valves seem to be aimed at blending tap water down to non-burn
levels and the flow may be questionable as well as the temperature range.

The other class are often sold as solar valves.

Is there anywhere else I can look or are solar suppliers likely to be the
best bet?

Navitron. Reliance for blending valves.


http://www.thermaflowheating.co.uk/f...s_27_03_09.pdf



Looking at their instructions the DHW pumps acts as a shunt pump as well -
mixing the temperature of the water right down the cylinder. It is always
on
with no flow switch to switch the DHW pump in and out. So an added cost
of running a pump maybe 24/7. What would that cost per year?

Interesting. I'll do some calculations on that. I was going to add an
intelligent timed run on the DHW plate pump later on to keep the plate hot
at certain times of the day for faster host water.

It is an electric heat bank using a pressurised thermal store cylinder. It
uses an external DHW plate heat exchanger and thus outside of G3. The
makers say in the instructions it is within G3, it is not, from what I
saw. Nu-Heat do one similar and specify no G3 is required.

There is no T&P valve just a normal pressure discharge valve. I would have
a second valve fitted near the cylinder just in case. They specify a
tundish when one is not legally required, however, good to put one in, as
drips will not ice up in winter and block the discharge pipe with a
potential explosion.

PeterK coughed up some electrons that declared:


DPS use Reliance Heatguard UHF valves as the heat exchanger mixer

PeterK

Ta - I'll look these up.

"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

I'm going for approx 100kW (that's expensive enough).

But the key point is extra 10C is extra energy stored. Not that it matters
much now, but it might later.

PeterK coughed up some electrons that declared:

Reliance Heatguard

Hi

Looks like the Reliance UFH blending valve is the one I'm after for most of
this:

Input range (Hot): upto 85C (Cold): 5-75C
Output range: 35-60C
0.6bar drop at 30 l/min (seems reasonable)

Cheers

Tim

Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

Did you mean plateX on the rads?

It will be direct from the cylinder.

Having just looked at this:

http://www.bsmw.co.uk/pdfs/A%20Guide...20O utput.pdf

It seems that perhaps 75C is a standard running temperature for radiators.
Certainly, I'd get the heat out output I'm after with fairly short 700mm
high double panel rads (useful as I have a few tight spots and can't get
long rads in).

Save 100 quid on a mixer and drop the store temperature slightly.

Anyone disagree that running rads at 75C is a good idea?

Cheers

Tim

Tim S coughed up some electrons that declared:

Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st
degree burns

Have a 150kW plate heat exchanger and it can be run at 70C.

Did you mean plateX on the rads?

It will be direct from the cylinder.

Having just looked at this:


http://www.bsmw.co.uk/pdfs/A%20Guide...20O utput.pdf

It seems that perhaps 75C is a standard running temperature for radiators.
Certainly, I'd get the heat out output I'm after with fairly short 700mm
high double panel rads (useful as I have a few tight spots and can't get
long rads in).

Save 100 quid on a mixer and drop the store temperature slightly.

Anyone disagree that running rads at 75C is a good idea?

Cheers

Tim

Just to add:

http://www.heatcodirect.com/index.ph...=Ultraheatline
Radiators 900 High Type 22 DF Double - Ultraheatline Radiators Type 22 DF
Double Panel Double Convector Radiator 900 x 400 4293 BTU&viewlist=723

seem to have some pretty impressive output powers (all quoted at DeltaT=60
according to bloke on phone). That 400mm wide unit equates to about 1.2kW
output power.

"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st
degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

Did you mean plateX on the rads?

It will be direct from the cylinder.

Having just looked at this:

http://www.bsmw.co.uk/pdfs/A%20Guide...20O utput.pdf

It seems that perhaps 75C is a standard running temperature for radiators.
Certainly, I'd get the heat out output I'm after with fairly short 700mm
high double panel rads (useful as I have a few tight spots and can't get
long rads in).

Save 100 quid on a mixer and drop the store temperature slightly.

Anyone disagree that running rads at 75C is a good idea?

You want them as low a temp as you can.
If you have the space for bigger rads, run them lower.
Remember that if the weather is really cold you can always turn the mixer up
10C or more.

dennis@home coughed up some electrons that declared:

You want them as low a temp as you can.
If you have the space for bigger rads, run them lower.

Ideally. I'll try to oversize them, but I'm rather tight for space in a
couple of places.

Remember that if the weather is really cold you can always turn the mixer
up 10C or more.

True.

Tim S coughed up some electrons that declared:

dennis@home coughed up some electrons that declared:

You want them as low a temp as you can.
If you have the space for bigger rads, run them lower.

Ideally. I'll try to oversize them, but I'm rather tight for space in a
couple of places.

Remember that if the weather is really cold you can always turn the mixer
up 10C or more.

True.

Further adding to that, I think, the correct answer for now is to run the
rads direct off the tank. I have the ability to regulate the tank
temperature, and technically lower = better boiler performance and is
easily adjustable at various times of the year (that could be automated
too).

If I ever (big if) add solar and it becomes desireable to run the tank
mentally hot for extra energy storage (depending on the output temperature
of solar tubes - which I think can be quite high) - then I can always add a
mixer to this circuit - I'll leave space to do so.

At least I'll have actual running data to base my decision on then.

Cheers

Tim

Tim S coughed up some electrons that declared:

Further adding to that, I think, the correct answer for now is to run the
rads direct off the tank. I have the ability to regulate the tank
temperature, and technically lower = better boiler performance and is
easily adjustable at various times of the year (that could be automated
too).

On that subject - the tank drawings I gave to Newark Copper Cylinders
include 6 extra evenly spaced (on the vertical) dry 10mm sensor pockets. Me
and my nephew had some considerable success this week in getting an AVR 8
bit microcontroller to talk to a Dallas 1-wire temperature chip (that looks
like a little transistor and needs only 2 wires to connect it, is accurate
and fairly cheap).

We take no credit because all we did was run up some example code someone
else did and tweak it.

But my longer term goal is to immediately rig this cylinder up with basic
relay interlocking controls to govern it in a basic and safe mode of
operation.

Then, later, by adding a extra few relays here and there, some of the above
sensors and a microcontroller or two (and maybe a proper linux PC) I hope
to be able to control it in a much more useful and efficient way (like set
back during summer, boiler hold off if solar is likely to be available
etc).

The basic relay controls remain as a failsafe (never trust a bloody
computer).

The Heatmiser roomstats I'm getting also have an RS485 bus which allows
remote interrogation and control, so the scope for total heating automation
and remote control exists

Cheers

Tim

On Thu, 30 Apr 2009 11:04:03 +0100, Tim S wrote:

Looks like the Reliance UFH blending valve is the one I'm after for most
of this:

Input range (Hot): upto 85C (Cold): 5-75C Output range: 35-60C
0.6bar drop at 30 l/min (seems reasonable)

Sounds like the Reliance UFH valve Toolstation do for about £60



--
John Stumbles -- http://yaph.co.uk

I can't stand intolerance

On Thu, 30 Apr 2009 12:36:00 +0100, Tim S wrote:

---8--- snip techie stuff ---8---

We'll be expecting a proper write-up Tim ;-)


--
John Stumbles -- http://yaph.co.uk

"I used to think correlation implied causation.
Then I took a statistics course and now I don't."
"Sounds as if the statistics course helped."
"Well, maybe."

On Thu, 30 Apr 2009 17:45:43 +0000, YAPH wrote:

On Thu, 30 Apr 2009 12:36:00 +0100, Tim S wrote:

---8--- snip techie stuff ---8---

We'll be expecting a proper write-up Tim ;-)

Absolutely definitely.

It sounds very similar to what I'll be doing if/when I buy this place.
And I have an Arduino or two sat around looking for something useful to
do as well ;-)

YAPH coughed up some electrons that declared:

On Thu, 30 Apr 2009 12:36:00 +0100, Tim S wrote:

---8--- snip techie stuff ---8---

We'll be expecting a proper write-up Tim ;-)



Sure

It'll be a few months before even the basics work. And a year+ before I try
and get clever.

But I am trying one or two non conventional things - so I'll speak of them
if they actually work.

BTW John - relevant to your DIY Heatbank Wiki: Farnell now do a flow switch
with inbuilt triac designed to switch mains at upto 3A:

http://uk.farnell.com/gentech-intern...-ac/dp/1006768

Do you reckon a trip point (flow switch sensitivity) of 1 litre/min is OK
for taps?

Cheers

Tim

"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st
degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

Did you mean plateX on the rads?

No DHW!

It will be direct from the cylinder.

Having just looked at this:

http://www.bsmw.co.uk/pdfs/A%20Guide...20O utput.pdf

It seems that perhaps 75C is a standard running temperature for radiators.
Certainly, I'd get the heat out output I'm after with fairly short 700mm
high double panel rads (useful as I have a few tight spots and can't get
long rads in).

Save 100 quid on a mixer and drop the store temperature slightly.

Anyone disagree that running rads at 75C is a good idea?

Size them to run at 60C.

"dennis@home" wrote in message
...


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st
degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

Did you mean plateX on the rads?

It will be direct from the cylinder.

Having just looked at this:

http://www.bsmw.co.uk/pdfs/A%20Guide...20O utput.pdf

It seems that perhaps 75C is a standard running temperature for
radiators.
Certainly, I'd get the heat out output I'm after with fairly short 700mm
high double panel rads (useful as I have a few tight spots and can't get
long rads in).

Save 100 quid on a mixer and drop the store temperature slightly.

Anyone disagree that running rads at 75C is a good idea?

You want them as low a temp as you can.
If you have the space for bigger rads, run them lower.
Remember that if the weather is really cold you can always turn the mixer
up 10C or more.

No need for a CH rads mixer.

"PCPaul" wrote in message
m...
On Thu, 30 Apr 2009 17:45:43 +0000, YAPH wrote:

On Thu, 30 Apr 2009 12:36:00 +0100, Tim S wrote:

---8--- snip techie stuff ---8---

We'll be expecting a proper write-up Tim ;-)

Absolutely definitely.

It sounds very similar to what I'll be doing if/when I buy this place.
And I have an Arduino or two sat around looking for something useful to
do as well ;-)

Use a Remaha Broag "dual temperature boiler with integrated weather
compensation. The cheapest way of doing it.

"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


"Tim S" wrote in message
...
Doctor Drivel coughed up some electrons that declared:


One for rads?

Yep - my cylinder is designed to run at upto 80c. With the kids around,
that's a tad hotter than I'd like the rads to run. But I can adjust a
mixer
to achieve a practical balance between heat output and lack of 1st
degree
burns

Have a 150kW plate heat exchanger and it can be run at 70C.

I'm going for approx 100kW (that's expensive enough).

But the key point is extra 10C is extra energy stored. Not that it matters
much now, but it might later.

Using a 150kW plate heat exchanger will lower the store temperature 10C or
more as it extracts far more heat from the supplied water - the return
temperature will be far lower. This promotes condensing efficiency. You
still have the option to raise to 80C if you wish.

Look on Ebay 150kW plates are available. Or maybe two 75kW plates in series
if the two are cheaper than one 150kW.

On Fri, 01 May 2009 01:39:27 +0100, Doctor Drivel wrote:

"PCPaul" wrote in message
m...
On Thu, 30 Apr 2009 17:45:43 +0000, YAPH wrote:

On Thu, 30 Apr 2009 12:36:00 +0100, Tim S wrote:

---8--- snip techie stuff ---8---

We'll be expecting a proper write-up Tim ;-)

Absolutely definitely.

It sounds very similar to what I'll be doing if/when I buy this place.
And I have an Arduino or two sat around looking for something useful to
do as well ;-)

Use a Remaha Broag "dual temperature boiler with integrated weather
compensation. The cheapest way of doing it.

I was hoping to use most of the existing stuff (a decent set of evacuated
tubes and a fairly new 24kW condensing combi that can be configured as a
system boiler instead - but can't take preheated input to use as a 'solar
combi').

So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil inside
the heat store? Sort of like a conventional tank, but inverted?

On Fri, 01 May 2009 17:40:51 +0000, PCPaul wrote:

So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil inside
the heat store? Sort of like a conventional tank, but inverted?

wiki.diqfaq.org.uk has an article on thermal stores and heat banks



--
John Stumbles -- http://yaph.co.uk

I forgot to take my amnesia medecine again

"PCPaul" wrote in message
news
On Fri, 01 May 2009 01:39:27 +0100, Doctor Drivel wrote:

"PCPaul" wrote in message
m...
On Thu, 30 Apr 2009 17:45:43 +0000, YAPH wrote:

On Thu, 30 Apr 2009 12:36:00 +0100, Tim S wrote:

---8--- snip techie stuff ---8---

We'll be expecting a proper write-up Tim ;-)

Absolutely definitely.

It sounds very similar to what I'll be doing if/when I buy this place.
And I have an Arduino or two sat around looking for something useful to
do as well ;-)

Use a Remaha Broag "dual temperature boiler with integrated weather
compensation. The cheapest way of doing it.

I was hoping to use most of the existing stuff (a decent set of evacuated
tubes and a fairly new 24kW condensing combi that can be configured as a
system boiler instead - but can't take preheated input to use as a 'solar
combi').

So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil inside
the heat store? Sort of like a conventional tank, but inverted?

Avoid coils if you can.

John Stumbles has doen a peice on them he
http://wiki.diyfaq.org.uk/index.php?title=Thermal_store

A bity short on some points but as an overview OK.

PCPaul coughed up some electrons that declared:


So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil inside
the heat store? Sort of like a conventional tank, but inverted?

Yes - although the tap hot water can be done buy pumping water through an
external plate exchanger (looks like a metal brick with two independant
water circuits). This is what I'm doing, although a 100kW exchanger is more
standard, and John aka YAPH used a 50kW on in his, which is well worth a
read:

http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank

I nicked all his ideas and a few from other sources

Cheers

Tim

On Thu, 30 Apr 2009 22:33:45 +0100, Tim S wrote:

BTW John - relevant to your DIY Heatbank Wiki: Farnell now do a flow
switch with inbuilt triac designed to switch mains at upto 3A:

http://uk.farnell.com/gentech-intern...-ac/dp/1006768

Doesn't say anything about inbuilt triacs - ?

And apart from the fittings it looks like the type that failed on a
customer's Pandora :-/


Do you reckon a trip point (flow switch sensitivity) of 1 litre/min is
OK for taps?

Can't remember off the top of my head what I found good. I think that's
about right. If it's not sensitive enough your hot will go cold when
you're running a low flow from a mixer tap (especially if you've got
aerators to reduce water consumption). Too sensitive, of course, and it
switches on if you have a slight leak, but you won't have that anyway,
will you? ;-)



--
John Stumbles -- http://yaph.co.uk

This message has been rot13 encrypted twice for added security

YAPH coughed up some electrons that declared:

On Thu, 30 Apr 2009 22:33:45 +0100, Tim S wrote:

BTW John - relevant to your DIY Heatbank Wiki: Farnell now do a flow
switch with inbuilt triac designed to switch mains at upto 3A:


http://uk.farnell.com/gentech-intern...-ac/dp/1006768

Doesn't say anything about inbuilt triacs - ?


"Material, Contact:Triac"

as opposed to ruthenium...

And apart from the fittings it looks like the type that failed on a
customer's Pandora :-/

:-


Do you reckon a trip point (flow switch sensitivity) of 1 litre/min is
OK for taps?

Can't remember off the top of my head what I found good. I think that's
about right. If it's not sensitive enough your hot will go cold when
you're running a low flow from a mixer tap (especially if you've got
aerators to reduce water consumption). Too sensitive, of course, and it
switches on if you have a slight leak, but you won't have that anyway,
will you? ;-)


Ok-dokey. Seems like a good enough bet then. Thanks. I shall double check
with some empirical measurements, but a litre/min seems pretty slow.

Newark called - made my cylinder already! It is however going to stay there
because I don't want it for 3 weeks... Making too much brick dust right
now. Ordered a GRP 27 litre F&E tank. 27l is on the low side for a system
with about 350l of capacity (expect 10l of expansion under normal
conditions) but space for tank is limited. Have to rig the tank so it's got
no more than 10cm of water in it when it's cold, but that's doable. It'll
have about 20cm when system is hot.

GRP because it's over my daughter's head, when she's asleep. Although it
would take a double wrongside failure to boil over (two stats or stat plus
boiler failure), it seemed a sensible precaution.

Cheers
Tim

On Fri, 01 May 2009 23:31:44 +0100, Tim S wrote:

Doesn't say anything about inbuilt triacs - ?

"Material, Contact:Triac"

D'oh!



Durr, on my planet triacs are for switching AC - wonder why the specs only
mention DC currents[1]? And what the difference is between
# Current, Contact DC:0.5A
and
# Current, Switching DC Max:3A
??


[1] leaving aside the oxymoron of AC or DC /voltages/



--
John Stumbles -- http://yaph.co.uk

My karma ran over my dogma

YAPH coughed up some electrons that declared:

On Fri, 01 May 2009 23:31:44 +0100, Tim S wrote:

Doesn't say anything about inbuilt triacs - ?

"Material, Contact:Triac"

D'oh!



Durr, on my planet triacs are for switching AC - wonder why the specs only
mention DC currents[1]? And what the difference is between
# Current, Contact DC:0.5A
and
# Current, Switching DC Max:3A
??


[1] leaving aside the oxymoron of AC or DC /voltages/




It's OK - Farnell's description is talking ********. The datasheet says 250V
RMS and 3A.

It does appear that it is pretty much designed to direct switch a pump, or
other low power mains equipment.

Cheers

Tim

On 1 May 2009 22:52:28 GMT, YAPH wrote:

Durr, on my planet triacs are for switching AC - wonder why the specs
only mention DC currents[1]? And what the difference is between
# Current, Contact DC:0.5A
and
# Current, Switching DC Max:3A

With mechanical switches it's down to arcing. With AC the power goes off
twice per cycle and thus the arc dies. This doesn't happen with DC the arc
burns until the gap is too big for the arc to be sustained.

How this applies to solid state switching I'm not sure unless it's down to
power disipation in the junction.

--
Cheers
Dave.

"YAPH" wrote in message
...
On Thu, 30 Apr 2009 22:33:45 +0100, Tim S wrote:

BTW John - relevant to your DIY Heatbank Wiki: Farnell now do a flow
switch with inbuilt triac designed to switch mains at upto 3A:

http://uk.farnell.com/gentech-intern...-ac/dp/1006768

Doesn't say anything about inbuilt triacs - ?

And apart from the fittings it looks like the type that failed on a
customer's Pandora :-/

The fittings failed or the flow switch?

On Fri, 01 May 2009 23:08:26 +0100, Tim S wrote:

PCPaul coughed up some electrons that declared:


So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil
inside the heat store? Sort of like a conventional tank, but inverted?

Yes - although the tap hot water can be done buy pumping water through
an external plate exchanger (looks like a metal brick with two
independant water circuits). This is what I'm doing, although a 100kW
exchanger is more standard, and John aka YAPH used a 50kW on in his,
which is well worth a read:

http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank

I nicked all his ideas and a few from other sources

Thanks to all for the link. I skimmed the FAQ a while ago but I didn't
know that was on there now..

I'm guessing there's enough cost saving in doing your own over buying a
commercial thermal store (£1000+) to make it worth doing?

PCPaul coughed up some electrons that declared:

On Fri, 01 May 2009 23:08:26 +0100, Tim S wrote:

PCPaul coughed up some electrons that declared:


So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil
inside the heat store? Sort of like a conventional tank, but inverted?

Yes - although the tap hot water can be done buy pumping water through
an external plate exchanger (looks like a metal brick with two
independant water circuits). This is what I'm doing, although a 100kW
exchanger is more standard, and John aka YAPH used a 50kW on in his,
which is well worth a read:

http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank

I nicked all his ideas and a few from other sources

Thanks to all for the link. I skimmed the FAQ a while ago but I didn't
know that was on there now..

I'm guessing there's enough cost saving in doing your own over buying a
commercial thermal store (£1000+) to make it worth doing?

More like 2000 quid for a commercial one

Give me a day and I'll put up some drawings of what I'm doing and the price
of the cylinder...

On Sat, 02 May 2009 10:21:33 +0000, PCPaul wrote:

I'm guessing there's enough cost saving in doing your own over buying a
commercial thermal store (£1000+) to make it worth doing?


That and it's easier to get an empty cylinder and sundry bits & bobs
upstairs or even into an attic than a humungous Pandora (BTDTGTTS - the
rectangular panny in the thermal store article was up a flight of twisty
stairs!)


--
John Stumbles -- http://yaph.co.uk

87.5% of statistics are made up

On Sat, 02 May 2009 00:36:22 +0100, Dave Liquorice wrote:

With mechanical switches it's down to arcing. With AC the power goes off
twice per cycle and thus the arc dies. This doesn't happen with DC the
arc burns until the gap is too big for the arc to be sustained.

How this applies to solid state switching I'm not sure unless it's down
to power disipation in the junction.

Triacs only switch off when the AC drops to zero so they're a chocolate
teapot for switching DC :-))

--
John Stumbles -- http://yaph.co.uk

Things don't like being anthropomorphised.

On Sat, 02 May 2009 09:36:19 +0100, Doctor Drivel wrote:

The fittings failed or the flow switch?

The switch: it simply refused to switch on. ISTR it went intermittent and
seemed OK after I'd replaced it, so I kept it and used it on another
project ... at which point it went on strike again :-(



--
John Stumbles -- http://yaph.co.uk

Procrastinate now!

YAPH coughed up some electrons that declared:

On Sat, 02 May 2009 00:36:22 +0100, Dave Liquorice wrote:

With mechanical switches it's down to arcing. With AC the power goes off
twice per cycle and thus the arc dies. This doesn't happen with DC the
arc burns until the gap is too big for the arc to be sustained.

How this applies to solid state switching I'm not sure unless it's down
to power disipation in the junction.

Triacs only switch off when the AC drops to zero so they're a chocolate
teapot for switching DC :-))


For that you need a GTO (gate turn off) thyristor, which is what they use on
trains (well, DC ones, sometimes...).

I suppose a GTO triac would be possible, but there's not much demand...

"YAPH" wrote in message
...
On Sat, 02 May 2009 09:36:19 +0100, Doctor Drivel wrote:

The fittings failed or the flow switch?

The switch: it simply refused to switch on. ISTR it went intermittent and
seemed OK after I'd replaced it, so I kept it and used it on another
project ... at which point it went on strike again :-(

That is about the most reliable make around. bad luck.

"PCPaul" wrote in message
om...
On Fri, 01 May 2009 23:08:26 +0100, Tim S wrote:

PCPaul coughed up some electrons that declared:

So - thermal stores - am I right in thinking it works by heating big
lump of water/slate/whatever to a highish temperature then giving
'instant mains pressure DHW' by passing mains cold through a coil
inside the heat store? Sort of like a conventional tank, but inverted?

Yes - although the tap hot water can be done buy pumping water through
an external plate exchanger (looks like a metal brick with two
independant water circuits). This is what I'm doing, although a 100kW
exchanger is more standard, and John aka YAPH used a 50kW on in his,
which is well worth a read:

http://wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank

I nicked all his ideas and a few from other sources

Thanks to all for the link. I skimmed the FAQ a while ago but I didn't
know that was on there now..

I'm guessing there's enough cost saving in doing your own over buying a
commercial thermal store (£1000+) to make it worth doing?

Google on this group "DIY heat bank" in the topic.