On older boilers (furnaces if you're American), when the heating isn't actually running (eg. the thermostat says the house is warm enough), there's no power to the boiler, so how does the pilot light valve stay open with the tiny voltage (40mV?) and current from the thermocouple?

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks. I thought the "press and hold" was just to keep the valve open until the thermocouple warmed up. So I'm providing the effort to open the valve with my thumb. That link states 0.2-0.25A - do you really get that much current off a thermocouple?

On 08/12/2018 17:40, wrote:
On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

And while the voltage may be tiny, the available current isn't so small
- after all, the source impedance is very low. Still not much power,
but enough.

Cheers
--
Clive

On Sat, 08 Dec 2018 16:41:17 -0000, Birdbrain Macaw (now "James Wilkinson",
"Steven ******", "Bruce Farqhar", etc.), the pathological resident idiot
and attention whore of all the uk ngs, blathered again:

FLUSH the abnormal sociopathic attention whore's latest idiotic,
attention-baiting bull**** unread again


--
about Birdbrain Macaw's (now "James Wilkinson" LOL)
trolling:
"He is a well known attention seeking troll and every reply you
make feeds him.
Starts many threads most of which die quick as on the UK groups anyone
with sense Kill filed him ages ago which is why he now cross posts to
the US groups for a new audience.
This thread was unusual in that it derived and continued without him
to a large extent and his silly questioning is an attempt to get
noticed again."
MID:

--
ItsJoanNotJoann addressing Birdbrain Macaw's (now "James Wilkinson" LOL):
"You're an annoying troll and I'm done with you and your
stupidity."
MID:

--
AndyW addressing Birdbrain:
"Troll or idiot?...
You have been presented with a viewpoint with information, reasoning,
historical cases, citations and references to back it up and wilfully
ignore all going back to your idea which has no supporting information."
MID:

--
Phil Lee adressing Birdbrain Macaw:
"You are too stupid to be wasting oxygen."
MID:

--
Phil Lee describing Birdbrain Macaw:
"I've never seen such misplaced pride in being a ****ing moronic motorist."
MID:

--
Tony944 addressing Birdbrain Macaw:
"I seen and heard many people but you are on top of list being first class
ass hole jerk. ...You fit under unconditional Idiot and should be put in
mental institution.
MID:

--
Pelican to Birdbrain Macaw:
"Ok. I'm persuaded . You are an idiot."
MID:

--
DerbyDad03 addressing Birdbrain Macaw (now "James Wilkinson" LOL):
"Frigging Idiot. Get the hell out of my thread."
MID:

--
Kerr Mudd-John about Birdbrain Macaw (now "James Wilkinson" LOL):
"It's like arguing with a demented frog."
MID:

--
Mr Pounder Esquire about Birdbrain Macaw (now "James Wilkinson" LOL):
"the **** poor delivery boy with no hot running water, 11 cats and
several parrots living in his hovel."
MID:

--
Rob Morley about Birdbrain:
"He's a perennial idiot"
MID: 20170519215057.56a1f1d4@Mars

--
JoeyDee to Birdbrain
"I apologize for thinking you were a jerk. You're just someone with an IQ
lower than your age, and I accept that as a reason for your comments."
MID: l-september.org

--
Sam Plusnet about Birdbrain (now "James Wilkinson Sword" LOL):
"He's just desperate to be noticed. Any attention will do, no matter how
negative it may be."
MID:

--
asking Birdbrain:
"What, were you dropped on your head as a child?"
MID:

--
Christie addressing endlessly driveling Birdbrain Macaw (now "James
Wilkinson" LOL):
"What are you resurrecting that old post of mine for? It's from last
month some time. You're like a dog who's just dug up an old bone they
hid in the garden until they were ready to have another go at it."
MID:

--
Mr Pounder's fitting description of Birdbrain Macaw:
"You are a well known fool, a tosser, a pillock, a stupid unemployable
sponging failure who will always live alone and will die alone. You will not
be missed."
MID:

--
Richard to pathetic ****** Hucker:
"You haven't bred?
Only useful thing you've done in your pathetic existence."
MID:

--
about Birdbrain (now "James Wilkinson" LOL):
""not the sharpest knife in the drawer"'s parents sure made a serious
mistake having him born alive -- A total waste of oxygen, food, space,
and bandwidth."
MID:

--
Mr Pounder exposing sociopathic Birdbrain:
"You will always be a lonely sociopath living in a ******** with no hot
running water with loads of stinking cats and a few parrots."
MID:

--
francis about Birdbrain (now "James Wilkinson" LOL):
"He seems to have a reputation as someone of limited intelligence"
MID:

--
Peter Moylan about Birdbrain (now "James Wilkinson" LOL):
"If people like JWS didn't exist, we would have to find some other way to
explain the concept of "invincible ignorance"."
MID:

On 08/12/2018 17:51, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks.* I thought the "press and hold" was just to keep the
valve open until the thermocouple warmed up.* So I'm providing the
effort to open the valve with my thumb.* That link states 0.2-0.25A - do
you really get that much current off a thermocouple?

Yes, it's a very low impedance source, a metal to different metal
contact. 10mV 200mA is 50 milliohms. It's only 2mW, but that's a very
small proportion of the pilot flame power.

Cheers
--
Clive

On Sat, 08 Dec 2018 18:02:14 -0000, Clive Arthur wrote:

On 08/12/2018 17:51, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks. I thought the "press and hold" was just to keep the
valve open until the thermocouple warmed up. So I'm providing the
effort to open the valve with my thumb. That link states 0.2-0.25A - do
you really get that much current off a thermocouple?

Yes, it's a very low impedance source, a metal to different metal
contact. 10mV 200mA is 50 milliohms. It's only 2mW, but that's a very
small proportion of the pilot flame power.

I see. I didn't realise you got a decent current off them. I guess it's enough to run a little coil to pull against a small spring which I've already opened with my thumb.

On 08/12/2018 16:41, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

Well they used to have a bimetallic strip to hold the pilot light valve
open rather than a thermocouple. Or maybe that's when boilers didn't
have an electrical connection at all.

--
Max Demian

On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.

--
Davey.

On Sat, 08 Dec 2018 18:32:08 -0000, Max Demian wrote:

On 08/12/2018 16:41, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

Well they used to have a bimetallic strip to hold the pilot light valve
open rather than a thermocouple. Or maybe that's when boilers didn't
have an electrical connection at all.

The electricity from the mains supply (on an old basic/system boiler/furnace) is nothing to do with the pilot light, it just operates the main gas valve. The mains connection to my boiler is only on when the room stat calls for heat. When the room is warm enough, no electricity is given to the boiler at all.

What do you mean "when boilers didn't have an electrical connection at all"? Surely they need something to tell them to start burning gas?

On Sat, 08 Dec 2018 18:39:25 -0000, Davey wrote:

On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.

I'm surprised a decent company like Honeywell would misuse the term "thermocouple".

Whatever I have in my Baxi boiler is a real thermocouple, it looks like one, and it produces 40mV, and it operates the pilot light valve without any mains power.

Bruce Farquhar wrote:

I didn't realise you got a decent current off them.* I guess
it's enough to run a little coil to pull against a small spring which
I've already opened with my thumb.

Plus, the coil has a lot of windings.

On Saturday, December 8, 2018 at 6:44:30 PM UTC, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 18:39:25 -0000, Davey wrote:

On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.

I'm surprised a decent company like Honeywell would misuse the term "thermocouple".

Whatever I have in my Baxi boiler is a real thermocouple, it looks like one, and it produces 40mV, and it operates the pilot light valve without any mains power.

Another type is "thermo-pile" which will produce around 500mA. The type that may operate a flue damper without an electrical connection.

On Sat, 8 Dec 2018 12:40:57 -0500, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety
Don't know about the UK, but MOST north American furnaces don't use
the thermocouple voltage to operate the valve. The thermocouple
"signal" uperates an electronic circuit that provides power from a
transformer to operate the gas valve for the furnace burner - the
thermocouple DOES operate the "hold" bias forthe(very small and low
powered) pilot valve.

Some gas fireplaces and non fan forced heaters use a
"thermopile" that does operate the actual gasvalve directly - allowing
use without grid power.

On 12/8/18 1:39 PM, Davey wrote:
On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.



Sorry, not so.

Just because it looks like a bulb and capillary, it's not.

See
https://customer.honeywell.com/en-US...uct.Rank&asc=1

On 12/8/2018 1:05 PM, Andy Burns wrote:
Bruce Farquhar wrote:

I didn't realise you got a decent current off them.* I guess it's
enough to run a little coil to pull against a small spring which I've
already opened with my thumb.

Plus, the coil has a lot of windings.

+1

--

On Sat, 8 Dec 2018 18:32:08 +0000, Max Demian
wrote:

On 08/12/2018 16:41, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

Well they used to have a bimetallic strip to hold the pilot light valve
open rather than a thermocouple. Or maybe that's when boilers didn't
have an electrical connection at all.
They USED to have "wild pilots" too - where the gas flowed to the
pilot even if the pilot light blew out.
Nasty things, those wild pilots.

On Sat, 8 Dec 2018 18:39:25 +0000, Davey
wrote:

On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.
No, that honeywell thermocouple is a 30mv thermocouple. It is not a
bourdon tube device, although it DOES look like one.

On Sat, 8 Dec 2018 12:40:57 -0500, "Retired, yet another brain damaged,
troll-feeding senile Yankietard, blathered:

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

....and troll-feeding senile idiot no.1 appeared to swallow the abnormal
sociopathic attention whore's latest idiot bait, hook, line and sinker,
again! LOL

On Sat, 8 Dec 2018 18:02:14 +0000, Clive Arthur, another obviously mentally
challenged senile idiot, driveled:

On 08/12/2018 17:51, Bruce Farquhar wrote:

Yes, it's a very low impedance source, a metal to different metal
contact. 10mV 200mA is 50 milliohms. It's only 2mW, but that's a very
small proportion of the pilot flame power.

Cheers

....and troll-feeding senile idiot no.2 couldn't resist taking the abnormal
attention whore's latest idiotic bait! LOL

On Sat, 8 Dec 2018 18:32:08 +0000, Max Demian, an especially dumb,
troll-feeding senile idiot, blathered again:


Well they used to have a bimetallic strip to hold the pilot light valve
open rather than a thermocouple. Or maybe that's when boilers didn't
have an electrical connection at all.

You KNOW what this abnormal attention whore and sociopath is all about, do
you, you ****ed up troll-feeding senile idiot no.3? But it's your advancing
senility that prevents you from not walking into his traps, time and again!
BG

On Sat, 08 Dec 2018 19:24:10 -0000, Clare Snyder wrote:

On Sat, 8 Dec 2018 12:40:57 -0500, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety
Don't know about the UK, but MOST north American furnaces don't use
the thermocouple voltage to operate the valve. The thermocouple
"signal" uperates an electronic circuit that provides power from a
transformer to operate the gas valve for the furnace burner - the
thermocouple DOES operate the "hold" bias forthe(very small and low
powered) pilot valve.

Some gas fireplaces and non fan forced heaters use a
"thermopile" that does operate the actual gasvalve directly - allowing
use without grid power.

My pre-2000 boiler in the UK uses the thermocouple to operate the pilot valve directly, without mains power. Mains power applied to the boiler operates the main burner valve providing the stat in the boiler says its own tank hasn't reached full temperature.

On Sat, 08 Dec 2018 19:26:49 -0000, Clare Snyder wrote:

On Sat, 8 Dec 2018 18:32:08 +0000, Max Demian
wrote:

On 08/12/2018 16:41, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

Well they used to have a bimetallic strip to hold the pilot light valve
open rather than a thermocouple. Or maybe that's when boilers didn't
have an electrical connection at all.
They USED to have "wild pilots" too - where the gas flowed to the
pilot even if the pilot light blew out.
Nasty things, those wild pilots.

Sounds like a drunkard that tears your clothes off.

On Sat, 8 Dec 2018 18:39:25 +0000, Davey, another mentally challenged,
troll-feeding, senile idiot, blathered:


When I lived in America, I was confused

You are STILL confused, mentally challenged, troll-feeding, senile idiot
no.4!

On 12/8/18 2:24 PM, Clare Snyder wrote:
On Sat, 8 Dec 2018 12:40:57 -0500, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety
Don't know about the UK, but MOST north American furnaces don't use
the thermocouple voltage to operate the valve. The thermocouple
"signal" uperates an electronic circuit that provides power from a
transformer to operate the gas valve for the furnace burner - the
thermocouple DOES operate the "hold" bias forthe(very small and low
powered) pilot valve.

Some gas fireplaces and non fan forced heaters use a
"thermopile" that does operate the actual gasvalve directly - allowing
use without grid power.


I was using the word valve to mean the pilot light's own valve that
closes if the pilot goes out, as used in the Wiki article.

BTW I've seen main line gas valves that have a lever to open them in
event of AC power failure. Although not much help on forced air furnaces.

Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

**** off and die Hucker.

On Saturday, December 8, 2018 at 2:36:45 PM UTC-5, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 19:24:10 -0000, Clare Snyder wrote:

On Sat, 8 Dec 2018 12:40:57 -0500, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety
Don't know about the UK, but MOST north American furnaces don't use
the thermocouple voltage to operate the valve. The thermocouple
"signal" uperates an electronic circuit that provides power from a
transformer to operate the gas valve for the furnace burner - the
thermocouple DOES operate the "hold" bias forthe(very small and low
powered) pilot valve.

Some gas fireplaces and non fan forced heaters use a
"thermopile" that does operate the actual gasvalve directly - allowing
use without grid power.

My pre-2000 boiler in the UK uses the thermocouple to operate the pilot valve directly, without mains power. Mains power applied to the boiler operates the main burner valve providing the stat in the boiler says its own tank hasn't reached full temperature.


That's how the typical basic water heaters with pilots work here. No electrical
connection, just the thermocouple that holds the pilot valve open.

On Sat, 8 Dec 2018 19:53:35 -0000, Mr Pounder Esquire wrote:

Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

**** off and die Hucker.

He will just wank off to his latest successful trolling! ;-)

On Sat, 8 Dec 2018 12:17:24 -0800 (PST), tardo_4 wrote, the brain damaged, notorious,
troll-feeding, senile idiot, blathered again:


That's how the typical basic water heaters with pilots work here. No electrical
connection, just the thermocouple that holds the pilot valve open.

Just HOW senile are you, tardo_4, you pathetic troll-feeding senile idiot no.5? BG

On Sat, 8 Dec 2018 11:20:49 -0800 (PST), bob_villa, another mentally,
challenged, troll-feeding, senile Yankietard, blathered:

Another type is "thermo-pile" which will produce around 500mA. The type
that may operate a flue damper without an electrical connection.

His the type that will wank off to the feedback you senile Yanks give him,
time and again, senile, troll-feeding Yankietard no.5!

"Bruce Farquhar" wrote in message
news
On Sat, 08 Dec 2018 18:32:08 -0000, Max Demian
wrote:

On 08/12/2018 16:41, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

Well they used to have a bimetallic strip to hold the pilot light valve
open rather than a thermocouple. Or maybe that's when boilers didn't
have an electrical connection at all.

The electricity from the mains supply (on an old basic/system
boiler/furnace) is nothing to do with the pilot light, it just operates
the main gas valve. The mains connection to my boiler is only on when the
room stat calls for heat. When the room is warm enough, no electricity is
given to the boiler at all.

What do you mean "when boilers didn't have an electrical connection at
all"? Surely they need something to tell them to start burning gas?

Doesn't have to be an electrical thermostat, can be
a bimetallic thermostat or a bulb and capillary tube.

wrote in message
...
On 12/8/18 1:39 PM, Davey wrote:
On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.



Sorry, not so.

Just because it looks like a bulb and capillary, it's not.

See
https://customer.honeywell.com/en-US...uct.Rank&asc=1

Server Error in '/' Application

On 12/8/18 3:36 PM, Rod Speed wrote:


wrote in message
...
On 12/8/18 1:39 PM, Davey wrote:
On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK


They do not use the differential metal concept, but rather pressure due
to expanding liquid.



Sorry, not so.

Just because it looks like a bulb and capillary, it's not.

See
https://customer.honeywell.com/en-US...uct.Rank&asc=1



Server Error in '/' Application

Oh well. Clicking on link works OK here. Thunderbird & Firefox on Mac OS X

On Sun, 9 Dec 2018 07:33:27 +1100, cantankerous trolling geezer Rot Speed,
the auto-contradicting senile sociopath, blabbered, again:


Doesn't have to be an electrical thermostat, can be
a bimetallic thermostat or a bulb and capillary tube.

Has to be a ****ed up sociopathic troll and his corresponding ****ed up
sociopath troll-feeding, senile Rot! Are you in for another round of
severest bitchslapping, my favourite senile punching bag? LOL

--
Richard addressing Rot Speed:
"**** you're thick/pathetic excuse for a troll."
MID:

I'm sure you know this but the Voyager spacecraft are using thermocouples
using the heat from decaying plutonium for power all the way out in the
cosmos. it may be reducing now but its been one heck of a long time.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Clive Arthur" wrote in message
news
On 08/12/2018 17:51, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks. I thought the "press and hold" was just to keep the valve
open until the thermocouple warmed up. So I'm providing the effort to
open the valve with my thumb. That link states 0.2-0.25A - do you really
get that much current off a thermocouple?

Yes, it's a very low impedance source, a metal to different metal contact.
10mV 200mA is 50 milliohms. It's only 2mW, but that's a very small
proportion of the pilot flame power.

Cheers
--
Clive

In article ,
Clive Arthur writes:
On 08/12/2018 17:51, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks.* I thought the "press and hold" was just to keep the
valve open until the thermocouple warmed up.* So I'm providing the
effort to open the valve with my thumb.* That link states 0.2-0.25A - do
you really get that much current off a thermocouple?

Yes, it's a very low impedance source, a metal to different metal
contact. 10mV 200mA is 50 milliohms. It's only 2mW, but that's a very
small proportion of the pilot flame power.

Indeed - a pilot flame is typically around 250W.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

wrote in message
...
On 12/8/18 3:36 PM, Rod Speed wrote:


wrote in message
...
On 12/8/18 1:39 PM, Davey wrote:
On Sat, 08 Dec 2018 16:41:17 -0000
"Bruce Farquhar" wrote:

On older boilers (furnaces if you're American), when the heating
isn't actually running (eg. the thermostat says the house is warm
enough), there's no power to the boiler, so how does the pilot light
valve stay open with the tiny voltage (40mV?) and current from the
thermocouple?

When I lived in America, I was confused that what Honeywell called a
Thermocouple was actually a bulb and capillary tube.

See:
https://www.amazon.co.uk/Honeywell-Q.../dp/B01H2SOZSK

They do not use the differential metal concept, but rather pressure due
to expanding liquid.



Sorry, not so.

Just because it looks like a bulb and capillary, it's not.

See
https://customer.honeywell.com/en-US...uct.Rank&asc=1


Server Error in '/' Application

Oh well. Clicking on link works OK here. Thunderbird & Firefox on Mac OS X

Does now too, must have just been a short term glitch on the server or
something.

On 12/8/2018 1:26 PM, Clare Snyder wrote:
....

They USED to have "wild pilots" too - where the gas flowed to the
pilot even if the pilot light blew out.
Nasty things, those wild pilots.

The little heater in the well house was one for over 50 years until I
swapped it out for a safety valve setup a couple years ago....the amount
of gas through the pilot is so small as to be essentially negligible
unless the area is extremely small and very tight...in the 10x16x8 well
house, it was difficult to smell the odor even if it had been a day or
more before discovered it was out.

But, the gas co guy during one leak check visit said he didn't dare let
it go any longer as "by the book" he could be as much as fired if
another tech came by after him and noted it and he hadn't...

Not that it isn't better to have than not, but they really aren't _that_
risky.

--

On Saturday, December 8, 2018 at 5:59:26 PM UTC-5, Andrew Gabriel wrote:
In article ,
Clive Arthur writes:
On 08/12/2018 17:51, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks.Â* I thought the "press and hold" was just to keep the
valve open until the thermocouple warmed up.Â* So I'm providing the
effort to open the valve with my thumb.Â* That link states 0.2-0.25A - do
you really get that much current off a thermocouple?

Yes, it's a very low impedance source, a metal to different metal
contact. 10mV 200mA is 50 milliohms. It's only 2mW, but that's a very
small proportion of the pilot flame power.

Indeed - a pilot flame is typically around 250W.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

It would be a hell of a pilot light to generate 250 watts.

On Sat, 8 Dec 2018 22:59:22 -0000 (UTC),
(Andrew Gabriel) wrote:

In article ,
Clive Arthur writes:
On 08/12/2018 17:51, Bruce Farquhar wrote:
On Sat, 08 Dec 2018 17:40:57 -0000, wrote:

On 12/8/18 11:41 AM, Bruce Farquhar wrote:
On older boilers (furnaces if you're American), when the heating isn't
actually running (eg. the thermostat says the house is warm enough),
there's no power to the boiler, so how does the pilot light valve stay
open with the tiny voltage (40mV?) and current from the thermocouple?

To *hold* the valve open only requires a small voltage & current. To
*pull* the valve open would require a larger voltage. That's why you
have to "Press & Hold" the manual knob to restart a pilot.

See here for more detail:
https://en.wikipedia.org/wiki/Thermo...pliance_safety

I see, thanks.* I thought the "press and hold" was just to keep the
valve open until the thermocouple warmed up.* So I'm providing the
effort to open the valve with my thumb.* That link states 0.2-0.25A - do
you really get that much current off a thermocouple?

Yes, it's a very low impedance source, a metal to different metal
contact. 10mV 200mA is 50 milliohms. It's only 2mW, but that's a very
small proportion of the pilot flame power.

Indeed - a pilot flame is typically around 250W.

A lot closer to 65 than 250 for MOST natural gas pilot lights (about
60 cu meters per year) Some of the really old ones may have used 4
times as much - - -
Nothing available today (in a furnace) (at least in Canada) has a
standing pilot. All have electric ignition as part of the "high
efficiency"standard.