Relay contact ratings.

Jim Thompson · Dec 9, 2011

On Fri, 09 Dec 2011 10:17:53 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Trevor Wilson wrote:

**IME, the vast majority of lightning problems occur via TV antennas.
Power line issues are massively over-stated. Again, the only time I can
pin point a power line "surge" as the direct cause of a problem was a
very long time ago, when a 5kV bearer fell across the 240VAC main
overhead lines. The damage was considerable and affected several blocks.

You wouldn't say that if you ever see an outlet explode and blow a
hole in the wall, when lightning hit the power line a mile away. I
have. The noise was deafening, and scared the hell out of my
grandparents & parents. It took out all the power on my grandparents
farm, as well.

Jim Thompson · Dec 9, 2011

On Fri, 9 Dec 2011 08:29:56 -0800 (PST), linnix
<me@linnix.info-for.us> wrote:

On Dec 9, 7:47 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Fri, 09 Dec 2011 10:17:53 -0500, "Michael A. Terrell"

mike.terr...@earthlink.net> wrote:

Trevor Wilson wrote:

**IME, the vast majority of lightning problems occur via TV antennas.
Power line issues are massively over-stated. Again, the only time I can
pin point a power line "surge" as the direct cause of a problem was a
very long time ago, when a 5kV bearer fell across the 240VAC main
overhead lines. The damage was considerable and affected several blocks.

You wouldn't say that if you ever see an outlet explode and blow a
hole in the wall, when lightning hit the power line a mile away. I
have. The noise was deafening, and scared the hell out of my
grandparents & parents. It took out all the power on my grandparents
farm, as well.

We have underground utilities here. Some years ago a lightning strike
at a substation 4 miles away blew out numerous appliances, several
PC's, a TV set, and every light dimmer in the house.

I also have dead microwave and furnace transformers. After installing
MOVs and FUSEs on the primary, i only have to replace them rather than
transformers. OEM transformers are ridiculously expensive too.

linnix · Dec 9, 2011

On Dec 8, 10:58 pm, ehsjr <eh...@nospamverizon.net> wrote:

linnix wrote:
On Dec 8, 9:48 am, ehsjr <eh...@nospamverizon.net> wrote:

Sylvia Else wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

Sylvia.

The price of the relay at the url you posted is ridiculous.
Surely you can get something much cheaper and equally robust.
There are relays made for appliances like air conditioners
available from Digikey for < $5.00 so it's likely you can
get something where you are for much less than the ~ $82.00 at
the RS Australia site. You might be able to use an automotive
relay. Generally their contacts are rated at 30 or 40 amps at
12 VDC, and they'll handle 240 AC nicely.

No, you don't want to use auto relay. If your house burn down,
insurance will not pay. It doesn't mater whether the part can handle
it or not.

I'm laughing at the turn this thread took. If she installs her
own circuit, she is modifying the thing with a non-oem part,
regardless of what parts she uses in her circuit. Thus any concerns
about fire/liability/insurance/local regulations apply. Doesn't
matter if it's flame retardant, 240VAC rated, gold plated, whatever,
the exposure is still there.

She has already indicated she would not use an automotive relay,
so it's moot as far as her project is concerned. But I wonder,
has anyone else here actually tested one of those relays at 240VAC?
I have, and it worked fine, but I did not test to destruction,
nor for dielectric strength or flammability.

Yes, i have, because they are cheap or free. I also use wire wrap
wire for 110V main, they are good FUSEs. However, i would not use
them for unattended applicants like fridge or furnace. And i
definitely would not advice someone asking for help on usenet to use
them.

linnix · Dec 9, 2011

On Dec 9, 7:47 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:

On Fri, 09 Dec 2011 10:17:53 -0500, "Michael A. Terrell"

mike.terr...@earthlink.net> wrote:

Trevor Wilson wrote:

**IME, the vast majority of lightning problems occur via TV antennas.
Power line issues are massively over-stated. Again, the only time I can
pin point a power line "surge" as the direct cause of a problem was a
very long time ago, when a 5kV bearer fell across the 240VAC main
overhead lines. The damage was considerable and affected several blocks.

You wouldn't say that if you ever see an outlet explode and blow a
hole in the wall, when lightning hit the power line a mile away. I
have. The noise was deafening, and scared the hell out of my
grandparents & parents. It took out all the power on my grandparents
farm, as well.

We have underground utilities here. Some years ago a lightning strike
at a substation 4 miles away blew out numerous appliances, several
PC's, a TV set, and every light dimmer in the house.

I also have dead microwave and furnace transformers. After installing
MOVs and FUSEs on the primary, i only have to replace them rather than
transformers. OEM transformers are ridiculously expensive too.

John Devereux · Dec 9, 2011

"Phil Allison" <phil_a@tpg.com.au> writes:

"Trevor Wilson"

**IME, the vast majority of lightning problems occur via TV antennas.

** Plus the telephone line - modems and TAMs drop like flies when there is
a thunderstorm.

Power line issues are massively over-stated.

** It's an issue in many rural areas - the solution to which is fitting
varistors in the power box.

**I agree. However, in terms of longevity, TRIACs win hands down.

** Funny how microwave ovens all seem to have relays turning on the big
tranny.

... Phil

Hey Phil, he's stolen your **'s tag!

--

John Devereux

linnix · Dec 9, 2011

On Dec 9, 8:55 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:

On Fri, 9 Dec 2011 08:29:56 -0800 (PST), linnix

m...@linnix.info-for.us> wrote:
On Dec 9, 7:47 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Fri, 09 Dec 2011 10:17:53 -0500, "Michael A. Terrell"

mike.terr...@earthlink.net> wrote:

Trevor Wilson wrote:

**IME, the vast majority of lightning problems occur via TV antennas.
Power line issues are massively over-stated. Again, the only time I can
pin point a power line "surge" as the direct cause of a problem was a
very long time ago, when a 5kV bearer fell across the 240VAC main
overhead lines. The damage was considerable and affected several blocks.

You wouldn't say that if you ever see an outlet explode and blow a
hole in the wall, when lightning hit the power line a mile away. I
have. The noise was deafening, and scared the hell out of my
grandparents & parents. It took out all the power on my grandparents
farm, as well.

We have underground utilities here. Some years ago a lightning strike
at a substation 4 miles away blew out numerous appliances, several
PC's, a TV set, and every light dimmer in the house.

I also have dead microwave and furnace transformers. After installing
MOVs and FUSEs on the primary, i only have to replace them rather than
transformers. OEM transformers are ridiculously expensive too.

After my event, I installed a full-phase MOV block at the entry
cabinet.

But i don't need to protect the microwave transformer, which draw
almost 10A. I put in the MOV and 1A fuse on the 12V controller
transformer. Next is to drill and mount the fuse externally, which
they should have done in the first place. I guess they would rather
sell new microwaves then fuses.

Joerg · Dec 9, 2011

Sylvia Else wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

2500VA? Wow, that is one heck of a fridge!

How many big cans of Foster's can it hold?

--
SCNR, Joerg

http://www.analogconsultants.com/

Phil Hobbs · Dec 9, 2011

On 12/09/2011 03:53 PM, Joerg wrote:

Sylvia Else wrote:
The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

2500VA? Wow, that is one heck of a fridge!

How many big cans of Foster's can it hold?

Well, the doctor said only one beer a day.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

Phil Allison · Dec 9, 2011

"John Devereux"

"Phil Allison"
"Trevor Wilson"

Hey Phil, he's stolen your **'s tag!

** Nah - he used it before me.

.... Phil

Joerg · Dec 9, 2011

Phil Hobbs wrote:

On 12/09/2011 03:53 PM, Joerg wrote:
Sylvia Else wrote:
The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

2500VA? Wow, that is one heck of a fridge!

How many big cans of Foster's can it hold?

Well, the doctor said only one beer a day.

No problem, Sir. This is how beer is often consumed in Dortmund
(Germany) where I grew up:

http://www.oktoberfesthaus.com/c=GO8L0j9Fp91NGznzQVIz9fEQj/category/beer-boots.3-liter-beer-boots/

A su salud!

--
Regards, Joerg

http://www.analogconsultants.com/

David Eather · Dec 9, 2011

On 9/12/2011 10:56 AM, Sylvia Else wrote:

On 9/12/2011 4:23 AM, linnix wrote:
On Dec 8, 9:01 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
wrote:
On Dec 8, 1:50 am, Sylvia Else<syl...@not.here.invalid> wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I
found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA
load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

Sylvia.

There are aftermarket universals better than the OEM
parthttp://compare.ebay.com/like/290638915750?var=lv<yp=AllFixedPriceIt...

There are plenty of relays you can salvage out of garage opener (12V),
microwave (12V) or furnace (24V). Add a micro or 555 for less than $5
and you are done. I am doing one for my furnace timer.

Not sure about getting a 555 to run at 1 cycle per six hours.

A PIC would no doubt do the job easily, but then I'd have to invest in
hardware to program it.

Sylvia.

Sylvia,

Try a PICAXE 08M2 - it costs $2.50 in one off's and programs in BASIC.
Software and examples are free from www.picaxe.co.uk
It is not uncommon for people totally new to the PICAXE have had them
running programs within 30 minutes of getting their first chip.

The only stuff you need to program one is a serial port (RS232 or TTL
level) and a resistor.

--
We have failed to address the fundamental truth that endless growth is
impossible in a finite world.

John Fields · Dec 10, 2011

On Sat, 10 Dec 2011 09:14:27 +1000, David Eather <eather@tpg.com.au>
wrote:

We have failed to address the fundamental truth that endless growth is
impossible in a finite world.

---
Not true; consider Moore's law.

--
JF

Jim Thompson · Dec 10, 2011

On Sat, 10 Dec 2011 09:14:27 +1000, David Eather <eather@tpg.com.au>
wrote:

We have failed to address the fundamental truth that endless growth is
impossible in a finite world.

Kill off non-productive socialists and you're left with LOTS of space

Dec 10, 2011

Hush....or are you trying to wind up B.S.?!

Sylvia Else · Dec 10, 2011

On 10/12/2011 10:14 AM, David Eather wrote:

On 9/12/2011 10:56 AM, Sylvia Else wrote:
On 9/12/2011 4:23 AM, linnix wrote:
On Dec 8, 9:01 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
wrote:
On Dec 8, 1:50 am, Sylvia Else<syl...@not.here.invalid> wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I
found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA
load.
So no real power being switched, but it would arc like crazy. What
am I
missing here?

Sylvia.

There are aftermarket universals better than the OEM
parthttp://compare.ebay.com/like/290638915750?var=lv<yp=AllFixedPriceIt...

There are plenty of relays you can salvage out of garage opener (12V),
microwave (12V) or furnace (24V). Add a micro or 555 for less than $5
and you are done. I am doing one for my furnace timer.

Not sure about getting a 555 to run at 1 cycle per six hours.

A PIC would no doubt do the job easily, but then I'd have to invest in
hardware to program it.

Sylvia.

Sylvia,

Try a PICAXE 08M2 - it costs $2.50 in one off's and programs in BASIC.
Software and examples are free from www.picaxe.co.uk
It is not uncommon for people totally new to the PICAXE have had them
running programs within 30 minutes of getting their first chip.

The only stuff you need to program one is a serial port (RS232 or TTL
level) and a resistor.

Interesting. Thanks.

I'm tempted to combine the timer with the thermostat, a replacement for
which I've been cursin..., er, I mean testing, today. (Sod's law
subsection 3.1 - a fridge must always enter defrost mode while a person
is attempting to adjust the upper and lower settings of a thermostat.)

Of course, I could just buy a new fridge.

Sylvia.

Sylvia Else · Dec 10, 2011

On 9/12/2011 4:01 AM, Fred Bloggs wrote:

On Dec 8, 1:50 am, Sylvia Else<syl...@not.here.invalid> wrote:
The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

Sylvia.

There are aftermarket universals better than the OEM part
http://compare.ebay.com/like/290638915750?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar

Though not 240V versions as far as I can see. Pity.

Sylvia.

Sylvia Else · Dec 10, 2011

On 10/12/2011 9:33 PM, kreed wrote:

On Dec 10, 8:28 pm, Sylvia Else<syl...@not.here.invalid> wrote:
On 10/12/2011 10:14 AM, David Eather wrote:

On 9/12/2011 10:56 AM, Sylvia Else wrote:
On 9/12/2011 4:23 AM, linnix wrote:
On Dec 8, 9:01 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
wrote:
On Dec 8, 1:50 am, Sylvia Else<syl...@not.here.invalid> wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I
found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA
load.
So no real power being switched, but it would arc like crazy. What
am I
missing here?

Sylvia.

There are aftermarket universals better than the OEM
parthttp://compare.ebay.com/like/290638915750?var=lv<yp=AllFixedPriceIt...

There are plenty of relays you can salvage out of garage opener (12V),
microwave (12V) or furnace (24V). Add a micro or 555 for less than $5
and you are done. I am doing one for my furnace timer.

Not sure about getting a 555 to run at 1 cycle per six hours.

A PIC would no doubt do the job easily, but then I'd have to invest in
hardware to program it.

Sylvia.

Sylvia,

Try a PICAXE 08M2 - it costs $2.50 in one off's and programs in BASIC.
Software and examples are free fromwww.picaxe.co.uk
It is not uncommon for people totally new to the PICAXE have had them
running programs within 30 minutes of getting their first chip.

The only stuff you need to program one is a serial port (RS232 or TTL
level) and a resistor.

Interesting. Thanks.

I'm tempted to combine the timer with the thermostat, a replacement for
which I've been cursin..., er, I mean testing, today. (Sod's law
subsection 3.1 - a fridge must always enter defrost mode while a person
is attempting to adjust the upper and lower settings of a thermostat.)

Of course, I could just buy a new fridge.

Sylvia.

Depends on how old, and how good the current one is other than this
current problem. New ones might be even worse

It would have to be at least ten, and it's been running all that time.

The big question, of course, is how much longer the compressor will
last, since it's probably not going to possible to source a replacement,
even if it would otherwise be economically worthwhile.

BTW, the wires are attached to the (mains-voltage) lamp socket by way of
spring clips. Seems a bit iffy to me.

Sylvia.

kreed · Dec 10, 2011

On Dec 10, 8:28 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 10/12/2011 10:14 AM, David Eather wrote:

On 9/12/2011 10:56 AM, Sylvia Else wrote:
On 9/12/2011 4:23 AM, linnix wrote:
On Dec 8, 9:01 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
wrote:
On Dec 8, 1:50 am, Sylvia Else<syl...@not.here.invalid> wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I
found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA
load.
So no real power being switched, but it would arc like crazy. What
am I
missing here?

Sylvia.

There are aftermarket universals better than the OEM
parthttp://compare.ebay.com/like/290638915750?var=lv<yp=AllFixedPriceIt...

There are plenty of relays you can salvage out of garage opener (12V),
microwave (12V) or furnace (24V). Add a micro or 555 for less than $5
and you are done. I am doing one for my furnace timer.

Not sure about getting a 555 to run at 1 cycle per six hours.

A PIC would no doubt do the job easily, but then I'd have to invest in
hardware to program it.

Sylvia.

Sylvia,

Try a PICAXE 08M2 - it costs $2.50 in one off's and programs in BASIC.
Software and examples are free fromwww.picaxe.co.uk
It is not uncommon for people totally new to the PICAXE have had them
running programs within 30 minutes of getting their first chip.

The only stuff you need to program one is a serial port (RS232 or TTL
level) and a resistor.

Interesting. Thanks.

I'm tempted to combine the timer with the thermostat, a replacement for
which I've been cursin..., er, I mean testing, today. (Sod's law
subsection 3.1 - a fridge must always enter defrost mode while a person
is attempting to adjust the upper and lower settings of a thermostat.)

Of course, I could just buy a new fridge.

Sylvia.

Depends on how old, and how good the current one is other than this
current problem. New ones might be even worse

Michael A. Terrell · Dec 10, 2011

Sylvia Else wrote:

There are aftermarket universals better than the OEM part
http://compare.ebay.com/like/290638915750?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar

Though not 240V versions as far as I can see. Pity.

Can't you find a cheap 240 to 120 VAC transformer?

--
You can't have a sense of humor, if you have no sense.

krw@att.bizzzzzzzzzzzz · Dec 10, 2011

On Fri, 09 Dec 2011 12:53:26 -0800, Joerg <invalid@invalid.invalid> wrote:

Sylvia Else wrote:
The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA load.
So no real power being switched, but it would arc like crazy. What am I
missing here?

2500VA? Wow, that is one heck of a fridge!

How many big cans of Foster's can it hold?

Being a purely inductive load, it can't cool many. ;-)

Relay contact ratings.

Jim Thompson

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