Relay contact ratings.

[Jim Thompson]

On Thu, 8 Dec 2011 16:08:21 -0800 (PST), linnix
<me@linnix.info-for.us> wrote:

On Dec 8, 4:00 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Thu, 8 Dec 2011 15:47:34 -0800 (PST), linnix







m...@linnix.info-for.us> wrote:
On Dec 8, 3:25 pm, Trevor Wilson <tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 10:22 AM, Jim Thompson wrote:

[snip]

In such socialist societies as Australia (and coming soon to the US),
you'd better use the exact replacement and have it done by a certified
technician... otherwise no insurance coverage at all.

**Idiot. EXACTLY the same situation exists in the US. And the US, like
all Western Democracies, is, in part, a socialist nation. Always has been.

--

I think the problem is your language.  You called my post irrevant
when we are agreeing on the same thing.  You called JT Idiot (He may
or may not deserve it)

Flattery will get you nowhere with me ;-)

I am not. Just stating the fact. You call someone an idiot to
counter his opinion and/or discredit him. I am countering your
flattery statement here. In this context, you deserve to be an
idiot.


when he is really saying the same thing:  The
US is getting more socialist, like AU.

You know what they say about people without a sense of humor... they
begin to look like Larkin ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Trevor Wilson]

On 12/9/2011 10:47 AM, linnix wrote:

On Dec 8, 3:25 pm, Trevor Wilson<tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 10:22 AM, Jim Thompson wrote:





On Thu, 8 Dec 2011 15:08:05 -0800 (PST), linnix
m...@linnix.info-for.us> wrote:

On Dec 8, 2:35 pm, Trevor Wilson<tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 8:43 AM, linnix wrote:

On Dec 8, 1:30 pm, Spehro Pefhany<speffS...@interlogDOTyou.knowwhat
wrote:
On Thu, 08 Dec 2011 12:48:13 -0500, 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.

Ed

I would not use a 12V automotive relay to switch mains voltage,
particularly inductive loads.. coil-to-contact dielectric strength of
those POS relays is<< 1kV. I like to see 4kV or so. Are the housings
required to be flame retardant?

Is the house (hosting the fridge) required to be fire retarded?

**Irrelvant. Whilst I don't know the specific legislation pertaining to
relays, here in Australia, ALL mains connected components (from
transformers to power leads) MUST have the requisite approval numbers
and, usually, fire retardant protection, or specific materials used in
their construction. Other jurisdictions may not have such legislation,
for whatever reason. Sylvia resides in Australia. As such, connecting
non-approved components may carry an insurance liability risk.

You are missing the point. Once they (insurance co) determined that
the fire is caused by mis-speced component, they will deny the whole
claim. They will tell you to sue the manufacturer, or whoever made
the modification. It is utterly irrespondable to use auto components
for house main.

In such socialist societies as Australia (and coming soon to the US),
you'd better use the exact replacement and have it done by a certified
technician... otherwise no insurance coverage at all.

**Idiot. EXACTLY the same situation exists in the US. And the US, like
all Western Democracies, is, in part, a socialist nation. Always has been.

--

I think the problem is your language.

**Very likely a misunderstanding.


You called my post irrevant

when we are agreeing on the same thing. You called JT Idiot (He may
or may not deserve it) when he is really saying the same thing: The
US is getting more socialist, like AU.

**The implication was clear.

1) That Australia was a Socialist nation.
2) That the US was not.
3) That the US was becoming a Socialist nation.

I will state again:

ALL Western Democratic nations operate as Socialist states. Every single
one. Including the US. Always has done. Ever since the US Federal, State
and local governments began collecting taxation, the US has been
operating as a Socialist nation.

What JT IMAGINES is that Australia is more socialist than Australia.
That may be true for some parts of the society and less so for other
parts. In the case of the medical system, for instance, Australia enjoys
a largely socialised medical system. Australians are very happy with
that system. The US lacks a cohesive socialised medical system. As a
consequence, some 50-odd million Americans have extremely poor access to
good medical services. Additionally, some 60% of personal bankruptcies
in the US are due to medical bills. Here in Australia, no one loses
their home so they can stay alive.

And to get the issue back on topic, the US regulatory authorities have
considerable influence of what can and can not be connected to US mains
power. In the US, however, due to the low mains Voltage, there is far
less risk to consumers than there is here in Australia.

--
Trevor Wilson
www.rageaudio.com.au

 

[linnix]

On Dec 8, 3:13 pm, Trevor Wilson <tre...@SPAMBLOCKrageaudio.com.au>
wrote:

On 12/9/2011 10:08 AM, linnix wrote:





On Dec 8, 2:35 pm, Trevor Wilson<tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 8:43 AM, linnix wrote:

On Dec 8, 1:30 pm, Spehro Pefhany<speffS...@interlogDOTyou.knowwhat
wrote:
On Thu, 08 Dec 2011 12:48:13 -0500, 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.

Ed

I would not use a 12V automotive relay to switch mains voltage,
particularly inductive loads.. coil-to-contact dielectric strength of
those POS relays is<<    1kV. I like to see 4kV or so. Are the housings
required to be flame retardant?

Is the house (hosting the fridge) required to be fire retarded?

**Irrelvant. Whilst I don't know the specific legislation pertaining to
relays, here in Australia, ALL mains connected components (from
transformers to power leads) MUST have the requisite approval numbers
and, usually, fire retardant protection, or specific materials used in
their construction. Other jurisdictions may not have such legislation,
for whatever reason. Sylvia resides in Australia. As such, connecting
non-approved components may carry an insurance liability risk.

You are missing the point.

**No, I am not, but continue....

   Once they (insurance co) determined that

the fire is caused by mis-speced component, they will deny the whole
claim.  They will tell you to sue the manufacturer, or whoever made
the modification.  It is utterly irrespondable to use auto components
for house main.

**I believe that is pretty much what I said.

Then, why is the fire/insurance issue "**Irrelvant"?

 

[Trevor Wilson]

On 12/9/2011 11:43 AM, linnix wrote:

And to get the issue back on topic, the US regulatory authorities have
considerable influence of what can and can not be connected to US mains
power. In the US, however, due to the low mains Voltage, there is far
less risk to consumers than there is here in Australia.

Why is this a bad thing? The governement won't stop you (or me) from
experimenting on the main, but would stop us from selling unsafe
products to unsuspecting customers. Otherwise, i would have sold you
a furnace with auto relays. Don't blame me for burning down the
house.

**I don't consider regulation necessarily a bad thing. LACK of
regulation is, in general, far worse.

--
Trevor Wilson
www.rageaudio.com.au

 

[linnix]

On Dec 8, 3:25 pm, Trevor Wilson <tre...@SPAMBLOCKrageaudio.com.au>
wrote:

On 12/9/2011 10:22 AM, Jim Thompson wrote:





On Thu, 8 Dec 2011 15:08:05 -0800 (PST), linnix
m...@linnix.info-for.us>  wrote:

On Dec 8, 2:35 pm, Trevor Wilson<tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 8:43 AM, linnix wrote:

On Dec 8, 1:30 pm, Spehro Pefhany<speffS...@interlogDOTyou.knowwhat
wrote:
On Thu, 08 Dec 2011 12:48:13 -0500, 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.

Ed

I would not use a 12V automotive relay to switch mains voltage,
particularly inductive loads.. coil-to-contact dielectric strength of
those POS relays is<<    1kV. I like to see 4kV or so. Are the housings
required to be flame retardant?

Is the house (hosting the fridge) required to be fire retarded?

**Irrelvant. Whilst I don't know the specific legislation pertaining to
relays, here in Australia, ALL mains connected components (from
transformers to power leads) MUST have the requisite approval numbers
and, usually, fire retardant protection, or specific materials used in
their construction. Other jurisdictions may not have such legislation,
for whatever reason. Sylvia resides in Australia. As such, connecting
non-approved components may carry an insurance liability risk.

You are missing the point.  Once they (insurance co) determined that
the fire is caused by mis-speced component, they will deny the whole
claim.  They will tell you to sue the manufacturer, or whoever made
the modification.  It is utterly irrespondable to use auto components
for house main.

In such socialist societies as Australia (and coming soon to the US),
you'd better use the exact replacement and have it done by a certified
technician... otherwise no insurance coverage at all.

**Idiot. EXACTLY the same situation exists in the US. And the US, like
all Western Democracies, is, in part, a socialist nation. Always has been..

--

I think the problem is your language. You called my post irrevant
when we are agreeing on the same thing. You called JT Idiot (He may
or may not deserve it) when he is really saying the same thing: The
US is getting more socialist, like AU.

 

[kreed]

On Dec 9, 9:22 am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:

On Thu, 8 Dec 2011 15:08:05 -0800 (PST), linnix



m...@linnix.info-for.us> wrote:
On Dec 8, 2:35 pm, Trevor Wilson <tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 8:43 AM, linnix wrote:

On Dec 8, 1:30 pm, Spehro Pefhany<speffS...@interlogDOTyou.knowwhat
wrote:
On Thu, 08 Dec 2011 12:48:13 -0500, 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.

Ed

I would not use a 12V automotive relay to switch mains voltage,
particularly inductive loads.. coil-to-contact dielectric strength of
those POS relays is<<  1kV. I like to see 4kV or so. Are the housings
required to be flame retardant?

Is the house (hosting the fridge) required to be fire retarded?

**Irrelvant. Whilst I don't know the specific legislation pertaining to
relays, here in Australia, ALL mains connected components (from
transformers to power leads) MUST have the requisite approval numbers
and, usually, fire retardant protection, or specific materials used in
their construction. Other jurisdictions may not have such legislation,
for whatever reason. Sylvia resides in Australia. As such, connecting
non-approved components may carry an insurance liability risk.

You are missing the point.  Once they (insurance co) determined that
the fire is caused by mis-speced component, they will deny the whole
claim.  They will tell you to sue the manufacturer, or whoever made
the modification.  It is utterly irrespondable to use auto components
for house main.

In such socialist societies as Australia (and coming soon to the US),
you'd better use the exact replacement and have it done by a certified
technician... otherwise no insurance coverage at all.

                                        ...Jim Thompson
--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon athttp://www.analog-innovations.com|    1962     |

I love to cook with wine.     Sometimes I even put it in the food.

Wouldn't it be more correct to call the USA a fascist Nation ?

The definition of Fascism is the merger of corporation and state IIRC.

The recent laws pushed through that allow any US citizen to be
grabbed
and held indefinitely without trial or any legal process is pretty
much cut and
paste 1930s Germany. Not to mention the "super congress" crap that
is
a copy of the German "enabling act of 1933". These sort of underline
the
fascism theory.


Not that it matters, whether you set up that or socialism, there is
only one result
mountains of dead bodies, economic collapse, lack of work ethic or
interest, decay, poverty
those at the top of the tree are rich and powerful and the people are
nothing.

This is why those in power and the mega rich love to push socialism.

 

[Sylvia Else]

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.

 

[F Murtz]

linnix wrote:

On Dec 8, 4:17 pm, Sylvia Else<syl...@not.here.invalid> wrote:
On 9/12/2011 9:38 AM, Spehro Pefhany wrote:





On Thu, 08 Dec 2011 08:30:00 -0500, the renowned Spehro Pefhany
speffS...@interlogDOTyou.knowwhat> wrote:

On Thu, 08 Dec 2011 21:28:28 +1100, the renowned Sylvia Else
syl...@not.here.invalid> wrote:

On 8/12/2011 9:04 PM, Trevor Wilson wrote:
On 12/8/2011 5:50 PM, 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.

**Transformers and motors are notoriously nasty for relays to deal with.
TRIACs are a much better choice for such loads. Easy enough to design a
simple circuit, or, if you want a really easy way out, just buy a
suitably rated Solid State Relay (SSR). SSRs and VERY easy and safe to use.

--
Trevor Wilson
www.rageaudio.com.au

It's complicated by the fact that the defrost timer switch is a SPDT -
it switches between the compressor (via the thermostat, I presume) and
the defrost heater. In my relatively cursory search, I haven't found a
SPDT SSR. Could use two, I suppose, but a failure mode that leaves both
heater and compressor running seems more likely than with an
electromechanical relay.

The existing switch has contacts just as a relay would; they just don't
have an electromagnetic actuator.

The switch only cycles four times a day, so it's not so demanding in
terms of contact life.

Sylvia.

Something like the Omron G7L is properly rated for motor loads. You
could use a second relay for the heater.

Come to think of it, do you really need two contacts? If the heater is
just a few watts maybe it could be connected in series with the
compressor and shorted out to turn the compressor on.

It's not just a few watts. The rating plate says that in defrost mode
the fridge draws 450 watts. That may be the initial power when the
element is cold, but even when it's hot, it's clearly going to be
drawing significant power.


A furnace relay should work: 8A @110V, 24V coil for around $10. I
use a 5V relay to activate the 24V coil, but you can also use a
MOSFET.

we use 240 volts

http://www.zorotools.com/g/00009756/k-G0796406?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CM3D-ZPd86wCFQJ8hwodjDwxUQ

 

[linnix]

On Dec 8, 4:00 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:

On Thu, 8 Dec 2011 15:47:34 -0800 (PST), linnix







m...@linnix.info-for.us> wrote:
On Dec 8, 3:25 pm, Trevor Wilson <tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 10:22 AM, Jim Thompson wrote:

[snip]

In such socialist societies as Australia (and coming soon to the US),
you'd better use the exact replacement and have it done by a certified
technician... otherwise no insurance coverage at all.

**Idiot. EXACTLY the same situation exists in the US. And the US, like
all Western Democracies, is, in part, a socialist nation. Always has been.

--

I think the problem is your language.  You called my post irrevant
when we are agreeing on the same thing.  You called JT Idiot (He may
or may not deserve it)

Flattery will get you nowhere with me ;-)

I am not. Just stating the fact. You call someone an idiot to
counter his opinion and/or discredit him. I am countering your
flattery statement here. In this context, you deserve to be an
idiot.

when he is really saying the same thing:  The
US is getting more socialist, like AU.

 

[linnix]

On Dec 8, 4:17 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 9/12/2011 9:38 AM, Spehro Pefhany wrote:





On Thu, 08 Dec 2011 08:30:00 -0500, the renowned Spehro Pefhany
speffS...@interlogDOTyou.knowwhat>  wrote:

On Thu, 08 Dec 2011 21:28:28 +1100, the renowned Sylvia Else
syl...@not.here.invalid>  wrote:

On 8/12/2011 9:04 PM, Trevor Wilson wrote:
On 12/8/2011 5:50 PM, 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.

**Transformers and motors are notoriously nasty for relays to deal with.
TRIACs are a much better choice for such loads. Easy enough to design a
simple circuit, or, if you want a really easy way out, just buy a
suitably rated Solid State Relay (SSR). SSRs and VERY easy and safe to use.

--
Trevor Wilson
www.rageaudio.com.au

It's complicated by the fact that the defrost timer switch is a SPDT -
it switches between the compressor (via the thermostat, I presume) and
the defrost heater. In my relatively cursory search, I haven't found a
SPDT SSR. Could use two, I suppose, but a failure mode that leaves both
heater and compressor running seems more likely than with an
electromechanical relay.

The existing switch has contacts just as a relay would; they just don't
have an electromagnetic actuator.

The switch only cycles four times a day, so it's not so demanding in
terms of contact life.

Sylvia.

Something like the Omron G7L is properly rated for motor loads. You
could use a second relay for the heater.

Come to think of it, do you really need two contacts? If the heater is
just a few watts maybe it could be connected in series with the
compressor and shorted out to turn the compressor on.

It's not just a few watts. The rating plate says that in defrost mode
the fridge draws 450 watts. That may be the initial power when the
element is cold, but even when it's hot, it's clearly going to be
drawing significant power.

A furnace relay should work: 8A @110V, 24V coil for around $10. I
use a 5V relay to activate the 24V coil, but you can also use a
MOSFET.

http://www.zorotools.com/g/00009756/k-G0796406?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kw={keyword}&gclid=CM3D-ZPd86wCFQJ8hwodjDwxUQ

 

[linnix]

On Dec 8, 4:29 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:

On Thu, 8 Dec 2011 16:08:21 -0800 (PST), linnix





m...@linnix.info-for.us> wrote:
On Dec 8, 4:00 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
On Thu, 8 Dec 2011 15:47:34 -0800 (PST), linnix

m...@linnix.info-for.us> wrote:
On Dec 8, 3:25 pm, Trevor Wilson <tre...@SPAMBLOCKrageaudio.com.au
wrote:
On 12/9/2011 10:22 AM, Jim Thompson wrote:

[snip]

In such socialist societies as Australia (and coming soon to the US),
you'd better use the exact replacement and have it done by a certified
technician... otherwise no insurance coverage at all.

**Idiot. EXACTLY the same situation exists in the US. And the US, like
all Western Democracies, is, in part, a socialist nation. Always has been.

--

I think the problem is your language.  You called my post irrevant
when we are agreeing on the same thing.  You called JT Idiot (He may
or may not deserve it)

Flattery will get you nowhere with me ;-)

I am not.  Just stating the fact.  You call someone an idiot to
counter his opinion and/or discredit him.  I am countering your
flattery statement here.  In this context, you deserve to be an
idiot.

when he is really saying the same thing:  The
US is getting more socialist, like AU.

You know what they say about people without a sense of humor... they
begin to look like Larkin ;-)

Nothing wrong with that. He is not even in this discussion.

 

[linnix]

And to get the issue back on topic, the US regulatory authorities have
considerable influence of what can and can not be connected to US mains
power. In the US, however, due to the low mains Voltage, there is far
less risk to consumers than there is here in Australia.

Why is this a bad thing? The governement won't stop you (or me) from
experimenting on the main, but would stop us from selling unsafe
products to unsuspecting customers. Otherwise, i would have sold you
a furnace with auto relays. Don't blame me for burning down the
house.

 

[linnix]

On Dec 8, 5:03 pm, F Murtz <hagg...@hotmail.com> wrote:

linnix wrote:
On Dec 8, 4:17 pm, Sylvia Else<syl...@not.here.invalid>  wrote:
On 9/12/2011 9:38 AM, Spehro Pefhany wrote:

On Thu, 08 Dec 2011 08:30:00 -0500, the renowned Spehro Pefhany
speffS...@interlogDOTyou.knowwhat>    wrote:

On Thu, 08 Dec 2011 21:28:28 +1100, the renowned Sylvia Else
syl...@not.here.invalid>    wrote:

On 8/12/2011 9:04 PM, Trevor Wilson wrote:
On 12/8/2011 5:50 PM, 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.

**Transformers and motors are notoriously nasty for relays to deal with.
TRIACs are a much better choice for such loads. Easy enough to design a
simple circuit, or, if you want a really easy way out, just buy a
suitably rated Solid State Relay (SSR). SSRs and VERY easy and safe to use.

--
Trevor Wilson
www.rageaudio.com.au

It's complicated by the fact that the defrost timer switch is a SPDT -
it switches between the compressor (via the thermostat, I presume) and
the defrost heater. In my relatively cursory search, I haven't found a
SPDT SSR. Could use two, I suppose, but a failure mode that leaves both
heater and compressor running seems more likely than with an
electromechanical relay.

The existing switch has contacts just as a relay would; they just don't
have an electromagnetic actuator.

The switch only cycles four times a day, so it's not so demanding in
terms of contact life.

Sylvia.

Something like the Omron G7L is properly rated for motor loads. You
could use a second relay for the heater.

Come to think of it, do you really need two contacts? If the heater is
just a few watts maybe it could be connected in series with the
compressor and shorted out to turn the compressor on.

It's not just a few watts. The rating plate says that in defrost mode
the fridge draws 450 watts. That may be the initial power when the
element is cold, but even when it's hot, it's clearly going to be
drawing significant power.

A furnace relay should work:  8A @110V, 24V coil for around $10.  I
use a 5V relay to activate the 24V coil, but you can also use a
MOSFET.

we use 240 volts





http://www.zorotools.com/g/00009756/k-G0796406?utm_source=google_shop....{keyword}&gclid=CM3D-ZPd86wCFQJ8hwodjDwxUQ- Hide quoted text -

Yes, it will handle 8A at 240V.

 

[Sylvia Else]

On 9/12/2011 5:59 AM, mike wrote:

A clock motor has about zero torque. Takes very little friction in
the first few gear reduction stages to stop it. hardened grease can
easily do it. Just cleaning out the dried up grease can make it work.

Mine ran for another decade after I cleaned/oiled it.
Replacement was about $13, but it failed after a week. Second replacement
timer lasted years before I retired the fridge.

The symptom of failure is that the motor is making a noise. It's a
familiar grating noise that I've heard from other aging clock motors. I
presume it's the rotor rubbing against the stator, given that the rest
of the mechanism consists of nylon gear wheels, though someone may want
to advise otherwise.

Sylvia.

 

[ehsjr]

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.

Ed

 

[Jasen Betts]

On 2011-12-08, Phil Allison <phil_a@tpg.com.au> wrote:

"kreed"

"TW"

**Transformers and motors are notoriously nasty for relays to deal with.
TRIACs are a much better choice for such loads. Easy enough to design a
simple circuit, or, if you want a really easy way out, just buy a
suitably rated Solid State Relay (SSR). SSRs and VERY easy and safe to
use.


Even though SSR's and Triacs are quite rugged, something like a surge
from a lightning strike or similar event could cause one or both of
these triacs/SSR's to short out,

** Nonsense.

If the max voltage rating of a triac is exceeded by a spike on the AC
upply - it simply turns on for the rest of that half cycle.

yeah, over voltage, or excessive dV/dt, will turn them on,
but couldn't subsequent over-current cause them to fail closed?

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Jasen Betts]

On 2011-12-09, Sylvia Else <sylvia@not.here.invalid> wrote:

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

CD4060, CMOS logic, an R-C astable and a 14-stage divider chain in
one DIP package, but not strong enough to drive a relay directly like
an LM555 would be.

Sylvia.

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Jasen Betts]

On 2011-12-09, Trevor Wilson <trevor@SPAMBLOCKrageaudio.com.au> wrote:

And to get the issue back on topic, the US regulatory authorities have
considerable influence of what can and can not be connected to US mains
power. In the US, however, due to the low mains Voltage, there is far
less risk to consumers than there is here in Australia.

less risk of fatal electric shock, more risk of fire from overheating
conductors.

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[Phil Allison]

"Jasen Betts Sheep Shagger "

yeah, over voltage, or excessive dV/dt, will turn them on,

** LOL .....

but couldn't subsequent over-current cause them to fail closed?

** So could an errant meteorite.

You fucking, autistic Kiwi moron !!!



.... Phil

 

[Michael A. Terrell]

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.


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