Left a 400 W dehumidifier running off a wattmeter. After a week
or two, the dehumidifier didn't work any more. The fan is on but
when the compressor tries to start, the display jumps to about
1200 W for a couple seconds, a click is heard (maybe a klixon)
and that's it.

The dehumidifier works fine without the wattmeter.

The wattmeter now reads 300+ W for three 36 W FT when it used
the read about 140 W.

Is this a well-known failure mode ? Bad shunt ?

Thanks in advance.

--
André Majorel http://www.teaser.fr/~amajorel/
J'ai des droits. Les autres ont des devoirs.

RoHS strikes again.



"Andre Majorel" wrote in message
...
Left a 400 W dehumidifier running off a wattmeter. After a week
or two, the dehumidifier didn't work any more. The fan is on but
when the compressor tries to start, the display jumps to about
1200 W for a couple seconds, a click is heard (maybe a klixon)
and that's it.

The dehumidifier works fine without the wattmeter.

The wattmeter now reads 300+ W for three 36 W FT when it used
the read about 140 W.

Is this a well-known failure mode ? Bad shunt ?

Thanks in advance.

--
André Majorel http://www.teaser.fr/~amajorel/
J'ai des droits. Les autres ont des devoirs.

Andre Majorel wrote:
Left a 400 W dehumidifier running off a wattmeter. After a week
or two, the dehumidifier didn't work any more. The fan is on but
when the compressor tries to start, the display jumps to about
1200 W for a couple seconds, a click is heard (maybe a klixon)
and that's it.

The dehumidifier works fine without the wattmeter.

The wattmeter now reads 300+ W for three 36 W FT when it used
the read about 140 W.

Is this a well-known failure mode ? Bad shunt ?

Thanks in advance.


The only thing I can think of is to find out what inrush current is the
Wattmeter designed for. In other words is it rated for motors?

Remember that a dehumdifier is a small regrigerator (with the door wide
open) and as such has a high initial current draw to get the compressor
motor started...

I'm sure someone here can answer the question of how much inrush
current/power to expect on a 400W dehumdifier, but at a guess I'd say 15
to 20A (1200 - 1500ish W).

So, yes, your shunt may well be compromised.

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On Wednesday, July 25, 2012 8:27:08 AM UTC-7, John Robertson wrote:
Andre Majorel wrote:
> Left a 400 W dehumidifier running off a wattmeter. After a week
> or two, the dehumidifier didn't work any more. The fan is on but
> when the compressor tries to start, the display jumps to about
> 1200 W for a couple seconds, a click is heard (maybe a klixon)
> and that's it.
>
> The dehumidifier works fine without the wattmeter.
>
> The wattmeter now reads 300+ W for three 36 W FT when it used
> the read about 140 W.
>
> Is this a well-known failure mode ? Bad shunt ?
>
> Thanks in advance.
>

The only thing I can think of is to find out what inrush current is the
Wattmeter designed for. In other words is it rated for motors?

Remember that a dehumdifier is a small regrigerator (with the door wide
open) and as such has a high initial current draw to get the compressor
motor started...

I'm sure someone here can answer the question of how much inrush
current/power to expect on a 400W dehumdifier, but at a guess I'd say 15
to 20A (1200 - 1500ish W).

So, yes, your shunt may well be compromised.

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

Since these meters like the 'Killawatz' are intended for monitoring power consumption of appliances [they even advertise 'refridgerator' in their blurbs] one would hope that they were designed to tolerate the starting currents of common compressors. That said, they were made in China and I would tend to suspect poor soldering of the shunt to the PCB although a voltage drop enough to stall compressor start would likely cremate the connection almost instantly. Time to look inside the meter.

Neil S.
PS. when mine went funny and always read 60Hz as 120Hz, the cost to have it repaired was $5 more than buying a new one.

nesesu wrote:
On Wednesday, July 25, 2012 8:27:08 AM UTC-7, John Robertson wrote:
Andre Majorel wrote:
> Left a 400 W dehumidifier running off a wattmeter. After a week
> or two, the dehumidifier didn't work any more. The fan is on but
> when the compressor tries to start, the display jumps to about
> 1200 W for a couple seconds, a click is heard (maybe a klixon)
> and that's it.
>
> The dehumidifier works fine without the wattmeter.
>
> The wattmeter now reads 300+ W for three 36 W FT when it used
> the read about 140 W.
>
> Is this a well-known failure mode ? Bad shunt ?
>
> Thanks in advance.
>

The only thing I can think of is to find out what inrush current is the
Wattmeter designed for. In other words is it rated for motors?

Remember that a dehumdifier is a small regrigerator (with the door wide
open) and as such has a high initial current draw to get the compressor
motor started...

I'm sure someone here can answer the question of how much inrush
current/power to expect on a 400W dehumdifier, but at a guess I'd say 15
to 20A (1200 - 1500ish W).

So, yes, your shunt may well be compromised.

John :-#)#

....

Since these meters like the 'Killawatz' are intended for monitoring power consumption of appliances [they even advertise 'refridgerator' in their blurbs] one would hope that they were designed to tolerate the starting currents of common compressors. That said, they were made in China and I would tend to suspect poor soldering of the shunt to the PCB although a voltage drop enough to stall compressor start would likely cremate the connection almost instantly. Time to look inside the meter.

Neil S.
PS. when mine went funny and always read 60Hz as 120Hz, the cost to have it repaired was $5 more than buying a new one.

Fair enough - I am not familiar with these devices as electricity here
in Vancouver, BC (Canada) is still pretty reasonably priced...

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

On 7/25/2012 1:49 AM, Andre Majorel wrote:
Left a 400 W dehumidifier running off a wattmeter. After a week
or two, the dehumidifier didn't work any more. The fan is on but
when the compressor tries to start, the display jumps to about
1200 W for a couple seconds, a click is heard (maybe a klixon)
and that's it.

The dehumidifier works fine without the wattmeter.

The wattmeter now reads 300+ W for three 36 W FT when it used
the read about 140 W.

Is this a well-known failure mode ? Bad shunt ?

Thanks in advance.

You've asked for help with the failure modes of a wattmeter while
giving no, zero, not any clues as to what kind of wattmeter.

It's like asking, "What's wrong with my car?" It doesn't work any more.

On 2012-07-25, John Robertson wrote:
Andre Majorel wrote:
Left a 400 W dehumidifier running off a wattmeter. After a week
or two, the dehumidifier didn't work any more. The fan is on but
when the compressor tries to start, the display jumps to about
1200 W for a couple seconds, a click is heard (maybe a klixon)
and that's it.

The dehumidifier works fine without the wattmeter.

The wattmeter now reads 300+ W for three 36 W FT when it used
the read about 140 W.

Is this a well-known failure mode ? Bad shunt ?

The only thing I can think of is to find out what inrush current is the
Wattmeter designed for. In other words is it rated for motors?

The manual only says 16 A / 3680 W (I'm not in 115 V-land).

Remember that a dehumdifier is a small regrigerator (with the door wide
open) and as such has a high initial current draw to get the compressor
motor started...

I'm sure someone here can answer the question of how much inrush
current/power to expect on a 400W dehumdifier, but at a guess I'd say 15
to 20A (1200 - 1500ish W).

So, yes, your shunt may well be compromised.

The shunt appears to be a cm-long piece of copper alloy wire, no
markings, CSA about 1 mm². When my free time becomes copious
again, I'll try to compare its resistance with a not-yet fried
unit.

Thanks everyone.

--
André Majorel http://www.teaser.fr/~amajorel/
J'ai des droits. Les autres ont des devoirs.