coffee-forum.net
Promoting coffee discussion.

Main
Date: 24 May 2007 14:53:46
From: Jim
Subject: Variac for poppery roasting
Any recommendations from those with experience? With a 1500W rating,
I'm guessing a 10A is a bit anemic and could blow internal fuses, even
with the fan on its own circuit.




 
Date: 26 May 2007 10:17:07
From: Steve Ackman
Subject: Re: Variac for poppery roasting
In <135c2b8cs04kd17@corp.supernews.com >, on Thu, 24 May 2007 14:53:46
-0700, Jim wrote:
> With a 1500W rating,
> I'm guessing a 10A is a bit anemic and could blow internal fuses, even
> with the fan on its own circuit.

People generally replace fuses on variacs with
oversized ones. In general, transformers are rated
at their 100% duty cycle. When you use it for short
intermittent loads such as 7 to 10 minute coffee
roasting duty, you can easily exceed that rating
by 50% to 100% without having the transformer overheat.



  
Date: 29 May 2007 09:51:52
From: Brent
Subject: Re: Variac for poppery roasting


>> With a 1500W rating,
>> I'm guessing a 10A is a bit anemic and could blow internal fuses, even
>> with the fan on its own circuit.
>
> People generally replace fuses on variacs with
> oversized ones. In general, transformers are rated
> at their 100% duty cycle. When you use it for short
> intermittent loads such as 7 to 10 minute coffee
> roasting duty, you can easily exceed that rating
> by 50% to 100% without having the transformer overheat.
>

Until you do repetitive back to back roasts for whatever reason, at which
point, um, bad things can happen... but 3 or 4 roasts isn't overly
repetitive...

Brent




   
Date: 28 May 2007 16:04:59
From: Jim
Subject: Re: Variac for poppery roasting
Brent wrote:
>>>With a 1500W rating,
>>>I'm guessing a 10A is a bit anemic and could blow internal fuses, even
>>>with the fan on its own circuit.
>>
>> People generally replace fuses on variacs with
>>oversized ones. In general, transformers are rated
>>at their 100% duty cycle. When you use it for short
>>intermittent loads such as 7 to 10 minute coffee
>>roasting duty, you can easily exceed that rating
>>by 50% to 100% without having the transformer overheat.
>>
>
>
> Until you do repetitive back to back roasts for whatever reason, at which
> point, um, bad things can happen... but 3 or 4 roasts isn't overly
> repetitive...
>
> Brent
>
>

I "won" a 15A Staco 3PN1510 off of ebay, so I'm set. When it gets here,
the Poppery is getting an additional power cord, fan only, to connect to
my small variac. The heater will connect to the big one. Then the
experimentation will begin...

Those with experience in a similar setup are encouraged to offer tips!