[Homeroast] Using a Variac to control a GeneCafe

Dean dean_schaffran at wildblue.net
Sat Aug 20 21:21:08 CDT 2011


Ken,

If your Variacs are set up to boost as well as adjust, 100% would 
probably be around 140 v (they will boost upwards of 17% if they are 
wired right),  so l'd start at the dot (around 85% if it's like mine) 
and use a volt meter to confirm.  Not all Variacs are wired to boost, 
so using a volt meter is important for safely.

Heat is proportional to the square of voltage (current) so boost 
conservatively!!  A 5% boost (6 volts) will give you 10% more power 
and probably reduce the heater life by as much as 20-25%, and motor 
life as well

Kill-a-Watt is a nice gadget to check voltage & power under load--I 
wish mine hadn't gotten damaged.

Have fun experimenting!

Dean
Too cheap to replace a broken toy in da weeds......

On 8/17/2011 7:30 AM, Ken Knott wrote:
> I have access to Variac's so I thought I might give them a shot to control my Gene CAfe.  I understand that power fluctuations at the outlet are common and can make a significant difference in controlling your roast profile's conistency.
> So...  My Variac's can be set to 120V or 140V.  I imagine I would want to use 120V.
> Second questions.  From there, I can set my Variac from 0 to 100%.  As wall outlet are supposed to provide 120V, am I correct in that I would set it to 100% and then plug in the old GeneCafe?  I'd rather not fry my GeneCafe if possible...  :)
> Thanks in advance,
> Ken 		 	   		
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