[Homeroast] Behmor Question

Martin Maney maney at two14.net
Sat Dec 5 11:52:15 CST 2015


On Sat, Dec 05, 2015 at 09:08:51AM -0800, John Nanci wrote:
> Someone correct me if I'm wrong, but I disagree with this.  A variac
> will not stabilize your voltage.  It only allows you to change it
> proportional to the incoming voltage (and sometimes boost it).  If
> your voltage is at drops by half, the output will drop by half also
> at a given setting.

Correct.  But if the problem is a persistently low line voltage then
the five or ten percent boost that many Variacs allow my indeed help. 
If the problem is line droop under load then it's more of a balancing
act, or playing with the variac as the roast progresses and the load
changes (afterburner kicks in - it's nearly a third of the total
power! - or thermostatting of the main heater towards the end). 
Frankly, if the problem is line droop under the Behmor's load, the
first choice would be looking for a more stable outlet anyway.

> Also, that listed variac is WAY undersized for a Behmor.  It is
> listed as 3.3 amps.  The Behmor draws around 14 amps.

Also correct, but...  Variacs are (or should be) rated for continuous
operation, and the limiting factor is generally heat rise (from both
the non-zero winding resistance as well as loss in the magnetic core). 
So for a relatively short roast cycle, you may get away with
overloading the variac, at least in the short term.  A properly sized
variac can easily outlive more than one roaster - I know a fellow who
simply plugged his second HotTop into the ol' variac and resumed
roasting.

-- 
No one likes change unless he makes it himself.
Then it's innovation.  -- Sherwood Smith




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