care is always important..
and just say you were using an electric heater/heavy power tools and the fridge turned on and *blam* no electricty
what i would be thinking about is WHY you had an electric heater/tools on that circuit in the place you had it..
and i would advise you find an outlet in a better place to run it if possible..

and yes your dryer circuit should be GREAT but you are gonna have to find a way to tap that power.. it is 220v...
and the washer MAY NOT be good cause it could be on a circuit that has OTHER stuff on it..
get a radio and go around the house plug it into ALL of your plugs and see where it turns off when you flip different breakers..
you might be surprised.
and DONT trust the writing on the panel..
mine was ALL fucked up bro.

my advice is look for a 20 amp breaker and trace what it goes to.. you may find one that goes somewhere interesting..

final advice have an electrician come in and run a 20 amp plug box to where ever you want to grow and say you want to set up a workshop and you think that it will trip MORE breakers if you do.. he should be able to do it with conduit and heavy wire for a couple hundred bucks and then you would have a DEDICATED circuit for growing on..
just my :twocents:

if you want more/different advice i will ask my roomie in the AM.. he is an electrician and could give you ideas i cant..
peace

~MG a.k.a. le Maine développé