I know I'm beating a dead horse here, but...
 

I wanted to discuss the merits of connecting a spa panel GFI to a 3-wire dryer outlet vs. having a 4-wire outlet installed. I know that the connection to the 3-wire outlet is safe, but I've had an electrician quote $275 to add a new breaker and line and don't really know if it's worth it. Seems pretty damn high to me, so maybe a different electrician might quote lower, but the question remains.

Use the 3-wire, or have an electrician add a new circuit?

P.S.
The one other variable is that he'd put the new outlet outside, so I wouldn't have to run my cable through a window or door for brew day.

Anyone?

its a dead horse... which means its already been beaten to death.. do a search

Clearly I've done a search and read a lot about it. Thanks for being so friendly.

Just wanted some discussion about my specific situation.

run a straight 240 volt system using the 3 wire system you already have. plug your pumps into a wall outlet. everything properly grounded. no problem.

Wait, why would I run my pumps on a wall outlet? Should be fine pulling 120V from the 3-wire, yes?

Also, my control panel is already done, and I don't want to re-wire it if I don't have to.

The problem you have with your dryer circuit is that you are short one conductor (wire) by running your pumps are the only thing that actually needs a neutral conductor. your pid and contactors (if you used 240v contactors) don't require a neutral conductor... Problem solved

Yes you can pull the 120V pumps from one leg of the 240.

Yes, the whole thing will work fine off 240V 3 wire. Ground all exposed metal to a a ground wire that bypasses the spa panel, connecting to the neutral before it reaches the panel. So, H-H-N to the spa panel, then use 4-wire H-H-N-G to the control box. 240V devices get wired H-H, 120V devices get wired H-N, and all exposed metal is tied to G. This way the GFCI will trip.

This is not ideal because you've got a ground wire tied to a neutral which is carrying current (the return from the 120V devices). But it will all work fine and might still save your life. If the neutral is loose going to the panel, and you get a live short in the pot, you might have a problem (besides the pumps not working), but you'll be the first to know.

Boy I'll bet I'll pay for responding to this thread. Damn the torpedos!

I'm not following you completely, but I understand I only have 3-wires with no ground. However, following P-Js diagram to hook up a GFI spa panel to a 3-wire outlet, it should work correctly, yes? That was my understanding.

The control panel is done I've been using it for a while. I already own the spa panel. Minimizing the changes is important to me.

I've never looked at a P-J drawing. Can't help you there. I built my two panels well before he was a member here.

If you're not comfortable with it, just get a electrician buddy to help you.