Is the circuit currently 115 or 230 (or your preferred interpretation there of of residential voltage levels)?

If it is currently setup for the lower voltage, the 18 amps will be about right for the startup current. It will drop some once the motor gets going. If it is currently wired for the higher voltage rating, the current draw will be down around 6-8 amps depending on the efficiency of the motor and a few other factors. A quick search popped up this file:

http://www.lockewell.com/pdf/aosmith/aosmith-UST.pdf

According to that, the 230 volt current draw is 18.6 on the 115 volt side of things and 9.3 amps on the 230 volt side of things. The H250 manual can be found here:

http://www.hayward-pool.com/pdf/manuals/Manual285.pdf

It lists the electrical requirements for you as well on page 15, and lists it at 0.3 amps.

The other issue of course is that if your 30 amp circuit is 230 volt right now, that won't be much help with hooking up a refrigerator which will likely be 115 volt. You can do it, just the last I checked it was a code violation (used to see people tap off from the legs of 230 volt circuits fairly often to add outlets in kitchens and the like). Since you say it is a 30 amps though, chances are better than not that it is a 230 volt circuit. 115 can be run at that high of current, but it is very rare for it to be done in that manner.

That means you will likely need to run a 115 volt circuit out to where you want the fridge. GFCIs and all of that as well - give your self an additional outlet for miscellaneous stuff like a radio. If you really don't want to run a new circuit, take a look at your lighting circuit. If you have one, pretty good chance that it is 115.