Geforce gts 250 workable at 22a ?

Yes. A 512 MB GTS250 needs less than 7 amps.

But your PSU sounds like an older generic unit. You might want to give some thought to upgrading it. I'd suggest a Corsair 400CX (30 amp 12 volt rail):
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

22Amps on a 450W PSU means its a low quality PSU.
A good 450W PSU should deliver 30-33 Amps.

Don't take any chances.

Get a new PSU.

Some options:
Corsair 400CX:
http://www.newegg.com/Product/Product.aspx?item=N82E168...

OCZ ModXstream 500W:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Actually it's quite good as most generic PSU's are only pushing 15 -17amps on the 12volt rail.

Efficiency around 58%(Theoretical   ).
That shows it is a low quality PSU.
I know it can handle that card but straining a low quality PSU for long might be harmful...

And may I ask how you got to that number.

Here have a look at this, a 450w PSU with less than 30amp on the 12v but 80% efficient.

P=VI
On 12V Rail
P=12X22
=264W

Rated 450W

efficiency=(Output/Input)/100
=58%

Don't get mad on me if I'm wrong somewhere  

If you click on the link in my post above you will see that it's not quite as simple as that.

i had the same problem when i bought my gts 250. i ended up buying a cooler master GX650W which gives 52A. A bit of an overkill alright but no chances taken whatsoever. it might just come in handy if u add another gts 250. the card's a beauty, especially in SLI, so the benchmarks say.