how many hinges on a door?

[seneca]

might seem like a pointless question, but I've noticed that hinges are usually sold in 3's. I'm replacing white moulded doors (2 hinges) with oak veneered (hardwood core) with glass panels. These are heavier than the old ones, so should I use 3 hinges?

I'm also considering using self closing hinges (spring type) and these come in 3's too. Could I get away with using 2 that are fire door rated. Not sure, but do the fire door kind take a heavier door?

 

[gregers]

on molded mdf type doors you an get away with 2 3inh hinges,but on heavier/fire doors it is recommended that 3no 4 inch hinges are used to distribute the weight of the door.

 

[ladylola]

Agreed I always prefer to use three even when it seems like overkill. Also it is said that three hinges make the door less prone to distorting.