Could installing a furnace to the floor joists cause the floor to slope?

[JKL]

I have a small 1920's house and about a year and a half ago had a new furnace installed. It is relatively small (for a 600 sq ft house) and the contractor chose a horizontal model and installed it in the crawl space in the basement to save space. It is attached to the floor joists. Within the past month or two, I noticed that the floor above seems to be sloping. I'm not sure if it has always sloped and I'm just noticing it (I was doing some other remodeling during which I started to notice every defect in the house), or if this is new. Are these furnaces heavy enough to cause the floor to slope? I'd estimate the slope to be about 1/4 inch. I'm a little suspicious because it seems to be sloping the most about where the furnace is. Thanks for any help.

[TJ1962]

Not knowing the size of furnace etc, it would be difficult to comment for certain. What is the span of the joists ie: length and width of home, spacing between the joists themselves, live load of home, etc.

As a general question of "if this may cause the beams to sag", if the load is too much for the joists they can be damaged.

You could consider pouring a raise slab for the furnace to rest on instead.