It is a PVC piece that when you cut to length and put inside the sill (right where the bottom sash goes) it is about 1/4" higher than the sill so that a window A/C will sit on the support and not on the sill itself to avoid damage to the sill.

Well, it sits perfectly inside the sill but the A/C unit simply won't sit on it. Few issues:
1. It slips out, there is nothing that supports the bottom rail form moving forward or backwards.
2. It is higher than the sill, which means there is a gap left underneath the side curtains.

It just doesn't make sense to me. It is meant specifically to have a window A/C unit and prevent sill damage, but it won't work.

Any idea?

 

I didn't see any product like you mentioned on the Harvey's site.

There is no perfect install product for window A/C's. Every window and every A/C is different.
I have a bin full of molding pieces and cutoffs. There is always that one window.

 

It is in their PVC Products catalog.



Question is - it is a Harvey window so clearly they made it to be 1/4" higher than the sill, so why would it not work?

How 'bad' is it anyways to lean the a/c on the sill?

 

That adapter looks like nothing more than a block of wood. Which most window A/C units would recommend. You want to spread the points of contact of the A/C across the sill as opposed to just setting it on the sill proper.

 

Looks like just a piece of plastic. Basically similar to what I use only plastic instead of wood.



I see no problem letting the A/C sit on the sill. It just needs to be protected from scratching.

 

Something doesn't make sense to me. I get it that there should be a support so that it won't sit directly on the sill itself, but how can it sit higher than sill (on a support) when there is nothing supporting the a/c from moving forward or backward? If you don't use a support, the sill itself supports the a/c's movement and because of the side curtain rails the bottom of the a/c is not flat. What am I missing here?

 

There should be a flange at the top that you insert screws in to the window sash to hold the unit in place. This prevents the A/C from falling out. It's always a challenge to hold in place while closing window on the top and securing the screws. Especially on an upper floor. For best results use two people.

 

I guess I was using the wrong terminology. I was referring to the front vertical part of the window frame, probably not the 'sill' (see below). So without this "Sill support", I suspect that the a/c unit is sitting on this part of the frame, which is what holds it from sliding forward. It sits perfectly this way, I am just not sure if it causes any damage to the frame like this (to the piece it sits on).

 

As PJ says it might scratch it a little but if it fits you're good to go.

 

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Thank you both!
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Yes, you don't want to set the window A/C on the window sill (with red arrow) without using some sort of block to raise the unit slightly above the red arrow piece, and distribute the weight across a wider area.

The weight of the A/C pulls down and out on the top lip of the A/C... and the bottom wants to push IN to the room, not fall out. Most units of any size whatsoever will have angle brackets on the bottom of the A/C box that are adjustable and brace the unit against the exterior side of the house so that it can't slide inward on the bottom.