I am looking to install toe heater by the kitchen sink. I'm l this just looking for a little extra heat in the kitchen is a 3 inch pipe off the trunk too small to do anything?

 

Three inch is a little small but every little bit helps. Are you limited to 3" due to the toe kick size ?

 

didn't want to take away more than needed from the trunk, might be a better idea to use 4'' and I can always use a damper to slow it down if needed.
I went to homedepot/lowes and found the ducts to get under the sink but was having a hard time finding something flipping 3'' 90degrees and then shooting out to a 2x14 or 3x14.
I have some options but am looking to do it cheaply.

I have about 5'' of space between the floor under the sink and the plywood shelf.

 

I cut out my toe kick. Took a piece of metal duct.... like 3x10. The duct was about 18" long. I capped the end that went towards the wall. About a foot, straight back from the toe kick opening, I drilled a 4" hole thru the floor. I inserted the duct where it was going to end up. I went down in the basement and traced the 4" hole on the duct. I pulled the duct back out and cut the hole. I put the duct back in. Took my 4" supply line and cut tabs at the end. Pushed the 4" line up thru the hole and bent the tabs over. Taped tabs and connection. Installed register.

 

Good idea did you use just a plate for the kick plate cover? Or an insert

 

When I installed mine under the cabinet I just moved the floor vent under the cabinet, added lumber under the cabinet base to contain/direct the air flow, cut the hole in the toe kick and installed the register. Works great.

 

PJ's answer is perfect. You use all standard fittings except for the hole you need to cut in underside of duct.

Price should be reasonable:
short 3.25 x 10 duct
Register for above
4" round duct
tape, and you are done!

I would put a register there in toekick so you can close it if needed.

 

Use the bottom of the cabinet area for a plenum and just install a register wherever you want it. You don't have to attach the duct to the register boot. Is that what everyone is saying?

 

I used an actual metal register but just a plate is also fine.

 

4in duct will only give you about 35 cfm if sized correctly

 

If anyone wants to see how it went, still need to find a grate the fits.

 

Looks like a "grate" job. The piping should be insulated, as well as the plenum.

 

I agree with adding insulation! ... I like your helper .... or is she the boss/inspector

 

The grates are around. Here's one in nickel finish. They also have other finishes.

Great grate in nickel finish at amazon

 

Thanks a lot that was exactly what I needed

 

That is what you call a professional job, and probably better than professional.

Looks very nice.

 

insulation is not required if the space is conditioned.