I am installing a 5000 Watt 240 Volt Single Phase Heater in my garage. I currently have 110 in the garage running from my house through 1" PVC undergorund. I want to remove that, run 50 amps to a sub panel in the garage, and run the heater from that, as well as the 110 outlets, lights and garage door opener.
I have a 50 amp double pole breaker in my house panel for this run. The existing conduit in the wall for the old 110 run is 3/4" from the panel to a 4 x 4 box about 15' away. It then drops to 1/2" conduit from that box, runs about 3' down the wall, and feeds an outside box on the outside wall of the house. From the outside box, the 1" pvc runs underground to the garage, about 35' away.
The 3/4" conduit run above has 4 12ga wires in it now, 2 hots and 2 neutrals. 1 set feeds a couple of outlets and the other set continues on through the 1/2" conduit mentioned above to feed my shed.
My first problem is, if I use UF for the outside run, 6/3 will not fit into 1" PVC. However, 8/3 fits comfortably. Secondly of course is the 3/4" and 1/2" conduit capacity.
So, can I use 8/3 for this entire run? That would be standard 8/3 copper from the 50 amp breaker in my house panel, through the 3/4" conduit with the 4 other 12ga wires, through the 1/2" conduit with the 2 other 12ga wires, tie into 8/3 UF in the box on the outside wall of the house, and run through the 1" PVC to the garage. In the garage, the 8/3 UF would tie into standard 8/3 copper in a 4 x 4 box and run from there to the subpanel. From the subpanel, the heater would run from a 25 amp breaker and the 110 would run from a 20 amp single pole breaker.
I understand it would be better to run 6ga the whole way and lay new PVC, as well as run additional conduit in the house. But since that is not an option right now, it's 8ga as described above, and through the exisitng conduit in the house, or nothing at all. So I'm wondering if this will work, or is it completely out of the question. What about using a 45 amp or 40 amp breaker in the house panel instead?
Thank you in advance for your help!