This is a question for both an HVAC installer and an electrician.

I have and (sic) electrician who has done the regular type of rural wiring from the transformer on the road to the potheads on the house and to the panel but and I say but I want to know what should be done correctly to make sure I get the safest and correct installation.. I am in the bush in a less developed area on an island, two dogs, five donkeys and a lot of ocean and need help with the installation of a Seisco tankless electric hot water heater. Electricity costs are a @#... so running a regular hot water tank is nuts.

I have a panel large enough and 120 or 240 power available. My water pumps are 240. Power outages are regular occurrences
I have a Seisco model # sh/ra- 14
V-240
A 29.2
KW 7
Hz 50/60

A large panel, a sub panel with space for two breakers and a knock off switch,

QUESTION:
1) what gauge wire do I use from the panel to the sub panel, and

2)what gauge wire doe I use from the sub panel to the seisco unit, the seisco unit has two wires with clamps/connectors for hookup.

3)what size breakers (double pole) 20 or 30?

I am using kitec piping (canadian tire brand) to the existing hot water line.
Copper 3/4 inch out take from the seisco to connect to the existing hot water house supply which is 1/2 pvc with
Copper 3/4 inch cold water intake on the seisco unit hooked into an available 3/4 pvc cold water supply, cold water is 70 - 90 degrees before heating
I have pvc and cpvc fittings with shark bite connectors. Connectors are copper to pvc/cpvc, and pvc to pvc The piping is not the problem, the electrical is.

I could really use some specific information so that I can make sure the electrician does this right.

My donkeys would appreciate your help. Next step solar.

This is a question for both an HVAC installer and an electrician.

I have and (sic) electrician who has done the regular type of rural wiring from the transformer on the road to the potheads on the house and to the panel but and I say but I want to know what should be done correctly to make sure I get the safest and correct installation.. I am in the bush in a less developed area on an island, two dogs, five donkeys and a lot of ocean and need help with the installation of a Seisco tankless electric hot water heater. Electricity costs are a @#.... so running a regular hot water tank is nuts.

I have a panel large enough and 120 or 240 power available. My water pumps are 240. Power outages are regular occurrences
I have a Seisco model # sh/ra- 14
V-240
A 29.2
kW 7
Hz 50/60

A large panel, a sub panel with space for two breakers and a knock off switch,

QUESTION:
1) what gauge wire do I use from the panel to the sub panel, and (Depends on the length of the wire not just the gauge)

2)what gauge wire doe I use from the sub panel to the seisco unit, the seisco unit has two wires with clamps/connectors for hookup. You will have two 120 legs 180 degrees out of phase, wires should be but don't have to be Red, (120) Black (120) and bare or green (ground)

3)what size breakers (double pole) 20 or 30? Follow the manufacturers directions, they usually supercede local codes.

I am using kitec piping (canadian tire brand) to the existing hot water line.
Copper 3/4 inch out take from the seisco to connect to the existing hot water house supply which is 1/2 pvc with
Copper 3/4 inch cold water intake on the seisco unit hooked into an available 3/4 pvc cold water supply, cold water is 70 - 90 degrees before heating
I have pvc and cpvc fittings with shark bite connectors. connectors are copper to pvc/cpvc, and pvc to pvc The piping is not the problem, the electrical is. Sorry I'm not much of a plumber

I could really use some specific information so that I can make sure the electrician does this right.
Do you have a building code inspector?

My donkeys would appreciate your help. Next step solar.
Hope this helps