Sometimes when we convert an existing water system to a Certified Water System, we run into some problems with the electrical service.
When we are upgrading electrical (installing a sub-panel for a surge suppressor or electrical receptacle to run a heat tape) the neutral cannot be connected to a ground lug at the remote location. Neutral wires carry the current imbalance and therefore are required to be an insulated conductor to carry this current all the way back to the point of origin. A bare ground wire cannot be used as a neutral.

This “extra” or leftover current can then be sent to ground at main panel or meter (switch) so long as it reaches the point of origin.
This means that if all you have coming from the house is 2-wires plus a ground, the wire  will need to be replaced with 3-wires plus ground (or add a neutral leg/wire if in conduit) to give you 3 conductors plus the ground.

Then we can put a neutral bar (isolated and insulated) in the remote or sub-panel and separate the ground. The white wire on a 120V circuit goes to the neutral and then back to the main disconnect (at the house or meter).
This will bring the system up to code and allow the receptacle and surge suppression, as well as any other 120v circuits at the equipment, to operate properly and safely.