Thanks for kick start this thread; I've been meaning to get back to for an update on what I did.

When I bought the house some 5 years ago. It can with a four season built in hot tub room. My problem was every time I used it my electric bill would sky rocket. Never owning one before I assumed at first this was the price you pay to run one.

Here's what I did.

The system was a Hercules designed sometime during the 70's I think, Excellent design for it era. When I opened the panel the wiring was old brittle and devices signs of corrosion.

First,

I gutted the panel. Keeping only the stainless steel tube, thermo overload devices, air tube switches and enclosure that mounted to the hot tub water system. (I will refer to this unit as Node2).

Second,

I added a 24-24-6 NEMA box for easy accessible troubleshooting and monitoring of the system (I will refer to this as Node1).

Third,

Ran 25cont 22ga cable from Node1 to Node2 for 24Vdc IO communication.

Ran 7-10ga wires for pump, blower, heater, and ground from Node1 to Node2.

Ran thermostat wire for temp monitoring

Forth,

Upgrades in Node1

Replaced 5kw heater

Replaced water flow sensor

Fifth,

New Node2 System

Micro PLC for control and monitoring of system

3 motor control relays with high amp contacts

Temperature controller

Theory,

Sequence of controller operation:

Every hour of processor time I have pump circulate water at low speed.

Auto sets temp controller for use or standby

Controls user blower and/or pump speed

Auto Pump/blower/heater timeout for energy savings (Teenager).

Final Note:

After replacing old wiring and relay components plus adding PLC control system. I have had the system running for the last four months without concern.