[LazyPup]

The super-stor water heaters are classified as external combustion water heaters. They operate by circulating hot water from a heating boiler through a heat exchanger coil in the bottom of the tank.

The aqua-stat senses the water temperature in the storage tank and regulates the rate of flow from the boiler to control the water temp.

Although they are extremely high efficiency units with a super long service life, unfortunately everything requires periodic maintence.

In my estimation changing the aqua-stat is probably a bit more complex than what I would recommend for even an advanced DIY project.

First of all, unless you are familiar with the temperature/prssure boiling characteristics of water, venting a boiler to atmospheric pressure can be a very dangerous procedure.

Changing the Aqua-stat is basically a simple task but In order to change the aqua-stat you will need to blow down the boiler and drain the water heater.

Prior to relighting the boiler you will have to prove the proper water level in the boiler, then insure that the water heater vessel is properly filled and vented.

In my estimation this is one case where the safe method would be to consult the services of a plumbing & Heating contractor who is familiar with the proper blow down techniques for boilers.