Water Pressure Switch, Unitherm Governor Operation

Water Pressure Switch

On Models 926-1223 built with a Unitherm Governor (UG), a water pressure switch is provided in the heater to shut down the gas valves in the event the water sup- ply to the heater is interrupted. It is very important to verify that the switch electrically opens and shuts off the gas valve when water flow to the heater is inter- rupted.

Otherwise, rapid and severe damage to the heater will likely occur. (The water pressure switch should be checked and adjusted for proper operation by a quali- fied service person at the time of installation and periodically checked thereafter. Refer to pressure switch servicing instructions in this manual).

WARNING: Operation of the heater without water circulation will cause rapid and severe damage to the heater.

Automatic Chlorinators and Chemical Feeders

All chemicals must be introduced and completely dilut- ed into the pool or spa water before being circulated through the heater. Do not place chlorine tablets or bromine sticks in the skimmer. High chemical concen- trations will result when the pump is not running (eg, overnight).

Chlorinators must feed downstream of the heater and have an anti-siphoning device to prevent chemical backup into the heater when the pump is shut off.

NOTE: High chemical concentrates from feeders and chlorinators that are out of adjustment will cause very rapid corrosion to the heat exchanger in the heater. Such damage is not covered under the warranty.

Unitherm Governor Operation

The patented Unitherm Governor (UG) is a thermosta- tic mixing valve specifically designed to maintain constant heater internal temperature between 105° and 115°F despite continually changing flow rates from the filter and changing pool temperatures. This narrow range is needed to prevent damaging condensation on the burners which will occur if the heater runs for any length of time below 105°F. It is also needed to inhibit scale formation in the tubes by maintaining tempera- tures well below accelerated scaling temperatures.

The Unitherm Governor is an available option on mod- els 926 through 1223. Where installed, it is built into the inlet/outlet header. The larger sizes, models 1287 through 4001, do not have a UG option. Instead, they have an externally mounted bypass pump that is designed to maintain the water entering the heater at the proper temperature to prevent condensation and scale. Thermometers are provided on the inlet and outlet to the heater.

Companion Flange Connections (Models 926-1223)

DO NOT use petroleum base assembly fluids (such as Petroleum Jelly or Lubricating Oil). If assembly lube is required use a silicone base such as Armoral etc.

The inlet/outlet header flange accepts a 2" copper tube as a slip connection directly into the header. The flange is also threaded for a 2" NPT copper male adapter.

Fig. 10: Companion Flange Connections

(Models 926–1223)