Installation Manual 5.1.2
8
for years to come. It can also cause air coil clogging,
condensate drain clogging, blower dust accumulation
and many other problems to the system. Running the
system during construction / remodeling will void the
system warranty.
5.0 DHW Heating
There are two methods used by Hydro-Temp to heat
hot water. They are a standard desuperheater and on-
demand priority hot water generation system. The
standard desuperheater utilizes a small desuperheater
coil as shown on the left of the picture, in-line with the
hot gas circuit to heat water any time the system is on
heating or cooling the space. The on-demand priority
method utilizes a much larger coil and a sensor
mounted on the DHW tank to monitor the tank
temperature. The on-demand priority method will heat
water any time the system is heating or cooling the
space, as well as starting the system as needed to heat
the DHW tank. When running to heat the DHW tank
alone, the blower will not run.
5.1 DHW Tank Preparation
If a hot water heating option is to be installed, electric
domestic hot water (DHW) tanks are regularly used,
although other fuel types are sometimes acceptable.
1. Turn off the power supply or the fuel supply to
the DHW tank.
2. Close the cold water supply valve to the DHW
tank.
3. Attach water hose to the tank drain connection
and empty the tank to a drain or outside.
4. Open the pressure relief valve or faucet nearby
to break the vacuum inside the water system to
speed up the draining process.
5. After the tank has been drained disconnect the
hose and remove the DHW tank drain fitting.
5.2 Desuperheater Option Installation (Only copper
tubing should be utilized)
Install the desuperheater circuit similar as shown in Fig.
5.2. Include isolation valves and two boiler drain valves
for tank draining and DHW system purging. Valves
allow for pump service without draining the DHW tank.
A horizontal swing check valve must be used to prevent
over heating of the tank. Use 1/2” copper tubing if up
to 30' tank distance. Over 30' adapt up to 3/4" copper
pipe for lower DHW pressure drop.
Remove existing drain port from the hot water tank and
insert a standard dielectric fitting (thread the male end
of the fitting into the water heater drain port using a P.
T. F. E. based thread sealer) and continue with
installation as shown. Insulate all desuperheater circuit
piping with pipe insulation.
5.2.1 Dual tank Preheat method Hot water loop
hookup.
Figure 5.2 shows the dual tank preheat method. The
preheat tank (Tank 1) is not powered and is heated to
116 ºF solely by the Hydro-Temp unit. The second tank
(Tank 2) is powered but receives “heated” water from
the preheat tank. The second tank will only turn on
occasionally to replace its heat loss.
5.3 On-Demand Priority Hot Water Generation Option
Installation
(Only copper tubing should be utilized)
Install the priority hot water circuit similar to the
desuperheater circuit. Size the copper according to the
fittings on the Hydro-Temp unit. Install all insulation,
ball, and check valves as discussed with the
desuperheater system. The horizontal swing check
valve is critical on all priority systems to prevent over
heating of the DHW tank. Never use plastic fittings
(CPVC or Pex) when connecting between the tank and
the Hydro-Temp system. Only copper or brass should
ever be used. Failure to do so could result in damage
to system and home!
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