A.O. Smith AHPM-270, User'S Information Manual

4

4.   In order to expedite your request, please have full model 
and serial number available for the technician.

5.   Carefully consider your intended placement and location 
for the HPWH. See Locating The Water Heater on page 9.

6.    Installation  and  service  of  this  HPWH  requires  ability                
equivalent to that of a licensed tradesman or Qualifi ed Agency 
in the fi eld involved. See Qualifi cations on page 3.

7.   For installation in California the HPWH unit must be braced 
or anchored to avoid falling or moving during an earthquake. 
Instructions may be obtained from California Offi

  ce of the State 

Architect, 1102 Q Street, Suite 5100, Sacramento, CA 95811.

8.   Ensure the power supply voltage and phase at the job site 
matches the power requirements on the HPWH rating label 
before installation begins. Energizing the HPWH with the wrong 
voltage or phase will cause permanent damage to the unit.

PRINCIPLE OF OPERATION

The units covered by this Instruction Manual are commercial 
modular water-to-water heat pump water heaters (HPWH).

Operation  of  the  HPWH  is  similar  to  that  of  a  package  air             
conditioning system. The primary diff erence in operation is that 
the HPWH unit utilizes the heat removed from the conditioned 
space to heat water where package air conditioning systems 
discard this heat outdoors. Recovering and using this waste 
heat increases the overall energy effi

  ciency of the building.

THE REFRIGERATION CYCLE

Refer to Figure 1 and the WATER TO WATER CYCLE on pages 
5-7  for the location of components mentioned in this section. 

Refrigerant is circulated through the refrigeration circuit by a 

Compressor

. The refrigerant is a high temperature high pressure 

gas when it leaves the compressor. Refrigerant fl ows from the 
compressor through the 

Hot Gas Line 

to the 

Condenser

. 

The condenser is a refrigerant-to-water heat exchanger with 
two circuits, refrigerant fl ows through one circuit and water 
through the other. The high temperature refrigerant gas transfers 
its heat to the water fl owing through the condenser. As the 
refrigerant gas cools inside the condenser it changes state 
(condenses) from a gas to a liquid. A customer provided Water 
Pump  circulates water through the condenser.

Refrigerant leaving the condenser is a medium temperature 
high pressure liquid. It fl ows through the Liquid Line to the 
Thermostatic Expansion Valve. The thermostatic expansion 
valve (TXV ) regulates the flow of refrigerant into the 
Evaporator. The evaporator is a single wall brazed plate source 
water-to-refrigerant heat exchanger. The refrigerant changes 
state (boils/evaporates) from a liquid state back into a gas  (vapor) 
in the evaporator. 

The refrigerant fl ows out of the evaporator through the Suction 
Line and into the Accumulator. The accumulator traps any 

liquid refrigerant the evaporator is unable to vaporize during 
low temperature operating conditions. The accumulator 
prevents liquid refrigerant from entering the compressor 
where it could damage internal components.

Low temperature, low pressure refrigerant gas (vapor) is drawn 
out of the accumulator by the compressor. The compressor 
increases the pressure and temperature of the refrigerant gas 
circulating it to the condenser again where the refrigeration 
cycle starts over or continues.

SOURCE WATER TEMPERATURE RANGE

The entering source water temperature operating range for 
the HPWH is 40°F to 100°F (4°C to 38°C).

When the HPWH is operating properly the source water 
temperature drop through the evaporator (heat exchanger) 
will be approximately 8°F to 11°F (-13°C to -12°C).

WATER TEMPERATURE RANGE

The inlet (entering) water temperature operating range for 
the HPWH is 40°F to 140°F (4°C to 60°C). The HPWH will heat 
potable water up to 

160°F

. 

When the HPWH is operating properly the water temperature 
rise through the condenser (heat exchanger) will be approximately 
8°F to 12°F (4°C to 7°C).

REFRIGERANT CHARGE

The HPWH is factory-charged with R-134a refrigerant. The 
refrigerant charge is weighed in at the factory. See Table 9 on 
page 25

. 

It should not be necessary to add or remove refrigerant 

during installation or start up.

EQUIPMENT DISPOSAL

This heat pump water heater contains R-134a refrigerant and 
is regulated as a stationary refrigeration appliance under Section 
608 of the Clean Air Act. Disposal of this unit must be performed 
in accordance with the provisions in Section 608 of the Clean 
Air Act and any state or local regulations that may also apply. 
See Qualifi cations on page 3.