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

13

Mixing valves are available at plumbing supply stores. Consult 
a Qualifi ed Installer or Service Agency. Follow the mixing valve 
manufacturer’s instructions for installation of the valves.

  TABLE 5

CONTAMINATED WATER

This HPWH unit must not be used to heat any fl uid other than 
water. Corrosive chemicals must not be introduced into the 
waterways in this HPWH unit.

TEMPERATURE-PRESSURE RELIEF VALVE 

This heat pump water heater should only be connected to 
a storage tank with a properly rated/sized and certified 
combination temperature - pressure relief valve. The valve 
must be certifi ed by a nationally recognized testing laboratory 
that maintains periodic inspection of production of listed 
equipment of materials as meeting the requirements for Relief 
Valves for Hot Water Supply Systems, ANSI Z21.22 • CSA 4.4, 
and the code requirements of ASME.

When the HPWH unit is connected to a storage tank a 
temperature and pressure relief valve must be installed in the 
designated opening for the T&P valve per the storage tank 
manufacturer’s requirements. The T&P valve’s Btu/hr rating 
must be equal to or greater than the total heating input rating 
of all water heaters connected to the storage tank. If more 
than one water heating unit is connected to the storage tank 
the aggregate total of all heating input ratings of all connected 
unit must be factored when choosing a T&P valve for the 
storage tank.

The pressure rating of the T&P valve should always be rated 
equal to or below the working pressure rating of the storage 
tank or water heater, whichever rating is lower.

Contact the manufacturer of the storage tank for assistance 
in sizing of a temperature and pressure relief valve. Follow the 
storage tank manufacturer’s instructions regarding the proper 
installation of these products.

TANK SELECTION

The HPWH unit is not an instantaneous water heater and must 
be connected to a storage tank. Storage tank confi gurations 
must meet these criteria:

1.  The HPWH must not be connected directly to a standard 

gas or electric water heater.

2.  If the HPWH is connected to a used storage tank, the tank 

should be thoroughly cleaned of scale and sediment before 
the HPWH is installed.

3.  Connection ports used on the storage tank must permit 

the recommended fl ow rate through HPWH. The connection 
ports used on the storage tank must not be smaller than 
the inlet outlet connection sizes on the HPWH unit. See 
Table 4 on page 12.

4.  Water heated by the HPWH should be returned to the 

tank at a location that is above the level of the tank’s cold 
water inlet and/or the heat pump’s inlet source.

5.  The HPWH unit’s inlet and outlet lines to the storage tank 

should be dedicated. Example: no other line (such as a 
building re-circulating loop or cold water supply) should 
be connected to the HPWH unit’s inlet or outlet water 
lines.

SOLAR TANKS

Solar tanks should be used with caution. Some solar tanks 
with top connections have dip tubes which may signifi cantly 
reduce the effi

  ciency performance of the HPWH unit. 

Before using any solar tank in this application, contact your 
representative or call the toll free technical support number 
on the back cover of this manual for further assistance.

Potentially harmful fumes and vapors could be introduced 
into occupied spaces. See Unit Placement on page 15.

STORAGE & HANDLING

The heat pump water heaters covered in this manual are 
stationary refrigeration units. Careful handling is necessary to 
prevent internal damage.