VII) COMBO HEATING
This section serves as a guide for the installation and use of
“Combo” heating systems utilizing a domestic water heater
which has been specifically approved for such use (see
Figure 19). It is written for those knowledgeable in the
required trades and professionals involved in the design
and installation of Combo Heating Systems.
It is the responsibility of the installer/designer to follow all
applicable codes to ensure the effectiveness and safety of
the installation.
System Requirements
The following requirements must be met for the installation
of Combo Heating Systems:
1. The piping and components connected to the water
heater for the space heating applications shall be suit-
able for use with potable water. The system should be
installed with new, non-ferrous piping. Do not use
pumps, valves, fittings, solder, gluing and pipe sealant
that are not completely compatible with potable water
piping.
2. A water heater which will be used to supply potable
water must not be connected to any heating system or
components previously used with a non-potable water
heating appliance. Do not use piping that has been
treated with chromates, broiler seal or other chemicals
and do not add chemicals to the water heating piping.
Do not introduce toxic chemicals, such as those used
for boiler treatment, into the potable water used for
space heating.
3. Do not use this heater as a replacement for an existing
boiler installation.
4. If the space heating water system requires water with
temperatures in excess of 60°C (140°F), a mixing valve,
or other means to temper the water and reduce scald
hazard potential, must be installed in the potable hot
water supply.
5. If the heater is installed with a back-flow preventer on
the incoming water line or in a closed system, a
diaphragm-type expansion tank must always be
installed in the system to prevent the T&P from relieving
due to thermal expansion.
6. Proper sizing of the water heater for the given space
and potable heating application is essential to ensure
adequate heating capacity. The sizing and installation of
such combination system must be performed by quali-
fied personnel and be in accordance with public utility
requirements and/or codes having jurisdiction.
The sizing of the water heater should be based on the
design heat loss of the structure to be heated plus the
potable water requirements.
IT IS IMPORTANT THAT THE WATER HEATER USED BE
OVERSIZED TO ALLOW ADEQUATE HEATING AND
POTABLE WATER HEATING CAPACITY.
WATER
HEATER
AIR
HANDLER
CIRC. PUMP
CHECK VALVE
COLD TO
WATER HEATER
RADIATOR OR RADIANT FLOOR PIPING ARE
VIABLE ALTERNATIVES TO AIR HANDLER.
HOT WATER
TO HOUSE
Figure 19
Example Of Combo Heating Piping Schematic
MASSACHUSETTS
CODE DOES NOT
ALLOW THIS TYPE
OF INSTALLATION.
– 21 –