Burnham MPC - Manual (Page 64)

6
c. BOiLER PiPiNG, DOMEsTic hOT WATER
(DhW) APPLicATiON – The MPC boiler can be
used in many different piping applications to produce
Domestic Hot Water (DHW). In some applications,
depending on the control strategy (outdoor reset,
setpoint operation, etc.) and size of the boiler, it is
recommended to isolate the space heating load from the
DHW load. For example, if the domestic load is more
than the space heating load, it is beneficial to dedicate
one or more boilers solely to DHW production and one
or more boilers solely to space heating, since during
mild weather conditions, the boiler(s) will have more
capacity than is required. Piped in the recommended
manner, the space heating boiler(s) can be shut down
during the summer months to conserve energy and to
avoid short cycling.
The use of indirect water heaters for domestic
hot water generation is commonly recommended
since they provide DHW storage. A tempering
valve and recirculation loop are advantageous in
these applications, because they provide both high
temperature and tempered domestic water to the
Figure 5: Discharge Piping for Pressure Relief Valve
system, eliminating the need to purge and waste water
until it reaches the desired temperature. See Figures
49a, 49b, 50a and 50b for recommended indirect water
heater piping.
NOTICE
DO NOT use the boiler circulator as an indirect
domestic hot water system circulator.
D. RELiEf vALvE DischARGE PiPiNG, see
Figure 54. Pipe discharge to within 4” of floor or to a
suitable drain. Do not reduce piping size or install shut-
off valve in discharge piping.
If discharge is weeping, do not plug relief valve or cap
discharge piping, replace valve immediately.
E. iNsTALL ELEcTRic WiRiNG in accordance
with National Electric Code and local regulations. A
separate ELECTRICAL CIRCUIT should be run from
meter with a Fused Disconnect Switch in this Circuit.
NOTICE
When possible, domestic hot water production should utilize dedicated boiler(s). This will allow the other
boiler(s) to be shut down and isolated during the summer months. If the boiler load is shared between
heating and domestic hot water, then one needs to determine if a hot water priority is required. If a priority
is not selected, erratic domestic hot water production may result during the beginning and end of every
heating season. Conversely, a priority for domestic hot water production may cause a significant heating
zone activation delay, in an improperly balanced system. Parallel piping conversions may require isolation
from the heating system to prevent system flow influence on DHW performance. Consult a qualified system
heating professional to design for the proper application.