Service manual

10
7.5 LOW WATER TEMPERATURE
SYSTEMS
In applications where the heating system
requires supply water temperatures below 130°F
(55
o
C), a recirculation line or thermostatic mixing
valve must be installed upstream of the
appliance pump so that outlet water can be re-
circulated to raise the inlet temp to a minimum of
130°F (55
o
C) for a recirculation line. Balancing
valves, preferably globe valves are used to
adjust flow. (See Figure 10)
• Adjustment procedure.
a. Fully open bypass and outlet
valves.
b. With appliance running, read
inlet temperature after 15
minutes.
c. If the inlet temperature is less
than 130°F (55
o
C) slowly close
outlet valve until the inlet
temperature climbs to 130°F
(55
o
C)
d. If the inlet temperature is
greater than 130°F (55
o
C) but
not greater than 140°F (55
o
C)
no further adjustment is
required.
e. Check the inlet temperature
after 5 minutes and make final
adjustments.
7.6 INSTANTANEOUS WATER HEATER
An instantaneous appliance is designed to
deliver hot water without the use of a storage
tank. It is suitable for applications with variable
load such as restaurants, condominiums,
apartments and motels. (See Figure 11). Call
manufacturer for recommendations.
7.7 HOT WATER SYSTEM PIPING
Piping and components connected to the
appliance must be suitable for use with potable
water. The appliance should not be connected to
any heating system piping or components
previously used with non potable water. Hot
water storage tanks used in potable water
system must be equipped with temperature and
pressure relief valve. Figures 12 and 13 illustrate
typical water heating piping arrangement for
single appliance and multiple appliances.
The storage tanks must be located as close as
possible to the appliance to prevent excessive
pressure drop. The required flow through the
appliance is based on normal water having
hardness between 7.5 and 17 grains per gallon.
Water hardness above this range will require
higher flow rates to prevent scaling and to
prevent erosion of copper-nickel heat exchanger
tubes. The manufacturer should be consulted
when water conditions outside the
aforementioned range are encountered.
The appliance could be fitted with an economizer
(secondary heat exchanger) to achieve nominal
efficiency of 95%. This heat exchanger is
fabricated from stainless steel and can accept inlet
water temperature as low as 40ºF.
7.8 CONDENSER HEAT RECOVERY
MODULE (CHRM)
The MicoFlame Grande All Stainless Steel
CHRM is mounted in a stainless steel inner
jacket chamber at the rear of the appliance. The
CHRM is constructed from all stainless steel
headers and special multiple horizontal stainless
tubes. This CHRM is designed to maximize heat
transfer efficiency by fully condensing flue
products and is suitable to resist the low pH of
condensate.
The CHRM must be supplied with adequate
water flow at all times during operation. Do not
operate the appliance with the CHRM piped out
or isolated.
The CHRM is mounted in the discharge of the
flue products from the primary heat exchanger.
This allows additional heat to be absorbed from
the flue products exhausted from the
combustion process. If isolation valves are
provided on the CHRM, the provision of a relief
valve at the outlet of the CHRM is
recommended. This valve is to be sized at
minimum for 10% of the input of the appliance
and is to be piped to drain.
When cold water supply with temperatures less
than 130ºF (55ºC) passes through the CHRM it
will cool the flue products below dew points
resulting in the formation of condensation.
Furthermore, the volumetric flow rate of the flue
gases will be reduced.