National Combustion Co., Inc.
Page 32
functioning properly, then burners should be inspected.
There should be no distortion or perforations in the
burners outside of the active burner port area. Replace if
indicated.
8.3 Short Cycling — Boiler
Because the Fire Coil 85 is a stage-fired boiler,
and its input will decrease when there is a reduction in
heating load, short cycling is greatly reduced. If the
heating load drops below the minimum input of the
boiler for an extended period, the boiler will have a
tendency to short cycle. This can be a symptom of
improper control strategy or setpoints, or a load
distribution problem. Contact your NATCO
representative to discuss possible remedies.
8.4 Short Cycling — Water Heater
Short cycling will generally occur only in
combination space heating and water heating
applications when the water heater is operating in the
space-heating mode. Because the Fire Coil 85 is a stage-
fired water heater and its input will reduce when there is
a reduction in heating load, short cycling is greatly
reduced. If the heating load drops below the minimum
input of the water heater for an extended period, the
water heater will have a tendency to short cycle. If short
cycling is frequently experienced, regardless of the
control’s attempt to limit it, the heating load should be
redistributed to control it.
If short cycling occurs in a water heater application,
it is probably caused by undersized piping between the
water heater and the storage tank or by some other factor
that restricts proper water flow through the water heater.
The cause should be determined and corrected.
8.5 High Gas Consumption
Appliances operating with an improper air/fuel
ratio are very inefficient and consequently, have very
high gas consumption. Because efficiency is high when
the CO
2
is high (or O
2
is low), appliances operating with
low CO
2
or high O
2
(especially LP appliances) consume
more gas. Adjust the CO
2
or O
2
for optimum efficiency.
If no combustion analyzing equipment (CO
2
or O
2
) is
available then a proper adjustment of the air/fuel ratio
(CO
2
or O
2
) cannot be accomplished. However, by
briefly sniffing the flue gases it is possible to determine
if the CO
2
or O
2
is within the proper range. No
significant flue gas odor should be detected when
combustion is proper. A strong piercing smell indicates
poor combustion and generally a lean mixture - low CO
2
or high O
2
. The CO
2
should be 8% at high fire. To check
the CO
2
, first verify that the supply gas pressure is
within 5" to 13" w.c. (1.2 to 3.2 kPa) With the Fire Coil
85 running with all stages firing, set the air box pressure
to 1.5" w.c. (0.37 kPa) (as a starting point), by adjusting
the air shutter(s) at the bottom of the fan(s). Check the
CO
2
, and adjust the air shutters if further adjustment to
the CO
2
is needed. Sizes 1250 to 2000 have two blowers
and two air chambers (boxes). The pressure of each air
box must be equal when the final adjustment is made.
SECTION 9.
Replacement Parts
Only genuine NATCO replacement parts should be used.
9.1 General Information
To order or purchase parts for the NATCO Fire
Coil 85, contact your nearest NATCO dealer or
distributor. If they cannot supply you with what you
need, contact Customer Service
(see back cover for
address, telephone and fax numbers)
.
9.2 Parts List -
see next page.
Summary of Contents for Fire Coil 85
Page 23: ...Fire Coil 85 500 2000 Page 23 Figure 19 Fire Coil 85 500 750 Connection Diagram ...
Page 24: ...National Combustion Co Inc Page 24 Figure 20 Fire Coil 85 1000 Connection Diagram ...
Page 25: ...Fire Coil 85 500 2000 Page 25 Figure 21 Fire Coil 85 1250 2000 Connection Diagram ...
Page 37: ...Fire Coil 85 500 2000 Page 37 Figure 23 Sheet Metal Components ...
Page 38: ...National Combustion Co Inc Page 38 Figure 24 Internal Components ...
