LAARS Rheos RHCV - Install and Operating Manual - Manual (Page 46)

LAARS Heating Systems Page 46
8.3.3 Defective Burner - Occurs on
Startup or at Burner Shutdown
A defective burner can cause a delayed ignition.
If the gas supply pressure is proper, the gas valve is
functioning properly, the burner should be inspected.
There should be no distortion or perforations in the
burner. Replace if indicated.
8.4 Short Cycling — Boiler
Because the Rheos is a modulating 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. See Section 5.5 regarding controller setup.
Contact your Laars representative to discuss possible
remedies.
8.5 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 Rheos is a
modulating 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. See
Section 5.5 regarding controller setup.
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.
8.6 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
) can not
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 to 9% at all firing rates. Do not
attempt to correct combustion. Contact factory if the
CO
2
is not within this range.
SECTION 9.
Replacement Parts
Only genuine Laars replacement parts should be used.
9.1 General Information
To order or purchase parts for the Laars Rheos,
contact your nearest Laars dealer or distributor. If
they cannot supply you with what you need, contact
Customer Service (see back cover for address,
telephone and FAX numbers).