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LAARS Rheos RHCV - Install and Operating Manual User Manual

Page 42

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LAARS Heating Systems

Page 42

7.2.8 Ignitor / Flame Sensor Assembly

The ignitor is a 110v “Hot Surface” type. It

is energized whenever there is a call for heat and

switched off when ignition is established and the flame

has been sensed. To replace the ignitor, shut off the

120-volt power to the appliance, disconnect the Molex

connector, remove the two mounting screws on the

ignitor flange, and pull the ignitor out. Always install a

new ignitor gasket with the replacement ignitor.

Caution

Ignitor gets hot.

7.2.9 Transformers

There are three transformers in the Rheos

unit. One is 24v to 110v, the second is 110v to 24v,

and the third is 110v to 220v. Be sure to replace the

transformers with factory parts. These transformers are

not capable of supplying control voltage for external

devices such as zone valves, which must have their

own separate power supply. Should a transformer need

replacing, shut off the 120-volt power. Unplug the

transformer wires, remove the mounting screws and

remove the transformer. Replace transformer in the

reverse order.

7.2.10 Blower

The combustion air blower is a high-pressure

centrifugal blower with a variable speed motor. The

speed of the motor is determined by the control logic.

If a blower change is required, turn off the 120-volt

power and gas supply to the unit. Take the front panel,

the two side access panels, and the top jacket panel

off. (If there is enough clearance on the side, the top

may not have to be removed.) Disconnect the gas

union between the blower and gas valves. Disconnect

the filter box assembly (at the air transition) from the

blower (six 8 mm bolts). Disconnect the two Molex

electrical connectors from the top right of the blower.

Remove the four nuts from the blower flange, and

pull the blower out. Replace blower in reverse order,

ensuring that all joints are made correctly and sealed.

After replacement, ensure that the unit operates

properly, by following the set-up procedure in this

manual.

7.2.11 Flow Switch

The Rheos uses a paddle-type flow switch to

ensure that the unit has water flow before ignition is

allowed.

7.2.12 Heat Exchanger Coil

Black carbon soot buildup on the external

surfaces of the heat exchanger is caused by one

or more of the following; incomplete combustion,

combustion air problems, venting problems and heater

short cycling. Soot buildup or other debris on the heat

exchanger may restrict the flue passages.

If black carbon soot buildup is suspected,

disconnect electrical supply to the unit, and turn off

the gas supply by closing the manual gas valve on the

unit. Access the heat exchanger through the side access

panels, and inspect the finned copper tubing using a

flashlight. If there is a buildup of black carbon soot

or other debris on the heat exchanger, clean per the

following:

Caution

Black carbon soot buildup on a dirty heat exchanger

can be ignited by a random spark or flame. To

prevent this from happening, dampen the soot

deposits with a wet brush or fine water spray before

servicing the heat exchanger.

1. Disconnect the electrical supply to the unit.

2. Turn off the gas supply by closing the manual gas

valve on the heater.

3. Disconnect and remove the wires, conduit and

sensors from all components that are attached to

the inlet/outlet header.

4. Isolate the heat exchanger from the water supply.

5. Drain the heat exchanger from the drain located

on the bottom of the heat exchanger.

6. Disconnect the header flanges from the inlet and

outlet.

7. Remove the heat exchanger from the unit.

NOTE: The heat exchangers are heavy and may

require two people to remove to avoid personal

injury.

8. Clean the heat exchanger: A light accumulation

of soot or corrosion on the outside of the heat

exchanger can be easily removed. Use a wire

brush to remove loose soot and scale from the

heat exchanger. Do not use water or compressed

air for cleaning.

9. NOTE: While the heat exchanger is out of the

unit, inspect the firewall refractory insulation

blocks for cracks, wear and breakage. Replace if

necessary.

10. Inspect the inside of the copper tubes for scale

buildup. Scale can build up on the inner surface

of the heat exchanger tubes, which can restrict

water flow. If the tubes show signs of scaling,

clean the internal surface. Laars offers a tube

cleaning kit part number R2000700.

11. Reassemble in the reverse order.

If heat exchanger removal is necessary, consult

the factory for instructions.

NOTE: The Warranty does not cover damage

caused by lack of required maintenance, lack of

water flow, or improper operating practices.

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