Burnham RSA Manuel d'utilisateur télécharger pdf (Page 50)

A 24 VAC LWCO is used primarily for gas red

boilers where a 24 volt control circuit exists within the

boiler. However, a 24 VAC LWCO can only be used

if the boiler manufacturer has provided piping and

wiring connections and instructions to allow for this

application.

How to Test

Shut off fuel supply. Lower water level until water

level is BELOW the LWCO. Generate a boiler demand

by turning up thermostat. Boiler should not attempt to

operate. Increase the water level by lling the system.

The boiler should attempt to operate once the water

level is above the LWCO.

X. Low Water Cut Off (LWCO)

Wiring of Typical LWCO

When

A low water cutoff is required to protect a hot water

boiler when any connected heat distributor (radiation)

is installed below the top of the hot water boiler (i.e.

baseboard on the same oor level as the boiler). In

addition, some jurisdictions require the use of a LWCO

with a hot water boiler.

Where

The universal location for a LWCO on both gas and

oil hot water boilers is above the boiler, in either the

supply or return piping. The minimum safe water level

of a water boiler is at the uppermost top of the boiler;

that is, it must be full of water to operate safely.

What Kind

Typically, in residential applications, a probe type

LWCO is used instead of a oat type, due to their

relative costs and the simplicity of piping for a probe

LWCO.

How to Pipe

A “tee” is commonly used to connect the probe LWCO

to the supply or return piping, as shown below.

LWCO Location

draining the heating system. Many probe LWCO

manufacturers recommend an annual inspection of the

probe.

How to Wire

LWCO’s are available in either 120 VAC or 24 VAC

congurations. The 120 VAC conguration can be

universally applied to both gas and oil boilers by wiring

it in the line voltage service to the boiler (after the

service switch, if so equipped).

The presence of water in a properly installed LWCO

will cause the normally open contact of the LWCO to

close, thus providing continuity of the 120 VAC service

to the boiler.

It is recommended to supply power to the probe LWCO

with the same line voltage boiler service as shown

below.

Select the appropriate size tee using the LWCO

manufacturer’s instructions. Often, the branch

connection must have a minimum diameter to

prevent bridging between the probe and the tee. Also,

the run of the tee must have a minimum diameter to

prevent the end of the probe from touching or being

located too close to the inside wall of the run of the tee.

Ideally, manual shutoff valves should be located

above the LWCO and the boiler to allow for servicing.

This will allow probe removal for inspection without

WARNING

DO NOT ATTEMPT to cut factory wires to install an aftermarket Low Water Cut Off (LWCO).

Only use connections specically identied for Low Water Cut Off.

In all cases, follow the Low Water Cut Off (LWCO) manufacturer's instructions.

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Burnham RSA Manuel d'utilisateur Page 50

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