Crown Boiler CWI345 Specifications download pdf (Page 14)

6) Low Water Cut-Off (Required in some situations) - A low water cutoff is required when the boiler is installed above

radiation. In addition, some codes such as ASME CSD-1 require low water cutoffs. Codes may also require that this low

water cutoff have a manual reset function. The low water cutoff may be a float type or probe type, but must be designed

for use in a hot-water system. The low water cutoff should be piped into the boiler supply just above the boiler with no

intervening valves between it and the boiler.

Use a low water cutoff that breaks the 120 VAC supply to the boiler. Do not attempt to wire a 24-volt low water cutoff into

the boiler factory wiring.

Manual Reset High Limit (Required by some codes) - This control is required by ASME CSD-1 and some other codes.

Install the high limit in the boiler supply piping just beyond the boiler with no intervening valves. Set the manual reset

high limit as far above the operating limit setting as possible, but not over 240°F. Wire the control to break the 120 VAC

electrical supply to the boiler.

Flow Control Valve (Required under some conditions) - The flow control valve prevents flow through the system unless

the circulator is operating. A flow control valve may be necessary on converted gravity systems to prevent gravity

circulation. Flow control valves are also used to prevent “ghost flows” in circulator zone systems through zones that are

not calling for heat.

Isolation Valves (Optional) - Isolation valves are useful if the boiler must be drained, as they will eliminate having to drain

and refill the entire system.

10)

Drain Valve - The drain valve is shipped in the boiler parts bag. Install it in the tee under the circulator as shown in Figure

Piping for Special Situations

Certain types of heating systems have additional requirements. Some of the more common variations follow:

Indirect Water Heaters - Figure 12 shows typical indirect water heater piping. Boiler piping is the same as for any two-zone

system. Figure 12 shows circulator zoning, which is usually preferred for indirect water heaters. Size the circulator and

indirect water heater piping to obtain the boiler water flow through the indirect water heater called for by the indirect water

heater manufacturer.

Large Water Volume Systems - The piping shown in Figure 13 will minimize the amount of time that the boiler operates with

return temperatures below 120°F on these systems. A bypass is installed as shown to divert some supply water directly

into the return water. The bypass pipe should be the same size as the supply. The two throttling valves shown are

adjusted so that the return temperature rises above 120°F during the first few minutes of operation. A three-way valve can

be substituted for the two throttling valves shown. If the circulator is mounted on the supply, the bypass must be on the

discharge side of the circulator.

Low Temperature Systems - Some systems, such as radiant tubing systems, require the system water temperature to be

limited to a value below the temperature of the water leaving the CWI. These systems also typically have return

temperatures well below the 120°F minimum.

Figure 14 illustrates the use of a heat exchanger to connect the CWI boiler to this type of system. The heat exchanger will

permit the transfer of heat from the boiler water to the low temperature system while holding the system supply and boiler

return temperatures within their limits. For this system to work properly the heat exchanger must be properly sized and the

correct flow rates are required on either side of the heat exchanger. Consult the heat exchanger manufacturer for sizing

information. The water in the boiler is completely isolated from the water in the system. This means that separate fill and

expansion tanks are required for the heating system loop.

There are several other ways to connect low temperature systems to non-condensing boilers like the CWI, such as four

way mixing valve and variable speed injection pumping systems.

Systems containing oxygen - Many hydronic systems contain enough dissolved oxygen to cause severe corrosion

damage to a cast iron boiler such as the CWI. Some examples include:

• Radiant systems that employ tubing without an oxygen barrier.

• Systems with routine additions of fresh water.

• Systems which are open to the atmosphere.

If the boiler is to be used in such a system, it must be separated from the oxygenated water being heated with a heat

exchanger as shown in Figure 14.

Consult the heat exchanger manufacturer for proper heat exchanger sizing as well as flow and temperature requirements.

All components on the oxygenated side of the heat exchanger, such as the pump and expansion tank, must be designed for

use in oxygenated water.

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Crown Boiler CWI345 Specifications Page 14

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