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HVACR216 - HydronicsHVACR216 - Hydronics

AquastatsAquastats

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AquastatsAquastats• High and low limit controllers

– As a high limit, the control works like any high limit control on any other system. It is a safety.

– It will shut the system off if the temperature gets to high. (usually 180 deg)

– As a low limit the control will turn the burner on if the temperature drops to low. (usually 160 deg)

– This maintains a minimum boiler temperature.

• High and low limit controllers

– As a high limit, the control works like any high limit control on any other system. It is a safety.

– It will shut the system off if the temperature gets to high. (usually 180 deg)

– As a low limit the control will turn the burner on if the temperature drops to low. (usually 160 deg)

– This maintains a minimum boiler temperature.

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AquastatsAquastats

• Low Limit

– Turns the burner on when the boiler temperature drops below the setpoint.

– Turns the burner off when the temperature of the water reaches the setpoint.

– In systems with domestic hot water the low limit maintains the boiler temperature when heat is not required (warm start).

• Low Limit

– Turns the burner on when the boiler temperature drops below the setpoint.

– Turns the burner off when the temperature of the water reaches the setpoint.

– In systems with domestic hot water the low limit maintains the boiler temperature when heat is not required (warm start).

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AquastatsAquastats

• Circulator Control

– Used in systems which have domestic hot water capabilities.

– Prevents the circulator from running if the burner is on the low limit side. Prevents the cooler water from being circulated for heating.

– Prevents the boiler from getting to cold for domestic hot water generation.

• Circulator Control

– Used in systems which have domestic hot water capabilities.

– Prevents the circulator from running if the burner is on the low limit side. Prevents the cooler water from being circulated for heating.

– Prevents the boiler from getting to cold for domestic hot water generation.

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AquastatsAquastats

• High and Low limit controllers

– Uses a sensing bulb and a capillary tube to measure the changes in temperature and transmits that to the bellows which moves a set of contacts.

– As the bellows expand and contract it moves the contacts which open and close the switch.

• High and Low limit controllers

– Uses a sensing bulb and a capillary tube to measure the changes in temperature and transmits that to the bellows which moves a set of contacts.

– As the bellows expand and contract it moves the contacts which open and close the switch.

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AquastatsAquastats

• Circulator Controls

– When there is a call for heat the circulator control turns on the circulator.

– If the temperature of the boiler gets to low the circulator is turned off until the boiler can warm up again.

– This prevents excess run time while the boiler heats up.

• Circulator Controls

– When there is a call for heat the circulator control turns on the circulator.

– If the temperature of the boiler gets to low the circulator is turned off until the boiler can warm up again.

– This prevents excess run time while the boiler heats up.

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AquastatsAquastats

• Dual Aquastat Controllers

– Combines the function of the high and low limit controls with the circulator control into one package.

– A SPDT switch is used on the low limit and circulator control with a SPST switch serving as the high limit.

• Dual Aquastat Controllers

– Combines the function of the high and low limit controls with the circulator control into one package.

– A SPDT switch is used on the low limit and circulator control with a SPST switch serving as the high limit.

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AquastatsAquastats

• Dual aquastat controller (cont)

– When the boiler temperature is below the setpoint the R-B contacts are closed (low limit) and the R-W contacts are open (circulator).

– When the boiler temperature is above the setpoint R-B is open, and R-W is closed.

• Dual aquastat controller (cont)

– When the boiler temperature is below the setpoint the R-B contacts are closed (low limit) and the R-W contacts are open (circulator).

– When the boiler temperature is above the setpoint R-B is open, and R-W is closed.

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Combination Aquastat ControlsCombination Aquastat Controls

• Combination aquastat controls come in two types:

– Aquastat Relay

– Triple Aquastat Relays

• Combination aquastat controls come in two types:

– Aquastat Relay

– Triple Aquastat Relays

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Aquastat RelayAquastat Relay

• Combine the functions of the switching relay for the circulator and the temperature control of the system.

• Used with systems that “do not” have domestic hot water coils installed.

• Combine the functions of the switching relay for the circulator and the temperature control of the system.

• Used with systems that “do not” have domestic hot water coils installed.

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Aquastat RelayAquastat Relay

• They contain:– Transformer for control voltage (24vac)– Relay to control burner and circulator– Temperature control for high and low limit operations.

• The boiler is not operating when the thermostat is not calling for heat. (cold start)

• They contain:– Transformer for control voltage (24vac)– Relay to control burner and circulator– Temperature control for high and low limit operations.

• The boiler is not operating when the thermostat is not calling for heat. (cold start)

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Triple AquastatsTriple Aquastats

• Used in systems that are required to provide domestic hot water.

• Some also provide zone control.

• There are single zone models for gas and oil fired applications.

• There are millivolt models available for gas millivolt applications.

• This type of aquastat will maintain a low limit temperature all year.

• Used in systems that are required to provide domestic hot water.

• Some also provide zone control.

• There are single zone models for gas and oil fired applications.

• There are millivolt models available for gas millivolt applications.

• This type of aquastat will maintain a low limit temperature all year.

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Triple AquastatsTriple Aquastats

• Triple aquastats provide burner control when there is no call for heat, keeping the boiler warm enough for domestic hot water use (warm start).

• This is on the low limit side.

• Upon a call for heat the triple aquastat runs on the high limit side providing very hot water for the heating circuit.

• Triple aquastats provide burner control when there is no call for heat, keeping the boiler warm enough for domestic hot water use (warm start).

• This is on the low limit side.

• Upon a call for heat the triple aquastat runs on the high limit side providing very hot water for the heating circuit.

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Triple AquastatsTriple Aquastats

• Most triple aquastats also provide circulator control. They will not allow the circulator to come on until the boiler is warm enough.

• This is controlled by the low limit setting. (usually 160 deg)

• Most triple aquastats also provide circulator control. They will not allow the circulator to come on until the boiler is warm enough.

• This is controlled by the low limit setting. (usually 160 deg)

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Aquastat Electrical ConnectionsAquastat Electrical Connections

• L1 and L2 are 120V power supply

• T and T are 24 volt thermostat connections.

• C1 and C2 are circulator motor connections.

• B1 and B2 are burner connections.

• L1 and L2 are 120V power supply

• T and T are 24 volt thermostat connections.

• C1 and C2 are circulator motor connections.

• B1 and B2 are burner connections.

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Aquastat Electrical ConnectionsAquastat Electrical Connections

• Voltage checks can be made at all of these electrical connections.

• The Honeywell L8148E has low voltage B1 and B2 for gas valve voltage.

• The Honeywell L8148A has high voltage B1 and B2 for an oil burner connection.

• Do not mix the two or damage to the control will occur!

• Voltage checks can be made at all of these electrical connections.

• The Honeywell L8148E has low voltage B1 and B2 for gas valve voltage.

• The Honeywell L8148A has high voltage B1 and B2 for an oil burner connection.

• Do not mix the two or damage to the control will occur!

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L8148AL8148A

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L8148EL8148E

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DifferentialDifferential

• All aquastats use a differential control. This allows the technician to fine tune the control for a specific application.

• The differential acts as the “other” side of a set point. If there was no differential an aquastat set at 180 degrees would turn the burner on at 180 and off at 181. This would be very inefficient and waste full.

• This is known as “short cycling”

• All aquastats use a differential control. This allows the technician to fine tune the control for a specific application.

• The differential acts as the “other” side of a set point. If there was no differential an aquastat set at 180 degrees would turn the burner on at 180 and off at 181. This would be very inefficient and waste full.

• This is known as “short cycling”

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DifferentialDifferential

• Most triple aquastat controllers will have

• high limit adjustment (usually 180 deg)• low limit adjustment (usually 160 deg)• differential adjustment (usually 10 deg)

• Most triple aquastat controllers will have

• high limit adjustment (usually 180 deg)• low limit adjustment (usually 160 deg)• differential adjustment (usually 10 deg)

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Triple aquastatTriple aquastat

High limit

Low limit

Differential

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Sequence of operationSequence of operation

• The R8182 is a triple aquastat. On a warm day where only domestic hot water is being used the system is running on low limit operation.

• The low limit may be set to 160 degrees. With a differential setting of 10 degrees.

• The R8182 is a triple aquastat. On a warm day where only domestic hot water is being used the system is running on low limit operation.

• The low limit may be set to 160 degrees. With a differential setting of 10 degrees.

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Sequence of OperationSequence of Operation• Boiler temp is at 159 degrees, nothing is running.

• Domestic water starts being used, the boiler temp starts to drop until it reaches 150 degrees.

• This is 10 degrees (the setting of the differential) below the set point of 160.

• The burner starts and warms the boiler up to the set point of 160.

• Burner shuts off.

• Boiler temp is at 159 degrees, nothing is running.

• Domestic water starts being used, the boiler temp starts to drop until it reaches 150 degrees.

• This is 10 degrees (the setting of the differential) below the set point of 160.

• The burner starts and warms the boiler up to the set point of 160.

• Burner shuts off.

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Sequence of operationSequence of operation

• On a call for heat the triple Aquastat is now running off the high limit side.

• The burner will come on and heat the water until it reaches the high limit side.

• The circulator is running since it is above the low limit setting.

• The burner shuts off at the high limit.

• On a call for heat the triple Aquastat is now running off the high limit side.

• The burner will come on and heat the water until it reaches the high limit side.

• The circulator is running since it is above the low limit setting.

• The burner shuts off at the high limit.

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Sequence of operationSequence of operation

• The water temperature in the boiler will drop until it reaches 10 degrees (our differential setting) under the high limit set point.

• The burner will then come on and reach the set point again and shut off.

• This continues until the call for heat is over and the burner goes back to low limit operation.

• The water temperature in the boiler will drop until it reaches 10 degrees (our differential setting) under the high limit set point.

• The burner will then come on and reach the set point again and shut off.

• This continues until the call for heat is over and the burner goes back to low limit operation.

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DifferentialsDifferentials

• The smaller the differential, the more the burner will cycle. The closer the water temperature will be kept to set point.

• The greater the differential the less the burner will cycle. The greater the swing in temperature variations.

• The smaller the differential, the more the burner will cycle. The closer the water temperature will be kept to set point.

• The greater the differential the less the burner will cycle. The greater the swing in temperature variations.

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AquastatsAquastats

• Keep in mind the Aquastat is an electrical device and should not be allowed to get wet.

• Special attention is required when servicing the plumbing side of the heating system.

• Protect the control from water by temporarily covering it with a plastic bag when the potential for spilling water exists.

• Keep in mind the Aquastat is an electrical device and should not be allowed to get wet.

• Special attention is required when servicing the plumbing side of the heating system.

• Protect the control from water by temporarily covering it with a plastic bag when the potential for spilling water exists.