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Accurately measure water temperature
Water temperature switch
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Heat
water to exact temperature Accurately measure water temperature Water temperature switch |
| Exact temperatures can be
accurately controlled with a PID (Proportional
Integral Derivative) Typically PID is an electrically powered device that receives incoming 100-240 volts of ordinary residential or commercial single-phase power. Temperature reading comes from a thermocouple, or RTD. When temperature reaches set point, the PID gives an output. The output can be either: 1) Some models of PID will yeild DC output for direct connect to SSR (solid state relay) that can turn off AC or DC circuit. These units also have secondary relay terminals 11-12 2) Some models of PID have Relay terminals which will switch 100-240 volt 3 amp line. The relay terminals can be wired to a contactor to control larger voltage of single phase, or commercial 3-phase power. Contactor can be used for heavy amp AC or DC load. Contactors A contactor can turn off any heavy-amp electrical device, water heater, blower, boiler, cook stove, motor etc. The PID can also control an alarm or buzzer or indicator light that notifies operator to remove pot of water from a cook top for example. Thermocouple is 2 different metals joined together that create small electric current when heated. PID interprets changing flow of electricity as change in temperature. Thermocouple is usally made from a copper material that can take time to cool down after PID turns off circuit. Likewise it takes time to heat up, making RTD a preferred method if quicker oscillations in temperature change are needed. However, water typically does not change temperature very fast either. This means thermocouple or RTD are good choice for water. RTD might be better control for heating air if quick changes are needed. RTD is a variable resistor that limits milliamp (current) flow through the RTD. PID interprets change in resistance as change in temperature. RTD is much smaller and will cool faster. RTD is more accurate than thermocouple and rated for wide temperature range -100 to +500°F. |
Digital
controller... activated by temperature probe
 Proportional
Integral Derivative/ PID controlPID controller is activated by temperature-sensitive thermocouple or RTD. Use the PID to control any other circuit, or to ring buzzer etc. Best to use PID to control a contactor or relay instead of directly connecting load to PID Use contactor or relay as shown in illustrations below ''Output actuator has a resolution of about 3%''. So if temp setting on PID is 140° then actual temperature is 140° ±3% or 4.2° margin of error. Using a separate contactor or relay that is rated for elements and motors allows millions operations without risk of overload and burnout of PID terminals. Buy: PID with relay output and thermocouple/ ITC-100HR/Temperature rang :-50～250ºC PID with SSR solid state relay output ITC-100V PID Temperature controllers Inkbird PID Digital temperature controller 30 amp contactors Omron relay Solid State Relay Board for Arduino Resources: Contactors Select breaker and wire size Inkbird .pdf Inkbird spec sheet |
 General information on PIDWiring on this page requires PID with relay output, and voltage rating 120-240 volt. The relay output includes terminals 8-7-6, with terminal 7 the COM, and 6 and 8 the switching terminals NO and NC.... (normally open, normally closed) Output relay max 3 amps ... sufficient to energize contactor. Add 3 amp line fuse to protect PID from 30 amps that ave available on the water heater circuit. Thermocouple is accurate for water heater. For more precise control of temperature, an RTD can be used. Buy: PID with relay output and thermocouple/ ITC-100HR Panel mount fuse holders at Amazon Fuse blocks at Amazon ANL fuseholder Din rail fuseholder 10 x 38 mm fuse |
Other
models of PID have 12-24Volt AC-DC input voltage, and some specify
solid state output (24 volts DC), instead of relay output.Solid state output terminal are 8 is + and 6 is - .... these terminals are connected to solid state relay that can activate a circuit. Solid state relays are generally not robust enough for 30 amp water heater circuit, and if they fail, they fail in ON position. Manual |
 Basic
wiring to control contactor with PIDBuy 2-Pole 40A resistive 120Volt coil At Amazon 240Volt coil At Amazon 24 volt coil at Amazon Mars 2-pole and 3-pole contactors Resources: Contactors and relays Inline fuseholders Enclosures (electric boxes) |
 Larger image |
What
is a contactor? Contactor is a switch. It is rated for high amp loads. High amp causes heat. Heat will damage regular electrical parts. Timers and wall switches can be damaged by high amperage. Each switch and timer has amp rating. Contactors are rated for more amps than ordinary wall switch or timer. The electrical circuit lasts longer when a contactor is used because contact points on a contactor are designed to switch high amp loads without melting or being damaged by heat. The electromagnetic coil can be switched on-off using ordinary wall switch or timer or relay output from PID. When voltage is applied to coil, then contact points close, and heavy amp circuit turns on. This lets you control heavy amp loads safely. Buy 2-Pole 40A resistive 120Volt coil At Amazon 240Volt coil At Amazon 24 volt coil at Amazon Mars 2-pole and 3-pole contactors |
 Contactor shown is safe for 1 residential water heater. |
Pull
boxes/ metal
DPST contactor bolted into a 6x6x4 enclosure using #8-32 bolts Buy: 6x6x4 Metal box: has knock-outs for 1/2 and 3/4" ... must drill 1/2" hole for fuseholder, bolt holes to hold contactor, threaded holes for 10-32 ground screw, metal box must be grounded. Indoor 6x6x4 metal pull box with cover and knock-outs/ Raco Indoor 6x6x4 pull box with knockouts on 4 sides/ Wiegman Indoor 6x6x4 pull box with knockouts on 4 sides/ Hoffman Outdoor 6x6x4 box with bottom knockouts Indoor 6x6x4 metal pull box with cover and knock-outs/ Raco Indoor/ hinged door 10x10 x 6 / Bud Industries Indoor / hinged door/ 6x8x4 box / Bud Industries Bud industries boxes at Amazon Arlington boxes at Amazon |
 Bud Industries 8 x 10 x 4 Electric box 10 x 10 x 4 Electric box Wiring and controls Buy: Bud Industries 8x10x4 Bud Industries 10x10x4 Bud Industries boxes at Amazon |
 Arlington 12 x 12 x 4 Electric box Wiring and controls Buy: Arlington choose sizes/ 12 x 12 x 4 Arlington 7 x 8 x 3.5 Arlington boxes at Amazon |
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 Project box/ Plastic / aluminum Electronic projects Buy: Project box Hammond project boxes Aluminum enclosure |
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