Finding the Right Intermatic Control for the Load
Intermatic numbering is old enough that the part numbers are the trade language, T101 means a specific thing to an electrician the way QO does. Most of the range, 287 items, files in the timer collection, and this page sorts the rest by what the control is switching.
Which Intermatic Line You Need
T100 Mechanical Time Switches
The legend of the catalog: 69 mechanical time switches plus 3 heavy duty models and 8 replacement mechanisms. The voltage is coded in the number: T101, T103, and T105 run 120V circuits, while T102, T104, and T106 run 208V to 277V. R versions come in outdoor metal enclosures, P versions in plastic cases, and the T7000 and T8000 families add 7 day and 14 day dials. An M suffix means the mechanism only, sold to rebuild an existing enclosure rather than replace the whole switch.
Spring Wound and In-Wall Timers
67 spring wound countdown timers split into FF commercial and FD decorator styles from 5 minute to 12 hour windings, the no-electronics choice for saunas, fans, and heat lamps. Electronic in-wall coverage adds 16 EI countdown timers, 11 programmable 7 day timers, 7 mechanical in-wall units, and 2 STW smart Wi-Fi timers.
Electronic Controls and Timer Modules
56 ET class electronic controls run 1 to 16 circuits, and 27 of them are astronomic, meaning they track sunrise and sunset by date instead of fixed trip times. Behind panels, 48 FM1, MIL72, and GMX timer modules cover panel mount, DIN rail, and flush mount formats from 12V and 24V control circuits up to 277V.
Photocontrols
42 photocontrols split into K series thermal and EK series electronic models from 120V to 480V, plus locking type units, the twist-lock heads that mount on area light receptacles, with one receptacle listed as ANSI C136.10 compliant. Most cross-file in the photocell collection, where 36 of the 42 currently appear.
Surge Protection
93 surge items run from AG service entrance units and IG panel devices with plug-in strips up to the commercial L and H frames, 50kA to 200kA in 4 mode and 7 mode builds reaching 347/600V systems. This family is the entire surge protection collection at the moment, all 93 of its items are Intermatic.
Pool, Spa, and Freeze Protection
The pool program is a system: 20 T and PE series pool load centers, which are all but one item in the load center collection, plus 6 control panels and 18 pool and spa transformers. Around the panels sit junction boxes, the PE653 five-circuit control with its PE953 wireless remote, air buttons, air switches and tubing, and PF freeze protection thermostats and timers.
The 12V PX safety transformers for pool lights also cross-list with the transformer collection, where 12 Intermatic units currently sit.
Sensors, Water Heater Timers, and the Rest
21 IOS occupancy and vacancy sensors cover in-wall, ceiling, dual technology, and high bay formats, with 7 currently reaching the occupancy sensor collection. Around them sit 7 WH and EH water heater timer switches, 4 DTAV40 defrost timers for refrigeration, 17 AC hour meters, and 57 in-use weatherproof covers. ABRA smart bulbs and plugs and the WG motors, trippers, and receptacles round out the list, keeping decades of installed switches running.
Reading Intermatic Part Numbers
Prefixes carry the family: T mechanical time switch, FF and FD spring wound, EI and EJ electronic in-wall, ET electronic control, and FM and MIL72 modules. The rest follow suit, K and EK photocontrol, IG and AG surge, PX and PE pool, WH water heater, WP weatherproof cover. Within the T100 family the pattern is voltage by digit, odd numbers ending 1, 3, 5 for 120V and even numbers ending 2, 4, 6 for 208V to 277V. Suffixes finish the story: R outdoor metal case, M mechanism only, and BC on the T7401 marking a much more expensive build.
Ordering Notes for Intermatic Gear
Two switch-family habits prevent returns. First, a mechanism SKU is not a switch, T101M rebuilds a T101 but arrives without the enclosure, so replacement jobs on rusted cases need the full number. Second, spring wound timers are ordered by maximum winding and plate style, FF is the silver commercial plate and FD the decorator style, and the hold feature versions carry an H in the number. On photocontrols, match the voltage code exactly, since 120V, 208 to 277V, 347V, and 480V heads are separate SKUs. Locking heads pair with the twist-lock receptacles on site fixtures, so confirm the receptacle on the pole when speccing heads for the area light collection.
Checks Before an Intermatic Order
Confirm load voltage and amperage against the switch rating, and whether the load is resistive, motor, or ballast, since ratings differ by load type on the product page. Confirm indoor against outdoor enclosure, 24 hour against 7 day against astronomic scheduling, and on surge devices the service voltage, mode count, and kA rating the specification calls for. Certifications vary by product line, so verify the listing on each product page.
Intermatic Timer and Control Questions
What is the difference between T101 and T103?
Both are 120V 24 hour mechanical time switches; the numbers differ by switch configuration, and their 208V to 277V counterparts are T102 and T104. Match the voltage family first, then pick the configuration the circuit needs from the product page, and add R to the number when the install is outdoors.
What does an M at the end of the number mean?
Mechanism only. T101M, T104M, and similar SKUs are the clock and switch assembly without the enclosure, meant to rebuild an installed unit whose case is still good. If the enclosure is damaged or missing, order the complete switch number instead.
What makes a control astronomic?
An astronomic control calculates sunrise and sunset for the date and location and shifts its trip times through the year, so dusk to dawn lighting never needs seasonal reprogramming. In this range the ET2800 and ET90000 families carry that feature across 1 to 16 circuits.
Are the FF and FD timers interchangeable?
Electrically they are the same spring wound countdown platform. FF models wear the silver commercial plate and FD models the decorator style that matches standard wallplates, so the choice is finish and the winding maximum, from 5 minutes to 12 hours, printed in the number.
Which surge protective device fits a residential panel?
The IG and AG families cover 120/240V single phase service, with IG panel mount units and plug-in strip versions for point of use. The L and H frame devices are commercial products for three phase systems up to 347/600V, sized by kA rating and mode count, and belong on jobs specified that way.
