Katy Paty Dimmers and LED Compatibility

A Katy Paty dimmer mechanism varies the light output of a compatible fitting. Specifying a dimmer correctly requires confirming that the dimmer mechanism, the light fitting and the bulb are all compatible with each other. An incompatible combination will result in flickering, buzzing, failure to dim, or damage to the bulb or dimmer. This guide explains what to confirm before ordering.

Fixed electrical wiring must be carried out by a competent person. This guide is for specification and ordering purposes only.

For an introduction to the Katy Paty range, see our Complete Katy Paty Buying Guide. For switch types and mechanism overview, see Katy Paty Switch Types Explained.

Why LED Compatibility Matters

Traditional dimmer mechanisms were designed for resistive loads, incandescent and halogen bulbs. LED bulbs present a fundamentally different electrical load. A dimmer designed for incandescent bulbs may not function correctly with LED bulbs, and vice versa. The consequences of an incompatible combination include:

Flickering — the light flickers at low dim levels or across the full range.
Buzzing — an audible hum from the dimmer, the bulb or the fitting.
Failure to dim — the light does not dim smoothly or does not dim at all.
Minimum load issues — the dimmer requires a minimum load to function; LED bulbs have a very low wattage and a single LED bulb may fall below the dimmer’s minimum load.
Reduced bulb life — an incompatible dimmer may shorten the life of the LED bulb.
Damage to the dimmer — in some cases, an incompatible load may damage the dimmer mechanism.

Trailing Edge Versus Leading Edge Dimmers

Dimmer mechanisms are classified by the method they use to control the load:

Leading edge (LE) — the traditional dimmer type, designed for resistive and inductive loads (incandescent, halogen, magnetic transformers). Leading edge dimmers are generally not compatible with LED bulbs unless specifically rated for LED use.
Trailing edge (TE) — designed for capacitive and resistive loads, including most LED and electronic low-voltage (ELV) drivers. Trailing edge dimmers produce less electrical noise and are generally more compatible with LED bulbs.

Confirm the dimmer type (leading edge or trailing edge) from the Katy Paty product specification before ordering. Do not assume that a dimmer mechanism is LED-compatible without confirming from the specification.

Minimum and Maximum Load

Every dimmer mechanism has a minimum and maximum load rating, expressed in watts:

Minimum load — the dimmer requires at least this wattage on the circuit to function correctly. LED bulbs have very low wattage; a single 5W LED bulb may fall below the minimum load of a dimmer rated for a minimum of 25W or 40W. If the total load on the circuit falls below the minimum, the dimmer will not function correctly.
Maximum load — the total wattage of all bulbs on the circuit must not exceed this figure. Exceeding the maximum load will damage the dimmer.

Calculate the total wattage of all bulbs on the circuit and confirm that it falls within the minimum and maximum load range of the dimmer mechanism. Confirm the load ratings from the product specification.

Dimmable Bulbs

Not all LED bulbs are dimmable. A non-dimmable LED bulb connected to a dimmer circuit will typically either not dim at all, flicker, or fail prematurely. Before specifying a dimmer:

Confirm that the bulb is rated as dimmable. This is stated on the bulb packaging or in the product specification.
Confirm that the fitting is compatible with dimmable bulbs. Some fittings with integrated LED modules are not dimmable even if the module appears to be an LED.
Confirm that the dimmable bulb is compatible with the specific dimmer mechanism being used. Not all dimmable LED bulbs are compatible with all dimmer types. The bulb manufacturer may publish a compatibility list.

Neutral Wire Requirement

Some dimmer mechanisms require a neutral wire at the switch position. In older UK wiring installations, a neutral wire may not be present at the switch position — only a switched live is run to the switch. If the dimmer requires a neutral and one is not present, the dimmer cannot be installed without rewiring.

Before ordering a Katy Paty dimmer mechanism:

Confirm from the product specification whether a neutral wire is required.
Confirm with your electrician whether a neutral wire is present at the switch position.
If a neutral is required and not present, confirm with your electrician whether rewiring is feasible before ordering.

Two-Way Dimming

A dimmer circuit can be controlled from two positions using a two-way dimmer configuration. This typically requires a specific two-way dimmer mechanism at one position and a compatible slave unit at the other. Key points:

Confirm that a two-way dimmer configuration is available in the Katy Paty range for the collection being specified.
Confirm the slave unit type and whether it is available in the same collection and colour.
Two-way dimmer configurations may have different minimum load requirements from single-position dimmers. Confirm from the product specification.

Rotary Versus Push Dimmers

Katy Paty dimmer mechanisms are available in rotary and push-button formats (confirm availability in the specific collection from the product listings):

Rotary dimmer — the light level is adjusted by rotating the control. The on/off function may be integrated into the rotary control (push to switch) or separate.
Push dimmer — the light level is adjusted by pressing and holding the control. A single press switches the circuit on or off.

Confirm the dimmer format available in the specific Katy Paty collection and colour from the product listings.

Flicker and Ghosting

Two common issues with LED dimmer installations:

Flicker — visible flickering of the light, particularly at low dim levels. Usually caused by incompatibility between the dimmer type and the LED driver in the bulb. Resolved by using a compatible dimmer and bulb combination.
Ghosting — a faint glow from the bulb when the switch is in the off position. Caused by a small leakage current through the dimmer. Resolved by using a compatible dimmer and bulb combination, or by adding a load resistor to the circuit (confirm with your electrician).

Pre-Order Checklist

Dimmer mechanism type confirmed: leading edge or trailing edge?
LED compatibility confirmed from product specification?
Minimum and maximum load ratings confirmed from product specification?
Total circuit wattage calculated and within the load range?
All bulbs on the circuit confirmed as dimmable?
Bulb compatibility with the specific dimmer mechanism confirmed?
Neutral wire requirement confirmed from product specification?
Neutral wire presence at switch position confirmed with electrician?
Two-way dimming configuration confirmed if required?
Dimmer format (rotary or push) confirmed and available in the collection and colour?

Product Validation Table

Verify before publication.

Claim	Requires verification
Katy Paty dimmer mechanism type (leading edge or trailing edge)	Confirm from product specification for each dimmer mechanism listed
LED compatibility of each dimmer mechanism	Confirm from product specification; do not assume LED compatibility
Minimum and maximum load ratings	Confirm from product specification for each dimmer mechanism
Neutral wire requirement	Confirm from product specification for each dimmer mechanism
Two-way dimmer and slave unit availability	Confirm whether a two-way dimmer configuration is available in the Katy Paty range and in which collections
Rotary and push dimmer availability	Confirm which formats are available in which collections from current product listings

Technical Claims Requiring Human Review

All load ratings, must be confirmed from official product specifications, not inferred.
Neutral wire requirement, confirm for each dimmer mechanism individually.
Two-way dimmer slave unit compatibility, confirm from official documentation.
Ghosting resolution methods, confirm load resistor approach with a qualified electrician before publication.