The Xpelair Simply Silent Contour Humidistat (C4HTSR, MPN 078360) is a 100mm near-silent bathroom extractor fan with automatic humidity-triggered control and an adjustable overrun timer. When relative humidity in the room rises above the set threshold — for example during a shower — the fan activates automatically without needing a light switch signal. Once humidity drops back below the set point plus the timer overrun, it shuts off. Powered by Xpelair's Ghost™ Air Movement Technology, it achieves 15 dB(A) on low speed. Supplied with both square (180×180mm) and round (200mm Ø) fascias included, it suits new builds, extensions and refurbishments where moisture control needs to operate independently of occupancy.
15 dB(A)
Low-speed noise
50–90% RH
Humidistat range
54/76 m³/h
2-speed airflow
6.3/7W
Power draw
IPX4
IP rating
2 Years
Warranty
Wiring — 3-Core Required: The C4HTSR requires a 3-core feed (Live, Neutral, and a switched Live from the lighting circuit for the Timer function). The humidistat operates the fan independently of the switch, but the switched live is still needed for the overrun timer circuit. Always isolate the supply and verify dead before wiring. The protective fuse must not exceed 5A. Connect via a double-pole isolating switch with at least 3mm contact separation.
Setting the Humidistat: The factory preset is approximately 75% RH. Adjust using control H inside the fan body — clockwise increases the trigger threshold (fan activates at higher humidity), anti-clockwise lowers it. For a condensation-prone bathroom, set towards 60–70% RH so the fan activates early in the shower cycle. The timer overrun (control T) is independent and set between 30 seconds and 30 minutes.
Automatic Humidity Control
The integrated humidistat sensor (50–90% RH range) continuously monitors room moisture levels. When humidity rises above the set point — such as when a shower starts — the fan activates automatically, even if the room light is off. This prevents condensation from building up during unoccupied humid periods, protecting surfaces, grout and plasterwork.
Ghost™ Air Movement Technology
Identical to the timer-only model, Ghost technology delivers 15 dB(A) at low speed — effectively inaudible in normal domestic environments. When the humidistat triggers the fan at night, occupants are not disturbed. High speed delivers 29 dB(A), still significantly quieter than a conventional extractor.
Humidistat + Timer Combination
Both the humidistat and the overrun timer operate simultaneously. The humidistat keeps the fan running as long as humidity exceeds the threshold; when humidity drops, the timer then runs for the set overrun period. This dual mechanism ensures the fan continues long enough to fully clear residual moisture, not just until the humidity drops to the detection threshold.
Square + Round Fascias Included
Both a contoured 180×180mm square fascia and a 200mm Ø round fascia are supplied. The smooth, rounded edges of the contour design are easy to wipe clean and resist the moisture-accelerated mould growth that can affect older flat-grille fans. The white gloss ABS finish complements contemporary bathroom tile and sanitaryware.
Integral Backdraught Shutter
The built-in backdraught shutter closes when the fan stops, whether triggered by the light switch circuit turning off or by the humidistat dropping below threshold. Cold air ingress through the duct run is eliminated, reducing heat loss and preventing condensation from forming inside the duct in winter.
Two-Speed Motor, Selectable at Fit
The 2-speed motor (15/21 l/s) is set during installation by a link inside the housing. Once set, the fan runs at the selected speed whenever activated by the humidistat or the light switch. The low SFP of 0.42/0.33 W/l/s means energy consumption over the fan's lifetime is very low despite automatic operation.
Technical Specifications
| Fan Performance |
| MPN |
078360 |
| Model |
C4HTSR (Simply Silent Contour Humidistat/Timer) |
| Speeds |
2 (selectable at installation) |
| Extract Rate — Low Speed |
15 l/s / 52 m³/h |
| Extract Rate — High Speed |
21 l/s / 76 m³/h |
| Sound Level — Low Speed @ 3m |
15 dB(A) |
| Sound Level — High Speed @ 3m |
29 dB(A) |
| Electrical Power |
6.3W (low) / 7W (high) |
| Specific Fan Power (SFP) |
0.42 W/l/s (low) / 0.33 W/l/s (high) |
| Motor Type |
AC |
| IP Rating |
IPX4 (Zone 1 with 30mA RCD; Zone 2) |
| Humidity & Timer Controls |
| Humidistat Range |
50% – 90% RH (adjustable) |
| Humidistat Factory Default |
Approx. 75% RH |
| Timer Range |
30 seconds – 30 minutes |
| Timer Factory Default |
15 minutes |
| Wiring Cores Required |
3-core (L, N, T) |
| Dimensions & Fitment |
| Square Fascia Size |
180 × 180mm |
| Round Fascia Diameter |
200mm |
| Body Depth (fitted) |
44.5mm |
| Rear Spigot Diameter |
98mm |
| Mounting |
Wall, ceiling, panel or window |
| Supply Voltage |
230V AC, 50Hz |
| Max Fuse Rating |
5A |
| Backdraught Shutter |
Integral |
| Colour / Finish |
White / Gloss ABS |
| Compliance |
Building Regs Parts F & L |
| Warranty |
2 years (Xpelair UK) |
Frequently Asked Questions
Does the humidistat model still need to be wired to the light switch?
Yes. The C4HTSR still requires a 3-core wiring connection including a switched live (T terminal) from the room light switch. The humidistat operates the fan independently of the switch — activating and deactivating based on humidity regardless of whether the light is on or off — but the timer overrun function still needs the switched signal to know when to begin counting down. The fan can operate in humidistat-only mode if preferred; refer to the wiring diagram supplied with the fan.
What RH level should I set the humidistat to?
The factory preset of ~75% RH is suitable for most bathrooms. For a room that suffers persistent condensation on walls or mirrors, reduce the threshold to 60–70% RH so the fan activates earlier in the shower cycle. For a well-ventilated room where the fan runs too frequently, increase to 80–85% RH. Adjust in small increments and allow a week of use before re-evaluating. The range is 50% to 90% RH.
When should I choose the Humidistat over the Timer-only model?
Choose the Humidistat (C4HTSR) when: the bathroom is used at unpredictable times (e.g. a guest bathroom or en-suite), when moisture control is needed independently of the light, or when the room is prone to condensation. Choose the Timer-only (C4TSR) when a simple, lower-cost solution is adequate and the bathroom is always used with the light on. The humidistat adds automatic, intelligent control that is particularly valuable in rooms without opening windows.
Will the humidistat cause the fan to run continuously in a very humid climate?
In areas with consistently high ambient humidity (above the set threshold), the humidistat could trigger frequent or prolonged operation. In UK conditions this is uncommon indoors, but if it occurs, raise the RH threshold using control H until the fan operates only during showering. Alternatively, switch to the Timer-only (C4TSR) model, which operates solely on the light switch circuit and is unaffected by ambient humidity.
Can this fan be used in a loft room bathroom without an opening window?
Yes, and this is an ideal application. Approved Document Part F requires mechanical extract in bathrooms without openable windows; the C4HTSR's humidistat ensures the fan activates automatically whenever moisture levels rise, meeting the spirit of Part F even without occupant action. Ensure the duct run exits through the roof or a wall to outside air and is as short and straight as possible for maximum airflow performance.
