STEGO MFR 012-1 Mechanical Hygrostat 35-95 % RH 01220.0-00

01220.0-00 is the STEGO MFR 012-1 mechanical hygrostat with a setting range of 35 to 95 % relative humidity and a changeover contact rated AC 5 A or DC 20 W. It measures 67 x 50 x 38 mm and weighs 60 g.

A mechanical hygrostat that reacts to humidity before condensation forms

Condensation depends on humidity as well as temperature, so a hygrostat adds a second control path for enclosure heating. The MFR 012-1 switches a changeover contact when the relative humidity passes the set value, without electronics.

STEGO states a switching differential of 4 % RH with a tolerance of 3 % at 50 % rH. Its datasheet notes that from a critical relative humidity of 65 % the temperature is raised, which matches how a heater is used to move the air away from the dew point.

Key features as printed in the datasheet

• Setting range 35 to 95 % RH.
• Changeover contact, AC 5 A or DC 20 W.
• Differential 4 % RH, tolerance 3 % at 50 % rH.
• More than 50,000 switching cycles.
• Operating temperature 0 to 60 C.
• 67 x 50 x 38 mm; 60 g; max torque 0.5 Nm.

Technical specification

Technical data, as printed on the STEGO datasheet

MFR 012-1 terminal use listed by STEGO

Selection and ordering guide

STEGO states that the hygrostat is used to prevent condensate and regulates heating and fans. From a critical relative humidity of 65 %, the temperature is increased so that the relative air humidity decreases and condensate is prevented from forming. Features are an adjustable relative humidity, a changeover contact for heating or cooling, high switching capacity and clip mounting.

Choose the MFR 012-1 when the enclosure risk is humidity-driven, for example in coastal or damp plant rooms where temperature alone may not show the danger. It is often combined with a thermostat on the same heater.

Because the hygrostat range stops at 35 % RH and 0 C, it is not for very dry or freezing environments; use a thermostat there.

Installation and operation notes

Wire using the STEGO connection example: terminal 2 for heating, L for the line and terminal 3 for cooling. Respect the 0.5 Nm torque limit on the adjuster.

Mount where the sensor sees circulating enclosure air and not directly next to the heater outlet. Verify with the current datasheet.

Applications in Oman and the GCC

Control cabinets in humid or coastal sites, water-treatment plants, marine and offshore enclosures and unheated panel rooms.

In Gulf coastal sites high humidity at night is a common cause of condensation even when temperature stays warm.

Because the contact is a changeover type, the same device can switch a heater on one output and a fan or filter fan on the other, so a single hygrostat covers both rising and falling humidity. The housing is plastic to UL94 V-0 in light grey with IP20 protection, and the datasheet carries CCC (CQC) marking, so it is meant for mounting on a rail inside a closed enclosure. Operating humidity is stated up to 95 % RH, which matches the top of the setting range.

Compatible accessories and related items

Related STEGO items: the KTO 111 thermostat (11100.0-00), ETR 011 electronic thermostat (01131.0-00), the HGL 046 heater (04641.0-00) and the CS 060 heater (06010.0-00).

Selection and maintenance notes

Hygrostats are especially useful in the region’s coastal areas, where humidity is high and condensation can form inside enclosures as they cool at night or when air conditioning cycles off. Switching the heater by humidity rather than by temperature alone means the heater runs only when there is a real risk of condensation, which saves energy and avoids adding heat in hot weather. A common setting is about 65 % relative humidity, but the right setting depends on the equipment and site conditions.

Mount the hygrostat in the upper part of the enclosure, away from the heater outlet and from the air stream of fans. Check the switching current of the heater against the contact rating, and use a relay for larger heaters. The hygrostat can also be combined with a thermostat, so the heater works on both temperature and humidity. Check the setting and operation during routine maintenance.

Where several enclosures share one design, the same hygrostat and heater combination can be repeated, which keeps spare parts simple for maintenance teams.

Information to send with an enquiry

• Heater or other device to be switched
• Switching current and supply voltage
• Whether a thermostat is also needed
• Quantity

Documents and quotation

This page carries the official STEGO datasheet for 01220.0-00. Seven Star LLC is an independent supplier in Muscat and sources STEGO products on request; tell us the quantity and delivery point to receive a quotation. Always confirm the order code and technical values in the document first. See more in the product category.