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Water boiler heaters (RT type)


The water boiler heaters and resistors on threaded fitting with rigid bulb unipolar thermostat (so called “RT” type) are designed for sanitary use water heating inside water boilers of small capacity, for mainly home use.

Their typology, both for standard and non-standard models, consists of a first quality copper heating tube bundle, made of 1 element (Single-phase type), “U” folded, or folded and welded on a brass threaded fitting G. 1″ 1/4, suitable for anchoring to the water boiler wall.

This heaters typology is generally installed in vertical position inside the boiler for the water direct heating.

The adoption of first quality materials within our production cycle, allows the water boiler immersion electric resistors of our production, to perform efficiently with an excellent thermal efficiency, a satisfactory use durability and a high safety level.


The use of a water boiler immersion resistor is essential for the water domestic heating, both of accumulation and instantaneous type.

Alternatively to the copper sheath, this type of resistors is excellent for uses also in presence of corrosion, where we manufacture specific RT type resistors with special alloys sheaths, such as  INCOLOY 800 and 825 and stainless steel threaded fittings AISI304 /309 and Brass


The entire industrial electric resistors on threaded fitting production cycle is subject to the strictest dimensional checks and to electric tests in compliance with the standards set forth by our own ISO 9001:2015 certified Corporate Quality System, and in full compliance with the CEI/EN requirements in force.


This type of heaters is made up of a tube bundle consisting of 1 element folded as follows:

To avoid the premature damaging of this type of electric resistors, the heating section must be constantly and fully immersed inside the fluid to be heated. In order to limit the overheating risk, this type of heaters can be properly equipped with efficient rigid-rod bulbs unipolar thermostats with adjustable temperature scale, suitable for protecting the heater from the overheating risk and possible premature damaging.