Which RTL Control Box Is Right for My Project?

Two control boxes are available for the heating kits to control the temperature and for connection to the existing heating system. In both cases, the heating water temperature is controlled via a return temperature limiter [RTL]. The table provides a direct comparison of the respective range of functions.

 

  RTL box for underfloor heating - inside view RTL kompabox for temperature control of underfloor heating
  Multibox 4k-RTL Kompabox RTL
Connection to conventional heating systems with 70°C flow temperature check_circle check_circle
Connection to panel heating systems with max. 50°C flow temperature check_circle  
Return temperature limiter check_circle check_circle
Connection for bathroom radiator   check_circle
Flow shut-off check_circle check_circle
Bleed valve - removal of air from the heating system check_circle  
Thermostatic head with V-exact II for carrying out hydronic balancing check_circle  
Smarthome ready* check_circle  
Installation dimensions in mm (H×W×D) 190×240×60 150×230×60
Product pages Details Details

 

* For integration into Smarthome systems, the thermostat head of the Multibox 4K-RTL can be exchanged and replaced with a wireless radiator thermostat. The Smarthome thermostat head must fit a 30 × 1.5 mm connection thread or have an appropriate adapter. Integration into a Smarthome system offers additional control convenience, especially when operating several heating sets.

question_exchange

The thermostatic head in the Multibox 4K-RTL can be replaced by a Smarthome servo drive. The retail market offers various brands for this purpose, depending on the Smarthome system. The product to be selected must have a connection thread of M30x1.5 and have the corresponding adapters for the IMI thermostatic head K installed as standard in the Multibox.

The control of the heating temperature via the RTL principle (=return temperature limiter) is an established control technique. It is particularly suitable if the new radiant heating is to be integrated into an existing heating system with higher flow temperatures. The RTL valve permanently measures the heating water temperature in the heating circuit. If this is too high for a radiant heating system (the limit is about 45°C), the valve interrupts the flow through the heating circuit and no further hot water flows into the heating circuit. Thus, the water in the heating circuit then cools down again. If the temperature falls below the maximum temperature of the radiant heating, the RTL valve opens again. Further details on how they work can be found directly on the product pages of our RTL boxes.

An RTL valve is required for connection to heating systems that feed water into the circuit at a flow temperature of up to 65°C. RTL stands for return temperature limiter.

The Multibox 4K-RTL limits the return temperature and has a flow shut-off including a vent valve and a regulating spindle with which hydraulic balancing can be carried out.

It is controlled without additional energy and can be individually adjusted using the thermostatic head supplied. This functions as a continuous proportional controller. The change in the room air temperature (controlled variable) is proportional to the change in the valve stroke (actuating variable). If the room air temperature rises, the temperature in the temperature sensor expands and acts on the corrugated pipe. This throttles or increases the water supply in the underfloor heating circuit via the valve spindle.

Even if the heat generator is to be replaced at a later date with a modern heat source with low heating temperatures, such as a heat pump, the Multibox 4k-RTL can still be used. Because the flow temperature will then be moderately below 45°C, the Multibox will not have to regulate and you can continue to use the actuator. Our alternative RTL box, the Kompabox RTL, is not suitable for this.