Hi Tim

Techman

I just attented a Burnham Boiler class on their Alpine boiler,that operates off of  4-20ma ,as compared to the 0-10vdc on  one of their other boilers. The instructor said the 4-20ma is the same thing as the 0-10vdc ,just different. How is that ? What did I not understand ? Thank you !

Tim McElwain

Alpine information

The Alpine equipped with the MCBA Honeywell control operated with a 0-10vdc input signal from Building Management Systems and other controls such as Tekmar controls. If the controlling source had a 4-20 ma signal it could be easily converted to 0-10vdc by bridging the input terminals with a 500 ohm 1/4 watt resister.



In working with Honeywell in developing the Sage 2 control system for the Alpine, a decision was made to make the input 4-20ma in lieu of the 0-10vdc signal as the bulk of Building Management Systems and external control devices operated with the 4-20ma signal. The exception to this is the new Tekmar 275 boiler control which unlike many of the other Tekmar controls such as the 265 control, operates with only a 0-10vdc output. many of the other controls operate with a 4-20ma signal that can either be converted with a resister or is selectable on the control. If someone ends up with a control like the Tekmar 275 that only operates with the 0-10vdc signal, an interface will need to be purchased and installed for each boiler connected to the external control. These interfaces can be obtained from a number of outside sources.



The Sage 2 control is also unique in that the control can be programmed to either have its modulation controlled by the external 4-20ma signal or to convert the 4-20 ma signal to a system setpoint temperature allowing each boiler connected to modulate on its own to target that system temperature. Hope this helps.



I confirmed this with the rep from Burnham.