[TRNSYS-users] Type 940 : Tankless Water Heater

Anas Majdouli majdouli_anas at hotmail.fr
Wed Jul 8 02:23:50 PDT 2015


Hi TRNsys community,

I am comparing Gas & Electric tankless water heater using the same component (Type 940). According to the description of the type, Electric tankless water heater is simulated by setting the efficiency to 1. When I plot the outlet temperature for both gas & electric heaters, some oscillations occur at the beginning of the first water draw for each day (7 days simulation) only for gas heater (efficiency set to 0.8). I tried to change the deadband, it is not affecting the results. But when I reduce the efficiency of the device, the amplitude of the oscillations increase. Why isn't this happening for the electric heater, i.e. when the efficiency is set to 1 ? Is it just from how the type was designed ?

Please find attached the file of the simulation and the corresponding weather data. The concerned plots are "Tout" of the 1st and 2nd graphs.
Thank you in advance.

Yours Sincerely,
Anas MAJDOULI
 		 	   		  
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