I think your simulation is correct (nice job, incidentally, in setting it up). I think the "problem" is that your collector is just too small to collect enough energy to add to the tank. As a result, whenever there is flow through the collector, the temperature rise is so small that the outlet temperature basically equals the inlet temperature and the controller decides to turn off. Imagine the limit; if you had a collector that had zero area, it couldn't collect any energy; it would just a pipe of water sitting in the sun. When there is no flow, the pipe heats up, the water gets hot, and the controller decides to turn on the pump. However, as soon as the flow starts, the water comes back to the tank at the same temperature with which it left. I doubled the area of your collector and suddenly it all went stable.
I did clean up the connections between the weather processor and the collector; there are a few more solar radiation connections that need to be made (diffuse solar, incidence angle, etc.). You also need to use Type69 to get the sky temperature. Alternatively (and much preferably) you should change Type109 for Type15; Type15 also reads TMY2/Meteonorm data files but has a number of advantages over Type109 (including calculating the effective sky temperature internally and outputting the wind speed.
Regards,
David
On 9/22/2011 15:50, Michael Bissett wrote:
I have taken your advice and made the timestep, 0.125hr
Still I cannot get it to work. it is still switching on the time step instead of the dead-band temp.
Mike
On Wed, Sep 21, 2011 at 3:33 PM, Matt Duffy <duffy@tess-inc.com> wrote:
Dear Michael,
Please make sure that you are using a reasonable timestep such as 0.125 hr (type in terms of hours to avoid problems with the Studio's minute conversion trucation). Also, make sure that you have the latest TRNSYS and TESS Libraries versions as well.
Best regards,
Matt Duffy
----- Original Message -----
From: "Michael Bissett" <mikebiscuit@gmail.com>
Sent: Tue, September 20, 2011 12:44
Subject: Re: [TRNSYS-users] Type 2b controller dead band problem.
On Tue, Sep 20, 2011 at 1:59 PM, Angel Carrera <angel.carrera@aiguasol.coop> wrote:
Mike,
you should connect the output control function of the controller to its own input control function (Input number 4). Also, you should increase the value of parameter 1, to the default value at least (the influence of this parameter is explained at the type 2 documentation, I recommend you to read it, together with the generic section for controllers at the trnsys help)
Regards
Angel
2011/9/19 Michael Bissett <mikebiscuit@gmail.com>_______________________________________________Dear TrnsysI am experiencing problems with a simple type 2b controller.I am using a solar collector type 564bI am trying to compare the temperature of the output of the collector with output of the tank, getting a temperature difference. I have set the dead band from 4-10 degrees C.In the simulation as the temperature rises to 10degrees difference, the control signal is 1 switching the pump on correctly. but after this the controller only switches every time step. I have tried shortening the time step... and changing other parameters.. still with no success.I have attached the file.Yours SincerelyMike BissettDepartment of Electrical EngineeringUniversity of Cape TownSouth Africa
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