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The plant loops iterate many time during a time step. The point where the figure shows 0.05C difference is the PlantLoop interface of the supply and demand side of the loop. The supply and demand side of the loop are simulated independently. When the supply side of the loop is simulation each component is simulated and the result is pushed from the plant supply side outlet to the plant demand side inlet. The demand side of the loop is then simulated with the same "push" of the plant demand side outlet to the plant supply side inlet. The simulation of each side of the plant continues until convergece or max iteration is achieved. If you let the plant iterate more this temperature difference between each side of the plant should ge smaller. More complex plants need more iterations. See the ConvergenceLimits object.

ConvergenceLimits,
     \memo Specifies limits on HVAC system simulation timesteps and iterations.
     \memo This item is an advanced feature that should be used only with caution.
     \unique-object
  N1 , \field Minimum System Timestep
     \units minutes
     \type integer
     \note 0 sets the minimum to the zone timestep (ref: Timestep)
     \note 1 is normal (ratchet down to 1 minute)
     \note setting greater than zone timestep (in minutes) will effectively set to zone timestep
     \minimum 0
     \maximum 60
  N2 , \field Maximum HVAC Iterations
     \type integer
     \default 20
     \minimum 1
  N3 , \field Minimum Plant Iterations
     \note Controls the minimum number of plant system solver iterations within a single HVAC iteration
     \note Larger values will increase runtime but might improve solution accuracy for complicated plant systems
     \note Complex plants include: several interconnected loops, heat recovery, thermal load following generators, etc.
     \type integer
     \default 2
     \minimum 1
  N4 ; \field Maximum Plant Iterations
     \note Controls the maximum number of plant system solver iterations within a single HVAC iteration
     \note Smaller values might decrease runtime but could decrease solution accuracy for complicated plant systems
     \type integer
     \default 8
     \minimum 2

The plant loops iterate many time times during a time step. The point where the figure shows 0.05C difference is the PlantLoop interface of the supply and demand side of the loop. The supply and demand side of the loop are simulated independently. When the supply side of the loop is simulation each component is simulated and the result is pushed from the plant supply side outlet to the plant demand side inlet. The demand side of the loop is then simulated with the same "push" of the plant demand side outlet to the plant supply side inlet. The simulation of each side of the plant continues until convergece or max iteration is achieved. If you let the plant iterate more this temperature difference between each side of the plant should ge smaller. More complex plants need more iterations. See the ConvergenceLimits object.

ConvergenceLimits,
     \memo Specifies limits on HVAC system simulation timesteps and iterations.
     \memo This item is an advanced feature that should be used only with caution.
     \unique-object
  N1 , \field Minimum System Timestep
     \units minutes
     \type integer
     \note 0 sets the minimum to the zone timestep (ref: Timestep)
     \note 1 is normal (ratchet down to 1 minute)
     \note setting greater than zone timestep (in minutes) will effectively set to zone timestep
     \minimum 0
     \maximum 60
  N2 , \field Maximum HVAC Iterations
     \type integer
     \default 20
     \minimum 1
  N3 , \field Minimum Plant Iterations
     \note Controls the minimum number of plant system solver iterations within a single HVAC iteration
     \note Larger values will increase runtime but might improve solution accuracy for complicated plant systems
     \note Complex plants include: several interconnected loops, heat recovery, thermal load following generators, etc.
     \type integer
     \default 2
     \minimum 1
  N4 ; \field Maximum Plant Iterations
     \note Controls the maximum number of plant system solver iterations within a single HVAC iteration
     \note Smaller values might decrease runtime but could decrease solution accuracy for complicated plant systems
     \type integer
     \default 8
     \minimum 2

The plant loops iterate many times during a time step. The point where the figure shows 0.05C difference is the PlantLoop interface of the supply and demand side of the loop. The supply and demand side of the loop are simulated independently. When the supply side of the loop is simulation each component is simulated and the result is pushed from the plant supply side outlet to the plant demand side inlet. The demand side of the loop is then simulated with the same "push" of the plant demand side outlet to the plant supply side inlet. The simulation of each side of the plant continues until convergece or max iteration is achieved. If you let the plant iterate more this temperature difference between each side of the plant should ge get smaller. More complex plants need more iterations. See the ConvergenceLimits object.

ConvergenceLimits,
     \memo Specifies limits on HVAC system simulation timesteps and iterations.
     \memo This item is an advanced feature that should be used only with caution.
     \unique-object
  N1 , \field Minimum System Timestep
     \units minutes
     \type integer
     \note 0 sets the minimum to the zone timestep (ref: Timestep)
     \note 1 is normal (ratchet down to 1 minute)
     \note setting greater than zone timestep (in minutes) will effectively set to zone timestep
     \minimum 0
     \maximum 60
  N2 , \field Maximum HVAC Iterations
     \type integer
     \default 20
     \minimum 1
  N3 , \field Minimum Plant Iterations
     \note Controls the minimum number of plant system solver iterations within a single HVAC iteration
     \note Larger values will increase runtime but might improve solution accuracy for complicated plant systems
     \note Complex plants include: several interconnected loops, heat recovery, thermal load following generators, etc.
     \type integer
     \default 2
     \minimum 1
  N4 ; \field Maximum Plant Iterations
     \note Controls the maximum number of plant system solver iterations within a single HVAC iteration
     \note Smaller values might decrease runtime but could decrease solution accuracy for complicated plant systems
     \type integer
     \default 8
     \minimum 2