My model whihc runs ok for design day simulations, when ran for weather file days give many Iteration warnings for VAV with REHAT box's. I have 5 VAV boxes and I am getting around 8 to 10 warnings - few of which are as below:-
** Warning ** SimHVAC: Maximum iterations (25) exceeded for all HVAC loops, at RUN PERIOD 1, 03/28 16:40 - 16:50
** ~~~ ** The solution for one or more of the Air Loop HVAC systems did not appear to converge
** ~~~ ** Air System Named = VAV WITH REHEAT did not converge for mass flow rate
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface mass flow rate check value iteration history trace: 4.427527E-002,4.367028E-002,4.334135E-002,4.394626E-002,4.427539E-002,4.367029E-002,4.334158E-002,4.394676E-002,4.427527E-002,4.367028E-002,
** ~~~ ** Supply-to-demand interface deck 1 mass flow rate check value iteration history trace: 0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,0.000000,
** ~~~ ** Air System Named = VAV WITH REHEAT did not converge for humidity ratio
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface humidity ratio check value iteration history trace: 9.052790E-008,9.673507E-008,9.731781E-008,9.111049E-008,9.052739E-008,9.673596E-008,9.731832E-008,9.110991E-008,9.052790E-008,9.673507E-008,
** ~~~ ** Supply-to-demand interface deck 1 humidity ratio check value iteration history trace: 1.237439E-004,1.236712E-004,1.235623E-004,1.236351E-004,1.237441E-004,1.236711E-004,1.235622E-004,1.236349E-004,1.237439E-004,1.236712E-004,
** ~~~ ** Air System Named = VAV WITH REHEAT did not converge for temperature
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface temperature check value iteration history trace: 5.214427E-003,5.149490E-003,5.110221E-003,5.175149E-003,5.214442E-003,5.149493E-003,5.110250E-003,5.175208E-003,5.214427E-003,5.149490E-003,
** ~~~ ** Supply-to-demand interface deck 1 temperature check value iteration history trace: 0.236625,0.236953,0.235742,0.235414,0.236626,0.236954,0.235743,0.235416,0.236625,0.236953,
** ~~~ ** Air System Named = VAV WITH REHEAT did not converge for energy
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface energy check value iteration history trace: 1067.752024,1053.156244,1045.222737,1059.816714,1067.755021,1053.156433,1045.228238,1059.828629,1067.752024,1053.156244,
** ~~~ ** Supply-to-demand interface deck 1 energy check value iteration history trace: 326.375391,-337.225776,325.235144,-335.177758,326.375846,-337.226459,325.236864,-335.180489,326.375391,-337.225776,
** ~~~ ** Node named VAV1 BOX OUTLET NODE shows oscillating humidity ratio across iterations with a repeated value of 1.438061E-002
** ~~~ ** Node named VAV1 BOX OUTLET NODE humidity ratio [kg-water/kg-dryair] iteration history trace (most recent first): 1.438061E-002,1.438068E-002,1.438061E-002,1.438068E-002,1.438061E-002,1.438068E-002,1.438061E-002,1.438068E-002,1.438061E-002,1.438068E-002,
** ~~~ ** Node named VAV1 BOX OUTLET NODE shows oscillating mass flow rate across iterations with a repeated value of 0.180034
** ~~~ ** Node named VAV1 BOX OUTLET NODE mass flow rate [kg/s] iteration history trace (most recent first): 0.180034,0.180051,0.180034,0.180051,0.180034,0.180051,0.180034,0.180051,0.180034,0.180051,
** ~~~ ** Node named VAV1 BOX OUTLET NODE shows oscillating temperatures across iterations with a repeated value of 20.346310
** ~~~ ** Node named VAV1 BOX OUTLET NODE temperature [C] iteration history trace (most recent first): 20.346310,20.346638,20.346310,20.346638,20.346310,20.346638,20.346310,20.346638,20.346310,20.346638,
The IDF file is here http://pastebin.com/baE0z4nP
