It seems that in type534, the TES losses energy faster and so needs to gain energy from the heat source quicker. The total heat delivered to the fluid before entering to port 1 is higher for type534 compared with type 158.
Type 158 is a derivative work from Type 534 so they should give nearly identical results when driven with the same inputs and parameters. Did you compare the outputs to see where the problem may be? Check the losses, stored energy term, delivered energy, etc. That should point you to the problem. If you still can't find it then I suggest you send it to your distributor for a quick check.
Jeff -- Jeff W. Thornton President Thermal Energy System Specialists LLC 3 N. Pinckney Street, Suite 202 Madison WI 53703 USA (608) 274-2577 www.tess-inc.com