State premere Derect vent or Ao smith Vertex Derect vent

Big Will

It is to be part of a solar thermal system. It feeds a small dairies cleaning and pasteurizing system. The spec sheet shows it can deliver 168 gallons first hour. This was higher by a bit than the heater that was in before. the problem is it will not produce nearly enough hot water. Not even close to as much as the old one (it was a State 75 gal 75 K btu 4 years old). I spent a lot of time on the phone with the tech help guy today to try and figure out the problem. He said because the sensor is at the top it takes longer for the heater to fire when there is a large draw. In this case the pasteurizing tank takes about 75 gallons to fill and needs to be 130 deg minimum. it fills in about 15 minutes so it is a quick draw. But this is half of the heaters 1st hour delivery. The tech guy said I needed more storage. So I added a 50 gallon storage tank today with a resurc pump between the two tanks. After doing this today It was producing enough hot water for the process but still not as much as the old water heater. I used the side high tap for the recirculating pump that feeds the storage tank. This tap is about 8 inches from the top of the tank. With the tank set at 160 deg and on standby i was getting 138deg water out of side tap. The water of the top was 160deg. Is stratification normally this dramatic? I am going to call them again tomorrow but I would like to think a thermostat setting of 160 deg means a tank at 160 if only at average. Am I wrong? has anyone else had problems with this water heater not meeting its rated delivery.