9 module slant fin w/indirect heating and Tekmar Control

MEP Dave

<span><span style="color:#000080">In a high rise apartment bldg, we have a water source heat pump, 9 module slant fin gas fired hot water boilers, three of these nine are prioritized for DHW, and two indirect DHW htrs.  We have a Tekmar control.  Below is the email I am getting from the contractor:</span></span>

 

<span>The system is designed and will deliver 180 Degree F water from the boilers to the heater/storage tanks.

The pumps associated with each heater work off the aquastat on the heater and will turn on the pump whenever the temperature on the aquastat is not being met.  When that pump comes on it triggers the boilers that there is a demand for heat and the boilers will start to modulate and supply 180 Degree water for the domestic heaters.  The modular boilers have their own controls that start and stops boilers based on demand.

That is where the current situation starts and is specifically what we discussed previously.  To date we have not had enough demand to leave all 9 boiler modules on and get the system 100% set up correctly.  On the several occasions that we tried to fully set up the system we could not get all the boilers to fire because the system demands would be met and the system would cycle off.  When we had all nine modules on it was very erratic because of the lack of load the system was getting satisfied so fast that the controls could not react.  The reason that we have has no load is because we were in cooling season and did not need to inject heat into the CW loop and there is nobody in the building to create a domestic load.  You need to realize that the boiler system is set up for worst case scenario which would be a large domestic load and a need for HW to be injected into the CW system.

As a result of not having any load and to try and find stability we left 3 of the 9 modules on so that any domestic HW needs would be met. 

As the weather gets colder or you get a significant number of people living in the building we will have the opportunity to fully coordinate our system and leave all 9 modules on and let the controls do their job.  Under normal conditions we would expect to leave all 9 modules on not turn any off based on the season.</span>



<span>Any ideas?</span>