Mosaic ChristianBuilding Automation
In 2016 Johnson Heating and Cooling L.L.C. was contracted to design, build, and intall a building automation system, provide mechanical plans, and perform an air balance report for a church in Detroit, Michigan.BAS Page
The structure of Mosaic Christian Church, in downtown Detroit, is approximately 100 years old. At the time that the church purchased the structure, the structure was in a state of disrepair. Behind the lath-board walls and above the lath-board ceiling there was no insulation, however, this structure had some tremendous potential because of it’s thermal capacity and also because we were basically given a “blank-slate” with which to work. The original mechanical systems were in shambles and needed to be replaced, so we had the opportunity to engineer systems at our discretion, so long as those systems were cost effective for the church. Basically, it was an engineer’s playground, as it pertained to the mechanical systems.At the time, the church was working with a shoe-string budget, to the extent that insulating the walls and ceiling properly was not included in the budget. Basically, the church could afford to get the building structurally sound, and could afford the bare essentials relating to cosmetic matters, but could not afford anything extravagant. The first step in the engineering process was for David (the owner of Johnson Heating and Cooling, LLC) to sit down with his father and develop a game plan for the design of the mechanical systems. A general scope was developed, however there were problematic aspects to the mechanical design which would have a major impact on operating expense of the HVAC systems if novel and unconventional solutions could not be developed and employed. After considering the dynamics of the structure and how no substantial plans had been put forth to insulate the hollow walls of the structure, David developed some plans to save the church money for the years that followed the initial construction, all while keeping the initial construction costs to a minimum. Furnaces are typically the most cost effective means of producing heat into a structure and also, furnaces provide for relatively high efficiencies relating to their consumption of natural gas to produce heat. Roof-mounted packaged HVAC systems (i.e. roof-top units), on the other hand are not nearly as efficient as furnaces and also have higher installation costs associated with them. Such as this is/was the case, it was desirable to utilize high efficiency furnaces to provide for the forced air heating of the church, because the church also needed the forced air systems for cooling. The mechanical room for the furnaces was extremely small and furnaces were packed into the room with very little margin for error in their placement. The ducting was run in the attic of the church because the attic was basically the only location suitable to run the ducting, given the tight cost constraints that the church was working under.
One issue of difficultly was the fresh air allocation for the church. The problem was that the furnaces had a maximum amount of fresh air, as a proportion of the total return air entering the furnace and that maximum amount of fresh air was insufficient to completely meet building code because the occupancy of the church was such that more outdoor air would be required than what the furnaces were capable of supplying. The furnace manufacturers specify a maximum amount of fresh air injection to the return air stream because the cold winter air may cause the rapid contraction of portions of the heat exchanger and cause the heat exchanger to crack if the temperature differences are too extreme. Such as it was/is the case that there was no more available room to mount additional furnaces in the furnace room and also because additional equipment would cause the project to exceed the already very tight budget, a very novel and unique solution was developed by David Jr. In his youth David Jr. had a paintball gun and he and his friends would play paintball. The inspiration for the design solution for Mosaic Christian’s fresh air predicament came from a time when David was reading a magazine about a paintball gun’s barrel design. The term touted by the manufacturer of the paintball gun barrel was “venturi”, which reminded David of the vortex effect evident by the Ranque-Hilsch vortex tube, which he had studied. Among the study of various fields of science is the idea that things can cause motion of the surrounding substances simply by their own motion. Water travelling down a fast moving river can cause a drop in the water level of an inlet off the river, magnetic fields can induce current in nearby conductors, and air streams of positive pressure can cause negative pressure regions nearby the positive-pressure air stream. David’s solution was to inject the outdoor air directly into the supply ducting of each forced air system by installing a duct within the supply ducting of each forced air system and by discharging the high velocity air-stream of outdoor air into the center of the supply ducting. Essentially, the configuration consisted of six feet of a ten or twelve inch duct mounted in the center of a 24” supply trunk for each of the systems. Because the fresh air was essentially “jetted” into the respective supply duct, a negative pressure region would become evident behind the injection location of the outdoor air injection location, which would induce a draft from the furnaces, down the supply ducting, past the fresh air injection location, down the supply ducting, and out of the supply air terminals, regardless of whether or not the blower drives of the respective furnaces were on or not. Additionally, because a negative pressure region was created just upstream of the outdoor air injection point, the volumetric flow rates of the furnaces were not adversely affected, so the operation of the refrigerant-based cooling systems maintained consistent operation regardless of whether or not fresh air was being injected into the structure. One problem was solved in a very novel way via supply-side fresh air injection utilizing the science of the vortex effect, but other problems remained. Churches are in a precarious position when relating to mechanical code because a certain amount of fresh outdoor air intake must have it’s provision accounted for by the mechanical systems, based on the maximum occupancy load of the structure, in order to meet code. In other words, a church’s mechanical systems must be able to bring in a whole lot of outdoor air, but in reality, a whole lot of outdoor air is hardly ever needed, if at all. Bringing in outdoor air is beneficial because it “freshens” the air inside the structure, but it is also detrimental because it causes the mechanical equipment to condition that air in order to maintain a comfortable environment inside the building. One way of considering the matter would be to think about opening a bunch of windows during the middle of winter- it doesn’t make too much sense unless the air quality inside the structure is very poor. To address this issue we did three things. Firstly, we engineered, installed and programmed a building automation system which would control all of the pertinent mechanical equipment and cause the equipment to function to save the customer money. Secondly, we selected, installed and programmed a variable frequency drive to operate the German-made centrifugal fan which induced outside air into the respective HVAC supply lines for the HVAC systems. Thirdly, we installed a CO2 detector in the structure so that we could provide for the intake of fresh air according to need and also meet the requirements of the State of Michigan’s Mechanical Code. One consideration which was foremost in our minds was the fact that the structure was in some ways ideal for the utilization of the patented CoolingLogic™ technologies, because the structure had/has a high thermal capacity and could be designed to utilize very efficient means of fresh air intake and indoor air exhaust. The structure was not ideal for the utilization of the CoolingLogic™ technologies because any data quantified from the utilization of the advanced/patented technologies would not appear to be overly impressive because the structure was not insulated, or was very poorly insulated. We gave much consideration to the licensing aspects of installing the patented technologies into the structure and decided to do something of a hybrid in the end. Instead of installing the “auto-tuning” technologies in the structure, we simply tuned the operation of the mechanical systems manually in the computer code controlling the mechanical equipment. This decision results in less efficient operation of the equipment as a whole, yet still provides returns which are incredibly energy efficient and very far beyond par. At the time that the programming took place we did not feel comfortable installing the patented technologies into the structure’s server, yet we did skirt the matter by applying the advanced knowledge which we gained through research into thermodynamics and the specific structure itself. The German-made fan that we selected during the engineering phase of the project was highly efficient. We also oversized the supply ducts of the respective HVAC systems such that the supply-side static pressures would be very conducive for the efficient intake of outdoor air. Additionally, we utilized a square hole in the ceiling of the church to install a low differential-pressure attic fan which would be operable to remove air from the sanctuary and also ventilate and cool the attic space. The computer code in the server operated such that in the morning and during the cooling season the German-made centrifugal fan would inject air into the church while the low differential pressure attic fan would remove air from the church and also cool the attic in preparation of the day’s “heat of the day”. By dropping the space temperature inside the church prior to the heat of the day, during the early morning hours, and by cooling the attic, something of a thermal-buffer is created, wherein the attic and the sanctuary must absorb substantial heat energy before refrigerant-based cooling would be needed. The net result of the implementation of this precooling resulted in energy consumption of this uninsulated structure being less than a newly constructed structure with standard insulation techniques. Due to the budgetary considerations of the church and also due to the fact that there is no baseline with this refurbished and very old building, it is difficult to quantify the exact energy savings, but an educated guess might be to state that 90% savings were realized due to the unconventional utilization of precooling and the utilization of the structure’s thermal capacity.
Air stratification was a major design consideration because the ceilings in the church are approximately 22 feet high in the sanctuary. For cooling, with the air terminals located at the ceiling, this was not an issue as the setup was well suited for cooling the structure, but for heating, the utilization of the HVAC systems was not ideal. For this reason in-floor hydronic heating was used on the first floor of the church. Pex tubing was installed on the underside of the floor and a Burnham Alpine boiler was installed. The computer code was programmed to utilize the furnaces only for cooling, ventilation, and emergency heating. The boiler system featured several zones which were operable to provide heating to specific parts of the church and we patched into the Sage 2 controller via the Modbus interface so that diagnostic and operational status information of the boiler could be accessed via the automation system. The pumps are controlled via the automation system, and the boiler’s modulation is controlled such that the boiler does not short-cycle, a greater differential temperature could be realized between supply and return temperatures, and the firing rate of the boiler is such that it is set to be the most efficient. Multiple servers were utilized in the automation system and were connected to each other. Additionally, multiple protocols were utilized in the system. E-mail and text message alarms are sent for a full complement of possible failures and the system has many built-in redundancies to compensate for various system failures until the problem can be resolved. The e-mail functionality of the automation system was tied in with our enterprise server and was provided free of charge to the customer, as is the domain-name forward that we setup for the church’s parishioners to use. Heavy-duty, lockable steel controls cabinets were used to house the controls/servers and the cabinets were fabricated off-site in our office before their installation. The functionality of the automation system is such that, as closely as is possible, it has been tailored to meet the needs of the church such that it’s operation is as simple as it can be, yet it’s functionality coordinates advanced sequences which reduce the energy consumption, relating to cooling the structure, to much less than what they otherwise would be with typical functionality. To make the user experience easier to adapt to we provided a free training course to parishioners, the secretary and the pastor. The user manuals, equipment information, engineering plans, hydronic plans, equipment OEM’s, and all other pertinent information was placed on the server so that the church could benefit from one package with everything in one place. No files needed on the equipment information and no lost or misplaced instruction manuals or blueprints. All in all, it was a first-class project working with good people and we feel very blessed to have a part in it.