The last 5 years of my career were spent in mainting the HVAC for a large sewage plant. (what an experience)
We had just moved into a newly constructed office building, (no commissioning!). My only training in HVAC was one semister in college, talking to father-in-law, who owned a heat and refrigeration business.
The building had direct fired absorption chillers, an air handler for each floor, and zoned reheat coils. The chillers also supplied the heating hot water in the winter. The air handlers had outside air dampers, and return air dampers that were linked together. The controls were electronic, and pneumatic mixed.
A couple of things that I noticed after I became familiar with the system was that there was no provision for exhausting the air from the building. Thus the outside air provision for the economy mode couldn't bring in enough outside air to cool the building in the spring and fall. Some of the air handlers were marginal in size for the anticipated future planned loads.
A real problem that I had was that the air handlers would kick out on low temperature in the winter. The colder the outside temperature the more frequently the outages. The information that was passed on to me by the inspecting engineer was that the hot water temperature had to be lowered to 110 degrees F to minimize the outages.
The heating coils in the air handlers were two section and stacked. The only thing that I could figure was that with the normal low water flow, and poor mixing of the air was that stratification occured in the heating coils. The upper coil would be favored by the water flow.
What I did was to reset the minimum outside air damper position. This basically eliminated the trips. But that certainly was not a good fix, since it cut back on the ventilation air into the building.
Another problem was that when the chillers responded to a demand of greater than 50% there was surging in the stack, and much condensation in the winter. The HVAC tech finally installed a relief dampers in the exhaust riser from each chiller.
The other major fault was that the heating hot water temperature was supposed to be controlled by the building management system based on the heating load. It never worked because when it increased the return water to mix with the hot water it would restrict the flow through the heater and shut it down on low flow.
The long and short of the problems in the building would have been addressed by a commissioning. All the equipment was decent quality. The sequence of operation was good, only the some of the controls could not do their job. This would have shown up in a commissioning. Had this been done the building's climate control would have been excellent and with much less attention.
We had just moved into a newly constructed office building, (no commissioning!). My only training in HVAC was one semister in college, talking to father-in-law, who owned a heat and refrigeration business.
The building had direct fired absorption chillers, an air handler for each floor, and zoned reheat coils. The chillers also supplied the heating hot water in the winter. The air handlers had outside air dampers, and return air dampers that were linked together. The controls were electronic, and pneumatic mixed.
A couple of things that I noticed after I became familiar with the system was that there was no provision for exhausting the air from the building. Thus the outside air provision for the economy mode couldn't bring in enough outside air to cool the building in the spring and fall. Some of the air handlers were marginal in size for the anticipated future planned loads.
A real problem that I had was that the air handlers would kick out on low temperature in the winter. The colder the outside temperature the more frequently the outages. The information that was passed on to me by the inspecting engineer was that the hot water temperature had to be lowered to 110 degrees F to minimize the outages.
The heating coils in the air handlers were two section and stacked. The only thing that I could figure was that with the normal low water flow, and poor mixing of the air was that stratification occured in the heating coils. The upper coil would be favored by the water flow.
What I did was to reset the minimum outside air damper position. This basically eliminated the trips. But that certainly was not a good fix, since it cut back on the ventilation air into the building.
Another problem was that when the chillers responded to a demand of greater than 50% there was surging in the stack, and much condensation in the winter. The HVAC tech finally installed a relief dampers in the exhaust riser from each chiller.
The other major fault was that the heating hot water temperature was supposed to be controlled by the building management system based on the heating load. It never worked because when it increased the return water to mix with the hot water it would restrict the flow through the heater and shut it down on low flow.
The long and short of the problems in the building would have been addressed by a commissioning. All the equipment was decent quality. The sequence of operation was good, only the some of the controls could not do their job. This would have shown up in a commissioning. Had this been done the building's climate control would have been excellent and with much less attention.
