Building services: chillers staged by habit, plants never tuned

Several chillers are staged by habit

What happens. Operators bring on the second and third chiller at a fixed load or time of day, because it has always worked. The machines then run at part load, often several together where one would be enough.

What it costs. Electricity, mainly. Part-load running with extra pumps and cooling towers draws more than the cooling duty needs, and more starts wear the compressors.

Why the usual fix fails. Staging rules are written once at handover for a typical day. When the building, the weather or the machines change, nobody revisits them, and a hand-made adjustment rarely survives a shift change.

How a fixed-price remote diagnosis checks it. From the chiller logs (loads, temperatures, flows, power, starts) I work out which combinations of machines would have covered each hour at lower power. The fixed-price remote diagnosis tells you whether an optimised staging plan is worth building on your plants, and what it would need from the controls.

Background: Economic predictive control

Ice storage is charged by timer

What happens. The ice store starts charging at a fixed hour every night and stops when it is full. Nobody asks whether tomorrow will be hot, whether the store is half full already, or what the power costs.

What it costs. Charging at the wrong hours or too much means paying for ice that melts unused, or running chillers in the afternoon peak because the store ran out. The point of a store, shifting load to cheap hours, is partly lost.

Why the usual fix fails. A longer charging window or a bigger store only moves the guess. Hand-set start times drift away from the real demand through the seasons.

How a fixed-price remote diagnosis checks it. I use the store’s charge level, the cooling demand logs and the tariff to see how a plan that follows forecast demand and price would have run. The fixed-price remote diagnosis answers whether price-led charging pays on your plant and what data the controller would need.

Background: Economic predictive control

Systems are handed over untuned

What happens. The plant works on the day of handover, but the controllers still carry default settings or the values from the first start-up. Rooms hunt, valves open and close, and the first complaints arrive in the first season.

What it costs. Complaints and call-backs, comfort problems, and energy wasted by oscillating valves and fans. Every visit by a technician is time that was not planned in the project.

Why the usual fix fails. Tuning on site takes a skilled person for each system and time the project no longer has. Safe default settings are made for the worst case, so they are never good.

How a fixed-price remote diagnosis checks it. From trend logs of the first weeks (temperatures, valve positions, fan speeds, setpoints) I estimate how each loop behaves and what settings would calm it. The fixed-price remote diagnosis shows whether tuning can be done remotely for your systems and what you would need to hand over to make it possible.

Background: Replacing hand-tuned parameter tables by a model

Service calls without data

What happens. A customer reports that the plant is too cold, too loud or too expensive. The technician drives out, finds nothing at the time of the visit and leaves a note. The problem returns a week later.

What it costs. Travel, repeated visits, and customers who lose trust. Whoever has to find the cause has only the customer’s description and what is on the screen at that minute.

Why the usual fix fails. More technicians or longer service contracts do not give anyone the history. Logs exist in the controller but are rarely stored beyond a few days, or nobody has time to read them.

How a fixed-price remote diagnosis checks it. If trend data and alarm logs exist, I look through them for what happened before the complaint and whether the cause is in settings, a sensor or the plant itself. The fixed-price remote diagnosis shows what a remote diagnosis of your installed systems can find and which logging you should switch on.