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I believe your question boils down to efficacy/efficiency. In general, a VFD is more effective at maintaining a certain flow rate. But it costs more. The difference between a variable speed pump with a VFD & the cost of a pump with an EC motor is not that great when looking at large pumps. If...

OTR, This may not be helpful, as I have not worked on any systems like this, but here are some general thoughts: -Typically domestic hot water systems are required to be capable of operating regardless of whether or not other systems are operating. The manner I usually see this is in terms of...

The old school way is "very positive". The buildings back in the day were very leaky, and the best way to ensure that the space is conditioned to the temperature you expect is to provide a lot more air at the temperature you want, than the outside will fill back in. Now, as the buildings have...

What is your pressure requirement, relative to various spaces? Are there multiple entrances, is this on an exterior? Now of the options that exist for maintaining positive pressure, the two most common are: -DP (differential pressure sensors) which try to affect the pressure by modulating a...

I concur with GT-EGR: International code requires that the equipment be "capable" of conditioning the space to 68 deg. on a design day. You get to decide what the design day is, and also what your expected heat gain in the space is. All you are required to do is provide equipment capable of...