#812 Demand heating/cooling

Ashkan Jalili Wed 13 May

Hi,

For the demand points in AHU, FCU, VAV ... I was looking for the proper tags. I thought maybe we can use the same demand tag like

Sensor, demand, cooling, AHU

Sensor, demand, heating, AHU

But then again in a project came across a project that had only one point for heating and cooling. so if the point is negative it shows for cooling. If positive it is for heating. so was wondering how can we work it out. Any suggestion would be appreciated, even maybe I was wrong from the first place to use demand tag for this purpose.

Kind Regards

Ashkan Jalili Mon 18 May

No comment yet. So any idea about the proposal below: sensor demand process

Brian Frank Mon 18 May

There was recently a post to add demand as a new tag to be a little more specific than power which resulted in elec-demand.

But the demand is probably generic enough for your needs. But worth considering if we should coin first class definitions for cooling-demand and heating-demand. Maybe something to discuss in AHU working group Jay?

Jay Herron Tue 19 May

Sure, we can loop it into our AHU WG discussions.

My first reactions:

My understanding, based mostly on VAVs, is that these points are typically a computed point based on how far the zone air temp is away from its setpoint. So the word demand is used in the way that the VAV is "demanding" that much cooling or heating. Reflecting that, I've also seen them called "cooling/heating need" or "call for cooling/heating". That understanding of "cooling demand" seems very different than how demand is used in elec-demand, and I'd hesitate to use them with that tag.

I think we'll need a new tag for these points if people find them valuable, but we'll discuss with the entire AHU WG.

Cory Mosiman Tue 19 May

Agree with above. Ashkan - can you provide a definition or reference to exactly what it is you mean by demand? That would be helpful to make sure we correctly understand the intent.

Ashkan Jalili Yesterday

What Jay explained is actually the case we are experiencing, but in AHU.

So it is basically how much cooling/heating is required, considering the setpoint and the actual measured value.

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