How to identify zones
What’s the quickest way to identify zones in a building without looking at the ductwork other than counting the thermostats?
1. The mechanical or control drawings.
2. DDC frontend
3. The two ways you already mentioned....
If you have the luxury, running each RTU or AHU individually and shooting the grills with a laser thermometer. I'm not even sure that "counting the thermostats" would help without some other info, so I assume you have a EMS/BAS that tells you how many stats are in each zone? If so, changing the Supply air setpt and shooting the grills will help ID the zones without interuption of service.
Drawings are only good if nothing has been changed. The only sure way to know nothing has been changed is looking at the ductwork.
If you want to match a zone to the zones shown on the front end, temporarily disconnect the room temperature sensor and see which zone temp went invalid at the front end. If a zone is averaging multiple sensors you might get an invalid or an unrealistic change in a space temperature depending on whether the averaging is done by the controller or the wiring.
If you use a setpoint change you run the risk of an adjacent zone serendipitously going into heating or cooling mode just when the zone you're checking changed.
I agree with your comment, visual verification is the most accurate, and the disconnection of the sensors will ID the stats, but IF you have control of supply air temp, it is very acceptable to raise SA setpt above the 55 deg norm to test the air temp coming from the grills to determine which unit controls which zone and how many grill/vavs are associated with the zone, of course assuming that all AHUs are working correctly and supplying close to the 55 deg original setpoint. The adjacent zone will only supply colder air if anything and will not effect the warmer air reading you will experiance from the raise SA setpt. This , of course, will not work as well with RA setpt but is still viable. I did assume cooling, which may be incorrect, but I'm a South Fla lifer, so thats how my mindset works. I guess when the question is "identify zones" you really need to clarify what you want to find out. Is it what AHU supplys the zone, and what vavs (again I assumed, maybe this is not correct either) are in the zone? I assumed this from the "ductwork" portion. If indeed this is a heating situation, then, if you turn off the heat on an AHU, raise the setpt on the remaining AHUs, they will produce more heat to compensate, but the grills associates with the zone/AHU you are testing will be supplying cooler air, and the test still fits. But I agree, actually looking at the ductwork is the best way, but as the question was "without looking at the ductwork", I gave my opinion on the the NEXT best way.
Counting thermostats may or may not be accurate.
Originally Posted by amustafa
Especially with older, existing buildings I'll utilize the method other have mentioned. That is shooting the diffusers with an infrared temp sensor.
The problem is that that drawings and plans may or may not be accurate. Even in the case of new construction, sometimes. But quite often in the case of older buildings where changes may have been made but documentation never updated.
Even if there is an installed DDC system, I've found it to be not uncommon for the front end graphics to have errors.
For constant volume zoned systems, I'll typically either shut down all units except one, raise or lower it's DAT significantly, at least 10, preferrably 20 'F or better, then shoot the diffusers to identify which are coming from which air handler. Or, if I can't shut down units, I'll put all but the unit I'm checking at, say 55'F DAT, and put the unit I'm checking into heating mode at at 80 or 90'F.
Then when using an infrared temp sensor to shoot the diffusers, I make sure I'm seeing a definite temp increase, or decrease as the case may be, looking for at least a 5 degree or better rise or fall as I'm shooting.
This is to avoid mistakes. Infrared temp meters can be iffy devices when shooting up at diffusers, often showing spurious results. Being affected by a number of various ambient factors. So I want to see the material of the diffuser grill DEFINITELY growing warmer or cooler over time, say ... a few minutes ... 2 or 3. (The infrared temp sensor isn't actually showing you the temp of the air itself.) So there is no mistake.
I've had the experience of having to go back to a site because the guy previous to me was in too much of a hurry and as soon as he saw what "looked like" a couple degrees of change, he moved on. In several cases, his results were wrong. Maybe his aim just wavered a little and the infrared gun saw a slightly different spot that was already a couple degrees warmer than the original spot, or he got a bit of error introduced due to aim hitting a little spot that was slightly more or less reflective than the adjacent spot, etc.
Better to take a little more time first time around to be SURE, than to have to redo things, or to accept bogus results.
For VAV systems, the procedure would be similar. If need be, cycle the air handlers to find what VAV's are served by which air handler (with any VAV reheats overridden and turned off). Then, one by one, open a VAV's reheat and do some shooting. Shut down the reheat on that VAV before moving on to the next. No, reheats? A little more difficult. Over ride and lock air dampers in some position (i.e. full open or half open), then open and shut air damper alternately on the one being checked and use feeely-touchy at the diffusers to figure out which are associated with that VAV. Then lock that VAV's air damper into some position before moving on to the next.
Note that if you don't do this locking of controls on everything except the item being checked, you can get fooled. Have seen it happen again and again. i.e. A guy shooting some diffusers looking for a temperature rise and sees one that's rising, assumes it belongs to the air handler/VAV he's checking ... but it's really served by something else which just happened to be responding to a call for heat at that moment.
Yeah, it's all a PIA. But if you're wanting to make sure that your results are accurate ... it is what it is, and its about what yah have to do.
Just my thoughts, based on the experiences I've had.
Counting thermostats will not always identify zones. Did you count them all? "Oh there was a stat up in the return grille? But all the others were on the wall!"
If it is one a BMS then how many are actually sharing sensors? Many times due to zone layouts it makes more sense to share a sensor than to put one near one that is already there.
The temp drop/rise method mentioned gives a pretty good idea overall, but even that is flawed - what if you have disconnected ductwork in the ceiling or the balancing damper is closed down? Granted if you map every single diffuser and then verify a temp increase/decrease at all then you'll know you'll have some to go back and physically check. All too often I've seen guys map out zones and not run every unit and assume all the diffusers without a temp increase/decrease were for the remainder unit/zone only to find out months later after numerous calls - "Oh that goes to a different zone"
If your asking this so you can give a proposal I would say count the stats and then in your proposal put x number of zones. If it comes out to be more zones then go back with a change order.
In the end you want to make sure it's right. I've done a lot of retrofits and the call backs are killer due to zones note matching up as thought. I've made my guys physically trace and draw out the ducting layout during install. They typically have to go through the ceiling anyway to pull wire, so paying attention to the duct layout and mapping it gives me an accurate layout for my graphics. That accurate layout has saved thousands of dollars in call backs, as when we get the call of an area being too hot/cold I can look it up on the BMS and say that area is served by zone 1 and zone 1 is satisfied. Numerous times it ends up in additional zone installations.
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