Okay, this post is kick off the work to formally define chiller plants. Once we have this work complete, I think boiler plants will flow pretty easily. To set the stage, it is important to note that I am not a chiller plant expert. Rather I have talked to several people to try and curate the most important characteristics into a strawman proposal to get going.

I do not think it is important that we cover every crazy edge case. Compared to AHUs, chiller plants take the insanity of sophistication and variety to a new level. So I think the best we can hope to achieve is to define a basic framework for the model that can be used across most chiller plants and allow variations to fit in with custom/future tags and point types.

NOTE: this topic is written assuming that we do make the change from in/out to sensor/cmd as discussed in Topic 25. For discussion purposes it will make things much clear.

Plants and Systems

Chiller plants introduce a new concept we haven't tackled yet in Haystack - the idea of a plant or system of equipment which has its own inputs, outputs and setpoints.

First of we need to model the chiller plant itself as a first class entity using the chillerPlant tag. Per Equip Level proposal we would tag also tag a chiller plant with the equip tag and its direct "plant-wide" points would be associated by the equipRef tag. Sub equipment entities like chillers, cooling towers, etc would be associated by the chillerPlantRef tag. AHUs would also be associated via the chillerPlantRef tag.

Here are the basic chiller plant level points:

chilled water leaving temp sensor
chilled water leaving temp sp
chilled water leaving flow sensor
chilled water leaving flow sp
chilled water leaving pressure sensor
chilled water entering temp sensor
chilled water entering flow sensor
chilled water entering pressure sensor

This assumes we have basic sensors on chilled water to/from the plant and that primary setpoints are on temp and flow leaving the plant.

Entering/Leaving

A critical aspect of the model is to come up with an elegant, unambiguous terminology for where in the pipework a sensor, pump, etc is located. At the same time we don't want to foist a foreign terminology that industry guys don't already use. In some case these two goals seem a bit at odds :-)

A lot of people seem to use supply/return and entering/leaving also seems common. I was hoping to maybe have consistency with AHUs, but the idea of using discharge/return for water systems seems to have zero traction. I also find it strange to not use entering/exiting since most APIs I've used consider "exit" the opposite of "enter'. For discussion purposes I will use terms entering/leaving - but feel to chime on this tricky topic. With the proposed change sensor/cmd we could potentially use in/out instead of entering/leaving too.

This terminology is especially confusing because it requires a frame of reference. Pipework from the chiller to the cooling tower is leaving the chiller, but entering the cooling tower. In this case whenever we use the term entering or leaving we must always ensure there is an equipRef or something like it to determine frame of reference. This is especially troubling for common pipework pumps/sensors that can't be associated with a specific chiller or cooling tower. One idea would to be use tags like chillerToCoolingTower and coolingTowerToChiller to explicitly specify the pipework and water flow direction.

Chillers

Here are some proposed basic chiller equip level tags:

waterCooled  // marker uses condensed water system for heat exchange
airCooled    // marker internal direct heat exchange w/out cooling towers
reciprical   // marker type of chiller (TODO need definition)
screw        // marker type of chiller (TODO need definition)
centrifugal  // marker type of chiller (TODO need definition)
absorption   // marker type of chiller (TODO need definition)
capacity     // total capacity in tons? (TODO)

Here are proposed points:

// chilled water to/from AHUs
chilled water leaving temp sensor
chilled water leaving temp sp
chilled water leaving flow sensor
chilled water leaving flow sp
chilled water leaving pressure sensor
chilled water entering temp sensor
chilled water entering flow sensor
chilled water entering pressure sensor
chilled water delta temp sensor
chilled water delta flow sensor
chilled water delta pressure sensor

// condensed water to/from cooling towers
condensed water leaving temp sensor
condensed water leaving flow sensor
condensed water leaving pressure sensor
condensed water entering temp sensor
condensed water entering pressure sensor
condensed water entering flow sensor

// other internals
capacity                     // runtime capacity 0% to 100% 
cond cmd                     // condenser on/off or 0% to 100%
cond refrig temp sensor      // condenser refrigerant
cond refrig pressure sensor  // condenser refrigerant
evap refrig temp sensor      // evaporator refrigerant
evap refrig pressure sensor  // evaporator refrigerant
efficiency                   // TODO kw/TON or SI unit?  right term?

We have overall total chiller capacity, then we have the current runtime capacity. Are these terms ok as tag on chiller and then runtime point under chiller?

What is right terminolgy and units for efficiency kW/ton?

Chillers are also essentially built with own "sub-metering" capability to sense electrical demand, current, etc. Richard had great idea that chiller just mixes in the elecMeter model with associated points. So at the very least we should flush out electrical sensor points we'd use in topic 7 (Christian did great job of getting this going).

As an aside, I think the much of the chiller work will feed into and have commonality with other refrigation systems like food freezers/coolers.

Cooling Towers

Cooling towers equips are tagged as coolingTower. Equip level tags:

openLoop
closedLoop

Points associated with a cooling tower equip:

condensed water leaving temp sensor
condensed water leaving flow sensor
condensed water leaving pressure sensor
condensed water entering temp sensor
condensed water entering pressure sensor
condensed water entering flow sensor
fan cmd
fan sensor

In a closed loop system we also have additional piping, are these monitored and what is the right terminology for that?

Pumps and Valves

Pumps and valvues associated with a specific chiller, cooling tower, or other piece of equipment are called dedicated. Otherwise we say the pumps, valves, are common if they sit in pipework shared between multiple pieces of equipment.

Pumps and valves are modeled as just points. In the case of dedicated pumps, valves, etc they should be associated ith the equipment directly via the equipRef tag. They should also use the associated positional tagging such as chilled water leaving.

Common pumps, valves should be associated at the plant level by having their equipRef point to the chillerPlant entity itself. After lots of brainstorming and discussion, I'm thinking we don't even try to bother modeling the positon of common pumps and valves. The terminology of entering/leaving is confusing and only works in the context of a single piece of equipment. I think trying to model where exactly a pump sits in common pipework requires a much more complicated model, and even then not sure it really provides enough info for analytics or auto-generated graphics.

Pump and value point tags:

pump cmd       // true/false (on/off) or 0%-100% if VDF
pump sensor    // proof of flow sensor
valve cmd      // true/false (open/close) or 0%-100%

Heat Exchanger

Sometimes a chiller plant might use a heatExchanger to by-pass the chillers for free cooling via the cooling towers. Assuming the heat exhanger sits between the chilled water pipework and condensed water pipework, we would have these points:

chilled water leaving temp sensor
chilled water entering temp sensor
condensed water leaving temp sensor
condensed water entering flow sensor

Other Stuff

Stuff that eventually we need to tackle, but probably can hold off includes:

• air cooled chillers (small case?)
• ice storage

Next Steps

We are going to need lots of feedback from domain experts. But specifically:

• validate the basic model and organization
• specifically answer questions/TODOs asked in this post

A few quick comments/opinions:

• I think its more intuitive to label the chilled water as Supply and Return as opposed to Leaving and Entering
• "Condensed" as a tag is somewhat awkward. "Condenser" "Water" seem more appropriate to me.
• It might be considered to incorporate the pseudo-standardized labels of CHWS/CHWR for Chilled Water Supply and Return and CWS/CWR for Condenser Water Supply and Return
• COP is the SI metric for efficiency

Here are my comments and thoughts based on the above sections:

You incorporated a tag called delta, a commonly used word is generally differential. This would influence the following points:

differential/delta temp
differential/delta flow
differential/delta pressure

Thoughts?

You kept valves very simple; I would recommend adding two different tags for specific types of valves isolation and bypass. As you'll see below I use isolation with valves associated directly with chiller's and bypass with valves associated with the chiller plant.

You came out and stated your intent with entering and leaving. I also would like to make it clear where we are going with chilled and condensed. It appears that these tags are describing which side of the chiller we are on, which I think makes sense.

Plants and Systems

I agree with the chillerPlant tag on chiller plant equipment. Then chiller equipment would receive the equipRef and chiller tags. What is the purpose for having a special reference for chillerPlantRef? Shouldn't we then have ahuRef, rtuRef, chillerRef, towerRef, etc... Just seems like this would lead to special Ref tags for every type of equipment.

I think we can add a few points to the ones you already have. Most of these could already be implied from the basic points you already have, but I just wanted to get them down.

chilled water leaving pressure sp
chilled water entering temp sp
chilled water entering flow sp
chilled water entering pressure sp
chilled water differential/delta pressure sensor
chilled water differential/delta pressure sp
chilled water bypass valve cmd
chilled water bypass valve sensor

condensed water bypass valve cmd
condensed water bypass valve sensor
condensed water differential/delta pressure sensor
condensed water differential/delta pressure sp

I'm assuming that entering, leaving and differential cannot be used in combination.

Entering and Leaving

I'm okay with entering and leaving as basic location terms. I also like the usage so far of chilled and condensed to describe what side of the chiller we are on.

Not sure if I'm sold on chillerToCoolingTower and coolingTowerToChiller. If sensors are directly related to a chiller or tower equip they can get the entering, leaving or differential / delta tag. If they are not directly related to an equip and belong to the chiller plant we would either put the chilled or condensed tag on the point to determine what side of the chiller it is on. I don't know if we need to go further than this?

Chillers

Theoretically you can have matching setpoints for all of the sensors you currently have listed as points, I stated these for the chiller plants above as well. I would also add valve points to chillers.

chilled water leaving pressure sp
chilled water entering temp sp
chilled water entering flow sp
chilled water entering pressure sp
chilled water delta/differential temp sp
chilled water delta/differential flow sp
chilled water delta/differential pressure sp
chilled water valve isolation cmd
chilled water valve isolation sensor

condensed water leaving temp sp
condensed water leaving flow sp
condensed water leaving pressure sp
condensed water entering temp sp
condensed water entering pressure sp
condensed water entering flow sp
condensed water valve isolation cmd
condensed water valve isolation sensor

I agree with flushing out the electrical points. This will also apply for VFD's (pumps and fans).

kW/ton is a commonly used unit, I would recommend putting this in the default units.txt in the SkySpark build.

Cooling Towers

For cooling tower points I would recommend not have the condensed tag on any of the points and only have entering, leaving or differential / delta. These points are very similar to the chiller points besides you do not have the chilled or condensed tags.

water leaving temp sp
water leaving flow sp
water leaving pressure sp
water entering temp sp
water entering flow sp
water entering pressure sp
water differential/delta temp sensor
water differential/delta temp sp
water differential/delta flow sensor
water differential/delta flow sp

Pumps and Valves

I would recommend that we start right away with making pumps their own equipment. For the reason that we will start having a lot of points for each individual pump really quick. As I mentioned above VFD pumps will also mix in with the associated electrical points.

We could then use the equipRef tag on all pump equipment to identify what equipment they belong to. If they belong to a chiller plant or chiller they would also need a chilled or condensed tag to determine what side of the chiller they reside on. I do not believe it would be relevant to put a entering or leaving tag on pumps.

Valves I agree at this stage would be associated to common pipework (plant) or a specific piece of equipment. As stated above I would recommend adding the tags isolation and bypass to describe valves further.

I agree with Joe. Adding primaryLoop and secondaryLoop markers would also distinguish the chilled water pump locations.

"Condensed" as a tag is somewhat awkward. "Condenser" "Water" seem more appropriate to me.

Question 1: what is the proper term and tag? condensed or condenser?

COP is the SI metric for efficiency

Question 2: what exactly is this in terms of units?

You incorporated a tag called delta, a commonly used word is generally differential. This would influence the following points:

I think delta seems more commonly used, and yes I agree we can add pressure and flow (if everyone agrees).

What is the purpose for having a special reference for chillerPlantRef?

Essentially we are using the equipRef and siteRef for "containment" in that a point is contained by exactly one site and one "equip" (term to be decided per other topic). But we still have lots of peer relationships. For example an AHU needs to reference it's chiller plant, so we'd use chillerPlantRef, not equipRef for that. And yes we do have special references like ahuRef to associate a VAV to its AHU. And we also have submeterOf and elecMeterLoad as other examples of peer-to-peer relationships.

Theoretically you can have matching setpoints for all of the sensors you currently have listed as points

Well I think the design pattern lends itself to obvious sensor/sp combinations. What I wanted to explicitly list was points that are commonly found - just to avoid a huge combination of every point combination imaginable.

Question 3: So are those sp things people actually would use? Do you ever actually configure your setpoint off delta temp instead of leaving chilled temp? Do you actually have pressure sp instead of flow sp?

For cooling tower points I would recommend not have the condensed tag on any of the points and only have entering, leaving

Great idea, really like that

Question 4: although do we have extra pipes to annotate in a closed loop tower?

As I mentioned above VFD pumps will also mix in with the associated electrical points.

I think this really needs to be discussed b/c its a big decision point. Do VFDs commonly provide electrical sub-metering sensors like amps and kw? If so that would make them better as equip instead of just points. But then wouldn't we have same problem with VFDs used in AHU Fans (where Fan is just a point, not a separate equip).

Question 5: pumps as equip vs points and what it means for VFD fans

recommend adding the tags isolation and bypass to describe valves further

Sounds good

Question 6: can you give me a definition you'd use for each tag?

Question 7: do we have valves built-into chillers? and aren't these by definition isolation values?

I labelled all my explicit questions, I'd love to get direct answers to (anybody please free to answer)

Question 1: kWr = Cooling Produced COP = kWr / kW or Cooling Produced / Demand. In plain english COP is the amount of cooling produced for every 1kW of power put into a chiller.

Question 2: There are no units it is just a ratio.

WRT differential vs delta, to absolutely confuse everything, we use differential for pressure and delta for temperature. That may be because we use a Differential Pressure sensor (DP Sensor).

Question 3: From a pure analytics point of view we don't use sp points that much. The most heavily used one would be the entering condenser water temp sp. That's not to say they shouldn't be modelled though. There may be some new analytics we can derive from looking at these sensor/sp relationships.

Question 5: We've modelled pumps in our PlantPro as equipment associated with the chiller plant. The distinction we made was between a constant speed vs a variable speed pump. In the case of a VFD pump we use the kW and frequency points. We estimate the power consumption of a pump by a)if only frequency is available we derive the kW or b) just calculate the kWh from kW over time. To be clear though, our aim is to understand the power consumption of the chiller plant, not work out how the consumption of a pump fits into the wider consumption of a site as per the elec modelling tags defined elsewhere. If we wanted to do that we would install a specific sub meters for all pumps.

Question 1: I do like condensed. On the other side of the chiller we are not using evaporator water, we are using chilled water.

Question 3: There is very often a delta pressure SP that is maintained by pumps. We are starting to see true flow sensors more often, but it has traditionally been delta pressure.

Question 5: VFD's are now commonly providing electrical information, so I think it is important that we do start jumping on that modeling. You are correct Brian, this will affect VFD fans as well. I think they should start being modeled as equipment as well.

Question 7: Other than tiny packaged chillers, they are pretty much always external and field installed.

Question 1: The fluid loop from the condenser to the cooling tower is most commonly referred to as the condenser water loop. The water on the evaporator side is actually chilled, hence the name, but water on the condenser side is not actually condensed; it is removing heat from the condenser. In buildings with steam systems, there is a loop for condensed water to carry condensate from steam traps and AHU's have condensate drains for condensed water.

For the delta vs differential debate, my vote is for delta only used. Even if someone is used to pressure differential, the intent of pressure delta would still be quite clear.

I think this proposal is mostly on track based on comments. Sometime in the next few weeks, I'm going to take another pass to try and clean up the spec and see how it turns out.

One thing that has come up from conversations I've had is that pumps should be treated as separate equip versus points.

On related note, is the idea that many VFDs often have lots of built-in electrical metering points (kw, kwh, amps, etc). That justifies the idea that pumps should be first class citizens. But at the same time it might also be justification that Fan VFDs in an air handler should be (or optionally might be) first class equipment under the AHU itself (seems ugly to me, but jives with other idea I posted that equip can be nested).

Any other comments on those thoughts?

Dear all, i have a project to relocate the 5 nos chillers in the same building.what are the menthos and ways as per ASHRAE to work this projects.how to shift the chilllers and reloacte them .the problem is to keeping the cooling of the building live during relocation of chilllers.chillers have to be shifting one by one petern.

Can any one give me good suggestion for this job

Gawhar from Qatar Doha

@gawhar - I believe you are on the wrong forum for you question. This discussion forum is for defining chiller taxonomies, not asking questions about how to run your chiller plants.

We really need to start defining.

pumps loop definitions primary and secondary

I am just trying to revive this topic again.

We can help. Will start tagging and going through some old ones and see how current tags work.

I'm confused by the condensed tag for cooling towers.

1. No water is condensed in a cooling tower.
2. Not all cooling towers are used for chillers (the condensing cycle of refrigerant).

It was just picked as the most common term for the points associated with that water are called. I don't actually know what the various terms commonly used are, but everybody is welcome to pick another term if you think that term is incorrect or not the most common.

condenser water (abbreviated CW) is the correct term chilled water (abbreviated CHW) is the correct term

For points associated with the actual evaporator and condenser vessels

evaporator and condenser are the correct terms

You typically will never have a chilled water pressure -- you would have a evaporator pressure, which is the pressure of the refrigerant in the chiller.

Only pressure you may have would be a differential pressure sensor across the chiller to be able to do a flow calculation via data given from chiller maker. This sensor should always be converted to flow.

I would not spell out condenser in some places, and then abbreviate it to cond in others.

Question 7: No. You could have an isolation valve, but that is not the only type. I've seen valves that put the chiller into a free cooling heat exchanger type operation. You may also have other smaller valves on the system that do different things (cool the chiller, and so on). Very few chillers (if any) have an isolation valve built in to part of the equipment by default.

condenser water (abbreviated CW) is the correct term chilled water (abbreviated CHW) is the correct term

Right now the tags are condensed water, not condenser water.

Should we change this?

To the best of my knowledge condenser water is the correct term.

Dan is also correct in his differentiation between the uses of chilled water and evaporator.

It may seem like splitting hairs but the actual points you are reading are totally different. To demonstrate what it should look like:

Evaporator Refrigerant pressure
point evaporator pressure sensor kind:"Number" unit:"kPa"

Chilled Water Differential Pressure
point chilled water pressure sensor kind:"Number" unit:"ΔkPa"

I think Alper's suggestion from 2011 to add primaryLoop and secondaryLoop markers should be moved into Haystack documentation. I am using rules which are specific to one or the other.

I agree on the addition of primaryLoop and secondaryLoop tags for pumps on the chilled water side.

How would we then differentiate condenser pumps? condenserLoop or something like coolingWaterLoop?

So sounds like a concrete proposal to add primaryLoop and secondaryLoop tags. And these would be applied to equip (pumps/valves) in the hydronic piping system?

Not sure about condenserLoop and coolingWaterLoop - seems inconsistent with tags we are already using for condensed and chilled water.

primaryLoop and secondaryLoop would only be used with chilled.

Alper is right, primaryLoop and secondaryLoop are only used for chilled water. So we still need a way to differentiate chilled water pumps from condenser water pumps.

In our work we model a cooling water loop, which connects cooling towers, condenser water pumps and chiller condensers.

We have been able to model many different chiller -> cooling tower relationships; 1 to 1, 1 to many and many to many. Not sure we've seen a many to 1 relationship but in theory we could handle that as well.

So it is definitely worth coming up for some good tags to model the condenser water/ cooling tower water loop pumps.

Primaryloop and secondaryLoop also work with hot water systems. Alper is right it's not on the condenser side.

Common vs Dedicated

For condenser side and chilled water side, I suggest following tags :

• common (M)
• dedicated (M)

These would be attached to pumps defining if they are dedicated pumps or common pumps.

Primary vs Backup

There are scenarios where pumps are common but one pumps is always primary and other pumps is back-up.

The following two tags would be for discussion.

• primary (M)
• backup (M)

lead vs lag

Option #1

To deteriorate the pumps at the same speed, we could have tag bool.

• lead (B)
• lag (B)

Having it bool would make it possible to write axon script where we could calculate run-time of condensed water pump 1 when lead is true and compare it to pump 2.

We would have to attach both tags in this case. This scenario is good for dual common pipe systems more than two pumps, we need to think of a broad approach for staging. I will thinker on that.

Option #2

The other option is having leadLag as a (string)

In this version all pumps would have this tag and we would have to trend the mode it is in.

• leadLag (S)

We would write a computed history to have bool version of lead/lag.

Let's discuss on these tags that would make the pumps more complete.

Condensed Water needs to be changed to Condenser water, Condensed water is not an option. I have done over 100 central plants in the USA, Europe, Asia and Africa and not once have we ever used Condensed water. I have seen it abbreviated with both CW(common) or CDW.

I realize there has been some tagging done with condensed already, I have seen condensate water in steam systems and I fear some people might assume condensed is somehow related to condensate from steam systems.

I have also heard people referring to the condensation/Condensate from a air cooling coil or Evaporator coil in AHU/RTU/AC

I move that we change Condensed to Condenser ASAP.

+1 for change to condenser tag.

+1 for condenser tag change too

Ok, let's consider that a final decision. The condensed tag will be renamed condenser.

However we already have the tag condenser being used with points inside the chiller's condenser system such as measuring its refrigerant. But I think that is ok because these points will be condenser water and those will be condenser refrig

Has anyone assembled a committee or a voting process when there is disagreement on these types of decisions?

If "condenser" is generally agreed upon, when should we expect the general documentation to support this change?

when should we expect the general documentation to support this change?

Yes, everything we have consensus on will be published to the docs. But I haven't had time in the past few months to catch up. Hopefully in next month or so