Listed below is a description of proposed (1) preheat tag, (2) glycol tag, (3) how the preheat/glycol tags would be used and (3) a revised description of the entering/leaving tags

preheat - Preheat coil as bool or numeric point used with equip such as an ahu

glycol - point associated with the measurement or control of glycol

• preheat leaving air temp sensor
• preheat leaving air temp sp
• preheat valve cmd
• preheat pump cmd
• preheat pump sensor
• preheat glycol entering temp sensor
• preheat glycol leaving temp sensor

Current Descriptions

• entering - Indicates water or steam entering a piece of equipment like a boiler or chiller.
• leaving - Indicates water or steam exiting a piece of equipment like a boiler or chiller.

Proposed Descriptions

• entering - Indicates water, steam, air, glycol, etc entering a piece of equipment like a boiler, chiller, heat exchanger, etc.
• leaving - Indicates water, steam, air, glycol, etc entering a piece of equipment like a boiler, chiller, heat exchanger, etc.

I think a glycol tag would be good to add detail to a loop, optionally it could even show the concentration and type like glycol: propylene 40%.

However I feel a glycol tag should not replace a water tag, but perhaps be used in conjunction with it. That would keep the transfer mediums to water, steam, and air. That way the glycol tag would only be added if the loop was known to contain glycol.

In fact I have seen some ground source loops use ethanol for antifreeze protection, so perhaps a more generic system of tagging a loop to be containing a freeze protection additive would be good. This certainly could be useful information to have available for freeze alarms, water make-up sequences, and heat transfer calculations to name a few. I would think the key pieces of information would be the type of additive and it's concentration. Maybe something like antifreeze: propylene 40%, and if the type and concentration were unknown it could simply be added as antifreeze; just to indicate the loop has some type of freeze protection additive.

Thanks Leroy

I prefer antifreeze to glycol with the ability to identify the various flavors possible.

antifreeze - point associated with the measurement or control of a liquid that has a lower freezing point than water. When the tag is used in the following format antifreeze: propylene 40% a mixture of 40% propylene and 60% water is indicated.

Very clear

I think using the term preheat to augment heat makes sense.

But my understanding is that most often glycol is mixed in with water, and not often 100% of the fluid flowing thru a given pipe. So I'm confused by this:

preheat glycol leaving temp sensor

Wouldn't that be:

preheat water leaving temp sensor 

The fact that some sort of anti-freeze is mixed in seems a secondary concern (and doesn't really seem like meta on the sensor itself)

If we see a water temp sensor go below freezing, we are concerned; but if it is an antifreeze temp sensor, we won't automatically generate a report.

What if the antifreeze info was referring to the water loop itself ref by the sensor ?

I think that makes the most sense Christian. However that also requires each loop to be modeled as its own entity, since a plant could have multiple loops each with unique characteristics. I know that concept was discussed before, but I don't believe it was finalized.

I think the tags

• antifreeze or
• antifreeze: propylene 40%

could be used on both/either the sensor or the "glycol/water loop" depending on the (1) project size, (2) software platform you are using, (3) the user's experience level, (4) desired type of reporting etc.

I would be hesitant to refer to it as water if it is not 100% water.

I haven't heard any comments relating to the preheat tag, that seems pretty straight forward unless anyone has another term to suggest.

So the core remaining question is this: what is the best tag or tags to model a loop of water with antifreeze mixed in? I would suggest the key concept there is that has antifreeze, not the specific type of compound being used. But on previous discussion, these are some options:

1. water
2. water antifreeze   // antifreeze is marker or string enum/description
3. antifreeze
4. water glycol
5. glycol