A/C economy

[matthewb0051]

Just left the courthouse, it was closed for long weekend that included Monday (Juneteenth). Some genius has figured that they can turn off the A/C for the weekends and save money.

I say bollocks. It was hot and sticky in there this morning and with 100+ degree temps since late last week, it will be hours if not a day or two before it gets back to normal in the building. I think today is predicted at 105 with pretty high humidity (this ain't El Paso with zero humidity)

My question is: does this actually cost more money since the A/C will almost certainly be running full bore all day today, tonight, and tomorrow to make up for being off for a weekend? OR is there money savings?

If I were a judge I would have a fit and call the building maintenance boss to my courtroom and give him/her an ear full. Kind of hard to conduct business when everyone is sweating buckets. There were jurors waiting in hallways that were like saunas, no way I'd hold them and I'd probably just cancel my docket until A/C was restored.

[asphaltgambler]

If the remote access control is set properly, should turn back on late ( after 9pm) and be back to normal by daybreak next business day.

[masraum]

Originally Posted by matthewb0051

Just left the courthouse, it was closed for long weekend that included Monday (Juneteenth). Some genius has figured that they can turn off the A/C for the weekends and save money.

I think it depends. I also think there's a big difference between turning it off and turning it up.

For instance, if it's normally set to 72º during working hours, I think it could be bumped up to 80-85º at the end of the day, and then if the system is of a good size and the building is well insulated, then a couple of hours before people arrive in the morning the AC should bump back down to 72º and should be at that temp when folks arrive.

If the AC is undersized, that's bad. I don't necessarily think it's a good idea to turn it completely off. Having it on but set to what most folks would consider an uncomfortable temp would having it running enough to keep the humidity down, and I think having the humidity it a comfortable level is paramount to comfort. AC dehumidifies the air.

But it should be automated, not something that someone flips a switch to off when they leave on fri. It should be a programmable thermostat.

[David]

I have the A/C in our 80,000 sqft shop come on for 6 hours during the middle of the day (9-3) when nobody's here mainly just to keep humidity in check. Within an hour of the A/C turning off it goes from 72° to 76° so it climbs pretty fast.

On working days in the summer, the A/C shuts off at 5pm, starts at 3am and by 6:30am when the work day starts, it's down to 72°.

[p911dad]

Sounds like a good plan in a place with a moderate climate that cools off all night. However, in your case it stays warm/hot all night and the whole building and everything in it gets hot. On Monday morning it's all hot and humid and now the A/C must cool off the building and everything in it and not just the air. I can't see any savings with this idea.

[David]

To the original post: it's likely either a problem with the system or more likely a building manager that doesn't know how or care to set the system properly.

I'm of the opinion based on what I see in our building, (and I have full trend data capability on a 480 ton system) that if there's nobody in the building there's no need to run A/C. Just make sure it's started early enough to be cool by the time people arrive.

For our building that's 4:30am in fall to spring and 3am in the summer.

[rwest]

Like mentioned above, a good system could be turned off and with proper programming could have an unoccupied setting that wouldn’t let the building get crazy hot.

It is possible that the system isn’t sophisticated enough, so it just turns on and off by a timer and yes, turning the system off for three days saves a lot of money.

The middle ground could be to have the system turn on several hours before the courthouse opened so it would be comfortable.

[billybek]

The system should be able to go into an unoccupied mode for the evenings. How this is set up is by knowing the past trends on the building in all types of weather conditions.

Having it "shut off" to save money could result in a system that is not able to catch the load and cool the space to a comfortable temperature/humidity.

A good automation system could make decisions based on outdoor ambient temperature and indoor temps and humidity levels. The time to get the space to a comfortable temperature could vary.

Look at the mass in the building as a giant flywheel. The more heat that the mass contains the faster the flywheel spins. The cooling system is like a braking system for the flywheel. There is only so much braking capacity to slow down the flywheel and in some cases, the flywheel will not slow down enough to offset the cooling load during the day. In some buildings, the peak load does not occur until mid to late evening.

Bottom line is that a heat saturated building is hard to bring back into control.

[rwest]

To maybe better answer the OP, generally a commercial system operates differently than a home system. In most home systems, it either heats or cools and only runs when it needs to do the cooling or heating.

A commercial system will have a constant fan and also take in a certain percentage of outside air that it then has to heat or cool. So leaving it running all the time can be quite costly and not very energy efficient, which for many buildings the energy conservation is more important to the owners than the actual cost of running. Think zero carbon goals and net zero energy etc. being that it is a courthouse it is probably government and they will most certainly be trying to reach some sort of zero carbon goals.

A commercial system also try’s to keep the temp within a certain couple degree range, so it might heat and cool at the same time for different zones or times of the day.

I used to say that “I can make everyone is this building comfortable until the second person shows up!”

Balancing comfort and conservation is not a fun thing.

[Tobra]

This sounds like the way they would do it in California

false economy and uncomfortable every Monday during the summer

[rwest]

Originally Posted by Tobra

This sounds like the way they would do it in California

false economy and uncomfortable every Monday during the summer

Hi Tobra,

It is done all over and not false economy, it can be proven to save money- but with proper management (human or computer) there isn’t a reason that the building couldn’t have been shut down for the 3 day weekend and either not let it get too hot or started up early enough to cool it down before occupation.

I will add that in certain situations where it is so hot or cold that the system design is on the edge, it might have had to be run 24/7. We don’t have enough information on that system to know.

[Tobra]

Presupposing competent management of state run operations is not a recipe for success, especially if it is the state of California.

In a normal situation, having money left at the end of the year is a good thing. Not so for a state operation. If you fail to spend, your budget gets cut

[David]

Originally Posted by rwest

To maybe better answer the OP, generally a commercial system operates differently than a home system. In most home systems, it either heats or cools and only runs when it needs to do the cooling or heating.

A commercial system will have a constant fan and also take in a certain percentage of outside air that it then has to heat or cool. So leaving it running all the time can be quite costly and not very energy efficient, which for many buildings the energy conservation is more important to the owners than the actual cost of running. Think zero carbon goals and net zero energy etc. being that it is a courthouse it is probably government and they will most certainly be trying to reach some sort of zero carbon goals.

A commercial system also try’s to keep the temp within a certain couple degree range, so it might heat and cool at the same time for different zones or times of the day.

I used to say that “I can make everyone is this building comfortable until the second person shows up!”

Balancing comfort and conservation is not a fun thing.

Yep

[masraum]

Originally Posted by David

I have the A/C in our 80,000 sqft shop come on for 6 hours during the middle of the day (9-3) when nobody's here mainly just to keep humidity in check. Within an hour of the A/C turning off it goes from 72° to 76° so it climbs pretty fast.

On working days in the summer, the A/C shuts off at 5pm, starts at 3am and by 6:30am when the work day starts, it's down to 72°.

Exactly, have the system kick on early in the morning (when it's still relatively cool outside and the temp should come down to an acceptable level in a few hours.

[matthewb0051]

Originally Posted by Tobra

This sounds like the way they would do it in California

false economy and uncomfortable every Monday during the summer

Day 2... hot as BA 11's in the courthouse still. I'm hearing that it was turned off and also that it is coming on then off. So it could be a combo of stupid and broken.

Mr. West I'm sure is correct. However, I don't think the good folks running this show are astute enough to do it so it works as he describes.

As to the quote above: last summer the City and/or County was asking everyone to set their home t'stats to 74-76. So it doesn't surprise me that they are taking this approach with the courthouse.

Bonus: today it will get to 105 with heat index warnings. Just preheating the oven down here.

[Tobra]

Man, I miss Texas

[hcoles]

Originally Posted by David

Yep

Yep +1

[matthewb0051]

Originally Posted by Tobra

Man, I miss Texas

I looked at the outside temp when I was driving home yesterday at 4pm: 111 degrees

And it didn't cool off much overnight: a whopping 87 degrees going to my office this morning around 8:30

That wouldn't be so bad in El Paso where there isn't any humidity but here it is like a wet electric blanket over the city