Turning cooler off in old auditorium when not in use damage anything?

[ccw]

Old auditorium, poorly insulated, with recirc only old HVAC system. Supply air by bountiful inleakage only. Freon loop refrigeration.

Ambient summer air: 2AM 74dB/65wB 75% RH
5AM 72dB/65wB 79% RH
8AM 70/67 86%
11AM 81/67 64%
2PM 88/65 48%
5PM 90/65 43%
8PM 85/65 52%
11PM 77/67 71%

When running, the cooler thermostat is set to hold 75-78F.
The only things I have found in reference material is getting things too dry potentially causes wood to shrink, crack, craze paint, and getting things too wet potentially causes mold or rot.

To save on electricity usage, it is proposed to shut off the system when not occupied or not about to be occupied for 12-24 hr stretches.

 

[imok2]

Your system seems to need some serious inspection so if your not willing to spend some money for an up grade then I would shut it down when not in use and do a calculation on energy savings and maybe you can save enough to improve the system also I would be curious to see how it would effect the interior conditions

 

[KiwiMace]

Your auditorium doesn't meet code and would need to be historic to not have a reliable provision of outdoor air into a public assembly space.

Poor insulation and excessive infiltration will cause your auditorium to track the outdoor conditions. More useful just to state your location or climate type - hot dry, hot humid etc. Once turned back on, your recirc system may struggle to regain control.

A complete dog of a thing it sounds like. Follow imok's suggestion.

 

[ccw]

Thanks imok2 and KiwiMace.

I have done the study, using comparable months (matching up recorded temp data from nearby NWS station). Last year keeping it on was 16,000 KWH/mo. This year turning it off when the auditorium was not in use, 8400 KWH/mo. At $.10/KWH that is a savings of $760/mo.

This is a temperate zone, with 4 seasons. In early spring, late fall, and winter KWH/mo drops considerably.

Some folks are concerned that cycling 90F at 43% RH down to 70F at 86% RH can cause functional damage to things like piano, organ, furniture, floor, wood trim, etc.

 

[KiwiMace]

In a temperate climate you probably won't have too many glaring issues, but conservationists like to keep the T & RH steady for wood and paper. Not too great a rate of change and minimise cycling.

Mould would have a much greater impact. Make sure you aren't promoting the growth of mould in the space.

 

[ccw]

Yes, Baldwin, Kawai, Steinway, all want RH controlled to within 40%-60%.

Contrary to what many expect, if I open the windows between approx. Noon and 9:00PM next to the piano, the RH would be perfect. If I open the windows between 10:00PM and 10:00AM the RH would be too high. If the AC thermostat is set to switch on above 72F, running with the windows closed at pre-dawn to 9:00AM, the RH would be too high (remember the high inleakage). If I run the AC in the heat of the day, dew point is reached at the expansion coils and the RH would probably be too low.

$550 will get a dehumidifier, humidifier system rigged on the piano, that will suit even Leonard Bernstein's piano tuning technician. That is less than one month's savings over running continuous at 72F set point. Sounds good, but this may be a losing point. Because, now we move to other wood laden devices and what to do about them. Also, observe that said piano has never shown any signs of stress after suffering RH swings noted above for about 10 years.

 

[chicopee]

Assuming that the items of interest are on the stage, I would maintain the desired temp. and RH within the stage by keeping the stage curtain closed and only provide conditioned ait for that area instead of the whole auditorium. Is that doable?

 

[ChasBean1]

If you drop the space to 70°F, the RH shouldn't be 86% anymore (closer to about 83% correlates with your OA conditions) with dehumidification at the coil. The space would be 70°F with an 83% RH if you sensibly cooled only. You should in reality dehumidify, with DX off-coil temps of 45-52°F.

For this system, assuming the infiltration is from breezes and the space is not excessively negative due to mechanical exhaust (and windows are closed), there should be less concern of mold/humidity.

Without a high degree of ventilation, the moisture in the space may not cycle too badly. The DX off-cycle heat up from 75 to 78 should mainly be sensible without forced in-leakage. Humidity control becomes more of a concern when the DX control tries to cool while providing enough ventilation. DX off cycles in systems with ventilation will bring in tons of moisture as the space warms from 75 to 78.

So oddly, as the system is antiquated and does not meet code (agree with all above) the moisture and humidity control may actually be easier than for a system that brings in the required ventilation.

 

[ccw]

Thanks for the suggestions. I am thinking about the "isolate the stage from auditorium" approach. There may be some structural problems there.

Also, I am going to use a recording bat. pwred temp/humidity instrument to get some 2 day histories, AC off and AC on, and see how the inside air conditions tracks the outside air conditions.