Okay, as we're all in a 'hold' situation, why not take this http://www.film-tech.com/vbb/forum/m...=1764#post1764 to here:
Since a while, I was wondering wether I should employ a smarter method for our auditorium heating. It is a decent room, about 14m wide, 24m deep, and about 6m high. It's a free standing historic building, so, little insulation, loads of heat loss through walls and ceiling/roof. Over the years, we employed a few methods and that essentially brought the heating cost down to around 50% (which is great, given that it didn't cost us much). However, I think we could do a little more. The auditorium heating is using hot air. The inlet can be switched from external to circulating air. During our heating season, we switch to circulating air, as then the energy is reused (heating up air in the range of 18-20 °C costs less energy than heating up external fresh air from e.g. around 0 °C). As the auditorium has such a huge air volume, as we only have one show per day, and the building is anything but air-tight, we usually don't have issues with air quality. Only when we are sold out (about 350-400 people) we are switching to external to improve air exchange. We don't employ explicit HVAC. During summer time, we can switch on just the blower of the heating system, and while being switched to external inlet, this also brings in fresh or cooler air from the outside. This, currently, is all manual.
Now, the time to heat up our huge auditorium is comparably small, as the heating system blows in a huge amount of warm air in comparably small time - we usually switch the heating on around 1hr before admission starts (during times with very low outside temperatures, this needs to be increased to 1.5hrs, sometimes 2hrs). This is done using a standard wall mount thermostat/week timer combo set to 1hr before scheduled admission time. This is adjusted manually, so when we start a long movie half an hour earlier, I have to adjust that timer on site. Similarly, when we have extra shows e.g. in the morning, I need to add extra timer points beforehand on site. I am not living near the cinema, I am not on site every day, and I'd hate to drive there an extra 1-2 hrs earlier in the morning or evening just to switch on the heating in time. Our general staff is not good in handling that clumsy current timer 'interface'. They could easily ruin important settings/schedules, leaving the heating off during show times, and when they usually arrive at the cinema for their duties, it is usually too late to enable the heating manually in order to achieve a decent room temperature until admission or even show starts.
The heat-up/preheat times have been found empirically using a range of temperature loggers some years ago. We found a more or less linear relation between time and temperature rise - around 1 °C per 10min of heating. The lowest I let the auditorium temperature drop in harsh winters during night and most of the day is to around 7-8°C (that is the lowest safety temperature our thermostat allows, and I also think this is still safe for building and interior. Our utility rooms use a separate heating and never drop that much). So, from these numbers, we can see that, to bring the auditorium to around 20 °C, we need a maximum of around 120min heating time. This has been verified in daily use over the recent years. The auditorium air temperature is measured using an external temperature probe attached the left side wall, half way into the auditorium. There is probably a bit of a bias there being so close to the external wall, but, this is usually easy to compensate by using a fixed offset. During the movie, the heating switches off and on based on room temperature and hovers around 20 °C. So, with a huge attendance, we use less energy, as their body-heat adds to the heating, means, we never over-heat.
However, me adjusting the timer pre-heat time of cause doesn't happen on a daily basis, I assume a general mid-term average temperature and set the timer accordingly, but, by a very rough estimate. So, during early autumn, the preheat time may be only 30mins, while in a cold January, I may set it to 2hrs. The Off-Time in the timer is usually set to straight times roughly based on the show length, but, not very precisely. E.g. it may be set to 22:00 for most shows. Only when we play an exceptionally short or long film this is adjusted for it's run time. We notice that the auditorium temperature drops 'noticeably' within around 15min after switch off, and we don't want people to start quivering already during the end of a movie.
I think this can be impoved by setting the preheat time automatically based on the auditorium temperature, and that is when a JNIOR comes into play.
- measure room temperature and switch on heating automatically based on a pre-heat time calculated from the room temperature and scheduled admission time, so, if the room is e.g. 12 °C, start heating 80min before admission time
- receive notification from the cinema server about show end and switch off automaticallly. This could e.g. be based on credit offset.
- maintain the existing manual timer and thermostat as a backup, so that, if anything goes wrong, it switches on heating a minimum of 30min before admission, and at a fixed safety time after a movie ends. Failsafe is important here. If necessary, I need to be able to tell general staff on the phone how to bypass the system if it fails for any reason. This also has implications on the way we wire/choose relay contacts break/make wise, e.g. a broken/hungup/disabled JNIOR or software function should not block the failsafe timer from working.
My idea would be to enter show times e.g. in an electronic calender, as currently, we don't have a TMS or POS.
Some luxury items could be added later - e.g. alarm if the room temperature doesn't rise even if it should (problem with the heating system not firing up). Notify in early autumn to enable the heating if the average temperature decreases (our heating is shut down completely from late spring to early autumn).
Now, for a short time a few years back, I actually had connected a JNIOR 3xx to the heating and was able to turn on remotely. However, we had a problematic relation with our landlord back then, and he did not allow us to mess with 'his' heating system. Now, the landlord has changed, and I'd like to pursue this task. The turn-on element for the heating is a simple 230VAC relay accessible from the projection room. This is in series with the thermostat, so, IF timer AND thermostat condition is met, heating is switched on. The current thermostat uses a 20mA wired probe in the auditorium. I would love to have a wireless probe, though, we could wire one, however, we would probably need 20-30m of cable run. Not sure yet which position of the probe in the auditorium would be best.
So, Bruce, or anyone...?
- Carsten
Since a while, I was wondering wether I should employ a smarter method for our auditorium heating. It is a decent room, about 14m wide, 24m deep, and about 6m high. It's a free standing historic building, so, little insulation, loads of heat loss through walls and ceiling/roof. Over the years, we employed a few methods and that essentially brought the heating cost down to around 50% (which is great, given that it didn't cost us much). However, I think we could do a little more. The auditorium heating is using hot air. The inlet can be switched from external to circulating air. During our heating season, we switch to circulating air, as then the energy is reused (heating up air in the range of 18-20 °C costs less energy than heating up external fresh air from e.g. around 0 °C). As the auditorium has such a huge air volume, as we only have one show per day, and the building is anything but air-tight, we usually don't have issues with air quality. Only when we are sold out (about 350-400 people) we are switching to external to improve air exchange. We don't employ explicit HVAC. During summer time, we can switch on just the blower of the heating system, and while being switched to external inlet, this also brings in fresh or cooler air from the outside. This, currently, is all manual.
Now, the time to heat up our huge auditorium is comparably small, as the heating system blows in a huge amount of warm air in comparably small time - we usually switch the heating on around 1hr before admission starts (during times with very low outside temperatures, this needs to be increased to 1.5hrs, sometimes 2hrs). This is done using a standard wall mount thermostat/week timer combo set to 1hr before scheduled admission time. This is adjusted manually, so when we start a long movie half an hour earlier, I have to adjust that timer on site. Similarly, when we have extra shows e.g. in the morning, I need to add extra timer points beforehand on site. I am not living near the cinema, I am not on site every day, and I'd hate to drive there an extra 1-2 hrs earlier in the morning or evening just to switch on the heating in time. Our general staff is not good in handling that clumsy current timer 'interface'. They could easily ruin important settings/schedules, leaving the heating off during show times, and when they usually arrive at the cinema for their duties, it is usually too late to enable the heating manually in order to achieve a decent room temperature until admission or even show starts.
The heat-up/preheat times have been found empirically using a range of temperature loggers some years ago. We found a more or less linear relation between time and temperature rise - around 1 °C per 10min of heating. The lowest I let the auditorium temperature drop in harsh winters during night and most of the day is to around 7-8°C (that is the lowest safety temperature our thermostat allows, and I also think this is still safe for building and interior. Our utility rooms use a separate heating and never drop that much). So, from these numbers, we can see that, to bring the auditorium to around 20 °C, we need a maximum of around 120min heating time. This has been verified in daily use over the recent years. The auditorium air temperature is measured using an external temperature probe attached the left side wall, half way into the auditorium. There is probably a bit of a bias there being so close to the external wall, but, this is usually easy to compensate by using a fixed offset. During the movie, the heating switches off and on based on room temperature and hovers around 20 °C. So, with a huge attendance, we use less energy, as their body-heat adds to the heating, means, we never over-heat.
However, me adjusting the timer pre-heat time of cause doesn't happen on a daily basis, I assume a general mid-term average temperature and set the timer accordingly, but, by a very rough estimate. So, during early autumn, the preheat time may be only 30mins, while in a cold January, I may set it to 2hrs. The Off-Time in the timer is usually set to straight times roughly based on the show length, but, not very precisely. E.g. it may be set to 22:00 for most shows. Only when we play an exceptionally short or long film this is adjusted for it's run time. We notice that the auditorium temperature drops 'noticeably' within around 15min after switch off, and we don't want people to start quivering already during the end of a movie.
I think this can be impoved by setting the preheat time automatically based on the auditorium temperature, and that is when a JNIOR comes into play.
- measure room temperature and switch on heating automatically based on a pre-heat time calculated from the room temperature and scheduled admission time, so, if the room is e.g. 12 °C, start heating 80min before admission time
- receive notification from the cinema server about show end and switch off automaticallly. This could e.g. be based on credit offset.
- maintain the existing manual timer and thermostat as a backup, so that, if anything goes wrong, it switches on heating a minimum of 30min before admission, and at a fixed safety time after a movie ends. Failsafe is important here. If necessary, I need to be able to tell general staff on the phone how to bypass the system if it fails for any reason. This also has implications on the way we wire/choose relay contacts break/make wise, e.g. a broken/hungup/disabled JNIOR or software function should not block the failsafe timer from working.
My idea would be to enter show times e.g. in an electronic calender, as currently, we don't have a TMS or POS.
Some luxury items could be added later - e.g. alarm if the room temperature doesn't rise even if it should (problem with the heating system not firing up). Notify in early autumn to enable the heating if the average temperature decreases (our heating is shut down completely from late spring to early autumn).
Now, for a short time a few years back, I actually had connected a JNIOR 3xx to the heating and was able to turn on remotely. However, we had a problematic relation with our landlord back then, and he did not allow us to mess with 'his' heating system. Now, the landlord has changed, and I'd like to pursue this task. The turn-on element for the heating is a simple 230VAC relay accessible from the projection room. This is in series with the thermostat, so, IF timer AND thermostat condition is met, heating is switched on. The current thermostat uses a 20mA wired probe in the auditorium. I would love to have a wireless probe, though, we could wire one, however, we would probably need 20-30m of cable run. Not sure yet which position of the probe in the auditorium would be best.
So, Bruce, or anyone...?
- Carsten
Comment