Trane Intellipak SVX36G Morning Startup

[angryjohnny]

Recently installed 130Ton unit that I monitor for KWH usage via ALC BMS. Noticed that unit goes full on every morning on startup command. Is this related to the rapid restart feature and if so is there a means to stage fan and cooling stages up more gracefully?

Thx in advance.

[Six]

It goes to "full on" because the space is warm and the RTU hasn't run for 12 hours. Trane's own internal control algorithms determine staging and unit capacity.

There is no practical reason to slow down the unit's initial staging process.


Also Rapid restart is only utilized after power is cycled on the unit.

[angryjohnny]

I would choose to differ on your opinion about no practical reason to slow down staging process. This is one of two units that support a 70,000sqft space. For instance unit runs also on weekends for 8hrs each day. If there are only a handful of vav's calling why would you want to it to go full on?

Trying to smooth out my energy spikes especially at start up.

[Six]

If there is a reduced load due to 70% of the VAVs being in a non-occupied status then the RTU would damper back the FAN rpm through the units VFD to maintain your static pressure setpoint.

Also the units going to respond to load and then stage down as it meets the demand faster.

Lower load lower energy usage.

If your trying to reduce total inrush stage start up times through your EMS. Other wise I'm not sure if there is any other options. 130 ton unit is going to go to full load after 12 hours of off time.

Verify that every compressor and the blower motor ( which should ramp up through a VFD anyway ) is being brought on instantly on start up.

I'm positive that units stages on start up.

[angryjohnny]

Thx,

Will look into staging times in hopes of reducing power consumption.

[Failure2Comply]

Being a VAV unit all it knows is discharge air temp setting and static pressure setting. It will ramp up and stage up accordingly. Make sure the time delay between rooftop units is set to allow enough delay between them to keep initial inrush blgd current down.

[XcelTech]

If you wanna lower your spiking cost get a control system.

You waste a ton of energy starting a building that hasn't had air to it for over 12 hours.

Instead, a control system will have unoccupied times where instead of allowing the building to get whatever temp it does naturally, you can set the unoccupied times to let the building get no higher then 85°F(which is a bit higher then I like).

Then instead of turning everything on in the morning you can stage the buildings cooling. Turn this area, on then this one, then this one.

You slowly cool down sections at a time. This will help prevent spiking AND help the longevity of your chiller. Plus it will lower your electric bill because instead of trying to cool 95°F air and 70% Humidity to 72°F you will be cooling 85°F air with 55% humidity.

[Six]

If you wanna lower your spiking cost get a control system.

You waste a ton of energy starting a building that hasn't had air to it for over 12 hours.

Instead, a control system will have unoccupied times where instead of allowing the building to get whatever temp it does naturally, you can set the unoccupied times to let the building get no higher then 85°F(which is a bit higher then I like).

Then instead of turning everything on in the morning you can stage the buildings cooling. Turn this area, on then this one, then this one.

You slowly cool down sections at a time. This will help prevent spiking AND help the longevity of your chiller. Plus it will lower your electric bill because instead of trying to cool 95°F air and 70% Humidity to 72°F you will be cooling 85°F air with 55% humidity.

Its a package unit but I hear you. It's basically the advice I gave him and most likely that's going to be on an EMS system.