Issue 4-2016

Nope, it’s not a misprint. The indoor design temperatures for this project were 24°C to 30°C with 50% to 90% RH.

This raises two really good questions: Who would want to live in those indoor conditions? and Can you actually deliver those conditions with standard air conditioning equipment?

The answer to the first question becomes more obvious when you realise the project is a large research glasshouse at the Hermitage Agricultural Research Station near Warwick, QLD. The inhabitants of the glasshouse are plants -- not humans. 🌿

“The ARGUS controls monitor weather conditions such as total solar radiation, wind speed, etc. This enables the Modbus controls for cooling / ventilation demand to be predictive. For example- when the sun shines out from behind a cloud (increase in total solar radiation), rather than wait for the return air temperature to rise and trigger increased cool demand, The ARGUS will act on total radiation to increase cool demand before temperatures begin to deviate from set point.”

“With sophisticated Modbus control programming coupled together with flexibility of the OPA ECO 1st stage compressor loading, control of EC fan speed and ability to monitor SST we have been able to provide a solution to this project that fits both the demanding requirements of the specification, while meeting budgetary constraints.”

Caleb who had no experience with Modbus controls before this project went on to say:“I have totally relied upon supplying data sheets from Temperzone to Argus in Canada with an outline of what I need to achieve. I monitor what happens on site and work with a technician in Canada to make logic changes where needed.

I was impressed however, when I found one of the units tripped on “compressor frost protection” after a demand for a very low fan speed was applied. This gave me peace of mind, knowing that even though I am relying on logic written by another person that there is still good compressor protection through the Temperzone UC6 controller no matter what the Modbus program is requesting.“

The glasshouse facility has been completely operational for 2- 3 months while the final operational commissioning tasks, including the Modbus programming is refined. It is expected to be handed over to the research team at the Hermitage Research Station in the next month or so.

Temperzone News is planning a follow up story on this project once agricultural trials are fully operational in 2017. If you want more information on Temperzone OPA ECO including information on BMS Integration, please contact your Temperzone rep.

Download OPA ECO Brochure here

Technical note on OPA ECO / Modbus integration from Caleb Sweet:

"What made the ECO Temperzone units really stand out was the fact that we could have control over many aspects of the air conditioner via Mod-bus. The following scenario is an excellent example of how the OPA ECO allows the Modbus controls to deliver an outcome that would not be possible with other package units."

e.g. In summer if a trial needs 24°C at 90% RH with an ambient of say 37°C (high radiant load on the room) Then it is expected that the SST would exceed 12°C and not provide adequate cooling for the compressor. With Mod-bus control all the key operating variables, such as SST, can be monitored by the controls system. ARGUS have written a Modbus control loop that looks at the SST of each stage when compressor is running. If SST exceed 12°C then the fan speed can be slowed down to temporarily reduce the extremely high latent load on the unit due high humidity set points. This enables some conditioning to continue without forcing the air conditioner to run outside its operating parameters and potentially trip safety controls which jeopardise valuable experiments.

Due to large range of air on conditions, the electronic valve in the OPA ECO is far better for superheat control than a mechanical valve. Superheat control is completely managed by the OPA ECO’s on board UC6 control logic.

OPA ECO Series

Border Refrigeration and Air Conditioning was established in 2003 by Ian and Barbara Marsden. They have two offices -- one in Stanthorpe and another in Warwick Qld. Specializing in air conditioning and commercial refrigeration, they are committed to offering their clients a professional and quality service.

Caleb Sweet – Service Manager