split ducted 60KW reverse cycle unit selection with -15 ambiants

[mattmechanic]

Hi all,
im am trying to select a unit that will work for my particular application

i need to replace an existing 60KW split ducted package that is reverse cycle untill ambiant reaches +5 then it shuts the unit down and brings on duct heaters....

i would like to replace this with a new unit and do away with the duct heaters and be 100% reverse cycle however the ambiants here reach -10 to -15 regulary

i would like some suggestions on unit brands as everything i find seems to only be rated to -10 and at this rang dose not give off much heat ( actron, temperzone, carrier ect)

however lennox seems to be the pick at the moment with acceptable performance to -15

what do you guys do around the world for heating in low ambiants and what would your unit of choice be?
cheers

[frank]

Whereabouts in australia does it reach -15C?

[AC_From_Hell]

Id say the easiest and most energy efficient system would be a DX AHU with recuperation and VRF outdoor unit.

[Magoo]

Hi Matt,
I am picking that you operate in the "Snowy Mountains" area of NSW / VIC., with those winter temps

[mattmechanic]

magoo you are correct

[Magoo]

Hi Matt.
a great place to live and work in, only seen it from a plane. Reminded me of Central Otago NZ. Hot summers and seriously cold winters. Talk to Bradway/ Temperzone they can do specials, purpose built packages for low ambient.

[mattmechanic]

there is temperzone units here on the hospital with a dodgy mechanical thermostat ( looks like one from a pie warmer) shutting the units of @ -5 and bringing on duct heaters as they begin to freeze up the outdoors.
some NSW health contractors came and installed them now i have to look after them and i swore i would never use them here if they cant work below -5, there are also acrton units connected the same
in winter the whole hospital and most other commercial buildings around here installed by Sydney based company's all have duct heaters and low ambient thermostats lawl!

[Magoo]

Hi Matt,
seems you have been left holding the can after all experts left town.
At least at -15 you are past the snow building RH factor on recovery coil,ok the rh will be high but absolute moisture will be low, so basically you need massive surface area to stop snow/ice build and reverse cycling, plus high fan speeds as well for max heat recovery.
where to start though ?

[nike123]

I think your only safe option is Mitsubishi Electric units with Zubadan tehnolgy, if any of their units fits your need!

http://www.mitsubishielectric.com.au/2167.htm

[AC_From_Hell]

Samsung DVM S is actually better than Zubadan, especially when looking at efficiency and I can assure you that an AHU can work at 100% fresh air with 0% heat recovery even at -15. Samsung books say it cant, but thats because they havent tested it, actually it works great.

[mattmechanic]

never herd of connected multiple outdoors to a single 60KW AHU

[nike123]

https://www.mitsubishi-electric.co.nz/product/group.aspx?cat=7952 (https://www.mitsubishi-electric.co.nz/product/group.aspx?cat=7952)

These are designed for hot water application but can be used as heat pump for heating in pair with any fan coil!
You can use duct type fan coil and this heat pump for your purpose!
You should contact local dealer for details.

[AC_From_Hell]

never herd of connected multiple outdoors to a single 60KW AHU

You just need 1 outdoor unit 18 or 20HP capacity (56 or 60kW in heating mode), then you connect it to the Samsung AHU Kit and add a refrigerant heat exchanger with two 10HP EEVs connected to the kit. The other option is to use an air to water heat pump as nike124 suggested, Samsung also offer it - DVM Chiller. It could be a better solution in some cases.