rooftop unit needed

zepfan

we are looking to replace a 10 ton gas fired, dx rooftop unit that serves a critical file area.The unit that is there now is more of a comfort cooling unit, and we are looking for more of a precision cooling unit, such a Liebert. In short the unit needs to provide mechanical cooling year around, and have a de humidification cycle. The conditions that the room needs to maintain are 65 degrees, and 45% rh. Any suggestions would be much appreciated. thanks to all.

nicholas bonham-carter

What area are you in? Some provision may be needed if the unit will operate at cold winter temperatures.--NBC

Mike

How critical is the Rh? Is that minimum or max? Aaron or trane make good units. May need to be custom built. Hot gas bypass and vfd. If the humidity is critical, verify that the room is constructed to hold that level.

njtommy

I agree with Mike both AAON and Trane will build you a custom unit to meet your specs. Both are very nice units. trane will be able to run AC down to 5-10 degrees out side with no problems.

ratio

I'd imagine everyone produces a humidity control unit. I've personally installed Trane, Lennox & York units with dehumidification. In fact the York (of all things!) is responsible for keeping the humidity under 40% in a 24/7 facility where going out of spec will lose a quarter million dollars & nearly two weeks of production-federally supervised. It does the job, but was a headache to dial in, not least of which was because it was two hours away... The Tranes I've installed were responsible for a printshop & their paper storage area. Seemed to work fine, but since the cheep idiots deleted the BAS package, they had to call Trane if they wanted to change the rh setpoint. The Lennox units managed rh in a large electronics repair shop (think EMC & Sun, not PCs).

Whoever you go with, make sure the salescritter understands the requirements. Go over the submittals & make sure it says it'll do what you need, if it doesn't call the mfgr's engineering dept & ask.

RJ_4

From past experience there can be a problem with a RTU maintaining humidity levels do to the access panels on the unit which if not gasketed can allow outside air filtration, also there can be an issue of water service to the humidifier in the winter. You may consider a Liebert unit or another manufact. Installed in the conditioned space

aircooled81

With a coil that cold, you might need humidification? Unless those files are all wet?
Are you looking for reliability, staging? Does the load stay the same all the time, or is changing due to environment?
Are you looking to keep the equipment on the roof, or put it down below now?
Do you need the humidifier in the equipment? Will you want dedicated controls or are you managing it with bms?

aircooled81

Check out this video by daiken,
Looks like this unit can provide the dehumidification.
Either put humidifier in the space, or find a dry steam type model. Go with traditional vapor humidification and you wanna get your duct work up to snuff.

http://www.daikinapplied.com/rooftop-rebel.php

SWEI

Ha!

Out here in the west, we worry about keeping the humidity in critical environments high enough.