Indoor package units?
Indoor package units?
(OP)
I have a customer that wants me to put package units (RTUs) on his control room which is inside a larger warehouse. The temperatures on the control room roof reach about 120 degrees and the roof of the larger warehouse is about 8 foot above. Everything in me says this won't work, but my client insist that if I enclose the roof (like an attic) and use a fan to draw in fresh air to pressurize the room, we can simulate outdoor conditions for the package units.
Can anyone give me a good reason why this won't work?
Thanks.
Can anyone give me a good reason why this won't work?
Thanks.





RE: Indoor package units?
Some things to keep in mind, if you continually pump outside air into this new plenum space you will need to exhaust either back outside or into the warehouse space. It you put it in a fake attic you will still need access to the unit. They will probably still need to reinforce the control room roof to handle the unit. You will still need to maintain all of the manufacturer's clearances to maintain proper airflow around the condenser coil, and you will still probably have to de-rate the capacity based on higher "ambient" temperatures.
All that being said you could probably cobble it together and make it work. However, I find it hard to believe that building a fake attic, installing supply and exhaust fans, and reinforcing the control room roof, would be better and cheaper than putting the unit on the roof and installing a couple of sections of supply and return duct.
RE: Indoor package units?
Will reduce your roof load substantially. You will not need to build a fake attic over a space.
RE: Indoor package units?
Wouldn't it be easier and cheaper to put the units on the wearhouse roof and simply run supply and return ducts eight feet straight down?
RE: Indoor package units?
Why the suggested solution?
It will probably cost more than putting it up on the existing floor, even if extra walls/roof for architectual visual reasons is needed. (Cost is reason enough in itself - direct placement on roof will be cheapest with best maintenance access)
If reason is total building height or aestethic, perhaps it would be sensible to use the area above the control room, but build it as an extra closed 'mezzanine' placed room, enclosed else with floor and walls, roofed over with new roof a bit above existing, with larger wall - vents above existing roof, and enforced circulation if needed.
RE: Indoor package units?
The client thinks that by installing package units inside the warehouse, we can avoid the exposure to chemicals in the air, so he'll save money by not having to coat the coils, etc. However, by installing the package units inside, we now have to create an environment for them to operate properly.
The client wants to do exactly what gerhardl said: use the area above the control room and build it as a closed mezzanine and force circulation to keep the room around 105 degrees F. I still think it is a bad idea and, at a minimum, it is another system (the ventilation system), that has to be maintained.
RE: Indoor package units?
An A/C or heat pump operates because a temperature difference is created in two places, the cooled air and the waste heat. By forcing the waste heat to dump inside the facility, you still have to remove in from the building, which potentially means an additional air handler. This is additional power that must be consumed and results in a net inefficiency in the overall system.
Placing all this inside increases the noise level. The waste heat is only efficiently removed if there's sufficient air flow over the exchanger. The added noise from the fans might be worse than the original heat.
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RE: Indoor package units?
Given your details, outside with proper corrosive protection and materials will be a commercially probably easily available 'standardized' solution (materials and protection for surface available).
And probably at much lower cost than construction of a complete new room and probably extra protected ducts, fans etc. and still having to protect the rest of your original equipment in much the same way anyway.
' Clima-control' of a room with a huge amount of outside air are a 'not so standard' solution with more uncertain parameters, and not, perhaps, so readily commercial avilable solutions? More untried and uncertain result.
A rough cost spreadsheet (plus/minus 30%) for the two alternatives should convince. Include in spreadsheet all uncertain aspects, even if you cant put an exact cost on them.
RE: Indoor package units?
You are going to be pumping the same air you are trying to avoid directly into the space if you use outside air to try and temper the space. The only way around that would be if you tried to move air from the warehouse space around and not get any outside air. From what you have said I would guess that the warehouse air is probably too warm and more than likely has the same contaminates.
Given this information I would say putting the units inside is an even bigger waste of money because you are probably still going to need to apply the appropriate coatings with all the additional costs associated with coming up with some custom solution and additional equipment to make them work inside.
RE: Indoor package units?
As the delta t decreases in the warehouse between the condenser and ambient air, cooling performance will approach zero.
Buy copper coils or get coated coils if there are corrosion problems....they are cheap and readily available
RE: Indoor package units?
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Indoor package units?
RE: Indoor package units?
RE: Indoor package units?
Either way your whole space contains a certain degree of the corrosive elements that you are worried about outside.
RE: Indoor package units?