Is there a reason to go with rooftop units?

[Paperman]

I own a small retail outlet with 4 separate store fronts. I bought the place for the 10,000' of warehouse in the back as my shop. One of the units is now vacant and its time for an upgrade. Is there a reason why most commercial places use rooftop units for HVAC? There is 14' of roof space over the drop ceiling that could easily house the new system inside out of the weather and with less thermal loss than there is now. Each unit is about 1500' so its not a giant space to heat.

 

[danski0224]

Service access to the equipment above the ceiling can be a problem.

Noise when the equipment is running.

Equipment warranty- residential furnaces and AC units will not be warrantied by the manufacturer when installed in a commercial space.

The RTU has provisions for an economizer and outside air that are almost impossible to fit into a residential type system without lots of extra controls.

 

[readhead]

If it is above a finished space what happens when the unit needs to be replaced. Hanging units inside may involve reworking the roof structure because it places different loads on the structure. You are not going to reinvent the wheel.

 

[Paperman]

These are OLD rtu's currently, just trying to find the best options going forward for both me and the tenants. I need to downsize them as they are 100K BTU units now and thats a bunch more than needed. I think the prior owned bought some take off units from a larger store and used them as they were cheap.

 

[readhead]

When I was in the crane biz we lifted a lot of RTU's. Usually all that is involved in a retrofit is either a new curb or a new flashing over the existing curb to install the new unit. You are not married to the size unit you have. Any commercial HVAC contractor can accomplish this. It's done every day.

 

[Milton Shaw]

One of the Home Depots here enlarged the building and the rooftop units were to far for any crane to reach and replace. They closed the store one Sunday and starting at midnight on Saturday, they used helicopters to lift and install the new units and remove the old ones. I would have loved to see it but was out of town that weekend.

 

[OccupantRJ]

Rooftop units help prevent vandalism and theft of the units. Filter changes require roof top access though, at least on the ones I dealt with. The units just sit on a roof curb with seals underneath to prevent air leakage. The unit overhangs the roof curb which flashes it for water infiltration. We used a boom truck when a unit needed to be replaced. We had one in the center of the roof that we did Egyptian style on plywood and pipe rollers from the roof edge to the roof curb. The roof curb is specific to the unit base and air outlets/ inlet locations, although some curbs can be modified to fit certain units.

 

[JamesFromAustin]

Our retail has roof top - I hate it. Can't go see what is going on with it on my own, even for simple problems like changing filters - too damn scary to climb up there. In our situation, there is no other place for it, parking spaces would be taken up. And vandalism as mentioned. My hunch is it also reduces a lot of the infrastructure requirements, such as line sets, electrical runs, condensate drainage lines, ect... never really studied them, but they may also be all in one, meaning compressor and condenser located in one unit, rather than being separated like a home unit.

 

[OccupantRJ]

Our retail has roof top - I hate it. Can't go see what is going on with it on my own, even for simple problems like changing filters - too damn scary to climb up there. In our situation, there is no other place for it, parking spaces would be taken up. And vandalism as mentioned. My hunch is it also reduces a lot of the infrastructure requirements, such as line sets, electrical runs, condensate drainage lines, ect... never really studied them, but they may also be all in one, meaning compressor and condenser located in one unit, rather than being separated like a home unit.

The ones I have dealt with were self contained package units, some were heat pumps, and some were gas packs. My home unit is a ground level package heat pump, but it can be converted to roof top duty by rearranging the inlet and outlet ports locations. As far as condensate, it usually just drains onto the roof.