RTU with 50 F coil discharge and modulating hot gas reheat.

[WAYNE3298]

I'm doing some work for a nursing home and would like to find a roof top unit that will dehumidify the air as needed but would like to avoid desiccant drying. The owner likes Lennox units so do any of you know if they make a 5 ton RTU that will cool the air to 50 F and reheat it with modulating controlled hot gas reheat to 58 F dry bulb?
Other manufacturers are OK if he can't get the Lennox he wants.

[heatingman]

Lennox does not make that. AON most likely has a unit like that, maybe Munters too.

Im sure theres others.


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[rider77]

Modine Atherion
JCI/York also have a hot gas reheat option in their packaged equipment. A duel enthalpy kit is required to make it run off of indoor humidity.

http://modinehvac.com/web/products/c...m.htm#content3

https://www.johnsoncontrols.com/-/me...D97B145916A358

[WAYNE3298]

Lennox makes a unit with modulating hot gas reheat but I couldn't find one that would produce 50 F cooling coil discharge air. I think Aon and Munters both make such a unit but aren't they a lot more expensive?

[WAYNE3298]

rider can the ones you listed produce 50 F coil discharge air?

[rider77]

Not certain about exact discharge temps.
Could call them and see, Modine is very helpful. JCI isn’t bad either.
Modine is good about selling exactly what the customer needs.

[WAYNE3298]

I plan to make some calls Monday. Just trying to get an idea where to call. The internet hasn't been much help so far. I'm not exactly in the loop now being semi-retired.

[rider77]

The Modine is a very nice unit. Extremely well made, has a Carel controller to run the unit, Copeland scrolls (some have digital unloading scrolls), easy to service, available with a condensing gas burner/a non condensing standard furnace/electric heat. I haven’t found much I don’t like about them.
Software updates for the Carel are easy but the process is difficult, they do have microchannel condensers, and units featuring gas burners can be tricky to set up (low fire gas pressure is 0.25” WC.)

[coolcoil]

If this unit uses a high percentage of outdoor air, then you want a DX-DOAS unit. Essentially it looks like an RTU but is designed to cool air and reheat as you describe. Some of the brands listed above are that kind of unit. They are typically used with 100% outside air and some kind of zone cooling like VRF, but many are capable of some recirculation.

Besides those companies listed above, both Trane and Daikin offer them as well.

Just type "DX-DOAS" into your internet search engine and you will get plenty of leads as well as some good info on how these units work.

[WAYNE3298]

Thanks all!! I knew you would have good info. The facility has a lot of problems. The first corridor of rooms balanced pretty smooth but no humidity control. The rest of the building was straight down hill with problems. The physical problems are almost all taken care of but a place like a nursing home puts a lot of moisture in the air that needs removed. I am going to recommend installing make-up units over the corridors to pressurize the corridors but want the 50 F coil discharge and modulating reheat for humidity control.
With Lennox and Daikin being connected there is a good chance they will go with Daikin. If I can get them to install the first unit over the first corridor the results should get them to do every corridor one at a time.

Thanks again and BBeerme was right once again. Collectively we know it all. I like the we part because being part of the we without knowing much individually I finally know it all and it's not even an arrogant statement. Never thought that could happen.

[71CHOPS]

we had a similar discussion at our last safety meeting. between the individual skills each of us possess, our company can tackle pretty much any task.

the knowledge base here is limitless.

[VTP99]

.

[WAYNE3298]

That's an excellent article VTP99. I'm not going to design this but will help an engineer friend of mine so this will come in handy. The owners know they have a problem but have only recently begin to make a profit. They do realize keeping the residents happy is very important.
I'll let you guys know if and when anything comes of this.

[icy78]

Daikin Rebel too I believe.

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[heatingman]

Lennox makes a unit with modulating hot gas reheat but I couldn't find one that would produce 50 F cooling coil discharge air. I think Aon and Munters both make such a unit but aren't they a lot more expensive?

Probably alot more expensive


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[Scoobie]

Daiken rebel, Trane horizon, Aaon “name” I can’t recall.

Several units that can work in this situation.

None are cheap. All can handle lots of outside air, cool it way down, reheat with discharge gas.

There are more reasonably priced units with hg reheat for more normal duty. That is, not so much outside air.

[Scoobie]

And, the modulating hg is no biggy. The modulating compressor to keep the coil leaving temp at 50 is the big deal.

[WAYNE3298]

Last I heard they are seriously considering AAON.
Thanks and as always some good info given.

[Cool breeze 38]

I have a building that has a Carrier 48LC VFD drive and 3 stages of cooling that work on a single evap.
I run the first stage of cooling and modulate the vfd to get a 40 deg suction line temp. Im discharging at about 42 deg sat I then control the first stage of gas heat for reheat. I reheat based on space temp.
with stage one cooling and a 34% vfd speed I don't have an issue over cooling.

[coolcoil]

I have a building that has a Carrier 48LC VFD drive and 3 stages of cooling that work on a single evap.
I run the first stage of cooling and modulate the vfd to get a 40 deg suction line temp. Im discharging at about 42 deg sat I then control the first stage of gas heat for reheat. I reheat based on space temp.
with stage one cooling and a 34% vfd speed I don't have an issue over cooling.

Just curious - what is the reason for running such dry air?