Humidity Eating Machine

[Carnak]

I have a challenging project here, constant volume of air for high fitlration rates, a high amount of outside air and I have to maintain 68F and humidity in the 50 to 60% range. No outside walls, no roof, no external heat gain.

So I am using a custom chilled water air handler with a built in 7.5 ton dehumidifer.

Had to have it built in two pieces it has to fit through existing mechanical room doors.



This is the coil section, you can see the 2.5" coil connections for a chilled water coil in the back. The coil visible in the front is a heresite coated condenser-reheat coil



This is a DX evaporator coil which is down stream of the chilled water coil and upstream of the condensing coil



This is the compressor, it turns on when there is a call to dehumidify, its DX coil gets air down to about a 48 dew point, the condenser coil reheats the air and when combined with the heat the fan and motor add, it will supply air at 65F with the low dewpoint.




Blower Section



BAF fan and 15 hp Premium efficiency motor - there are external filter banks in the duct work, fan will be up against about 6 inches of total static

[zw17]

Sweet.

What is this "heresite" coating that you speak of? What does it do?

[Carnak]

heresite is a corrosion protection coating

I deal with salt air problems down here, this unit has a lot of outside air on it

[pstu]

I am pretty impressed. Thanks for posting the pictures and description. Maybe you should publish a paper on this problem and its solution?

Regards -- Pstu

[absoair]

I would love some of that. I have done a few similar to this at the hospital. I love that type of work, every now and then.

Let's see some pictures during and after the install, PLEASE

[Carnak]

its up and running now 3/4 commissioned. I expect to get complaints it is too dry in there now

It is not under a full load yet, was sized for a bit of an expansion. So far holds about 69F and 40% RH. I can drop the temperature it maintains easy enough, I can also raise the humidity as well.

There will be an increase in fresh air on it in the near future, I figure it will naturally hunt towards 50% RH

When it goes into dehumdifying mode it blows 65F bone dry air. This is all internal loads so space temp will hold about 6 degrees higher than the supply air temperature at the moment.

I use the dehumidifier as a reheater when it gets to cold in there as well. So the 'warm it back up' function at the moment is pushing RH down low.

So if it gets too humid it blows dry 65F air, it gets too cold, it blows dry 65F air.

[Carnak]

right now it will blow air with a 48 dewpoint on demand. If they drop the chiller temperature I can get a 45 dew point.

[Carnak]

I am pretty impressed. Thanks for posting the pictures and description. Maybe you should publish a paper on this problem and its solution?

Regards -- Pstu

See I use dehumidifiers when they are needed

I worked for this particular manufacturer back in the day, mainly in the design department. This is about the thrid project I have done with them down here with the hot gas reheat scheme.

York has roof top units that do something similar, except they blow air about a degree or 2 warmer than they draw in in this situation. I have used them here.

Bard offers a similar set up in their wall mounted units, I have used them here as well.

I like the scheme because you use the energy you pay for twice.

[Carnak]

an extra coil, a solenoid and an extra refrigeration line and could do the same thing to a house, it would eat up a little more fan power though

[Carnak]

condensate is coming out at about 0.4 GPM, that adds up over the course of 24 hours

[pstu]

Very interesting. What wattage does it draw at that rate of work?

Thanks -- Pstu

[Carnak]

hard to say pstu, 15 hp blower motor, the chiller does a big chunk of the work

But this is a project that needs reheat because of pyschrometric reasons, and the condenser heat doubles as the reheat, rather than burning fuel or using electric heaters

I removes well over '4000 pints per day', compared to the electric reheat alternative, it pays for it self fast, in less than a year on 24/7 operation

[madhat]

What, no Desiccant dehumidifing



BTW, still can't get desiccant dehumidifier to work, they want 50 to 85% (Adjustable by lab personal) at 4.0 C. Wondering if this is even possibly, as no ones desiccant graph goes this low.