100% RH through fans

[JohnWeal]

We have 4 fans vertically mounted pulling air from a plenum and delivering into a plant room throu louvres. Flow rate is 60,000m3/h per fan with only 3 fans running at any one time. Each the fans are long cased axial type with internal motor.

The manufacturer states that the maximum RH for the fans is 95% and if this is to be exceeded, the manufacturer has to be notified of this.

Why is the 100% likely to be a problem? Is it the motor? Or is condensation likely due to pressure changes within the unit?

Also, has anyone any experience in mounting fans such as these within a structural floor which currently has a square void for accepting the fans.
There will be louvres on top of the discharge. The flanges has flanged ends which I assume would have a ring adaptor plate fitted to bolt down via anti vibration mounts from the floor above. Which in effect means the units are hanging from the floor above. This detail TBC with manufacturer. The units weigh approx 900 kg each.

Regards
John

 

[GT-EGR]

I think almost all equipment manufacturers will put that upper 90 or 95% limit, and it's likely applicable to anything that isn't meant to get wet. If you have a space that close to dewpoint, the equipment is going to get moisture on it anytime the space temp rises and your fan surface is a little colder and doesn't get up to temperature as fast.

Why do you want to install the fans directly in the structural void? Depending on the type of fan you have, the box fan types can usually come from manufacturer with something called a wall mount kit. This is essentially just a built up frame - which is something that passes through the opening, and on the non-fan side has a flange to connect that end into the slab, and on the opposite side it will have a flange that the fan can get mounted directly onto. What I described I know from experience with sidewall fans, but I have to assume there is an option to do the same thing with a horizontal opening.

Link to what I'm describing:

https://content.greenheck.com/public/DAMProd/Original/10001/451424WallmountCollar_iom.pdf

 

[berkshire]

JohnWeal,
Most of the long case or Tube Axial fans have a 95% Rh rating, then as a general rule right after that it says , " For controls non condensing.", however for the most part the units are fitted with a TEFC motor so unless you actually have a stream of water impinging on the unit you should not have much of a problem. Usually these fans are simply bolted to a paired flange in a duct or to a flat plate with a matching holes. As far as vibration mounts go , a lot depends on the fan type, in some fans they are part of the motor mount , in others The whole fan is mounted on isolation mounts and canvas sleeves are used.
Is this the type of fan you are using?

https://www.globalindustrial.com/p/...rackCatKey=6981&webCatKey=5463&presentType=99

B.E.

You are judged not by what you know, but by what you can do.

 

[chicopee]

Think about 100%RH is. 100%RH might have well be water being poured on electrical equipment.

 

[chicopee]

I am rereading my response and it looks terrible. This is what I meant: Think about the meaning of 100% RH. 100% RH when weather is forcasted in newsreports means rain, so in essence the manufacturers do not want water poured on their electrical equipment.

 

[EnergyProfessional]

Draw-through fans downstream of a cooling coil are exposed to ~100% RH. But since the motor and controls electronics in the air stream are warmer they are above dew point.

 

[Drazen]

I have lot of experience in fan mounting, and that experience says: fans are mounted according to desired performance and fan curves scrutiny is a part of that performance assessment.

Dimensions of available space can have its importance, but that's secondary issue.

So, roughly, if your axial fans are specified to such from the plenum, it is possible that they have low available pressure drop, against large flow. That means: if you put them in confined space with enough resistance to flow, they can either deliver below performance, or be completely suffocated.

Their capacity can be checked from specs. Resistance of concrete opening is another story, it relies much of concrete walls interior surface finish and can easily vary in, say, 1:5 range. It's, therefore near to lottery to just put them where they can fit, without all proper checks.