Effects of high humidity

[joemach]

Can anyone give me some idea of the effects of high humidity on a system as regards subcool & superheat? How about Delta T?

I am seeing some low Delta T's where there is high humidity. Granted floor supply with floor returns account for some of this.

[JayMan7]

Well with high humidity you have more btus going into latent heat (this takes away from sensible heat). In other words, you have energy being removed that results in phase change of water and not in a change in temperature of the air. Therefore, high humidity indoors can reduce the delta t some. As far as sub cool and superheat it's been my experience that those are not affected that much. I mean if the charge is correct and the txv is good the subcool and superheat should be fairly normal.

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[R600a]

I would think that high indoor humidity could cause symptoms of high evaporator load at slightly lower temps than normal.

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[ehsx]

Per JayMan7, higher humidity- lower DT, lower humidity- higher DT. The change is in the latent/sensible ratio's. Changing air flow changes DT & latent/sensible ratio.

TXV units should have no change on SSH, SC may be slightly lower with lower humidity.

Orifice units will change a good bit on SC & SSH. Note the differences on the charging charts at different return evaporator air WB's.

[JayMan7]

Per JayMan7, higher humidity- lower DT, lower humidity- higher DT. The change is in the latent/sensible ratio's. Changing air flow changes DT & latent/sensible ratio.

TXV units should have no change on SSH, SC may be slightly lower with lower humidity.

Orifice units will change a good bit on SC & SSH. Note the differences on the charging charts at different return evaporator air WB's.

Oh very true! I completely didn't think about pistons. Definitely the reason charging with target sh and wb is so important.

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[joemach]

Great explanation guys. Thanks.

Makes total sense now. But to tell the truth, it was something I already learned/knew. Just needed confirmation

[TechmanTerry]

I'm gonna say that the higher humidity does not change the operation of the CU ,due to, the CU is operating on a TD between the HOT freon and the "air". The "air" and the hot humidity/water are both at the same temp.

[beenthere]

I'm gonna say that the higher humidity does not change the operation of the CU ,due to, the CU is operating on a TD between the HOT freon and the "air". The "air" and the hot humidity/water are both at the same temp.

With high humidity in the conditioned area. The refrigerant returning to the condenser, would be warmer than if the humidity was low. So the condensers SC would drop some from normal operation.

[joemach]

With high humidity in the conditioned area. The refrigerant returning to the condenser, would be warmer than if the humidity was low. So the condensers SC would drop some from normal operation.

This is all great info.

Sometimes I am so fascinated by the physics and technology of the trade.

Makes me so proud to be part of it.

[mpenney]

I just had a post about humidity issue and low SH, high suction, low head and low subcooling....

[R600a]

I just had a post about humidity issue and low SH, high suction, low head and low subcooling....

That is almost exactly what I came across today.

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[TechmanTerry]

I'm gonna say that the higher humidity does not change the operation of the CU ,due to, the CU is operating on a TD between the HOT freon and the "air". The "air" and the hot humidity/water are both at the same temp.

I did limit my response to the CU only.