high humidity in my house

plumbergid

would anyone have answer to high humidity in chilled water high velocity system what can i do to get humidity from 65 to 45-50

Jamie Hall

Is that percent relative humidity? And at what space temperature? And how many air changes per hour?

The idea will be to get the dew point of the supply air low enough. If the air temperature is 70 and you want 45 percent relative humidity, you need to chill the air to below 48 F and then reheat it.

mattmia2

Slow down the airflow to drop the supply air temp. How long are the cooling cycles? What is the supply and chill water temps?

HVACNUT

Air seal the house.

Oversized system?

Air handler in attic with leaky return ducts?

pecmsg

Chilled Water High Velocity system?

Make and model please.

plumbergid

this for Jamie

yes that is 65 RH

Space temp is at 72

i have an hrv that's doing 110 cfm for air change in a two level house with 1300 sq ft per level the HRV is dumping fresh air into the return 6 feet before the cooling coil and the HRV exhaust to outside is 3 feet before the fresh air also into the return air a hvac.

i had next to no condensation of off my chilled water coil until i cranked down my air flow through coil and dropped the chilled water temp to 32 degrees Fahrenheit (which is kind of low) i am reheating also but than the hvac is not quite keeping up what do you recommend i have the reheat temp it is a hydronic hot water coil

also i am afraid i am putting excess moisture into my ducts and creating mold with reheat is that possible?

plumbergid

this for HVACNUT

It is a new house and to my opinion very tight house

as for oversized i am not sure but i know my basement needs next to no air conditioning so when the chilled water is going the basement damper is closed it is a vfd operated hi-velocity system which claim you want 1100 to 1200 fpm per minute out of every diffuser in the house which is in my opinion to high (but not scared to be proven wrong)i have it cranked back to 950 fpm and than can bring the RH down only to 55-58 so wondering what you mean with oversized could that be an issue?

Jamie Hall

Not in a position to run all the numbers right now, but that HRV isn't helping you a bit. Consider: all the moisture it is bringing in from outside gets into your inside air unless it is taken out on the cooling coils.

You want to crank that chiller coil as low as it can safely go — and since it is water, 32 is it. Then crank up the air flow in the return (not the HRV) and the chiller power to run as much air as you can to get a discharge air temperature from the coil not higher than 40 (lower will be better)..

mattmia2

i believe an erv would bring in less moisture, the hrv is making it so you're essentially trying to remove the latent heat from outside.

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1862216#Comment_1862216

This is true — but in a colder season, the latent heat recovery benefit of an ERV is more than offset by the potential for poorer (maybe much poorer) indoor air quality, and you can't just switch the operating mode from one to the other — they are very different beasts.