Thread Number: 84923  /  Tag: Air Conditioners
2-pipe Hydronic heat/cool. One Question for the Experts
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Post# 1093890   10/20/2020 at 18:47 by warmsecondrinse (Fort Lee, NJ)        

I'd like to run a situation by you to make sure I haven't missed anything major.....

My mid-60's building ( ~200 apartments and 14 floors) has a 2-pipe heat/cool system. The air handlers (aka 'terminal units') are original. At the latest board meeting (just before the switchover from cooling to heating) a number of people complained that the units were "damp", "smelly", "moldy", etc. A sufficient number of people agreed to authorize the board to 'look into doing something about the situation'.

Every spring the building crew checks units to make sure condensate pipes are clear & functioning. They also change the air filters. The building is responsible if something breaks but owners/renters are responsible for maintenance.

Given the 'demographics' of the people complaining, I'm willing to bet none of them are aware the units even need to be cleaned, much less how to do it.

I'm pretty sure the laws of physics haven't changed lately so there's really nothing to be done, correct. Perhaps give the condensers and casings a thorough cleaning and make sure the drain pans are flat and tilted properly so no excess water pools.... and that's it, right? Dehumidification during the cooling season is a function of the temperature of the chilled water flowing through the unit in comparison with the temp & humidity of the air flowing over it, right.

I have seen some corrosion of the fins around the edges of the condensers, but certainly nothing at a level that would warrant concern if this were a window a/c unit, know what I mean? i have noticed that the units need cleaning every other month during the cooling season, else mold starts growing. But that's normal, right?

Has condenser design/construction really improved so much since the 60's that it'd be economically worthwhile to replace them? I'm leaning toward "no" but I'd like the advice of some of you experts.

The units certainly have enough COOLING power at present, but I have dehumidifiers totalling 130pts/24hrs capacity running 24/7 and I rarely get the humidity below 55% during the summer.

The ONLY thing I can think of is that the condensers have corroded more in the interior so dehumidification efficiency is lost and mold growth is encouraged.



Post# 1093896 , Reply# 1   10/20/2020 at 20:12 by Tomturbomatic (Beltsville, MD)        

Because of the temperature of the cooling water in the system, you do not get the dehumidification with a hydronic system that you do with a system using refrigerant in evaporators. We used to have trouble with the drains clogging in the condensate pans in the convector due to dust and warmer temps of the condensate water in the high rise. The problem is not in your head, but in your system.

Post# 1093966 , Reply# 2   10/21/2020 at 12:59 by warmsecondrinse (Fort Lee, NJ)        


Putting aside the tenants' lack of understanding about how the system works and the need for cleaning.......

If the convector is keeping the rooms warm or cool (temp-wise) enough without a problem, how likely is it that replacing the convector would increase heating/cooling/dehumidification efficiency/performance enough to be worth replacing? I'm thinking not very likely. Agree?

I wonder how many condensate pans in the building are warped and/or not tilted properly so condensate pools and sets the stage for a mold fest. I wonder to what extent fixing that would reduce/eliminate complaints......

Thoughts or places to look for info? I've tried run by Dan Holohan, author of "The Lost Art of Steam Heat" but there isn't much there....

Muchas gracias por la ayuda :-)

Post# 1094020 , Reply# 3   10/21/2020 at 23:29 by GusHerb (Chicago/NWI)        

First thought that comes to mind is they're not running the chilled water cold enough. You want it around 40-45, they probably have it running around 55, maybe even higher based on your complaints of high humidity.

Corrosion of the fan/coil unit should have zero effect on dehumidification abilities, even a dirty caked up coil shouldn't necessarily reduce dehumidification abilities (loss of airflow will result in loss of cooling and thereby loss of dehumidification however).

I'm sure going through each unit and checking the fan/coils for any issues that need addressing would be smart, but more so I would find out what temperature they're running the chilled water loop at because that's directly going to affect moisture removal on the type of system you're dealing with.

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