AmericanStandard air chillers/heaters

[warmsecondrinse]

The maintenance guys came in to clean the condensate drains and otherwise prep the 2 units in my apartment for summer switch over. I asked him the temperature of the water flowing through the heat exchanger when it's in cooling mode. He told me 60-65F. I raised my eyebrows as I thought it'd be more like 45-50. I commented that there can't be much dehumidification with such a small temperature differential. He agreed and suggested putting a container or 2 of Damp-Rid in the corners of the inside of the unit. I smiled, nodded, and kept my mouth shut.

My question is this: How can one compute the actual rate of dehumidification? For that matter, how much cooling could there be? Should I get a dehumidifier? I cannot handle humidity.

The heat exchanger has a vaned volume of 36"x8"x4". I don't know the flow rate, but I believe it is constant as there's a small amount of heat flowing out now when the unit if off. I don't know if turning on the fan opens a valve to increase the water flow. There is NO thermostat. One manually turns the fan on or off. There are 2 squirrel cage fans in each unit and even on low the output is very impressive.

Heating season water temperature is 120-125F. I can tell you that on all but a few nights this winter ONE unit was able to keep my 950 sq ft (8' ceilings) apartment toasty warm and the window/door seals are NOT good.

Every person I've talked to here, including the friend who seduced me into this building says the units are more than adequate in the summer, no matter how hot it gets.

I'm not an HVAC expert, but I'm having difficulty reconciling these water temps with overabundance of heat and the apparently more than adequate cooling. More to the point I'm worried about being stuck with a cool, clammy apartment come summer.

Any ideas?

Thanks,

Jim

 

[gusherb]

If someone told me that I wouldn't believe them. It should be anywhere between 40-55 like you said. If it's warmer somethings wrong with the system. I don't think you'd have hardly any cooling with a chilled water supply temp of 60-65.

If it were my place I'd wait til they finally do start the chillers and go from there. Worse comes to worse you'll probably need a dehumidifier.

 

[retro-man]

I live in a building that has this type of system also. I have a thermostat that controls the blower motor. From living with this system the flow rate through the coils is the same with or without the blower running. In the winter I also have heat that rises through the system and comes out the main vent. The 2 bedrooms have vents also. In the summer when the chillers are on I usually have about 55-60% humidity. I live directly on the ocean so moisture is higher. I do have a dehumidifier to help it down to 45-50%. Cooling is adequate except on really sunny days when I have to close the blinds to eliminate the sun exposure. When I am gone for 2-4 days and leave the blinds closed and the unit on it will be 68-70 degrees when I return. During summer nights it will get into the mid 60's. So I guess the water in this system must be lower that what you have or they were giving incorrect info. I know 2 winters ago the thermostat shorted out while I was not there and upon returning 5 days later it was 106 degrees in my condo. Not sure about the temp of the water flowing through but will check the output temp once the system comes on in June.

Jon

 

[iheartmaytag]

at work

our building uses the water chiller type of cooling.  It keeps the building comfortable for temp, but the humidity is very high.  When we first moved the offices we were having a lot of problems with the humidity, now that we have been there for awhile everything has stabilized and we don't feel it anymore.

 

I actually looked in our copy room yesterday, as the copiers were having the hardest time with the humidity.  The temp was 75 and humidity was 77.

 

 

 

[warmsecondrinse]

Thanks all for your input. I suspected that the cooling temp was a bit high.

I don't handle humidity well. I never have and it seems to bother me more each passing year. Wherever I've lived I tend to 'under air condition' my place (in terms of btuh's) so the units run longer to keep the humidity down.

I guess I'll pick up a dehumidifier as soon as I can free up some cash.

Thanks again,

Jim

 

[toploader55]

Hi Jim

Back in the 70s when I was a Junior in High School I worked after school for one year for an appliance store. It was during the time that WCI was making Kelvinator and appliances were beginning to go down the crapper so to speak.

We sold Chrysler Airtemp Air Conditioners. They were beasts. The Titan series which ran 18,500 thru 33,000 BTU weighed a ton !!! Back then except for the front grills that were made of mostly plastic, the units themselves were steel. So a 33,000 BTU weighed in at about 250 lbs.

All the Airtemps blew Ice Cold Air.

And I always remembered the salesmen telling customers that it was better to undersize a slight bit so the unit wouldn't cut out and redeposit the moisture back in the air to make the room "clammy".

I attached a link to the Airtemp brochure I scanned years ago.

1971 Chrysler Airtemp Brochure

With my idle time this winter, I've been going through boxes of "stuff" and found this

www.automaticwasher.org

 

[cuffs054]

Warm, any chance you could get the maintence man to let you take pictures of the chiller and boiler? Maybe the cooling tower as well.

 

[retro-man]

System is now running

Finally summer is arriving. System has been on for 3 weeks but really haven't need it as of yet. Had it on last night and took a reading. It is blowing out air that is at 58 degrees. So no frost build up on the vents at that temp. After thinking about this type of system I believe that these have more air flow thank a regular compressor system. The air flow is very strong coming out of the vents. Did speak to the building super and he is going to give me a tour of the top of the building soon so I can take some pics of all the equipment running up there.

Jon

 

[whirlcool]

Years ago I noticed whenever I was in a commercial building that used chilled water for cooling you could feel the clamminess in the air and the buildings had a peculiar odor to them. This was mostly in buildings in the south and if the building was built in 1960 or earlier. The buildings where I went to college were like this, especially the administration building.

 

[warmsecondrinse]

Sorry, TopLoader55. I missed this back when you posted. Thanks for the brochure! Very interesting reading. I wonder why the heat pump aspect was not heavily promoted by the electric companies it because it would have resulted in people using more electricity. Post-Oil Embargo, I remember heat pumps getting a brief round of PR (for CENTRAL heat) which faded again for no apparent reason.

Yes, I know the additional ductwork needed to optimize a heat pump for both heat and a/c makes it not cost effective for a retrofit...... but for NEW construction? Sorry, there're other factors involved.

On the same topic, I've always wondered why electric companies never pushed electric underfloor heating as retrofit (if accessible) and new construction. The customer would have a higher electric bill but lower overall heating cost. Win-win for all concerned.

Back to topic:

Yup, 'undersizing' is very important IMO. I follow a '5 for 8' rule: If 8K btu's are supposedly needed, I buy a 5K unit. I've done this for years and have had no complaints yet

I bought a 30 pint dehumidifier set to 45% and the units runs constantly. I have it on 24/7 unless I know I'll be out of the house longer than it'll take for the bucket to fill. I should've bought a 50 pint unit, lol.

I just found a little electronic thermometer/hygrometer combo with and outdoor sensor. I'll take some readings and post.

I'll need to ask around to find out whom to talk to about seeing the machinery. While everyone working in the building of 400+ units is polite and professional, the mentality is definitely "Only plumbers are interested in or concerned with plumbing". Still, in a building this size I'm sure there's someone who understands the concept of geekdom.

One question so I can maybe get some 'ammo' to use: This building went up in the mid 60's. Is this system for heat&a/c unusual in any way? Is it still used widely? I'm looking for something factual about the system to explain why my out-of-state friends who are HVAC pro's would love for me to get pics and tech specs.

Thanks,

Jim

 

[gusherb]

Chilled water cooling is not uncommon in larger buildings, and still is widely used to this day even in new high rises/large complexes etc though it was far more common in the 50s-70s. Later on "packaged rooftop" units took the place of one single chilled water system for smaller buildings, department stores etc.

A few examples would be: a Kmart by me (was originally Venture), the building was built in 1975, originally had a central cooling plant using chilled water and a few very large air handling units. Later on they converted it to 6 very large packaged rooftop systems.

There's a Menards here (like Lowes and Homo Depot for those of you unfamiliar), occupying a 1970s building and they to this day have a central cooling plant using chilled water (the setup is very similar to how Kmart had it).

The Morton Arboretum visitor center in Downers Grove, IL is a fairly large single story building, a very nice place and used for large events. It was built in 2004, and again they chose a central heating/cooling plant over packaged rooftop units. Presumably because of the architecture of the building would prohibit having rooftop units spread everywhere.

As for chilled water systems not dehumidifying well enough, that issue is simply an engineering error - too much airflow across the evaporator coils and/or too warm of a loop temp.

I can use the last two mentioned above places as examples of places that cool with chilled water and do not have this problem. I was at the Morton Arboretum visitor center for a 500 person wedding July 2nd 2011, which was sunny, exactly 95 degrees with a dew point of 75 degrees (that means oppressively humid like down south, the heat index was somewhere around 115).

Meanwhile inside with 500 people packed in, the occupied areas still managed to maintain 70-72 degrees with a RH in the 45% range, and later on 68 degrees in the dining area with people dancing, food being served etc. it was what one might say "dry as a bone" inside.
It was so humid outside that the glass wall later on started sweating on the outside like crazy.

I have been in many other places that use chilled water and never noticed a problem with clamminess either.

 

[arbilab]

Juzbout everybody sells electronic temp/humid meters. I've had at least one over 10 years, two right now. They track each other pretty closely but not always exactly.

77% humidity at low-70s temp is clammy. Warmer, swampy. 65F supply temp for a chilled water system is.... wrong. It should be no higher than 45-55. And indoor conditioned air should be no higher than 40-50% RH.

 

[warmsecondrinse]

Readings as promised

Thank you all for your input. I used the temp/humidity doohicky I found.

I stuck the sensor through the grill of the unit. I let it hang about 6" above the coils. After 10 minutes I had a reading of not quite 54F. I'm confused by the humidity reading, though. I'm pretty sure if the humidity actually were that high my sinuses would be extremely swollen and they're only moderately so. According to the dehumidifier the humidity is 65%. I have the unit set to 45 and the compressor never turns off.

The doohicky is still in the bedroom and reading 73F & 59% as I type this. The readings match how I feel: Still too damp for me, but certainly better than the halls or lobby of the building and better than the outside.

I should explain that I'm a bit more sensitive to humidity than most people. I have sinus problems, very oily skin, and I sweat A LOT. Add high humidity and the result is NOT pleasant.

To summarize:

1. With a discharge temp of about 54F, the air chilling system is doing its job properly. Am I correct in that?

2. I should probably get another dehumidifier for the bedroom if I want lower humidity, yes?

Thanks,

Jim

 

[gusherb]

53-56 isn't too bad, our central Systems put out air around 50-52 degrees and they dehumidify extraordinarily well. The RH on the outlet is usually higher because of the low temperature, but 87%RH seems excessive even at 56 degrees, which means the air it's blowing out has a dew point of 52 degrees which is just above what's considered the maximum you want the indoor dew point to be - 50 degrees, as anything above that is usually considered uncomfortable.

59 % RH at 73 degrees brings a dew pt of 58 degrees which is way too high for it to be considered comfortable. Something isn't right, whether it be lots of moist outside air getting in, too high of a loop temp, or too much airflow across the coil.

Going from the looks of that grille in that picture, is that an under-window type of fan/coil unit? Does it have an adjustment for fan speed? If not, if possible try an experiment of partially blocking the return with some paper to reduce the airflow and do some measurements again and leave it that way a little while to see if the humidity is reduced.

 

[retro-man]

Jim your system is a different set up than mine is. I have a main blower in the wall and duct work going to the different rooms. In the main unit is a drip pan under the coils that collect the water and funnel it down a drain. The water is usually running down the drain quite well when in use. Do yours have a pan under connected to a drain? If not or they are blocked, would cause excessive humidity. Mine usually will not get over 50-55% even on the most humid days.

Jon

 

[cuffs054]

Warm, does that unit have a filter? You may want to check. If the coils are really dirty you can trap moisture that should go out the drain in the dirt.

 

[warmsecondrinse]

Hello all,

 

Sorry, I've been working late these past few evenings. I'll check everything Friday/over weekend and post.

 

I've checked and filters are clean. Humidity consistently reads 80+ % from livingroom unit and high 50's from bedroom. 

 

Yes, there is air infiltration but there seemed to be little from within the units themselves when I checked during the winter.

 

Jim

 

[arbilab]

What is the measurement system? Relative humidity (%) is referenced to temperature. If you're putting an indoor temp/RH gauge right in the outlet air, that's not how that gizmo is intended to work and the results can be misleading. I mean, that's about the only way-- other than a swamp cooler-- to get RH readings of 80%+. I've seen (room) readings as high as 77% with the system off overnight and windows open. But that quickly resolves with the system running. If you chill the humidity sensor by putting it in the outlet air, I'm pretty sure it's going to read disproportionally high.

A sloppy conversion factor is 3% RH for every degree temp is above dewpoint. IOW, if the temp is 75 and the dewpoint is 74 the RH is 97%. The more diff between temp and DP, the greater inaccuracy in that conversion.

 

[warmsecondrinse]

There was significant air infiltration in the livingroom. I've just finished sealing all the gaps I was able to find and reach. There's a much smaller amount through the unit itself but I cannot reach through the pipes, etc. to do anything about that. The bedroom has little that I've been able to identify. 

 

The units are motel-type under window models. They have no thermostat, just a fan switch. Low has provided more than enough heat and cooling (in terms of temperature) since I moved in here in December.  AFAIK, all the units in the building are the same size. My friend's apartment has one unit for an open living room/kitchen/dining room that's almost the size of my apartment. The coils are cold so it's safe to say that water recirculates 24/7. Both filter and coils are clean.

 

I have the temp/humidity gizmo on a table about 6 feet away from the unit (which is off) and it reads 71F and 53%. Dehumidifier reads 60%. It's quite cool today so if I run a unit for more than a half hour it gets too cool.

 

I suppose it'll take a day or so to see if my sealing up the cracks has any effect. 

 

Another thought occurred to me. Assuming the compressor is running constantly,  a conventional a/c unit effectively dehumidifies the indoor air at the same rate because the coils are so much colder than the indoor air. I.e. indoor air temp of 70 vs 80F does not result in a huge difference, correct?

 

With an air chiller, dehumidification occurs as a result of the temperature differential between indoor air and the temperature of the water flowing through the coils. The temperature differentials are much smaller. If the coils are 50F (just to pick a reasonable number) there'd be significantly less dehumidification at an indoor temp of 70F than at 80F. Is my reasoning correct?

 

Is there anything else that might be done? Or should I start scoping out a quiet dehumidifier for my bedroom?

 

Thanks again for all your help and advice.

 

Jim