Air Conditioning

It depends. With building-wide central AC the co-op or condo pays to chill the water and pump it to all the apartments' HVAC units. If that system is efficient the added pumping cost, and the added cost to cool areas that don't need it, is less than the cost of electricity you'd pay to run your own ACs.

You still pay directly to run the fan that circulates the cooled air in your apartment, but that shouldn't be much.

Or in other words, maintenance/CCs are higher with building-wide central AC than in the same building without it, but your share might be less than running your own.

Thank you, I was surprised when the broker told me this b ecause I want to be able to run the a/c whenever I want to, and with the HVAC's that isn't possible. Didn't know about the main/cc's also being higher.

But you can run it whenever you want to. The building is circulating the chilled water all the time, and your thermostat controls the water valve and fan in your unit.

The problem is, in most such buildings the chilled water is seasonal, e.g. from May through October. The rest of the year, October through May, the same pipes are delivering heated water.

That's called a two-pipe system: one to deliver chilled/heated water and one to take away the less-chilled/less-heated water.

Some fancier buildings have a four-pipe system, where you can have either heating or cooling in each room regardless of the season.

Didn't know that. Thought it was one or the other. Now I know what to ask. Thanks so much again all of your useful info.!

I live in a building with the two pipe system - it is generally very convenient, and I believe it saves several hundred dollars per year in electricity costs.

We sometimes have a few uncomfortable days right around the changeover point (warm days in October, or cool days in April/May) but they are the exception. Our building can get the changeover done in a few days, and they usually time it very well.

Based on what friends pay for AC in similar sized apartments, I think it saves me about $100 per month in direct electricity costs in June/July/August and probably $50 per month in May and September.

While our maintenance is not cheap, it is competitive with other similar buildings on a per square foot basis, so the utlity savings above feels like real savings.

Finally - you feel no guilt running the AC a lot - so you are very comfortable. Since the cooling plant on the roof is running anyway, the incremental cost of the fan in the apartment is not even noticeable from a cost perspective.

Lanzz, thank you so much for the info. It's much appreciated. As I am always on fire and overheated this is great to know!

"Finally - you feel no guilt running the AC a lot - so you are very comfortable. Since the cooling plant on the roof is running anyway, the incremental cost of the fan in the apartment is not even noticeable from a cost perspective."

This is why I'm skeptical that this approach actually saves money. Everyone ends up overusing air conditioning, which more than overcomes the efficiency gained from the common compressor. Unless you are one of those people who runs your AC all the time and just pays a really high electricity bill, I suspect you come out behind with this arrangement, but it's almost impossible to tell since it's hard to figure out the exact portion of the maintenance that is applicable to cooling/heating.

"Finally - you feel no guilt running the AC a lot - so you are very comfortable. Since the cooling plant on the roof is running anyway, the incremental cost of the fan in the apartment is not even noticeable from a cost perspective"

If your guilt is coming from an environmental or aggregate cost perspective, then you are mistaken. The cooling units run harder when you use more cooling. Your guilt should be assuaged by the fact that you are using an efficient cooling system, and by the fact that leakage of your apt's coolness goes more into the rest of the building rather than out in the air (helping maintain the building's desired ambient temperature), but it is wrong to think that your use of cooling does not draw more energy.

Right, it's tough to quantify. Then there's the eventual cost to replace the in-apartment equipment, which is always the owner's responsibility.

E.g., Olympic Tower has those vertical PTACs in columns between each set of windows. Per http://www.theolympictower.com/contractors.htm each one costs $11,000 to replace, since drywall has to come down, etc.

At 535 WEA the equipment is in closets scattered through the interior of the apartment, so less mess.

Hey Primer05, how is it done at the Laureate? No vertical PTACs by the windows, and no space in the plans for them to be in interior closets, so are they up in the ceilings?

One other advantage of a two-piped or four-piped system is that you are hooked into a massive cooling plant. When you turn on the AC, the entire room will be chilled literally in a matter of a few minutes. Beyond the convenience, this also has efficiency advantages in that you won't need to run the AC early in anticipation of events.

Thanks everyone. All I knew was that when looking for an apartment to purchase I definitely wanted a wall a/c unit so I could use the a/c whenever I wanted to, being that I am always hot, no matter what month it is. And also I clean my filters everyday, and with an HVAC unit it is cumbersome to do so. I clean by soaking the filter, air drying and then spraying with Lysol. With the HVAC units I have no idea what air I am inhaling.

Cleaning filter every day seems a little crazy. Fascinating thread nonetheless.

When it's easy access to the filter, you do it and know that the air is clean. What's so crazy about that?

Clean the filter every day? Really? Isn't all that clean air effort ruined when you take your lungs outside to the street? Or worse yet, the subway?

A central A/C is much more efficient/cheaper than a bunch of those little window units. If the Compressor is located in shady area, or under some sort of vented cover, the efficiency is increased substantially.

Anybody has experience with a post-cooling HEPA-filter? There are also HEPA filters to be installed over the outlets.