What do we need to do to get our Central Air working well?
March 15, 2017 11:25 AM   Subscribe

We've replaced both the furnace and AC units, but heating and cooling are really uneven through the house, no matter what we've tried (opening/closing vents, adjusting the dampers in the ducts, keeping unused room doors open/closed, etc.). We've been told by other people in our community that the ducting in our units isn't designed very well. What are our next steps? What kind of professional is best to have come in to evaluate the system? Bonus points for specific recommendations in the northern NJ area.

We bought our condo two years ago, which means we've had two summers in the place. The first summer, we thought the AC wasn't working as well as we hoped, but we dealt with it as we were adjusting to being new homeowners and had tons of things to deal with.

Before the second summer, we had the furnace, AC, and hot water heaters replaced through a state program that was designed to increase overall energy efficiency (they also reinsulated the whole house). Everything was pretty much at the 20 year mark anyway, so we figured it made sense to take advantage of this program and replace everything before they had a chance to break down on their own.

Then last summer hit, and we had constant problems with the AC. It was almost once a week through the entire summer where the coils would freeze up and the air would stop moving through the system. We had the company that installed the stuff come out several times to investigate (since this was the first time the AC was being used), and they insisted that nothing was wrong with the equipment. The explanation I was given was that during heat waves, there's more demand on the power grid, and sometimes you're not being delivered the normal amount of power, and so the fan isn't receiving what it needs to blow the air over the coils. This seems insane to me. I could understand if it only happened once or twice during crazy heat waves, but this was happening almost weekly for us. Plus, it's a brand new unit - it shouldn't be freezing up!

In addition to the freezing coils issue, we found that the AC couldn't keep the main, open areas (kitchen/den, dining room, living room) and the upstairs bedrooms cool, but the master bedroom and bathroom would be an icebox. The same happens in the winter - open areas are cold, but the master's an oven. Obviously something is out of whack with the ducts, but we've tried everything we can think of to fix it ourselves.

When I asked about it on our condo community's internet discussion board, I learned that the ducting wasn't designed well (lots of bends) when the units were built (early 1990s), and that they really should have made it multi-zone. A lot of our neighbors experience problems with uneven heating/cooling. Some people solved the problem by installing attic fans, which sounded like a great idea. But when we had a company come in to give us a quote, they told us that it probably wouldn't make sense for us, since our attic was really well insulated.

I can deal with a cold house in the winter. What I cannot deal with is the stress of having another summer like the last one - never knowing whether the AC will be working that day, not wanting to invite people over in case it gets too hot, not wanting to use the stove because it'll heat up the house unbearably, etc. We'd like to get whatever the issue is corrected before the weather starts getting warm.

So, what should we do? Who do we contact? And how do we make sure we don't end up spending a ton of money on something that still won't fix the problem? And does anyone have any specific recommendations for companies in the northern NJ Essex County area?
posted by MsVader to Home & Garden (10 answers total) 1 user marked this as a favorite
A good HVAC company should be looking at ducting and air flow issues. Every time I've had major HVAC work done in any house I've owned, a major part of what they have done is actually do the measurements and calculations to figure out how much airflow is required, and use that not only to size the equipment, but to evaluate the needs of the ducting and (very importantly) returns. It's an entire system that needs to work together and be sized correctly to work. I'd seek out another HVAC company — one that will take the time to do the necessary measurements and calculations. It may turn out that your air conditioner is undersized, or that your ducts need to be replaced, either of which could be expensive projects. But it's better to know that than not (and if you know that stuff, you might also be able to make more informed decisions about less expensive workarounds).
posted by primethyme at 12:06 PM on March 15 [3 favorites]

The original occupants of our house removed an interior (load bearing) wall which originally held giant (they left the useless ducts in the ceiling (along with a brick)) which we found when we needed to take down the ceiling to have an engineer draw up plans to fix their half-done work. They had routed small 3" circular ducts through the exerior walls up to the bedrooms (and didn't add any air returns). Which is to say they majorly ruined the airflow for the three bedrooms and bathroom. Typically there'd be a 5-8C difference (9-14F) between the main floors and the top floor (the house is a side split).

The upstairs vents are 4"x10" rectangular; we bought vents that have a plugin fan. They're not hard wired in, they're just normal 120v AC plugs. There's a temperature control that one can set so once there's some heat/cold air in the vents it detects this and auto-turns on, thus pulling air rather than just being a passive vent opening. We just put this in the two used bedrooms, not the guestroom nor bathroom, but it's had a noticeable effect on the entire area. I think they were $40 CDN per vent.
posted by nobeagle at 12:24 PM on March 15

Is it an outdoor heat pump for the AC? You have a separate furnace? Electric, gas, what? Your thermostat is where? Intakes? More about the floor plan?

The icing up thing explanation doesn't make sense to me either. Been through that a few times and I think it always involved the compressor.

Can you rent a camera and snake it through the ducts? You might need them cleaned after 20 years. What kind of ducts do you have? Hope not but I'm guessing flex, kind of like a large plastic covered wire slinky-toy that gets stretched around to the vents. That gets done mid-construction and is easily damaged by the other crews that finish the house. The claws of a rodent can perforate it. Especially if the animal is climbing up.

If you open the plumbing access panels or any other holes in walls do you feel air coming out?

More questions than answers here, sorry. I'm dealing with uneven heat distribution myself and I found the remains of something that couldn't possibly have gotten in there. But it did. Trying to figure out how.
posted by Mr. Yuck at 12:56 PM on March 15

Nobeagle makes a good point about return air ducts. Not having sufficient return air capacity from some of your rooms is a possible cause for the symptoms you list. AND, it is a possible cause for coils freezing. The business about the power grid is not. Get a different HVAC outfit to check it out (when it's running in AC mode), determine the real cause(s) and offer a solution.
posted by beagle at 12:58 PM on March 15

Our floor plan is a mess of levels. Basement is where the gas furnace and AC live (there's the outside fan part of the AC - is that the heat pump?). Up a level is where the living room is, half a level up from that is the dining room (thermostat lives here), kitchen/den, master bed and bath are, up another half-level is bedroom two, and one more half-level is bedroom three. All connected by open hallways and high ceilings.

From what we see of the ducts in the basement, they're straight rigid metal. But once they're in the walls, I'm not sure. There are returns in every room (except the bathrooms, I believe). And we made sure to keep those returns unblocked. The HVAC guy didn't believe that I wasn't blocking any of the returns, so I brought him around the house to show him that they were, indeed, all clear.

I can't think of any holes in the walls where we'd be able to check to see if there's air coming out. I'll look around for access panels, but I think there may not be any.

I guess a good next step is to get those ducts looked at. When we first started having issues, I looked into getting the ducts cleaned, but there's a ton of conflicting information out there about whether or not it needs to be done.

Also, Mr. Yuck, I'm almost afraid to ask about the remains, but I gotta know...
posted by MsVader at 1:13 PM on March 15

I would ask your condo list if they have recommendations for a good HVAC company. In my experience there are definitely good companies that send qualified techs at a reasonable price, and shitty companies looking to sell new hardware and service contracts who give nonsensical answers like "an overloaded power grid causes your fan to run slower, which causes your compressor to ice up" (I think you would know if your city was experiencing brownouts, and even then I think it would have to be pretty significant to cause icing).
posted by muddgirl at 1:28 PM on March 15 [1 favorite]

I can't think of any holes in the walls where we'd be able to check to see if there's air coming out.

Look in closets that are adjacent to the bathrooms. There must be someway to get to the innards of the plumbing. I wanted to change the angle of a shower head and opened one of those and there was a blast of warmth that should have been going upstairs when the heat kicked on and that got me going on this project.

That outside part is what froze up?

If you pull a vent cover and reach in, is it metal?

It was a late-term pregnant racoon. I think it got stuck and baked trying to get away from the heat. Amazing remains.

Bus dropped off the kids and they came in on that one. Boy said it was pretty cool. Girls: We've been breathing THAT? And snakes. Pretty sure racoon predated our living here. Would have smelled that. We have had surprise snakes in the house, in Winter.
posted by Mr. Yuck at 2:18 PM on March 15

What froze up were the coils on the inside part, where the blower is. Then they'd melt and we'd end up with puddles on our floor. Luckily, it's an unfinished basement, so there's no water damage. But it happened enough that you can clearly see where the water collected.

I've gotten a few recommendations for local places which I'll start calling soon. I didn't know if there was some kind of specialist that would be better to contact than a generic HVAC company/service. I'm just wary of getting more bullshit answers like we got from the company that installed this new stuff. They came highly recommended too, and look where that's gotten me. I hate feeling like a sucker.

By the way, all of these stories of things in the walls and vents are horrifying and fascinating. I hope we don't have a dead thing in our vents, but I wouldn't be terribly surprised. The previous owners didn't take care of the place very well, so I wouldn't be shocked to find shit in the walls.
posted by MsVader at 6:42 PM on March 15

Is your condensate pump working?

Do you hear your compressor running for a really long time before the central fan kicks on?

Also, see if you can rent a thermal imaging camera. Interpreting the data can be challenging if you're not quite sure what you're looking for; you could get a lot of false positives/things that are normal, but you might also see some overly cold joist bay where all the cold air is leaking out of a duct.

I was just doing some work in our basement that involved opening up some of a ceiling and I discovered hot air blowing in a joist bay that had duct work in it that went to two rooms with poor heat!
posted by MonsieurBon at 9:49 PM on March 15

My sister discovered during their kitchen remodel that one of their return air ducts was open to the attic. Closing that up helped the air handler efficiency.
posted by LoveHam at 4:44 AM on March 16

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