A/C Repair guy said don't block the 2nd floor registers.

[NiceGuyEddie]

Hi Guys. A/C guy came to replace the capacitor and inspect the whole system.

I have a 1700 sq. ft. two story home with three rooms upstairs. I don't use the upstairs rooms very much in the summer, so I close the vents. I also close all the doors upstairs. The HVAC system doesn't do a very good job blowing to the far end of the house downstairs, so that's another reason I close the vents upstairs.

He said don't so that, and that's one of the reasons the a/c system was strained. He said HVAC tubes need equal pressure all around. Seemed odd to me.

Blower unit is 2nd floor top of stairs, there is a return register there, and also one just below on the 1st floor ceiling. It's a single zone system, thermostat is on the 1st floor if that matters.

:confused: :confused: :confused:

[Pearldrummer7]

I am not an HVAC specialist (and I'd love to hear from one!) but as far as I understand it, you can overpressurize your HVAC system. I was told 0.5" water column is ideal static pressure (just the delta between ambient and outlet above blower), and I should try to balance it while keeping it in that range.

I've yet to set up a sample port for mine, but I've been wanting to. I see some cheaper static pressure gauges online and plenty of guides (such as this (https://www.contractingbusiness.com/service/article/20868162/measure-static-pressure-in-six-simple-steps)) out there.

[Big Blocker]

Eddie,

Your A/C guy is telling you the truth, don't block off the second floor registers. You are asking your blower fan to work against a static pressure it wasn't designed to work against. Also moving air feels cooler than not moving air. that's why your blower works at a slower speed when in heat mode - don't want the heated air to move too fast, it won't be warm when it gets to the registers.

Here's a thought . . . since cool air flows down and hot air rises, you should let the upper floor cool as needed, also keeps the ceiling heat down a bit so attic air doesn't reach over 200°. If your unit is in the attic, well, you get the picture, it's already working in a hostile environment.

Put a small rotating fan at the stairwell to help the cool travel downwards. If you have ceiling fans run them. Even low speed will help distribute the cool air from above.

I live in Vegas, it runs 115° here in the summer months and these things will help out.

Doc

[NiceGuyEddie]

https://www.homedepot.com/p/Frost-King-E-O-Magnetic-Vent-Covers-MC815/100345609

Very strange - Home Depot sells magnetic register covers that are made by our friends from Frost King. You'd figure they wouldn't, right?

Doc: great tip about the fan upstairs, it's a weird layout and the stairs take a turn but I'll definitely leave the doors open upstairs. All three rooms have fans so I'll keep them on - blowing DOWN I assume?

I have no idea the blower works at different speeds heat vs. a/c - thanks for the info!

[acmikee]

does your coil ice up when you close the registers, are the open registers noisy if not don't worry about it. do you have a way of measuring amps? if so check your amps with the registers open and closed and name plate amps...keep your filters clean and water wash your condenser coil.

[GWL]

Here is my take:

If those 2nd floor rooms have ceiling fans there is no need to run them. It would only be circulating the air within the room to keep that room more evenly cooled. It will not help cool the downstairs and that 2nd floor rooms air may actually loose some of its cooling because it's circulating in the room more effectively cooling that room and becoming slightly warmer air. You want that cool air to slowly move it's way down stairs, which it will through the cooling of the floor/1st floor ceiling(conduction) and its movement to the stairway and down (convection). A fan at the top of the stairs may or may not help but I'd think experiment by putting it on low and see how it works, keeping it pointed down the stairs. (You don't want to disturb the rising warm air coming up the ceiling of the stairway.) The return air to the second floor will be the hotter air on the first floor that will make its way along the ceiling to the stairway and up the ceiling to the second floor and move its way along the second floor ceiling. Keep all the room doors on the second floor open to allow air to move in and out.
Definition-Convection: the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.

George

[NiceGuyEddie]

OK GUYS

Interesting stuff here. Turns out the fan at the top of the stairs thing didn't work - the second you get there it's HOT and all it would do is blow hot air downstairs. The blower unit is right there at the top of the stairs, and the upstairs return is there as well, so that would mess things up. ALSO - in the back of the closet that houses the blower unit there is a vent to the outside roof, likely because of the gas heater. I bet if a fan was at the top of the stairs blowing down it would suck hot air from the roof, through the closet, and out the return.

One thing I forgot to mention which might be significant is the entire system is from 1976, except for the outside compressor, new capacitor, and squirrel motor for the blower. I have a simple thermostat on the 1st floor. I have no idea how to measure the amps, and I could not find any water column that is showing the static pressure.

One of the reasons the cold air doesn't make its way to the far end of the house (master suite) is there is a break in the 1st floor duct somewhere. I know this because one day I drilled a hole in the ceiling of the coat closet to run a wire, and cold air spilled out. It's been many years and I've pulled a few ceilings down during renovations, but I have not been able to locate the leak. sucks.

[GWL]

Okay Eddie, it sounds more complicated than originally stated. I'm rambling on here as I think about it all and writing......

Go from simple to more complex. If you think you would be pulling air from that closet you need to plug that up because it's then leaking especially during the heating season and during the cooling. But it's not going to pull air into the house from leaks because the fan is blowing downstairs. It will just move air around within the house. The make up air for the fan will come from air on that second floor. Again, I'm not sure the fan would even work but you should only run it when the A/C is on which is probably not something you would want to do.

Why not call back that HVAC guy and get his opinion on improving the entire system. Go around and note all the weaknesses you can think of to tell him.

Maybe it's time to rethink the entire system. That leak from the hole you drilled may not be coming from a broken duck or leaking one. What they used to do is use the spaces between studs or floor joists, seal them off and use them as ducts to move the air from one part of the house to the other, so it may actually be a duct space between the floor joists.

The water column test is something you do to find out how much air is moving in the ducts. It's a kit I think you can buy and is noted previously.

George

[NiceGuyEddie]

^^^ Funny you should ask... the technician did give a quote for replacing the whole thing, he did say the compressor outside will last "x" more years and it might be a good time to replace the whole thing with something energy efficient. The HVAC system is actually the only original thing in my entire home, everything else has been replaced.

As time goes by, this particular home is becoming more like a pied-a-terre so I'm not worried.

I used to rent out the downstairs master suite but not anymore. For the first time in 18 years, I've moved my master bedroom downstairs. It's much, much cooler downstairs and there is no carpet downstairs so that helps.

I don't use the heat at all in the winter, but that's another story.