AC Usage & Humidity

[beenthere]

The general pleated filters are usually ok. Those are the ones that the pleats are rounded curves, not sharp angles.

Although 130 CF of 50* air is heavier then 130 CF of 52 degree air.(a tenth of a pound or so)
Lowering to the next lower fan speed should not drop off air flow enough to make any rooms lack air flow.

Its no different then setting a VS blower to a lower CFM.

[pstu]

Some more questions regarding high humidity levels.

I was recently told by my new HVAC guy that the original installer never installed filters in either of my units (he actually left the construction filter in) so I went out and purchased some disposable 3M three month filters which I installed. In addition I set the small fan in my attic to automatically turn on when the temp reaches 75 instead of 90 like previously set.

After installing the filter and turning on the attic fan I noticed the humidity in my second level jumped to 62 percent during the night time hours but during the day the level dropped down to 49 - 52 percent. Could installing the filter or turning on the attic fan made my humidity problem worst?

Also, while at Home Depot picking up the filters I started talking to the sales guy and explained my situation. He said if my return register was too small (its only 25" X 18") that my system could be straining to suck in the humid air. Is this true? If so, how large should I make my return if I have a total of 14 supply registers, 9 which I constantly leave open.

Thanks.

Your return is 25 by 18, which is 450 sqin of filter area (did you ever say the size of duct behind it?). And your AC is 2 tons. Are these correct statements for your house? Is there any other evidence your return is restrictive?

Thanks -- Pstu

[t527ed]

if your "new" guy does not know about matching blower speed to the outdoor unit and ductwork it may be time for a "new new" guy........

[CoquiLostInNY]

Pstu,

You're correct. The Weatherking model servicing my upstairs level is a 2 ton unit and I only have 1 return grill which is about 25" x 18".

As for evidence the unit is be restricted.... I'm going by a couple of people tellign me that one 25" x 18" return for an area that has 14 supply registers (which 9 are always open because of that high / low registers configuration) is small. In addition I don't feel a great amount of air coming out of the supply registers when the unit is on.

Something else that came to my mind while reading various post on this site is that since I never had a true filter installed in this unit that there's a good chance my indoor coil could be dirty. Would you guys agree? Would it be easy for an HVAC pro to see it the coil needs to be cleaned?

Thanks!

[beenthere]

Its relatively easy to determine if the coil is dirty or not.

[jax1]

Its relatively easy to determine if the coil is dirty or not.

OK I'll bite. How? Hopefully not by looking at it because I can only see the side edges of mine. And if it is dirty, how would you clean it if you can't see it? I've been thinking of cutting a hole in the plenum to gain access. Good idea or creating a bigger problem?

[beenthere]

One way is pd across the coil.
Anotehr is by SH, and SC readings.

[CoquiLostInNY]

One way is pd across the coil.
Anotehr is by SH, and SC readings.

What's does pd, SH and SC mean? Can any of these things be done by the standard home owner?

Also, I'm thinking about expanding the size of my return register byself (times are getting wrough) so if anyone could give me suggestions on what size I should convert my current 25" x 18" return I would greatly appreciate it.

On a side note, can anyone recommend an entry level book on HVAC design/installation. (It would be great if there was a "HVAC for Dummies" book!)?

[beenthere]

PD=presure drop
SH=superheat
SC=subcool

You need the guages,meters and probes to check. And then know what they readings mean.

Adding a second return some times works much better then just increasing an exsisting return.

[CoquiLostInNY]

Thanks for the breakdown. I'll leave it up to the pros to determine if my coil needs to be cleaned.

As for adding additional returns, I ideally would like to add additional returns in each of my three bedrooms. Would this be a bad thing? If not, can the returns be the same size as my supply registers?

[beenthere]

The rooms will benefit from teh returns. As far as size, that needs to be determined by an on site evaluation.

[CoquiLostInNY]

Guys,

I'm back to having some serious AC issues, this time with upstairs unit. Yesterday I had my system off for a couple of hours and when I turned it back on I noticed that it took several hours for the temp to go from 78 - 79 degrees down to 75. Once it hit 75 the unit never turned off as if it was struggling to maintain that temp.

This morning I heard a humming sound coming from the attic so I got my proble thermometer and started to check the air temp coming out of my vents. The temp in the hallway where my return and thermostat are located was 75 but the air that came out of my vents ranged from 64 - 69 degrees.

At this point I turned off my system and went to my attic to see what was going on and that's when I noticed the copper supply pipe going to my coil was really cold and had frost/ice forming on it (I had to move the insulation to see this). I also noticed the return copper pipe going back to the compressor was also cold. To try to remedy this situation I removed the 3M filter and installed the old stock filter and left the unit off for about an hour.

I recently started the system back up and took some new temp reading. The temp in the hallway reads 77 degrees and the air coming out of my vents is ranging from 66 - 69 degrees. Another thing worth mentioning is that frost / ice has not reformed on the supply pipes but on a negative note the supply line doesn't feel as cold as it should (its only slightly cold).

Also, I finally measured out the house to get an accurate measurement of my square footage so here it goes.

Basement = 450 sq ft w. 8' ceiling
First Floor = 850 sq ft w. 8' ceiling
Second Floor = 800 sq ft w. 8' ceiling

The AC servicing my basement and first floors is a new Goodman 2.5 ton upflow unit located in my basement. The AC servicing my second floor is a Weather King 2 ton horizontal unit located in my attic.

If you guys could let me know what I should be checking for I would greatly appreciate it! My current HVAC install believes my upstairs unit is undersized and may have a leak. The reason he thinks it may have a leak is because one day he saw I was low in freon so he added a pound of so to my upstairs unit. About three weeks later I encontered the same problem I'm encountering now and when he came back out he noticed I was low on freon once again (about a pound).

As always, thanks for any suggestions and sorry for the long thread!

[beenthere]

Good chance your low again, if he had to add a pound 3 weeks after the first time.

Call him back to find the leak. And give you options for repair and replacement if its an order unit.

If it cooled fine other years before the leak started, doubtfull its undersized.

[CoquiLostInNY]

Thanks Beenthere!

I called the guy up and he's going to come by today (hopefully) to add some more freon and then he's going to schedule a time with me next week to check the system for a leak. He said he's going to disconnect the two pipes that come into the coil and soider them together after which he's going to pressurize the lines and check his gauges to see if there's a leak.

As for the unit cooling in the past, this is my first summer in this house and the unit was just installed so I don't know if its cooled adiquitely in the pass.

By the way, this will probably by the third or forth time this unit had to checked with the last three months. I hoping if there is a leak that its near one of the units because if not then he's going to have to break walls to find the pipe and all the connections!

[beenthere]

New unit.
Braze joints. TXV connections, access valves, and fittings, indoor coil.
Those are what should be checked before tying the lines together.

Electronic detecters can save a lot of time.

[CoquiLostInNY]

Beenthere, it's so easy to see that you know your trade very well! Thanks for the advise. I wish you serviced my area!!!

I'm going to print out your comment and have it handy from when I talk to the HVAC tech about the work.

One question, when you menting braze joints... are you talking about the visable ones outside of the walls?

In terms of an electronic detector, I know this guy has one because he tried using it before having to replace my last unit so let's hope that it finds the leak in one of the locations you mentioned.

[beenthere]

Yes, the joints they made during the install. Or any old ones that may be visable.

[Carnak]

One way is pd across the coil.
Anotehr is by SH, and SC readings.

High subcool reading could mean a dirty condenser

[CoquiLostInNY]

Hello,

Has anyone ever used an application called HVAC-Calc? I recently purchased this app and inputted all my info and it told me that for my entire house, about 2,000 sq ft located in Bergen County, NJ I only needed a 2.5 AC unit. I currently have a 2.5 ton unit servicing my lower lever and a 2 ton unit servicing my upper level.

In addition when I ran the duct calculator its told me that I would need for the following duct sizes;

Master Bedroom
-Currently have three 6" flex pipe ducts
-HVAC Calc reports that I only need one 8" duct

Master Bathroom
-Currently have one 6" flex pipe duct
-HVAC Calc reports that I only need one 5" duct

Office / Second Bedroom
-Currently have two 6" flex pipe ducts
-HVAC Calc reports that I only need one 6" duct

Baby's Bedroom
-Currently have two 6" flex pipe duct
-HVAC Calc reports that I only need one 8" duct

Guest Bathroom
-Currently have one 6" flex pipe duct
-HVAC Calc reports that I only need one 5" duct

Does this sound right?

The one thing that I guessed while inputting data into the duct sizing page was my HVAC systems CFM's. I guessed that my two ton unit had 800 cfm but after reading some threads I'm wondering if I put too little.

If anyone would like to see the reports this application can generate let me know and I would be more than willing to send you a copy. From a homeowner's standpoint the app looks pretty cool. My only issue is trying to figure out the duct thing as well as what happens in a split system like the one I currently have.

Thanks!

[Jopopsy]

New air handlers have multispeed blowers, Either 3 or 4 speed. (low, med low, med high, high) He should be able to set it to a lower speed.

Are systems (duct work included) generally spec'd to run at a certain speed, or do most run of the mill installers drop the unit it and leave the speed alone? Meaning, if he lowers the speed, will he cause strain someplace else (condensor maybe)?