Any HVAC guys in the house?

[SZR48207]

Meh. Hvac-Talk is an OK resource but very protective of the trade at the same time. I don't blame em since we all gotta eat, but maybe the HVAC industry needs a good kick in the rear so that we can start getting mainstream adoption of the tech in the minisplit units coming over from Asia.

 

[mattwithcats]

14 inches of blown in is not enough, Energy Star says R50-R60
https://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table

Insulation comes in two widths, 15 inch between wall studs, and 23 between attic/floor joists...
It also comes faced, a paper liner to keep moisture in, and unfaced.

Scoop the blown in to one side, and put 23 inch faced in, R30 minimum. Put the paper toward the living space, on the bottom in an attic. Put the blown in back on top. You don't need to get all the blown in on top, a little can remain under the faced insulation...

I have two layers R19 in my house in Virginia, bottom is faced, top is unfaced. Bottom layer is between the joists, top is cross hatched over the bottom...

 

[sleddriver]

Originally Posted By: AZjeff
....Are there industry standard formulas for HVAC sizing? thanks Jeff
Yep. It's called an ACCA Manual J.
Did one on my own house.

 

[AZjeff]

Originally Posted By: Iowegian
Oh and whay are you asking this on a auto/oil forum


I asked if there are any HVAC guys in the house. The usual opinions and unqualified answers are expected. I'm just trying to get an idea if she gets this unit fixed and moves on or if she should fight for a bigger unit. And you gave me a lead I knew nothing about so thank you.

 

[KrisZ]

I'm not an HVAC guy, but I did have an HVAC course back in my college days and to make a long story short, a properly sized, per Manual J heat load calculation, unit will work continuously, or with very short OFF times during the hottest period of the day, which is usually all afternoon and part of the night.

Your daughter's unit sounds like it was properly sized and the part was defective.

Also, no HVAC professional worth his/her salt will be able to tell you if a unit is sized properly from just a description of the house and what's already in there. It's a much more complicated process than that to do it properly.

 

[Linctex]

Originally Posted By: KrisZ
a properly sized, per Manual J heat load calculation, unit will work continuously, or with very short OFF times during the hottest period of the day,


I had a 1944 house (Insulation quality = unkown) that would run continuous on a 3-ton unit on a hot day, but the layout of the house was weird, with the master bedroom furthest away from HVAC unit.

I had to install a 5,000 BTU window unit (SEER 14? pretty decent) to keep that one room cool enough.... the rest of the house was fine.

 

[AZjeff]

Another question, is there any concern with a unit running continuously when the ambient high temp is 100 or over for weeks? It sits on the north side of the house so it doesn't get baked by direct sunlight.

And thanks for the replies so far. It all helps gain a little understanding of what she's dealing with. Problem is while this is all going on they have no AC.

 

[Coprolite]

My neighborhood is still undergoing build out. Our FB group chat has many houses in the 2-3 year range with failing coils. I checked with an HVAC tech and unofficially the story is that this is when the mandated refrigerant changes went into effect. The new refrigerant works under higher pressure and the coils have been failing. Newer design coils have taken care of the issue, but that age range is susceptible.

My house is 9 yrs old, so I was working on the replacement budget to get ball park figures. I figure mine will last a few more years. If not, then no new car for me...

 

[EA82]

Here in FL without doing a manual J we normally go 400-500 square ft per ton, based on the square ft of her house one would suggest that the unit is undersized. The ac running nonstop when it's hot is another indication that it is undersized. I would personally go with a 3 ton 15 seer, and make sure the ductwork is sized to handle a half ton increase.

 

[sleddriver]

Originally Posted By: Iowegian
Oh and why are you asking this on a auto/oil forum


Why Not?

Your previous answer indicates you have some knowledge of the field. Yet you return later to blast the guy for asking a question? As if oil is all that's ever talked about on BITOG??

We may be gearheads, but we're not narrow-minded gearheads. BITOG is a fine place for any member to cast a wide net for advice.

The site you ref'd him to takes a dim view of 'amateurs' messing with HVAC they paid for with their own money. Even skilled, experienced amateurs. Makes no difference to their mods. BTDT. I'm beginning to think your one of these true believers.

A very interesting book could be written on HVAC fraud, incompetitence & shoddy installations that run rampant in the industry. BTDT part II.

It's not Rocket Science but it IS Science.

Anyone can borrow ACCA Manual J & D from a local library, setup their own spreadsheet, and crunch the numbers. I've done so myself on both and discovered my duct system was completely inadequate and restrictive, on both supply & return. I designed a new one and installed it myself. What a breath of fresh air.....

Speaking of HVAC Iowegian, you need to CHILL and go powder your nose.

 

[Mr Nice]

That's why it's call General and Off Topic.

 

[Number_35]

That intense dry heat is quite different from what we face here. Our house is about 1250 ft^2, and the summers are more humid than extremely hot. I was told that undersizing the unit a bit was better as it would run longer and thus dehumidify the house. A larger unit would act more as a 'chiller' - dropping the temperature without reducing the humidity.

On that basis, we bought a 1-1/2-ton unit 10 years ago and are happy with it. Probably wouldn't cut it in Arizona!

 

[Killer223]

Jeff ever heard about Rosie on the house? it's a radio show here in AZ. might look into it. also look into super cooling to help lower the bills.
That said those parts do go south. it happens. Lenox are some of the best units made. i'd say this is a fluke incident.
As far as size you want it to run all the time. uses less energy than if you were to start and stop. they are designed to start up and run, and will run like that for YEARS and YEARS.
lots of people put way to large of units in their house, then wonder why they have a 400$ electric bill.

I'm not an HVAC tech, but dad and two uncles were for the past 30+ years. I've picked up a thing or two.
the SEER is just how efficient the unit is, not how much it can cool. make sure the tech will air balance the house. if they bock at that request, find a different hvac company.

 

[SHOZ]

My AC is a bit too big for the house seeing as I have made insulation and other modifications over the years. I've found that you can mitigate the "too big" with reducing the fan speed. This will still chill the house down but remove more humidity.