OPPO LIVE: Answering  residential and commercial A/C questions

Kinja'd!!! "EL_ULY" (uly)
07/16/2017 at 12:05 • Filed to: OPPO community service

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Will be fully live around near 2pm TX time. I will answer all your A/C, heating, insulation and ventilation questions both residential and commercial.

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DISCUSSION (23)


Kinja'd!!! Highlander-Datsuns are Forever > EL_ULY
07/16/2017 at 12:19

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Be careful!

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Kinja'd!!! Dr. Zoidberg - RIP Oppo > Highlander-Datsuns are Forever
07/16/2017 at 12:22

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Free insulation!


Kinja'd!!! EL_ULY > Highlander-Datsuns are Forever
07/16/2017 at 12:31

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No step on snek! The thing we see more of here is red wasp and yellow jacket nests.

One time we were attacked by millions of killer bees removing some units off a warehouse. So many that they went down the boom of the crane and attacked the driver/crane operator. Those cheap cans of instant kill spray did nothing. Had to call in the pros and they indeed confirmed that they were Africanized killer bees


Kinja'd!!! Jarrett - [BRZ Boi] > EL_ULY
07/16/2017 at 12:33

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I want AC connected to my central air very badly. The problem is, is that my furnace is bolted laying down to the ceiling of a 2.5' crawl space.

I fear the cost implications of this.


Kinja'd!!! Urambo Tauro > EL_ULY
07/16/2017 at 12:42

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I’ve heard that R134a is an ozone-friendly alternative to R12. If that’s the case, then why is it still illegal to vent into the atmosphere?


Kinja'd!!! vondon302 > EL_ULY
07/16/2017 at 13:10

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What’s the easy way to get the condenser fan off of the motor.

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Had to cut the end of the shaft off and grind it down. That’s after the 3 jaw puller bent the hell out of it.


Kinja'd!!! RacinBob > Urambo Tauro
07/16/2017 at 13:14

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There are two issues related to refrigerant regulations; Ozone depletion and Global Warming

As you can see, R-134a is a lot better than R-12 in Ozone depletion levels. R-134a has no ozone depletion.

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But R-134a is a not a very good global warming gas. Every pound emitted is the equivalent of 1430 pounds of carbon emissions. The R-134a replacement is R1234yf has the equivalent emissions of 6 pounds carbon. Multiply 1430 pounds of carbon times 2 pounds per car by 10 million cars per year in EU and US and that is a lot of avoided emissions.

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Kinja'd!!! RacinBob > Jarrett - [BRZ Boi]
07/16/2017 at 13:29

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Depending on where you live, central systems are not necessarily the best choice. If you only need 3 months of cooling a window unit might save a lot on installation and operating cost. If you want something pertinent, install a couple of mini splits throughout the house.

You can go with central air in the attic, but the downsides of trying to make an attic unit into central cooling are;

1. Your cooling unit and ductwork is in a 120+ f attic. As such a lot of your cooling operation will be used just cooling down the ductwork and unit and not your house. A unit in the basement and ducts in the wall are a better deal.

2. The unit will need to have a condensate drain. When the drain gets plugged(and it will), it ruins your drywall ceiling. If you do go the attic route, make sure it has a secondary drain pan and alarm.



Kinja'd!!! Full of the sound of the Gran Fury, signifying nothing. > EL_ULY
07/16/2017 at 14:11

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I live in a 120 year old house that was updated and converted to three units. It has central electric heat, and looking at the specs I see that the heater/blower was designed for a mobile home, but this is probably OK since my place is about 1200 sq. ft.

The first year I was here I set the thermostat at 68 degrees and the heater ran nearly constantly, resulting in an electric bill over $300. The next winter I set it down to 63 degrees and the electric bill was closer to $250, this last winter I kept the bill in check by only setting the heater to 57 degrees and using electric oil-filled radiators in the bedroom and home office, and pretty much stayed out of the other rooms. In the Summer months I just stay in the office with a window air conditioner running, as well as a tower fan upstairs. I know that by comparison my energy costs may not be that bad, but I think I’m not getting my money’s worth out of this system.

Although it can get cold here in STL it doesn’t get that cold. What is a good balance of economy and heat; if I only want to spend $150/mo on electricity, where should my thermostat be set? Is there something wrong with my central heat that makes it so inefficient? I’ve sealed up around the windows (double pane) and added that heat-shrink film to the windows. I don’t feel a lot of drafts coming in, but I don’t know why the heater is so seemingly inefficient.

Oh, and one other question. In the summer, what’s the cost difference in running just the fan on the central A/C system for a little airflow as opposed to running the air conditioning. 25%? 75%? 5%? Nothing?


Kinja'd!!! Wurrwulf > EL_ULY
07/16/2017 at 14:23

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Half of my duct work is flexible insulated duct and the other half is rigid (appears to be galvanized steel piping) wrapped in insulation. Do they have similar service lives? I’m assuming the flexible, coil insulated duct is the cheaper material with a lower life span.

I bought a house built in the ‘70s with an 18 year old AC system. I’m assuming the duct work is the same age, but the rigid stuff looks far older than the flex duct.


Kinja'd!!! diplodicus forgot his password > Full of the sound of the Gran Fury, signifying nothing.
07/16/2017 at 14:31

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Wtf I’ve never heard of electric heat before. Idk who your energy supplier is, but mine has a device they’ll give you which syncs with their digital meters and you can connect to it with an app to see your real time energy consumption which would answer your last question.


Kinja'd!!! EL_ULY > Jarrett - [BRZ Boi]
07/16/2017 at 15:44

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One option is sacrifice a closet or the corner of a room to that air handler. This will provide much easier access for servicing. It’s going to have to move for sure. Draining could be avoided the manor RacinBob says by adding an evaporator water pump.


Kinja'd!!! EL_ULY > Full of the sound of the Gran Fury, signifying nothing.
07/16/2017 at 15:55

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I recommend something heat pump high efficiency unit. It basically runs your a/c’s outside condenser which produces heat, heat which through a valve runs that heat through copper lines into your air handler. The unit also has it’s own traditional heater element as a backup if it needs more heat. Helps a bunch getting any humidity out of the house which make you feel the heat to start with.

For your second question, it depends a lot on the relative humidity. Im low humidity, the fan is fine to circulate the air.

Thermostat should be as close to 5ft to the return air source


Kinja'd!!! EL_ULY > vondon302
07/16/2017 at 15:57

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They sell a twisting type fan puller to use after letting some 5w30 engine oil sit there for 15 min. Tapping it helps but I’ve found car engine oil to work kickass


Kinja'd!!! EL_ULY > Wurrwulf
07/16/2017 at 16:01

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1st, the life is noted on the insulation itself, not the inner ducting. Life is the same. It’s cheaper just replace the metal ducts with R8 flex than re insulate the metal ones. The thing that gets wear and tear per say is the insulation on the ducting.

Side note, you will loose a little air speed with flex.


Kinja'd!!! Full of the sound of the Gran Fury, signifying nothing. > EL_ULY
07/16/2017 at 16:34

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Well, it’s a rental unit, so I won’t be making that kind of investment in a property I don’t own. I was hoping that I was missing something obvious that could improve the efficiency of the system. I’ve been tempted to rent a thermal imaging camera to look for heat loss, but perhaps I should start with measuring the temp at the registers.

Humidity in STL is rather high, although not as bad as Florida or Hawaii. There are times I miss my old place in Los Angeles, near the airport, where year-round temperature control involved opening or closing a window or two. I never used the heater, and hadn’t run the air conditioner in years.

The thermostat is fairly close to the return air source, maybe 5-7 feet away. It’s kind of hidden by some bins full of CDs, but since I’m not using central air or heat these days I figure that this really doesn’t matter.

Hopefully I’ll be buying my own place in a year or so. The Mazda will be paid off in October, and the extra $357 will be going to paying down debt and saving for a down payment. Updated HVAC and energy efficiency modifications will be high on my list of priorities for a home. One friend of mine just dumped $17K into a new HVAC system in a house that was thoroughly remodeled a few years ago, and another friend is struggling with broken A/C in both her home and her car. I’m not sure who’s in worse shape...


Kinja'd!!! vondon302 > EL_ULY
07/16/2017 at 17:18

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Thanks that thing was frozen on there. I swear someone mushroomed it before me.


Kinja'd!!! Pixel > EL_ULY
07/16/2017 at 19:37

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I have a 100+ yer old house with a crawl-space attic. Right now the insulation up there is a layer of paper-backed Fiberglas that is almost completely crushed flat, and blown-in fiberglass on top of that that is also pretty matted. All of it has some amount of small pieces of tar-paper & shingle from some roof repairs when I bought the house.

I am going to need to rip out part of the 2nd floor ceiling around the chimney to fix something, and after that I want to re-insulate. What is the best way to do that? More pink fiberglass? More blown-in (walls have recent cellulose blown-in)? Spray-foam on the underside of the roof?

Also should I pull out the old insulation or just build up on top of it?


Kinja'd!!! Jarrett - [BRZ Boi] > RacinBob
07/16/2017 at 20:16

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I’m all about those savings, so I’ll likely stick with the window units. (got a couple refurb 8000 BTU units for the bedroom and office when I moved in). I only need it for the 3 months/year.

Lesson learned though - Make sure my next home just has it built in!


Kinja'd!!! Jarrett - [BRZ Boi] > EL_ULY
07/16/2017 at 20:18

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Because my house is so tiny and I have no basement or garage, closet and storage space is at an extreme premium!

Should I ever have to do major service to the furnace, I would definitely consider moving and and even building a wall/closet in my living room to hide it behind.


Kinja'd!!! uofime-2 > Full of the sound of the Gran Fury, signifying nothing.
07/17/2017 at 10:48

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For an A/C system the fan is by far the minor contributor to energy usage in comparison to the compressor pump. I would estimate it contributes less than 20% of the total energy usage


Kinja'd!!! uofime-2 > Full of the sound of the Gran Fury, signifying nothing.
07/17/2017 at 10:59

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For heat, using pure electric that far north is a crappy option, it is too cold for too long and as you’re seeing your bills are suffering.

You could look at a portable kerosene indoor heater like this:

https://www.amazon.com/Kero-World-KW-24G-Portable-Convection/dp/B000050I7X/ref=br_lf_m_a9s99vcyhmng9yu_ttl?_encoding=UTF8&s=home-garden

That thing could keep your whole house uncomfortably hot for 4 gallons, or about 12 dollars a day (unless your insulation is reallllly bad). That thing would pay for itself in 2 months and you’d be so much more comfortable, though I admit fooling around with kerosene isn’t ideal.


Kinja'd!!! Yowen - not necessarily not spaghetti and meatballs > EL_ULY
07/21/2017 at 16:39

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I’m late to this party, but! I bought a townhouse a year ago with a furnace that’s about 10 years old. The house is 1450 sqft. My inspector informed me that (to his surprise) the coil is already in place.

Can a current-model air conditioner mate up with that?