$680 zoned HVAC instead of $5000 central system

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nutnspecial
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Re: $680 zoned HVAC instead of $5000 central system

Post by nutnspecial » Dec 23, 2017 2:25 am

Wow, I'll just trust you about 'most' people/situations in some other areas like Seattle. But people HATE it here.

And the maths work out to 'resistive heat' being 3 or 4 times less efficient than other forms of electric heat including simple infrared type, though. Or 'expensive' 500$ minisplits etc. So even when electricity is 'cheap', 3x the usage isn't 'cheap' in comparison, imo.
--
Like I said, I'm curious how my fridge works out since it's almost like it's outside (maybe 70%). So far it's staying balanced at 10f/34f with barely any input energy but I wonder what will happen to the fridge side when it gets colder haha.

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Re: $680 zoned HVAC instead of $5000 central system

Post by Chalo » Dec 23, 2017 3:45 am

nutnspecial wrote:
Dec 23, 2017 2:25 am
And the maths work out to 'resistive heat' being 3 or 4 times less efficient than other forms of electric heat including simple infrared type, though.
How do you reckon? If you're using electricity to make heat, a watt can't become more than a watt. Infrared heating can sometimes be better at putting the heat where it's most appreciated, but it doesn't somehow make more heat from the same power.

Only a heat pump gives you a different equation to work with. And it has to work against its added cost.
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Re: $680 zoned HVAC instead of $5000 central system

Post by dogman dan » Dec 23, 2017 8:42 am

Havent looked at this thread in quite some time, so this is a bit of a highjack back to last summer.

FWIW, I've been on combined swamp cool, and window coolers for about 25 years now. On the very dry spring/ early summer days we have here in the high desert, swamp cool can be great. Half the summer though, the summer rains make them suck. That's when I switch to window units entirely.

They are noisy, but you know what's much noisier? The fan in nearly every central heater I've had. Last summer we got stuck in that rental house while my home got rebuilt after the fire. It had a central refrigerated AC. Noisy as hell! And in the crappy insulated house, it ran close to 24/7. The bill was double what we were used to, for a much smaller house. If you could just set the fan to a lower speed, it would be better. This particular one made the whole roof rattle. Really shitty install, should have put the compressor on the ground outside.

To be fair, when it's 90f outside at midnight, our window units run 24/7 too, but no need to run the one in the living room. I have 1300 square feet to cool, with three units. The two bedrooms have 8000 btu coolers, and the living room has a 12,000. On a particularly nasty day, it can still be a bit hard for them to keep up, but that takes a 110F day. Most days the bedroom AC's run all day, but at a low setting that just circulates air 50% of the time.

The trick to making them quiet, is don't install them in the actual window. Mount them in the wall and they get half as noisy. Use some rubber or foam, and isolate the rattle so it does not make the whole wall rattle. If I had it to do again, this time I would not mount them under the window. What I do hear comes through the glass. The fan itself is noisy on high, but I can set it on low and its much quieter than my central furnace in winter.

As for lifespan, all three of these AC's are over 15 years old now and running fine. Most of the summer, I run the swamp cooler for about an hour right at dawn, which gives my house a good air change out. Then the house stays cool enough for the window units to stay off till almost noon. By night though, hot enough to keep running most of or all night.

That swamp cooler is on the roof, and when off, it makes a nice solar chimney. The hottest air in the house vents out through the ceiling ducts, helping the house keep its cool longer in the AM. Some kind of way to vent out the hottest air in the house can do wonders. I still want to do the duct to a huge hole in the ground, deep enough to tap earth cool. But digging in my yard is like digging in rock.

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Dec 23, 2017 8:52 am

nutspecial
i can see your point, gas is so cheap.
it is worth it just to have a quiet kitchen.
.
I'm under the impression that a fridge is a type of heat pump, and that the waste heat is 1/3-1/2 the cost of resistance heat. Or think of it this way; a 300 watt fridge may be putting out heat, like from half a dozen 100w bulbs, into the room!
.
Hi dan
thanks for chiming in!

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Feb 10, 2018 12:08 pm

UPDATE:
the goodman condenser coil cracked and leaked. RIP
will not try to fix as new window units are so cheap.
So now i can possibly use some of the old ducts for unit 2. Sure would be easy to hook into the old ducts. i plan to delete 1 room, about 20% of the house.
.
Hooked up unit 1 for AC, using the tips and tricks i've read about. (like 3 bends in the supply duct and rubber feet)
It is so quiet, i cant believe it! 8) :D
46.2 db,
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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Feb 19, 2018 4:07 pm

Have decided to put a 20" fan in the attic window, as with several ac's running at once, it will surely benefit with fresh air.
.
BUT, today was warm enough 80F to do a torture test to simulate summer with just unit 1.
I kept the window closed and no fan!
after 40 minutes the attic got up to 105F(was 90 ac off)
room got down to 73 and vent was steady 63. Fantastic! 8)
So, if the old goodman did not fail, it might not even need a fan in the summer, with the window open. A lot of heat can go out the ridge vent.

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Feb 22, 2018 7:26 am

Was even hotter, unusual for Feb., so i did another test yesterday.
This time with the condenser exhaust hooked up to a 12" flex duct, to the gable exit on the side of the house.
Still window CLOSED and no fan yet.
Attic was 95F at 3:10 PM, 5 more than last test.
Ran 40 min same as before.
Attic steady 100F (5 less)
room vent 59F(2 lower) so unit 1 likes being vented.
uses 700 watts to cool 1 room. i estimate a 50-65% duty cycle in the summer.
20" fan will add 51 watts on low, but will be on a switch in my BR, so only on as needed (not in the morning)
Unit 1 has a total cost so far of $200.

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Mar 01, 2018 8:20 am

IMG_20180228_130817.jpg
(114.69 KiB) Not downloaded yet
pic of the 1st step in converting window ac to central. cut hole in top for duct, top exit flows, like TWICE as much air!

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Mar 01, 2018 8:25 am

IMG_20180228_130906.jpg
(92.94 KiB) Not downloaded yet
Left vent supplies fresh air to attic ac room. 20" fan on low (51 watts)
Upper right vent is exhaust of hotter condenser air, for unit #1. (no extra fan)

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Re: $680 zoned HVAC instead of $5000 central system

Post by amberwolf » Mar 01, 2018 1:05 pm

Matt Gruber wrote:
Mar 01, 2018 8:20 am
. cut hole in top for duct, top exit flows, like TWICE as much air!
That's an idea I should've tried years ago, and knowing how squirrel cage blowers work I don't know why I didn't think of that. ;)

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Mar 21, 2018 11:05 am

So i have wired 3 switches in my BR for the fan, unit 1, and units 2+3, simple ON/OFF.
I was never satisfied with a thermostat, so i'm using the $1.72 one just to remote measure the attic temp.
Used the $79 electric hoist to lift the small ac's into the attic. While i could lift them now, as i get older i don't want to hurt my back.
I've been using resistance heat in my BR AND SOLAR heat in the rest of the house. Have a 30" fan(40w) that blows warm attic air into the unheated rooms. This is fantastic, but no good on cloudy days or really cold days. and it doesn't work until afternoon when the attic heats up. But, it does wonders when conditions are good, and is almost free.
2 neighbors have had the ac truck in the driveway, including the 1 with the $6000 new system. I can't help smile :P as i may never call them again :D

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Apr 15, 2018 5:11 am

Nearing test time for units 2+3. The whole set-up is different than i imagined. Some things you just can't plan out.
Today i'll be attaching a drop cloth across the open trusses in the 5'x10' ac area. This is because the window fan creates a circulation that pulls down very hot air from the attic peak, about 4' higher. The plastic sheet should block most of it.
Will be testing it within 2 weeks, and expect a really hot day within 1 month.
Great hobby, i can't wait for the sun to come up so i can work on it for an hour or 2. (too hot up there after 11 am)

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Re: $680 zoned HVAC instead of $5000 central system

Post by Matt Gruber » Apr 23, 2018 8:25 am

1st tests of central units 2+3. very quiet, can barely hear it. 75F outside at 9:15am, so will have to wait for better torture test.
After 53 minutes it dropped humidity in the kitchen/dining to 55% from 62% Feels real cool, temp down 4, 73 was 77F
This is only 10,000 btu (old was 35,000btu)
BUT my BR has unit 1, so it is blocked off.
also blocked LR and 1 bath.
good so far! :shock:

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