We live in AZ. Have both an Evaporative Cooler and AC, use the evap April-June, switch to AC July-August, then back to evap. The Southern AZ Home Show flyer from an AC Co advertised a free AC check if you went to their booth and signed up. Spent $6 on tickets, and got the appointment. My evaporator is from 1993, and the condenser/compressor was an emergency off-brand replacement in 2004 for $1,600 (4 ton on a 1,800 ft^2 house), and hasn't been touched since then, other than filters and clean condenser. Good news, low pressure is 75, high pressure is 260, no problems other than noisy bearings when the blower starts. FREE!

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noisy bearings when the blower starts

Where I live the humidity is so high that no one uses evaporative coolers, so we have no backup relief plan.

To avoid downtime, I would replace the blower motor.

It seems like things like that always go out late on a Friday afternoon when you can't get someone out until Tuesday or so of the following week.

Worse, some of the modern blowers are PWM controlled and thus specific to the brand and model you have -- and the odds are NOBODY has one in your town.

Gen wrote..

the odds are NOBODY has one in your town.

Happened to me last time.

Not only did they not have one in my town, they didn't have one at the factory.

The guy swore to me they were going to have to actually _make_ the motor.

My unit is 7 years old, a top of the line Trane.

Yep.

I had a blower fail on me at 0-dark-****-me in front of the July 4th weekend last year. Fortunately the local guy I used to install it originally has a deep bench of parts and is a good friend; he was able to physically fit a different blower motor in there with a standard AC feed which allowed the unit to RUN, although not very efficiently, until we could get a replacement shipped in.

If he hadn't had a motor that would physically fit in the cage in his local warehouse.......

Yeah, well, my "modern" blower is from 1993 in a Carrier Weathermaker furnace. Checking a on a replacement is a good suggestion, thanks.

My next house (lol) is going to have two zones. So if one goes I can at least be comfortable in 1/2 of my house. That also greatly reduces the panic aspect of an AC failure, also a heating failure as well.

Flap

If I ever own a house I'll build a bespoke system using standard industrial motors and control components.

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I'll build a bespoke system using standard industrial motors and control components

I believe that is certainly doable with various heating options available today.

However, with AC, I would be surprised if you could do so cost effectively with a cost effective energy use.

If you do so let us know. Would be interesting to see how you go about it.

If you were going to attempt this the best path would probably be to figure out the blower wiring from the controller and intercept it, then use that to drive a VFD and ordinary motor (rated for that.)

The reason is that the compressor is nothing special other than being a compressor. If it fails you can put in a new one. The evaporator is just a coil. The issue is the controls and blower, which is how they get the efficiency and a (most of the time) reasonable cost.

The amusing part of the failure in my case was that the motor was under warranty. The not-amusing part is being without AC for a holiday weekend. Dual zone is one solution to this as now you have two units and if one is down the other still works, so half the house still has cooling. I had that in Chicago but I also had two floors in Chicago -- here I have one, and it makes no sense to split the system like that unless you were going to go to one of those micro systems that the Japanese have come up with (and that may not make any sense in terms of operating and installation cost.)

Swingtrader wrote..

However, with AC, I would be surprised if you could do so cost effectively with a cost effective energy use.

If you do so let us know. Would be interesting to see how you go about it.

Cost effectiveness would only be a secondary goal. I would pay more up front for high-quality components in order to achieve reliability and capability.

It's energy efficient to have a heat pump system that's only rated to cool the inside of the house up to 20 degrees below the outside air temperature. When it's 112 degrees outside and your AC is struggling to keep the inside temperature under 95 you generally don't appreciate the fact that you're saving a couple dollars on your electric bill.

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Cost effectiveness would only be a secondary goal. I would pay more up front for high-quality components in order to achieve reliability and capability.

Wouldn't surprise me if a "bespoke" A/C system would cost three to four times a production unit - when finalized, and quite possibly more. While operating at lower efficiency, and quite possibly a lower comfort level.

Some of the high SEER units reach a level of sophistication and efficiency that I doubt that you could match with off the shelf components.

I have a high SEER twin compressor unit heat pump, with variable speed fans, that I have had seven years and still makes me grin at the consistency and comfort level.

The smaller compressor handles most work. However, mid summer, or heavy load, the second compressor kicks in, and as the situation changes the fans speed faster or slower to meet the specific load conditions.

This all works together to keep inside temps stable regardless of the ambient conditions, but also increases comfort due to stabilized dehumidification, versus a more powerful unit that merely cycles on and off. In my area, summer humidity most be taken into consideration.

The control system panel in this unit and its abilities would be cost prohibitive as a one off.

I'm not saying it can't be done. I am saying I believe it likely is not practical or feasible to do with off the shelf components. Sure, if you want - you can pay three or four times or more for something that will cost more to operate, and not do the job as well.

My last automation project was a seven axis welding machine. Any HVAC system I built for my own use would do more than "merely cycle on and off".

well.. last summer here in Texas my ancient AC system went out while on vacation and came home 9:30 at night and the house was 95 degrees inside.. Went down to Walmart and bought a window unit to get through the night..

replaced a capacitor in the compressor, but the unit was never the same after that.. bought a new 5 ton system in Jan and enjoying it now..

High SEER two stage systems are all the rage here in AZ right now - IF you have the coin... a BETTER investment, if you are building a new house, is to foam the entire shell - I used traditional batt and blown in cellulose in '03 when I built my 3300sf home - we foamed my fathers 4300sf home I worked on in '06 - his house was 20 degrees cooler than ambient with NO AC - he put in the BEST AC system available at the time and his monthly juice bill is 33% less than mine in the dead of PHX summer heat and his home is 25% LARGER than mine AND is a two story Tuscan (lots of stone and venetian plaster) - all in, he probably spent 10k MORE than I did at the time but he broke even two years ago, considering house size, he went positive (using my house as a traditional baseline) a few years after he moved in... money WELL spent - I am a builder but not a rich one:-).

Does anyone here have any experience with Solar Hybrid air conditioning that uses the vacuum tube condensing temperature booster? Seems to be catching on in the Far East. Design seems, simple and eloquent. Would like to know how it's functioning in the real world.

Wow - My thread from May got resurrected. Managed to run the Evaporative Cooler until 6-15-12 when the meter got read. June electric bill was $108 (including the 2 HP pool pump at 3 hours per day). Meter will get read on Monday 7-16-12 with AC on full time. 1,800 sq ft house with insulated attic, fresh filter with clean AC bill of health as in original post... Will advise...

Whenever I see references to dual zone AC systems, I wonder why they don't design them to allow different settings in (just) the bedrooms versus the rest of the house. I've seen them split floor by floor, or side to side.

Why aren't they designed to cool the bedrooms only after dark (with lead time) and cool the common spaces the rest of the time but not the bedrooms. During this heat spell, we set AC at 77 for most of the day, but that's still too warm for sleeping. But I also don't need (or want to pay extra for) low 70s at night throughout the rest of the house (or even any AC for that matter), just the bedrooms.

My bedrooms in Chicago were all upstrairs; there was no common living space there. And I had split systems there.

It worked very well and in the overnight hours I had the downstairs (main floor, living space) unit effectively turned off.

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High SEER two stage systems are all the rage here

I have had a High Seer two compressor system for about 8 years now.

Love it.

In addition to the obvious economic benefits - the house is noticeably more comfortable. Granted, the unit it replaced was ancient.

Even so, I think because of the variable fan speed and running so frequently, it keeps a more even temperature.

Whatever, the house is more comfortable, more consistent.

No, it's humidity control.

The high-SEER variable speed systems control the FAN speed. They run the fan as slow as they can while keeping the coil from freezing to control humidity. The colder the coil (provided it doesn't freeze!) the more water condenses out of the air. These systems have a humidistat in the system and they not only target temperature they also target 50% RH, and will bring that down first if both are over the desired setpoint.

That's where the comfort advantage comes from.

A traditional system's design is a compromise; you can't (ever, in the operating range of the system) freeze the coil. TXVs have mostly eliminated this but you still have the air temperature drop over the coil which the TXV cannot precisely measure.

In the high-dollar high-SEER systems you have a variable-displacement compressor that targets the low-side pressure and thus self-regulates the amount of refrigerant displaced, a TXV that regulates the evaporator and a VFD-driven blower that is capable of circulating less air when more humidity removal is desired and more air when more-rapid cooling is desired.

The system targets humidity removal first as that's far more important to comfort than absolute temperature stability. It also can run at a much lower output (in total) than the older systems since the compressor is variable displacement and the fan is variable speed, so it adapts to the cooling load and is more efficient in operation (start/stop is much more inefficient than nearly-continuous operation); since it can regulate output it runs in a much-more efficient envelope.

We like to add humidity here in the desert which is really cheap cooling (when we can).

Humidity is my biggest bitch about living here. 70 degrees right now, but 97% humidity. Pointless to turn on the air because I'm sure as hell not setting it THAT low, but it's uncomfortable in the house even though it's not hot.

I can usually keep the house comfortable until outside temps get >85 by using vent fans and the basement, but with no way to control the humidity it's often too humid to really be comfortable even if the air temp is way cooler than I'd set the thermostat on the AC.

Asi: Get a dehumidifier. It's basically a small console AC unit with BOTH coils in the same space. It will slightly heat the space it is in (by the amount of energy it consumes) but will drop the humidity indoors and make a HUGE comfort difference. You'll need to either put it somewhere it can drain the water off or dump the water.

Yea, but that would mean cutting out the ventilation because I'm constantly pulling fresh air through the house from the cool side (usually basement) and venting it out the hot side of the house.

If I stop that, then it's AC time anyway. :/

Actually, we do have a dehumidifier in one room in the basement that doesn't have good airflow and is slightly damp without it. It does help in there, but that's also the coolest room in the house because it's completely underground. No windows though, so no way to make use if it like I do the rest of the basement. (Basically as a heat sink, pull cool air in there at night and when it gets warm upstairs, shut the windows upstairs and pull the air up from the basement.)

Probably cuts $50-$75 off our electric bill in the summer by doing that, but once it gets over about 85 outside we have to use the AC anyway.