Home A/C Problem

There shouldn't be anything "special" about the contactor, it's a standard industrial contactor. I'm away on business, but am certain the Bryant Evolution air conditioner at my hobby farm and at my home use standard industrial contactors

The most common failure mode is never cleaning out the contactor. For some reason, spiders and bugs *love* to build nests in them. They eventually stick. I use a container of nitrogen gas to blow out my contactors before the start of the cooling season, and usually inspect them every month or two during cooling season

In your case, it sounds as if the spring in the contactor broke. The spring is designed to open the contact once 24 v has been removed from the solenoid. Most industrial contactors have replaceable springs, though it ususally isn't worth the effort

Most contactors also have unsused terminals on the solenoid. These are to provide a run signal to the motor control center. If the device has tripped, the solenoid will remain closed, or if the spring has broken, the solenoid will never open, and a "command disagree" alarm is issued. AFAIK residential A/C never monitor for this

Although keeping a spare is probably a good idea, the failure you experienced isn't frequent. A far more common problem is corrosion in the plug for the low and high side pressure limit switches, so the compressor will lock out even though it has proper R-22 charge

 

Patrick

If the solenoid arm on the old contactor moves freely, it's possible the actual contacts were lightly welded together. Most contactors have spring loaded contact pads, this is in essence a purely mechanical "debounce" to prevent arcing when engaged and disengaged

With years, especially a decade or two, of use, the contacts themselves can pit and corrode to the point they will stick just enough that the solenoid spring cannot pop them apart again when 24 v is removed. Although the contactor can be rebuilt, no sense monkeying with it, you did the right thing chucking it

There is a bit of confusion regarding the function of high pressure limit trip and low pressure limit trip. First of all, it really shouldn't do any harm or extensive wear to an air conditioning compressor to run 24x7, *assuming* it has correct R-22 charge and oil charge. Your system is old enough to probably have R-22, my systems have R-410a

Indeed, many commercial, industrial, and institutional compressors *will* run 24x7 and last +10 years

High pressure limit trip: This can be caused by a number of things. First, a severely overcharged system will trip out on super hot days. On cooler days, it won't. If the condenser coil is plugged with dirt, leaves, blocked by shrubs or other things, of if snot nosed brats have used their fingers to collapse the condenser fins, that will cause a high limit trip

The condenser fan is essential to keep the system running. If for any reason the condenser fan should quit, expect a high limit trip fairly soon. My first house in Salt Lake City, had an old A/C and one day I happened to hear a loud buzzing sound just before it tripped.

The A/C was so poorly made, the fan wires were loose, they finally contacted the fan blades, were severed, and the compressor overheated. I was able to fix that myself, and fortunately it kept working when I sold the home

Low pressure trip: this is almost always caused by undercharged R-22. Another reliable indicator of low charge is that - as long as the system is still working - the evaporator coil will start icing up

If you don't mind waiting a couple of weeks, when I return I could take a photo of the control board and contactors of my home A/C condenser

Hope this helps

 

As others said, there isn't anything special I can see about these relays (er contactors), other than their pretty high current.

You can find them online (I replaced mine from there). Nothing special about them, I believe, but they do 'wear' and eventually stick on (what happened to mine), or the coil can burn out (so it won't trip on).

My advantage is that I have 2 AC's, so could run 'reduced' on one waiting for the part.

I don't really understand why they wouldn't sell to you, although even the online sites offer a minimal warranty.

Mine stuck on as well. I've had to replace my well pump relay for the same kind of problem (other than it stuck off). If you get it stuck on, you may be able to short-term fix it by smacking the relay (er contactor) with the top of the screwdriver (with power off), or manually poke to relay to get it to disengage. But, I think once it does that, it's likely to stick itself on again (arc-welding itself a bit).

There is a LOT of power floating around in there, so just for the record, if you don't have a pretty good idea how to troubleshoot power as well as an idea how air conditioning works, I'd stay away from do it yourself. At the very least, you need a voltmeter...and make sure BOTH inside and outside units are off, pull the safety to make sure.

Also, I've had mine freeze up in the past, and for any folks who may find this, according to the research I could find, freezing means either dirty coils (inside or outside, could be filter too), or low refrigerant (which by law you can't purchase unless licensed).

Hope this is at least some help...I'm am amateur at this myself.

pat

 

I'm curious why you guys in the US have very few inverter type of home A/Cs.
In Japan, the market share of the inverter home A/C is more than 90% in these 10 years. I think the US market is more than 5 years behind Japan.

The efficiency is up to 40% better than a conventional A/C, and we feel very comfortable under its precious temperature and fan speed control.
Mitsubishi Electric - Product Information for MSY-A15NA

Ken@Japan

 

Hi Patrick,

Mitsubishi has their full line-up of products.
http://www.mrslim.com/UploadedFiles/Resource/MrSlim_catalog.pdf
I think Daikin has the largest share in the inverter A/C market worldwide.
Daikin AC:

Ken@Japan

 

Hi Patrick,

I'm not an A/C equipment expert, but I believe the individual indoor units on each room is more efficient than the central system using ducts.
The heat pump heating is also very efficient, but I don't know how good it is compering the natural gas-powered heater.

We were told that we'll see a certain profit within several years replacing the conventional (more than 10 years old) A/C with the inverter A/C, something like replacing gas gazzler vehicle with Prius.

Anyway, since your A/C system is 14 years old, why don't you contact them asking your merits and the estimated costs?

Ken@Japan

 

In a week I'll be back and post photos of my A/C

Generally, the A/C that Ken refers to is great for adding A/C to an older home that has no ductwork, or for a new home with radiant slab floor heat. Around here, you see them used in homes that have a "cabover" master bedroom over the garage - it's difficult to properly zone a regular system to get good performance in a 1.5 story home

The biggest hurdle to installing something like Mitsubishi's Mr Slim is cost. For a 1 ton - 12,0000 BTU - system, expect to pay at least $2,200 for a cool-only system. For a conventional home with ductwork, adding a 2 ton system usually costs that, and you can then cool and dehumidify the entire home

The new outdoor units are very efficient. The Bryant Evolution system I have is rated SEER 17, the newer ones are SEER 20, I noticed the Mr Slim is rated SEER 13

The Mr Slim heat pump is not suitable for use much below -10 C, and will require supplemental electric heat. The best solution for heat pumps in my climate is ground source geoexchange, requiring heat transfer piping buried deep in the ground

For cold regions, it's still hard to beat gas furnace. I have the Bryant Evolution Plus 90i system, it uses two stage heat and variable speed blower fan

If you live in a very hot region of the US or Canada, that has A/C need for at least half of the year, it makes sense to upgrade an older system. For example, Patrick's system is probably SEER 10, maybe even as low as SEER 8.

He could expect a 5 year ROI if he replaced the condensors and evaporator coils with new ones based on non-Freon coolant, and rated SEER +18. The ROI is much shorter if the utility offers a rebate for Energy Star certified systems

What I like about my Bryant Evolution system is that the Evolution control system will stage the two-speed outdoor Scroll compressor, and the variable speed indoor fan, to save energy and increase comfort

 

Patrick

Ok finally made it back. As promised, I took photos of my Bryant outdoor condenser. The relays are standard industrial contactors, I can get them from an industrial electrical jobber for $15 each.

Thinking about what happened to yours, they usually quit in the middle of the night or on Sunday, when everything is closed. I'm going to order a couple of spares just to cover my a**. Will also get the start capacitor too

jay

 

Damn,

Me too.

 

The file was created with Adobe Acrobat Professional 9, which we have been using at work for about 2 months now. I just checked the metadata and noticed the default work security settings were applied to the docuement: printing allowed, editing not allowed, commenting not allowed.

You will need the latest version of Adobe Acrobat Reader to open the document. I tried to open the document using the latest version of Reader on my test machine, it opened fine.

 

Ok, I checked on another machine running Adobe Acrobat Reader 8. The error message was "failed to decrypt."

The file can be opened with the latest version of Reader, which is version 9.

 

Uh-oh, Geek Envy: my circuit board is bader than *your* circuit board

Seriously, it's 4 years old and still works flawlessly

You may have noticed the 4-wire interface. That is for the Bryant Evolution control network. The furnace and HRV are networked to the Evolution control