Maybe bump up the contactor(s) rating size for starters? Maybe minimally sized cheap contactors? Technical rep.? may/may not have answers?

 

3 pole contactor will give better protection in case one leg welds. Use aux for heater. AE10-1244 R17 Copeland bulletin list specif ratings for contactors, all are not the same.

I wonder how the breaking arc is affected or different on 2 vs 3 pole?? Could not find any evaluations?

 

Interesting, per copeland tech support, not recommended.

2 pole on 3 phase not listed in any technical bulletins by copeland.

 

Is you transformer tapped correctly? Did someone start them up and leave it on the 230V tap from the factory instead of moving it to the 208 tab? Low voltage will make them chatter.

 

Every time i get a new customer i check those taps , most are wrong

That .... and pulley alignment

 

Low control voltage causing chatter.....when not being observed?
Short cycling, restarting under high head pressure....again not when you are there?

Now for something completely different;
When the contactor opens there is a split second, (if that), when the feed thru from the wire nutted leg feeds back thru the windings and presents itself at the load side of the contactor. So you only disconnect 2 legs but get the 3rd leg feeding back towards those contacts for that nanosecond.
That 3rd leg is trying to push thru the contacts as they open, adding, IMO, to the arc flash at that point.

Just an idea from an old guy who overthinks many situations too much.

Now the little resi AC units use only single pole contactors and surprisingly, last a long time, usually. I always replace them with double pole when needed.
Less load and maybe the run cap absorbs that back EMF.

 

"Just an idea from an old guy who overthinks many situations too much."

Can be the sign of a good tech! I'm always thinking worse case or , but what if...

 

So youre thinking try a 3 pole ?

 

Yes, in addition to checking the control voltage tap, I would put 3 pole contactors on the compressors , (sizing by the inductive (motor load) rating of the contactor).
Are the cond fans running thru these contactors also....usually not much draw there.

What does the OEM factory wiring diagram show?

This is even before my pipe dream thinking idea.

However, I have noticed on Utube by HVAC people that there were some RTU's with 2 pole contactors for 3 phase. IDK, if these were factory OEM setups or previous "what was on the truck repairs".

 

90% of the small tonnage units shipped any more have 2 pole contactors for 3 phase equipment. Space and money saving steps I am sure.

 

Thanks for that info.

Money savings I would guess. The 2 pole would most likely make it thru the warranty period for materials on commercial products, is that one year or more?

So, as stated above, if one pole of the two welded together then the comp would single phase because of the 3rd leg wire nutted. Comp is supposed to lock out on over load, that would happen, but how many times after cooling down?

Manufactures must have actuaries on board to weight the cost of a 3 versus 2 pole contractor, (plus the wire nut of course) with the history of compressor replacement from
single phasing occurring.

Just a rant about the race to the bottom.

If there is a solid reasoning for this engineering, would someone please comment.

 

I know that a single pole contractor is often used to energize the CCH during the off cycle. It wouldn’t surprise me if the purpose of the two pole contractor with your three phase unit is for the same reason. They have a hot leg on the compressor that backfields to the other side of the contractor. The CCH is wired on the same pole of the contractor but on opposite sides from each other. When the contractor pulls in current does not flow, but when the contractor opens then it now has a path and energizes the heater. You will probably need to rewrite your CCH if you change the contractor out for a three pole.

Running a hot leg on the compressor allows for a cheeper contractor to be used and saves on an auxiliary switch. They get to shut off the CCH in the on cycle to boost efficiency numbers while keeping cost down for competitive reasons. If people would start looking at the specs instead of the price when they shop then the market might move in a better direction, but until that happens then they will keep giving people what they are asking for... cheeper prices and higher efficiency units.

 

Are the contactor points badly burnt and pitted, or are you just seeing carbon powder inside?

If the points are still smooth, then there aren't any electrical issues.

Could be airborne contaminates.

 

What kind of amperage are you talking about? Maybe one of the electronic contactors (SureSwitch from Emerson comes to mind) would work? They don't make a 3 pole that I'm aware of, but one of their claims to fame is the reduction/elimination of arcing between the contacts.

 

I see now the CCH feeding thru the comp windings.
So there was a reason for the 2 pole.

Many small resi AC's are wired the same way. But only some have a CCH.

Some old Copeland-matic units had a extra relay that would shut off the CCH when comp ran. Might have been a NC relay.

So maybe a heavier duty 2 pole is the answer.

 

https://climate.emerson.com/documents/49p11-843-sureswitch-contactor-upgrade-en-us-2884324.pdf


Is this my salvation ?

 

https://climate.emerson.com/document...us-2884324.pdf

Is this my salvation ?

Bad Link

 

https://climate.emerson.com/documents/49p11-843-sureswitch-contactor-upgrade-en-us-2884324.pdf

 

The carbon tracking issue is just an annoyance on a 208 unit. It pops breakers on a 480 unit. The carbon mixes with a little snow that finds its way into that compartment, and BAM, the feeder breaker in the electrical room opens, because it has a shorter rise time.

Replacing the contactors once a year IS excessive. I wait until I get some real pitting on those contacts.

I never replace these with a three pole breaker. When I find one, it means "joey" has been there. JMHO.

 

Yeah , "joey" has good intentions but doesn't realize the manufacturer uses the 2 pole contactor as a CCH

Or a 1.5 pole in residential .. same idea using CCH

 

3 phase 3 pole
As far as the CCH nothing wrong with running it during cooling. Otherwise a small relay or isolation switch mounted to the contactor works.

 

But when the next guy comes along whos never played Engineeer before and is like WTH ... looks at diagram and gets even more confused

 

so are the contacts burnt and pitted?

 

post 21 has a picture exactly like this contactor , except add a little black dust around

I was about to purchase 2 of those fancy contactors but read they are Single Pole / W shunt ( they claim it replaces 2 poles as well ) and I guess you "could" replace a 2 pole in residential because they have a spade connector specifically for the CCH on that fancy unit ..... but you couldnt get away with that in 3 phase

 

I always throw away the single pole and go with a two pole on residential and move both CCH wires across L1 and L2. The cost difference isn't a big deal between a single and double. As for commercial that is a different story, to go from a two to a three poll can sometimes be a substantial jump in cost. I would usually stay with a two pole over upgrading to a three pole for this reason, unless for very specific reason. Also these EURO style contactors I am seeing seem to have some exaggerated ratings, IMO, they have very small contact pads in comparison with your plain old contactor that have a bit more meat in the same rating. And older contactors from the 60's, 70's, and into the 80's were much larger with larger contact pads compared with present day contactor of the same rating. Getting to the point with some of these older contactors that there are no longer contact replacement kits, as I go to replace it, I get a contactor half the size, with smaller lugs, and really garbage in quality when compared to the old.

As for that Emerson SureSwitch, I can't remember the year, maybe 2010 or so, I was at Johnstone and the rep gave me one. Fast forward to this last September, I decided to lay a large cement pad down to cover the embarrasing desert area of the side of my home I gave up trying to grow anything. I had to remove my AC. Not a big deal, only a 20ft line-set and AL finned-Copper tube condenser, so I thought it a breeze to just throw the gauges on, push in the old contactor, suck her on down, valve off, ....EASY PEASY... NOPE, I totally forgot that I installed this mystical box...LMAO, there is NO WAY to think around this damn thing to pump down a system in a conventional way. Ended up wire nutting the LINE and LOADs together and used my main disconnect there...100psi , 90, 80, 70, 60, 50, 40, 30, 20, 15, hurry close suction before in vacuum...10psi..sweet...Pull Disconnect!...whew. As for how the mystical box works and if it is any better and how much more life I will get out of it, I do not know, so I can not give it any ratings other than it works and has been working for a decade. Nothing internal you can look at without breaking it to judge arcing, carbon build up, etc.

 

What benefit do you see in replacing the single pole contractors with double pole contractors? Seems like it would just cost the customer more in either parts required to install a relay or in energy and slightly less capacity if the CCH is let run continuously.

The Emerson contractor must be a solid state relay. I haven’t looked at the specs that close. Or maybe it’s contacts but they’ve added a snubber to it? [emoji2369]

 

ok, if your compressor contactors look like that every year, I would suspect short cycling, but would also tighten all connections back to the main breaker, and verify wiring is good and tight at the comp. terminals.

if wiring is all good, upsize contactor rating, switch to an IEC type, or the type you linked too.....getting a higher amp rated unit would prolly lessen the wear. UNLESS there is an equipment sizing, or other issue causing short cycling.

 

While at it ...lets make it a dependable Mercury Relay !

 

Yeah it has contacts , but they are controlled by electronics somehow to keep them from arcing

 

I have not seen a version of the sure switch for three phase, or even two pole installations.

If you have excessive carbon deposits, I would look at cycles per hour, and limit that in the stat setup.

 

Simple. You're using the wrong contactor for the job. Get yourself a AC-3 category contactor with damping resistors. Problem solved.