Fun with hard starts and second opinions!

[PaysonHVAC]

So I am at this call today in Sun City Grand on a York split straight cool el' cheapo builder special.

I guess he's had problems with his breaker tripping and another company already came out and is supposed to come back out and "give options" on replacement or comp change out. Luckily they didn't show by time he had me out there.

Anyway, I don't know the whole story except what the customer says not being there. I think one of the other guys on this forum works for the competitor who was the one out there so I have to be careful with this one! :p



Anyway. It took me longer than the 30 minutes I expected to spend there.




http://www.paysonarizona.net/HackeryII/images/100_0915.JPG
So I am checking it out. First thing I see is the unit stops and hard starts when I wiggled the wires on this pull out disconnect. But it wasn't melted yet. So I justexpanded the copper thingies here for a tight fit again.






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Ah. A POS Bristol like Goodman likes to use.




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While I read no fault to ground from the compressor, I did see a burnt wire down there. THAT could be another problem.




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So I replaced that terminal.




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See whre it says "space for start assist accesory" or something like that?

While I don't sell a hard start on every scroll or comp I see, THESE comps actually NEED one and are lucky to ever start without them around here!




http://www.paysonarizona.net/HackeryII/images/100_0920.JPG
NOT my favorite hard start brand at all. But it was the ONLY type of Hard Start "kit" on my van and after I use these up I get some 5-2-1's which are a lot better.

[PaysonHVAC]

SO I get it together.

ZERO current from through the start kit. WTF?



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Hmm.. One of the wires fell off of the spade terminal.


I try it again. POOF! It lets the smoke out! WTF???




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I HATE these POS ones. The thing blew jizz out of the start cap!



Screw this POS!





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Found enough discrete parts on the truck to make one from scratch.
Had to remember today. 5-2-1, common - start - run!
LOL!





The compressor starts every time now as long as you wait 10 seconds for the potential relay to close.


This POS MAY actually run for a few years now. Although I did tell the guy I wouldn't bother with a compressor c/o if it comes to that. This builder special isn't worth the money and if that time comes, he should upgrade.

Who knows. So now he will a)go ahead and buy a unit form the competitor,
or b)leave it as is until it dies again.

Hope I didn't step on anybody's toes out here if the other tech is form here http://hvac-talk.com/vbb/images/icons/icon12.gif but I did have to try and fix it.
He said "Do to it what you would do to yours. And I said "it's worth wire repair and a start kit. Then run it till it dies and get a BETTER system!"

Oh yeah. He said he was supposed to have one more co. come out. That way he would have three opinions :p

[mark beiser]

Originally posted by PaysonHVAC
He said "Do to it what you would do to yours."

That is quite frightening actually, he doesn't know you like we do. ;)

[PaysonHVAC]

Originally posted by mark beiser

Originally posted by PaysonHVAC
He said "Do to it what you would do to yours."

That is quite frightening actually, he doesn't know you like we do. ;)

True. You have been around long enough to know about my "Variable Speed Motor" install in my little tight Rheem air handler up in my own attic LOL!

2 years now and that is working awesome still :D

[Swampfox]

Is that the correct potential relay for that compressor?

also turn those upside down run caps over, less likely to catch fire when it explodes :D

BTW, Goodman dropped Bristol a few years ago

[dutchcool]

Originally posted by PaysonHVAC

Originally posted by mark beiser

Originally posted by PaysonHVAC
He said "Do to it what you would do to yours."

That is quite frightening actually, he doesn't know you like we do. ;)

True. You have been around long enough to know about my "Variable Speed Motor" install in my little tight Rheem air handler up in my own attic LOL!

2 years now and that is working awesome still :D




Or the adiabatic cooler :D http://img197.imageshack.us/img197/5923/verolas1com45685ax.png for your garage.

[PaysonHVAC]

Yup! Today I was at a friends house nearby to help him more on his Z28 getting the new engine wired up and all.

We used the cooler outside over there. Works GREAT!









Originally posted by swampfox
Is that the correct potential relay for that compressor?

also turn those upside down run caps over, less likely to catch fire when it explodes :D

BTW, Goodman dropped Bristol a few years ago
Well, if you are talking about the Start Kit that blew up. The potential relay is NOT a real potential relay!
They use a TIMER board to hold the relay in almost a FULL SECOND each start up!!!! It's a fixed time!

That's why those SuperBoost and those like them SUCK!


The 5-2-1 is better as far as KITS go.


The second one I just measured the running back EMF and selected the best one I had on my truck as far as pick up and drop voltages go of the potential relay.

It worked great!

[dugfish]

Kickstart best one out there.

[brent]

why do you say it is a builder's grade? It looks like a stellar model which is the standard line. What was the model no? HDB...?

Brent

[wormy]

Originally posted by PaysonHVAC


The second one I just measured the running back EMF and selected the best one I had on my truck as far as pick up and drop voltages go of the potential relay.



Can you explain what you mean by 'measuring the running back EMF'

I've never had to 'build' a start kit before.

[PaysonHVAC]

So to explain in some simple terms...
When a single phase motor is up and running you have current at different times when you compare the run winding to the start winding. It's kind of like in sequence similar to a 3 phase motor (which has current to the 3 windings one after another in sequence) but with only two windings, to get the motor to turn the proper direction, and have any torque. You have current flow to one winding, then currecnt flow to the other. Not really both at once thought.

So once the motor is running you actually get a voltage induced across the run and start windings back to the run cap and you will actually read a voltage HIGHER than that applied. They call that Back EMF, Electro Mechanical Force.

For instance, on a 240V single phase compressor, you could read 380VAC across run to start while it is running.


So, I don't know exactly what potential relay should be used but you can get close enough to work at LEAST as well as a Kick Start or a 5-2-1 does since they are basically one-for-all kits anyway and different units with different compressors are not all the same.

So on a compressor that has 380VAC acrossed run and start when it running and you use a potential relay that picks up (opens contacts) at 300 volts and say drops (closes contacts) at 180 volts, that could work since the running back EMF would open the relay thus removing the start cap from being paralleled with the run cap after it is up and running close to full RPM's.
The start cap value is used to match up the current through the start winding. A 250 or so MF will allow more current than a 180MF, etc.



I am tired right now and keep making many typing mistakes, so maybe someone else could post a link or somethink if my tired eyes and brain are confusing anyone. :p

[mark beiser]

To select a potential relay, measure the voltage between run and start with the compressor running.

Pick a relay that has a "continuous coil voltage" rating higher than the measured voltage, and a maximum "pickup" voltage that is around 75-80% of the measured voltage.

The "pickup" voltage will have a minimum and maximum range. Make sure the maximum is not more than 80% of the measured voltage and the minimum is not less than 50%.

The "dropout" voltage is not important.

Put in the smallest start capacitor that will allow the compressor to start every time, and install a discharge resistor across the terminals of the start cap.

After a few years, I realized that there are only about 4 different potential relays that are usefull. ;)

[PaysonHVAC]

Ahh yes. I'm a little more awake now this morning :)
Was up till 2AM Fri night/Sat morning fixing my friends a/c and towing a car. Got more sleep last night :)
Now Mark explained it more clearly with less words.

And one more thing. Remember "Five, Two, One. - Common, Start, Run" because that's how you need to wire them potential relays :D


Once you realize how hard starts are SUPPOSED to work. You wont want to use a SUPER BOOST or any similar 2 wire one with an "electronic potential relay" ever again! They actually can DAMAGE compressors since they hold the relay in for a full second no matter what! That could be 3 times longer than needed each and every start!

[ruud-man]

Payson-

If I understand your explaination of a 5-2-1, it is basically a timer that has a one second delay on before it opens at start and a 10 second delay after shutdown before it resets.

My question is how is this relay effective if there is a momentary power interuption? A true potential relay would instantly reset and put the start cap back in the circuit. The compressor would have the added boost to start against an unequalized system.

The way you described the operation there would be about ten seconds during which the compressor is stalled and drawing LRA.

That just doesn't sound very good. If I used a booster it would be a Kickstart since it would reset almost instantly.

The potential relay, start capacitor, and a bleed resistor is still the best system.

Best regards...

[PaysonHVAC]

It's the dreaded Supco brand SUPER BOOST, also sold under the MARS label and other brands, that have the POS electronic potential relay that holds the start cap on too long.


The 5-2-1 brand, while is a universal working more accurate on one comp than another, works good too for instant restarts like a regular potential relay hard start because it uses a REAL potential relay.
It's just prewired and one size fits all type of thing.



The kick start works good. They did a TRICK to use two wires by using a diff voltage pot relay and hooking it up diff. Working virtually the same.
The relays on the kickstart are their weak point. But the KS1 has to be the BEST for busting loose a frozen comp. If a KS1 don't bust it free, the other brands wont!

[wormy]

Preciate the insite on how to 'design' your own hard start
kit.

I never put two and two together so far as back emf and
start relay pick up voltages.