Hard start kit opinions.

[Glennhvac]

i am a fan of the properly sized 5-2-1 hard start kit. the relay must be in the correct position. there has been big debates on putting a hard start on a scroll. rheem has put them on scrolls since the beginning. if you think about it a scroll has a motor just like a recip does or a rotary. its a motor so put a 5-2-1 on it and be done. any system that has a hard shutoff expansion valve should also have a real 5-2-1 hard start.

if you have intermittent breaker trips then i would look for a couple other things as well;
1. a crankcase heater that has a broken band
2. loose wires on the peckerhead
3. fan motor that randomly over heats
4. dirty condenser coil
5. intermittent shorting motor(megaohm the compressor)

Good info but Rheem or in my case Ruud has not been installing them on the units I have purchased for some time now. This was part of the reason I was concerned about installing them on scrolls as they have not been shipping with start components.

[gravity]

Good info but Rheem or in my case Ruud has not been installing them on the units I have purchased for some time now. This was part of the reason I was concerned about installing them on scrolls as they have not been shipping with start components.

this might be why rheem/ruud is quoted cheaper to me then trane. is this whith their base equipment or all equipment?

i have found many scrolls that needed hard start kits

[mark beiser]

AS/Trane factory installs start assist kits on their heat pumps with scroll compressors, and has called for the addition of them to scroll equipped AC units, used for low ambient cooling, for a number of years.
Since scroll compressors have more mechanical friction than recips to overcome when starting, they use larger motors, with higher LRA, than similar capacity recip compressors.
Because of the higher start-up current, the motors in scroll compressors, as well as the contactor, etc., benefit from start assist components even more than recips.
This is especially true when the compressor is cold, due to the increased friction from the oil thickening, and contraction of the metal parts.

I think some of the "debate" over hard start kits on scrolls stems from past, maybe current, cautions from various sources about using them on scroll compressors that have mechanical problems that cause them to stick.
Those cautions have often been strongly worded, or even labeled as warnings.

It has always been common with mechanically stuck recip compressors to get more life out of them by installing a hard start kit when one is found not starting due to a mechanical issue. It can't hurt to try it, and compressors often run that way for years.

Scroll compressors are mechanically very different than recips, and due to the nature of how the scroll mechanism works, and the tight tolerances, just need to be replaced if they are mechanically sticking enough to not start without a start assist.

Adding a start kit to eek some more life out of a recip with mechanical issues typically won't result in anything worse than further mechanical damage.
Adding a start kit to a scroll compressor with mechanical damage is a high probability path to a burnout.

Never hesitate to add a proper start assist to a scroll compressor to reduce light dimming due to voltage drops on startup, and/or stress on the motor windings, or to help with starting in very low ambient temperatures.
I wouldn't install one on a scroll compressor that is mechanically stuck though, unless it is just to get it going for a day or two until you get back out to replace it.

[Glennhvac]

this might be why rheem/ruud is quoted cheaper to me then trane. is this whith their base equipment or all equipment?

i have found many scrolls that needed hard start kits

I'm finding they may with these new coils that do not equalize. I typically install their 13 seer rectangle units and they have not been coming with start components. A few years ago when the 13 was the next up in line they did come with them. At that time I was under the impression that they were added along with a HP cutout because they carried a ten year parts/compressor over the 1/5 on the base model.
I guess in the end its always cost. The same reason they start putting in contactors for 15 cents less then the ones with nice lugs!

[Chuck]

AS/Trane factory installs start assist kits on their heat pumps with scroll compressors, and has called for the addition of them to scroll equipped AC units, used for low ambient cooling, for a number of years.
Since scroll compressors have more mechanical friction than recips to overcome when starting, they use larger motors, with higher LRA, than similar capacity recip compressors.
Because of the higher start-up current, the motors in scroll compressors, as well as the contactor, etc., benefit from start assist components even more than recips.
This is especially true when the compressor is cold, due to the increased friction from the oil thickening, and contraction of the metal parts.

I think some of the "debate" over hard start kits on scrolls stems from past, maybe current, cautions from various sources about using them on scroll compressors that have mechanical problems that cause them to stick.
Those cautions have often been strongly worded, or even labeled as warnings.

It has always been common with mechanically stuck recip compressors to get more life out of them by installing a hard start kit when one is found not starting due to a mechanical issue. It can't hurt to try it, and compressors often run that way for years.

Scroll compressors are mechanically very different than recips, and due to the nature of how the scroll mechanism works, and the tight tolerances, just need to be replaced if they are mechanically sticking enough to not start without a start assist.

Adding a start kit to eek some more life out of a recip with mechanical issues typically won't result in anything worse than further mechanical damage.
Adding a start kit to a scroll compressor with mechanical damage is a high probability path to a burnout.

Never hesitate to add a proper start assist to a scroll compressor to reduce light dimming due to voltage drops on startup, and/or stress on the motor windings, or to help with starting in very low ambient temperatures.
I wouldn't install one on a scroll compressor that is mechanically stuck though, unless it is just to get it going for a day or two until you get back out to replace it.

Good info Mark, I'm glad your back to posting here again.

[gravity]

yes...very informative. thank you

[suBcools]

Agreed, very good information. Thanks for posting that.

Sent from my PG86100 using Tapatalk

[alex13177]

anybody use the starter pow-are-paks with any problems?

[Cooked]

.......2. loose wires on the peckerhead.......

I resemble that remark and find it highly offensive.

[timebuilder]

Yeah if I can find them near me! Plus I guess they are not advised for scrolls so that is another issue.

I think the "not advised" wording is a little misleading.

What the scroll guys are saying is that because a scroll starts basically unloaded, there should be no need for a start assist device. However, there are times when one is indeed indicated. The scroll motor is electrically identical to a recip motor. Only the method of compression is the difference when it comes to loading on startup.

[Glennhvac]

I think the "not advised" wording is a little misleading.

What the scroll guys are saying is that because a scroll starts basically unloaded, there should be no need for a start assist device. However, there are times when one is indeed indicated. The scroll motor is electrically identical to a recip motor. Only the method of compression is the difference when it comes to loading on startup.

I admit some ignorance on the internal mechanics of the scroll compared to a recip. I think what I gather by 'unloaded' is that they can and will start easier than a recip under the non equalized pressures you find so often with the new txv coils?

[Paul Bee]

There are a lot of informative videos on youtube, just search refrigeration compressors. I also like the 5-2-1.

[timebuilder]

I admit some ignorance on the internal mechanics of the scroll compared to a recip. I think what I gather by 'unloaded' is that they can and will start easier than a recip under the non equalized pressures you find so often with the new txv coils?

It's a smoother, more gradual start because the scrolls take several revolutions to build a pressure that is greater than the discharge line pressure, whereas a recip builds that pressure in a stroke or two of the pistons, which is often one or two revolutions, so the load on the recip motor is much steeper from rest to running at RLA.

[Glennhvac]

Thanks for all the feedback , help and advice. I really had not heard of those 3-2-1 kits and hope to find a parts place around me that handles them. I also hope there is enough room in these downsized control sections to install them.

[mark beiser]

I admit some ignorance on the internal mechanics of the scroll compared to a recip. I think what I gather by 'unloaded' is that they can and will start easier than a recip under the non equalized pressures you find so often with the new txv coils?

The internal pressures on the pumping mechanism in a scroll compressor equalize nearly instantly when it turns off because there are no discharge or suction valves to prevent it.
There is a check valve in the discharge outlet of the compressor shell to prevent the system pressures from equalizing through the compressor, but there is no pressure difference across the actual pumping mechanism, so scroll compressor always start fully unloaded.

TI really had not heard of those 3-2-1 kits

"5-2-1"

[Glennhvac]

The internal pressures on the pumping mechanism in a scroll compressor equalize nearly instantly when it turns off because there are no discharge or suction valves to prevent it.
There is a check valve in the discharge outlet of the compressor shell to prevent the system pressures from equalizing through the compressor, but there is no pressure difference across the actual pumping mechanism, so scroll compressor always start fully unloaded.



"5-2-1"

Today was good! I learned this. Thanks

[SoFlaDave]

Another 5-2-1 Convert here. No more kickstart for me. Still use OEM kits for Trane stuff whenever possible though

[JWB]

so I meter the start caps when diagnosing and find some of them bad, I sometimes reuse the existing pot relay and just change the cap. Keep some in my van. Usually the relay is still good. Anyone object to this, I am talking about getting a compressor up and running when it just won't start.......meter goes up and then down on a start cap, I crimp a terminal end on the resistor and reconnect to the terminal when done. What would happen if the resistor was left unattached?

[jnsrose]

I guess I will be throwing away all my super boost. Great thread. This is why I am here every day. Very informative. Thanks for all the info gentleman.

[timebuilder]

so I meter the start caps when diagnosing and find some of them bad, I sometimes reuse the existing pot relay and just change the cap. Keep some in my van. Usually the relay is still good. Anyone object to this, I am talking about getting a compressor up and running when it just won't start.......meter goes up and then down on a start cap, I crimp a terminal end on the resistor and reconnect to the terminal when done. What would happen if the resistor was left unattached?

Here you go!

http://hvac-talk.com/vbb/showthread.php?t=467142