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Recently, install crew added a txv to a lennok coil that would supposedly bring the SEER rating up from 14 to 16. After install, i get called out for servvice and the unit is pulling LRA. (Lennox by the way). Scroll compressor. I added a hard start to the unit, and have not been called back this summer. That was in June.

Originally Posted by nismo1

Scrolls have check valves in the discharge to keep them from spinning backwards like the old Carlyle carrier scrolls( the green ones) when they shut off. Put a hard start on it and remove the exceeds refrigerant. York Trane carrier Ducane, pretty much all condensers except goodman have time delay built into defrost control board. Apparently yours does not but hard start will roll that compressor over even under loaded startups.

I don't see where the OP said this is a heat pump.

I think he may be mistaken on what compressor is in the unit, and its a recip, not a scroll. York/Luxaire uses recips in a lot of their lower lines.

Even in the York LX series, the YCJD uses a recip, the YCJF uses a scroll, but the condensers look the same.

Using the largest listed matching coil/air handler, which takes 8 oz of additional charge, a YCJD uses .62 oz per foot over 15, so his additional length would need to be 77.5(total lines set length of 92.5 foot) foot to need 3 pounds.

Originally Posted by SBKold

Hmmm. I have never ever witnessed a scroll not start up within seconds with no addl start components.

That may be true. I can't say that I've run that test. I read somewhere that Copeland calls for a minimum 2 minute time delay on break. Maybe I assumed that this meant that equalization could take longer than a few seconds in some cases.

Adding that much is scary. What is it - .6 ounces a foot above 15'? Yea, that sounds like 110' lineset.

I read something about blockages (air locked or something like that) in the microchannel coil. Eventually it will likely knock loose and you'll be taking a lot of that 3.5 pounds back out. We had a few Nordynes do that. Took a lot on startup but soon after, even a couple months after, the full charge presents itself. If that sucker has a HP switch, it will open in seconds.

I have a stupid question....did the Luxaire call for the same size line set as the Lennox?

Scrolls have check valves in the discharge to keep them from spinning backwards like the old Carlyle carrier scrolls( the green ones) when they shut off. Put a hard start on it and remove the exceeds refrigerant. York Trane carrier Ducane, pretty much all condensers except goodman have time delay built into defrost control board. Apparently yours does not but hard start will roll that compressor over even under loaded startups.

Originally Posted by hvacrmedic

It takes a minute or two to for it to equalize.

Hmmm. I have never ever witnessed a scroll not start up within seconds with no addl start components.

Originally Posted by SBKold

A scroll starts unloaded.

It takes a minute or two to for it to equalize.

the only problem is the fast intermittent starts. eliminate this rapid recycle and problem is gone

i do however suggest a 5-2-1 hard start and a time delay

FIRST OF ALL you need to make sure the system is equalized before you are turning it on and off....

Def. sound like an installer with all this talk of locked rotor amps etc.

if it was pumped down to 300 microns I don't think LRA would be a problem.. UNLESS you are not allowing a delay.

At this point I would suggest a hard start and crossing your fingers..

Since your out in the field dealing with some old r22 lineset, you need to follow your heart...

good luck...

No text book can explain your situation...

A scroll starts unloaded.


So I don't think its that alone causing problems.

Is that line set over a hundred feet? That's how long it would need to be above 15 feet for it to require that much gas. If so, then like said above you have other problems to deal with. A time delay is nice but nothing is going to help that compressor if it is grossly overcharged.

I would assume that the new condenser with R410a came factory charged? So the addition of 3 pounds and 8 ounces of to the new system would tend to tell me that you have a hell of a long lineset. If this is the case, you may need to touch base with the manufacturer as for what in addition may be required to operate this unit. Possibly hard-start kit, liquid line solenoid, etc. Many manufactures have Refrigeration Piping Manuals to make sure that you are not only properly sizing the piping, but also following good piping practices and adding necessary components to help the compressor stay within it's operational envelope.

Like said earlier 3.5 pounds of R410a seems like a lot. It is VERY EASY to overcharge a R410a system and if per chance this condensing unit uses aluminum micro-channel outdoor condenser...you could be in a whole world of hurt.

As with everyone else....a time delay is a MUST.

410A

[QUOTE=dcx516;14166851]Removed a 3 ton lennox r22 split system on saturday and replaced it with a luxaire 3 ton r410a system. There was no place to run a new line set so we flushed it with par flush and nitrogen and did a bunch of leak checks. We installed the A/H with a TXV and installed the new condenser, pulled a 300micron vac that held, opened the valves and added 3.5lbs of refrigerant. The unit was running PERFECTLY: 20 degree split, 11 degrees of subcooling, no problems what so ever.

Not sure on length of line set but 3.5 pounds seems like too much too me. We usually are adding ounces to ours, not pounds.

Change out the stat, or buy a time delay relay.

Originally Posted by Crazecodyk

Most condensers don't have a board for time delay. Time delay cones from stat which this one doesn't have. Almost any system that tries to start right after being turned off won't nothing is wrong with the equipment. Just needs tine to equalize between cycles.

Agreed. If you want you could add a time delay, there's usually plenty of room in the control cabinet.

thats what i figured, thanks for your help guys

Most condensers don't have a board for time delay. Time delay cones from stat which this one doesn't have. Almost any system that tries to start right after being turned off won't nothing is wrong with the equipment. Just needs tine to equalize between cycles.

let it equalize

Most new condensing units have delay built into the board. I'm not sure about Luxaire though. rtfm

The damn stat doesnt have a 5min delay. I thought all stats had that