Trane XL16i heat pump problems

[cashless]

I have installed a three zone Trane XL16i heat pump with variable speed air handler. One of the zones has a programmable thermostat, the other two zones have non-programmable thermostats(TCONT800 and TCONT402).
The heat pump is sometimes very noisy when it is powered on, but settles in after a bit and runs quietly -- most of the time. Occasionally it does not quieten down and the contractor indicates it is running backwards. I can shut if off for an hour or so and it will restart normally. I think I have seen this referred to as "slugging". What are possible reasons for this happening?
The contractor replaced the first compressor, and it ran fine all summer. But when I switched back to heat late this fall, the problem resurfaced.

[hvacgreg]

the trane 16 seer units are not approved for zoning

[gerryh31]

hvacgreg, I'm curious why you indicate the XL16i is not approved for zoning? I have a similar configuration, 3 XL16i but all with programmable t-stats (8300). This configuration been posted on this site, and actually asked for recommendations on this configuration before purchasing. This is the first time I've heard it's not approved for zoning?

[gerryh31]

Cashless, sorry I forgot, as I mentioned I have the similar configuration except the t-stats. no problem with noise when in heat pump mode, all units generally quite. Two of the systems I have the fan on all of the time, the other I have in Circ mode.

[jimj]

hvacgreg, I'm curious why you indicate the XL16i
is not approved for zoning? I have a similar configuration, 3 XL16i but all with programmable t-stats (8300). This configuration been posted on this site, and actually asked for recommendations on this configuration before purchasing. This is the first time I've heard it's not approved for zoning?


;)XL16i's will not work with Trane zoning, they will work with other zone manufactures like Jackson systems.

[cmajerus]

Cashless, sorry I forgot, as I mentioned I have the similar configuration except the t-stats. no problem with noise when in heat pump mode, all units generally quite. Two of the systems I have the fan on all of the time, the other I have in Circ mode.

zoning is with 1 unit, 3 control dampers for the separate areas.

[cmajerus]

;)XL16i's will not work with Trane zoning, they will work with other zone manufactures like Jackson systems.

we use the honeywell TZ4 panel, next job we are using the new totalzone panel, will see how that one is for installing, can't be any more confusing.

[cmajerus]

not sure how the compressor would run backwards on single phase power, but definitely sounds like you have issues with the refrigerant circuit, could be too little of airflow, or charge not correct. Is there a bypass damper in the zone system? possibly the low voltage wiring is not hooked as it should be, the tech should have it wired per the OUTDOOR unit wiring diagram, not the indoor diagram

[jimj]

[
QUOTE=cmajerus;1684269]we use the honeywell TZ4 panel, next job we are using the new totalzone panel, will see how that one is for installing, can't be any more confusing.[/QUOTE]


;) The new Honeywell panel looks like a great system, just mite have to try it.

[mark beiser]

not sure how the compressor would run backwards on single phase power

The only thing I can think of is if, for some reason, the controld deenergizes then energizes the contactor very quickly, the compressor could start back up in reverse.
Scroll compressors VERY briefly spin backwards when they shut off, as the internal pressures equalize. If you reapply power during that brief period, the compressor will run backwards, until it shuts off on overload.

A delay-on-break time delay added to the outdoor unit may stop the backwards running problem.

[cashless]

Contractor tried the delay. didn't work. Isn't there a few minutes delay anyway to keep the compressor from restarting too quickly?

This always seems to happen at startup after significant idle time.

There is a bypass duct. Not sure if it has a damper. Guess it would have to have one, wouldn't it?

I will try the fan on and see if that helps. Have not had contractor check refridgerant charge on this compressor, but he did the first one.

What is it about XL16i and honeywell panel that's a problem?

[jimj]

What is it about XL16i and honeywell panel that's a problem?[/QUOTE]


:D No problem it will work.

[cmajerus]

no problem for you, just fun for us to wire them up;) Best panel I have used.

[mark beiser]

What is it about XL16i and honeywell panel that's a problem?

No problem, the "not approved for zoning" comment someone made was for the XL16i with Trane's zone control system.
Trane's system controls the variable speed blower directly, and uses modulating dampers to manage airflow without the use of a bypass duct, or dump zones.
It was developed for use with single stage systems and the XL19i 2 stage system that uses 50% airflow for 1st stage, and is not set up to handle the 1st stage airflow requirements of the XL16i.
It would be nice if they would update their zone system to handle the XL16i, it really is a great zone system.
I suspect that department may be more focused on the controls for the system that will be replacing the XL19i, just a suspicion though. ;)

[cashless]

Thanks for all your replies.

My control system and dampers are honeywell.

I tried leaving the fan on and it seems to help. At least it's not growling like it did before, when it powers up.

[second opinion]

Thanks for all your replies.

My control system and dampers are honeywell.

I tried leaving the fan on and it seems to help. At least it's not growling like it did before, when it powers up.

Make sure your equipment is installed per its application limits, maximum vertical seperation of 25 feet, maximum linear length of 80 feet and correct line size for the tonage.

Have your dealer install a sump heater on the compressor unless you have the 5 ton.

From your description it sounds like during long off cycle the compressor is getting refrigerant migration.

[cashless]

Vertical and horizontal distances are o.k. I agree it may be the refrigerant migration. This would seem to be more likely in cold weather. Never heard of the sump pump solution. Tell me more.

Thanks

[second opinion]

Vertical and horizontal distances are o.k. I agree it may be the refrigerant migration. This would seem to be more likely in cold weather. Never heard of the sump pump solution. Tell me more.

Thanks
It is a sump heater or crankcase heater. It attaches to the compressor and keeps it warm during the off cycle to prevent liquid migration. It comes from the factory on the 5 ton.

If you have narrowed the noise down to long off period / start-up leave unit completely off before tech arives. Have tech attach gauges, record ambient temp, indoor coil temp, static pressure of refrigerant, then start unit and see if refrigerant pressures and noise change simultainiously. Record static voltage and monitor it for voltage drop at start up during the noise period, and then pressures and temp with all zones open.

If you can post that info we can give you a better idea of what your system is doing. There are a lot of issues that can cause noise at start up. Good luck

[jibroni69]

Have your dealer install a sump heater on the compressor unless you have the 5 ton.

From your description it sounds like during long off cycle the compressor is getting refrigerant migration.

Thats what I was thinking, also is there a thermal blanket wrapped around the compressor? As for the compressor running backwards, this is a trick carrier has been using with there bristol compressors. I think it is the bristol, anyways they have a special start capacitor at about 450uf that will startup the compressor in reverse, in effect dropping compressor output by about 15 percent for first stage heat. it will then offcycle for about a minute and open a bypass port in the compressor , equalize preassures and startup in forward for 2nd stage heat. The noise is problably a combination of 2 things, liquid migration and overcharge. Probably sounds like a couple marbles rattling around in the can?

[mark beiser]

All sizes of the XL16i heat pump come with a crankcase(sump) heater and sound blanket factory installed.

It should be checked to make sure it is actually working though.

[cashless]

Contractor indicated there was a blanket. Didn't say anything about the crankcase heater. This is a two ton unit (about 1500 ft2 area). Cooled fine in heavy heat this summer.

It actually sounds like a loud air compressor when it runs backwards, if that's what it is doing.

I appreciate your interest and suggestions

[second opinion]

Did he check the pressures during the noise period? This will tell you what it is doing.