Lennox Blues

[vt]

Split variable speed Lennox heat pump (details available upon request), was struggling to get the air going hot enough as the ambient temperature was dropping to about +5C (41F), as if it was its balance point. Eventually, gave up the ghost one night and just started blowing cold air.

Contractor came, declared TXV dead. Ordered, replaced Friday morning. Supply air around 96F with the ambient in low 50s.

Come 3AM Sunday, the unit started dying, and by 9AM was dead again, with the same symptoms.

Contractor came again yesterday evening, couldn't find anything more, noted that there appears to be a restriction in the system, but couldn't identify what it is. Also noted that the pressures are jumping erratically. Expressed concern about reversing valve.

After a while, the system stabilized with the supply air being just about the same 96F and the ambient being again in low 50s.

1AM, the unit is dead. The last breath was - supply temperature rose to 80F within about two minutes, then quickly dropped back to return temperature.

Contractor decided to give up and call for second opinion; waiting.

Any clue from distinguished audience here?

[natej]

Moving enough air across the coil? Kink in lineset? Charge correct? Dipswitches set properly? Correct TXV for R410A/R22 system? Is it a cooling only TXV?

[vt]

Moving enough air across the coil? Kink in lineset? Charge correct? Dipswitches set properly? Correct TXV for R410A/R22 system? Is it a cooling only TXV?

- I'd say moving more than enough air across the coil. DeltaT too high never was a problem, rather the opposite - 20..22F is as high as it ever gets;

- kink in the lineset - dunno, will ask the new contractor to see. On the other hand, no kink could spontaneously appear by itself to cause the first failure... Also, is my understanding correct that a kink or an internal restriction in the lineset would cause a local temperature gradient?

- charge correct - yes, according to the contractor. No leaks were detected;

- Correct TXV - well, it was ordered from Lennox and took two weeks to get delivered, I'd be pissed if it is not;

- Cooling only TXV - again, I doubt that it is since it's now a heating season.

But will ask the new guy to check.

I wonder what are the chances of crap getting into the system as the new TXV was brazed on and causing problems afterwards...

[lentz]

Surely the service man had a service manual with him. So he could tell where the restriction was.(If One) He should tell the different tempertures on each side of each component. The compressor could be going bad.

[vt]

Surely the service man had a service manual with him. So he could tell where the restriction was.(If One) He should tell the different tempertures on each side of each component. The compressor could be going bad.

Well, I don't think there was a service manual.

As for the compressor going bad, what are the chances of a 6 year old scroll to do so? Seems unlikely, though again, I'll ask about that, too.

[4l530]

About the scroll. It can happen. Depends on how good of install practices were used.

Originally posted by vt
Also noted that the pressures are jumping erratically.

This makes me think about non-condensables / contaminates inside the system.

[vt]

About the scroll. It can happen. Depends on how good of install practices were used.

Dunno how good (ductwork sounds like tornado, but for all I know, the previous owner could've been a scrooge or didn't care), but some pretty unusual elements are there: the condenser is walled in with the pool equipment, within the wall twice as high as the condenser. So, to make it work (instead of regurgitating hot air around), the installer put an exhaust pipe good 5 ft high on top of the condenser. Again, don't know whether this is smart or dumb, it's just a touch to show the personality of the installer. Maybe one recognizes himself here and jumps in

This makes me think about non-condensables / contaminates inside the system.

What would be the correct procedure to remove those? Evacuate, blow with nitrogen, charge?

[Milk man]

Posting the model and serial numbers of both the outside and inside units.

[vt]

Posting the model and serial numbers of both the outside and inside units.

Air handler: M/N CB31MV-51-1P, S/N 5800G 12XXX
Condenser: M/N HP26-042-7P, S/N 5800G 18XXX

Hope you don't need the missing part of the serial numbers.

[tinknocker service tech]

you said he brazed in the txv when he did the repair

this model lennox uses a screw on txv. i have been doing lennox for years and cant remember any that were braze

did he install the correct one and did he pull a vacune on the system before charging it. Sounds like noncondensables in system

[vt]

you said he brazed in the txv when he did the repair this model lennox uses a screw on txv. i have been doing lennox for years and cant remember any that were braze

May have been my mistake; I assumed he brazed it on - I tried to avoid breathing down tech's neck

did he install the correct one

Well, I guess I'll find out tomorrow morning, when another tech comes out

and did he pull a vacune on the system before charging it.

That I don't know. I felt uneasy asking him if he'd blown it and/or pulled the vacuum, knowing by experience that some people get quite touchy if you start teaching them to do their job...

Sounds like noncondensables in system

that'll be the second time this opinion is expressed. I'll make sure the tech knows about it.

[bonafide]

sounds like non condensables but probally is the wrong txv I went nuts on a lennox system a few years ago and concluded the very same thing however after a leanthy clean up of the system, the same fluctuations in the pressures was happening. Turned out to be poor bulb placement on the evaporator.

good luck
let us know how you made out

[nvr2old]

Indoor txv is usual problem. Lennox part# 56j20. Your service techs fault it took 2 weeks to get, not Lennox's.