Every zone went warm together: branch distributor leak

CH38 on an LG system flags low refrigerant, and a shared fault like this often points to the outdoor unit. But this ducted office system in Choa Chu Kang had every zone fading at the same rate, a pattern that pointed somewhere else first.

By Team Snowflake | Updated 11 Jul 2026

Case summary

LG Ducted5 years oldIndustrialChoa Chu Kang, Singapore

Concern: Facility staff feared a major outdoor unit fault and were bracing for a large repair or full replacement quote.
Found: A slow leak at a joint on the branch distributor feeding the duct zones, with the outdoor unit itself testing normal throughout
Key check: Checked whether the even, all-zone pattern pointed at the outdoor unit or at a shared fitting downstream of it, then traced the leak to the branch distributor before any outdoor unit work was considered
Result: Cooling returned evenly across every zone within the same day. The CH38 error cleared and has not returned. No outdoor unit parts were replaced or quoted.

What we were told

Every duct zone in the office was fading at close to the same rate, not just one area. Cooling had gone from fine to barely there across the whole space in a short stretch. Facility staff expected a major fault in the outdoor unit.

What we checked

Every zone fading at the same pace pointed toward something shared, not a fault building in one duct run alone. On a system feeding several zones from one outdoor unit, that shared point can sit in the outdoor unit itself. It can also sit in the fitting that splits the line into each zone's branch. We checked the outdoor unit first, since that was the original fear.

Refrigerant readings confirmed a genuine loss, not a sensor fault or blocked outdoor fan.
The outdoor unit's fan, coil, and wiring all tested normal, with nothing pointing to a fault there.
Following the shared line downstream led to the branch distributor, where every zone's supply splits off from one point.
A bubble test found an active leak at one joint on that distributor, with every other joint clean and dry.

What we found

The leak sat at a joint on the branch distributor, the fitting that splits the single line from the outdoor unit into the separate runs feeding each duct zone. Every zone draws from that one shared point. A leak there lets refrigerant escape from all of them at close to the same pace, rather than draining just one zone's line. The outdoor unit itself was never short of anything to send out.

What fixed it

We resealed the leaking joint on the distributor and checked the fitting to confirm no other joint was letting gas out. The system was then recharged to the correct level and run across every zone to confirm even cooling had returned. We flagged the distributor for a closer look at future services, since one joint aging faster than its neighbours can mean the others are not far behind. No outdoor unit work was needed.

Outcome

Cooling returned evenly across every zone within the same day. The CH38 error cleared and has not returned. No outdoor unit parts were replaced or quoted.

What this case teaches us

When every zone fades together, check the shared distributor before the outdoor unit

If every zone on a ducted system loses cooling at the same pace, look at a shared fitting first. On this kind of system, that fitting is the branch distributor, not the outdoor unit.
A leak on just one zone's own line only drains that zone. When every zone fades at a similar rate, the fault sits somewhere they share.
Before approving major outdoor unit work on an even, all-zone fault, ask whether the branch distributor has been checked first.

Questions this case answers

Why did every zone on our ducted system lose cooling at the same time?

Because the fault sat at a point all the zones share. A leak on one zone's own line drains that zone alone. In this Choa Chu Kang office every duct zone faded at close to the same rate, which pointed downstream of the outdoor unit to the branch distributor, where a single joint was letting refrigerant out.

What does CH38 on an LG system actually mean?

It flags refrigerant that has dropped below the level the system expects. That reading was genuine here, not a sensor problem and not a blocked outdoor fan. What the code cannot tell you is where the gas escapes, and on this ducted system it escaped from one joint on the fitting that splits the line into each zone.

Low refrigerant error on a ducted system: is the outdoor unit the cause?

Not automatically. The outdoor unit's fan, coil and wiring all tested normal on this system, and it was never short of anything to send out. The trap is approving major outdoor work on an even, all-zone fault before the shared distributor has been bubble tested. One joint there leaked while every other joint stayed clean and dry.

What does it mean if only one duct zone goes warm?

That pattern implicates something different. A leak confined to a single zone's branch line drains that zone and leaves the others cooling as normal. The even, whole-office fade seen here was the signal to look at shared pipework instead. Matching the pattern to the fitting it points at is what keeps the search narrow.

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