Chemical Washing Procedure.
1. Pump out gas form evaporator [FCU and piping] into condensing unit and lock[close] service valves [These valves are at outdoor unit]. This is called gas saving.
This is tricky part. There are a few steps and you need to be careful.
If not, you will lose gas and need to top up.
How to save gas?
- Switch On the indoor unit which you are going to clean in cooling mode for 5 mins. Then, you need to go to outdoor unit. You can feel the air coming out from fan at outdoor unit was a bit warm. That means compressor is running normal.
- Close the service valve at discharge port [at the outdoor unit].
- Let the Air-Cond run for ~3 to 5mins. You will feel the air coming out from fan at outdoor unit become cold. That means compressor is running without gas. Condenser coil is not hot anymore.
- Close the service valve at suction port.
- Switch Off the indoor unit.
2. Switch off the main Air-Cond circuit breaker.
3. Disconnect flare joints [2 copper pipes], electrical wiring and drain pipe from FCU.
4. Dismantle the FCU down from the wall.
5. Dismantle the electrical circuit board, evaporator coil, drain pan, fan motor and fan blower.
6. Tape up flare opening of evaporator coil, to prevent water going in while washing.
7. Bring FCU coil to washing bay, flush with water and spay chemical. Use alkaline chemical [Not acidic chemical].
I bought 5litre bottle @$15 from Daikin. I think ½ litre is more enough to clean 1 unit.
The chemical solution will react with the water and the dirt to cause a forming process. The forming process will extract dirt trapped deep inside the parts.
8. After soaking the coil for about 5 min, flush the coil with water to remove all residual chemical solution.
9. Wipe dry all parts and reassemble the FCU.
10. Clear the drain piping at the wall with vacuuming or flushing.
11. Install the FCU back at the wall. Secure the flare joints, connect the electrical wiring and drain pipe.
12. Purge out the air from the FCU and piping. Proper way is to vacuum out. But, I don’t have vacuum pump. So, I just purge out. I think even those Air-Cond guys don’t use vacuum pump.
Purging is done like this.
- Loosen the joint at suction pipe.
- Open [a little] the serve valve at discharge port to let some gas out from already loosened suction pipe joint.
- After a few second, tighten that joint.
This is actually illegal [in US] as you cannot let CFC gas out into the air. But, I think all the Air-Cond guys here do that.
13. Unsecure[open] both service valves and test for leakage at FCU flare joints. I use Elitech WJL-6000 gas detector.
14. Switch ON the main Air-Cond breaker
15. Test run the air conditioner and check gas pressure.
16. Top up gas if needed. Usually, you won’t need it.
