Mitsubishi Heavy industries Duct type leak

[Christos]

Hi i have a leak on an FDU250VD MIHI indoor
the water is jumping out of the water pan towards the fans and then inside the duct.
The evaporator is clean, i have installed a drain water trap without any results (MIHI says in the manual that a trap is not needed),the drain pan is clean, the drain pipe is ok,
If i open the bottom sheetmetal on the unit while operating in cooling i can actually see the water jumping outside the pan. I took the unit apart to see what is wrong and i found that the insulation strip between the evaporator and the drain pan was damaged so i replaced it but the water still jumps out of the pan.
I am an experienced engineer and these kind of problems usually get fixed with a proper drain trap.
I was thinking that the evaporator is icing and i left it on fan only and tested it by pouring water in the drain pan.The water was still jumping out of the pan.
It is an inverter unit so i shouldn't be worried about the coil temp being too low.
Other engineers try to fix it before me with no results.
The evaporator looks like its touching the drain pan correctly.
Please help me on this one,
Thanks!

[charlie patt]

Is return air restricted causing a part vacuum and pulling water into airflow

[Christos]

no the return is open just a synthetic-foam clean filter
the only thing i can think of is the evaporator being dirty from the insight it is a thick evaporator witch i cleaned with condenser clearer because it was very dirty
the airflow seems fine on the outlets so i am confused

[eggs]

I have exactly the same problem on a 25kw daikin system ?? No idea what is wrong with it ��
My train of thought was that there was too much pressure being developed by the fan for the installed ductwork.

Eggs

[PaulZ]

Hi Christos
Have you tried running without the return air filter in to see if the problem still exists?
Is the return air duct too small for the volume of air being moved by the fan causing a low pressure?
Paul

[Magoo]

Face velocity too high, blowing water off the coil. Increase static by fitting a suitable return air filter which will reduce flow and face velocity.

[iwan_seltech]

Hi,
Agree with Magoo, face velocity exceed 2.5 m/s, water from coil carry over.

Try to reduce the speed of motor or try to adjust the return grilles.


IW

[redroge]

is there a bend in the supply duct close to the unit

[charlie patt]

On the ducted system u can adjust the velocity of evap fans depending on number of ducts size and bends I remember doing it on a mhi course you can go in controller and reduce speed not just hi or low speed actuall rpm of motor

[Christos]

there is no return duct, is just the unit with a new clean synthetic filter. I tested the unit without the filter and it does the same thing. Customer claims that the unit was working for 4 years without any problems.
The only two things i suspect is the evaporator itself being dirty from the insight or the evaporator getting too cold due to faulty liquid line-suction sensors.
i will test it on low speed as well to see if that stops the water form jumping out of the tray.
Those MiHI units are really cheap quality, the frame that holds the evaporator is rusted and maybe the evaporator is not in the right place or angle. It says made in PRC.

[iwan_seltech]

If it has been running well for 4 years, than it has nothing to do with fan speed.
You have to make sure the water is from coils or from drain pan first.

[Christos]

while the unit was running i half opened the bottom-sheetmetal and with my torch i saw the water jumping out of the pan towards the fans
nobody had this problem with MIHI before? please reply

[Magoo]

of course it will by taking access cover off, you increase fan flow rate.

[PaulZ]

Hi Christos
You have said the water is jumping out of the pan towards the fan.
Why is there that much water in the drain?
If understand you correctly and the water is jumping out of the pan as droplets is there a lot of vibration when the fans are running?
Paul

[frank]

Check your condensate drainage. You should not have that amount of standing water in the pan if the drain is correctly trapped and has the correct fall.

When you switch the unit off, does the drain pan empty?

[eggs]

Frank, what do you call correctly trapped?
On my system I have tried no trap, standard trap and inverted p trap. It still fires water down the duct and it drips out about 2m away from the fcu.

My system also runs with no return air duct. Before I give up and flog 'em a new 'un, I still need to try a thicker filter with more resistance to see if that helps.

Cheers

[Magoo]

eggs,
water trap has to have water head what ever that exceeds, the suck factor of fan expressed in inches of water head. Best to fit a clear plastic tube in a circular loop and watch what the water is doing, if bouncing around no water will drain, add inches for a stable water level in trap.
With no return air ducting and just a filter the fan static drop so fan will over perform , either add balance louvers or double filter resistance. Either that or select a lower fan speed and gauge performance. If you have an anemometer get flow velocity average across filter multiply by area and get flow rate , check against AHU design and adjust accordingly.

[Segei]

Each fan create some vacuum between evaporator and fan. if air filter or evaporator is dirty, vacuum will be greater. To drain condensate from vacuum space, water column in the trap should be greater than vacuum. In your case trap can be undersized. Increase height (distance from bottom of the pan to bottom of the trap) of the trap. Water should not stand in the pan and pan should be sloped to the drain.

[Christos]

Thanks for all your help. I tried everything and nothing works, the trap is small but i cannot put anything bigger since the unit is on low level ceiling in a Gym and there is no space for a bigger trap.
The space is very humid and i think the evaporator is dirty from the insight, it looks clean on both sides but it is very thick and i think dirt is stack in the middle.I washed it 3 times even with condenser chemical and i can still see dirt coming out.I think the air restriction caused by the evaporator is why i get water in the duct.
I said to the owner that he needs a new unit, i spend a lot of hours trying to fix this issue. I advised the owner to use a unit with an internal water pump. Again thanks for your help!

[Magoo]

Now you tell us system is in a gym.
With new system add lots of fresh air and extract as well. If coil core is blocked beyond recovery it is all the skin and body particules that over heated bodies express and lack of suitable filtration initially.

[Segei]

Thanks for all your help. I tried everything and nothing works, the trap is small but i cannot put anything bigger since the unit is on low level ceiling in a Gym and there is no space for a bigger trap.
The space is very humid and i think the evaporator is dirty from the insight, it looks clean on both sides but it is very thick and i think dirt is stack in the middle.I washed it 3 times even with condenser chemical and i can still see dirt coming out.I think the air restriction caused by the evaporator is why i get water in the duct.
I said to the owner that he needs a new unit, i spend a lot of hours trying to fix this issue. I advised the owner to use a unit with an internal water pump. Again thanks for your help!
You can use condensate pump.

[Christos]

the reason i recommend a unit with internal pump is that those systems don't require any traps and usually the fans are blowing on the evaporator instead of sucking the air.