help - lots of condensation on insulated pipes

[goldpau]

Any help / advice would be much appreciated: -

so here is the problem: -

got called out to a customers a/c system in a server room who was complaining that there was water leaking onto his floor.

turned up and found a wall mount system with large white trunking under the indoor unit which goes along the wall to the outside wall (approx 2 metres). Pipes have been run into trunking with condensate pipe, out the wall and up and then into the outdoor unit. Looks like a good install (neat, tidy good pipe bends etc) and customer advised it has worked fine for approx 18months which is when it was installed.

Problem is when i removed the front cover of the trunking there is loads of condensation on the insulation of the pipes and condensation on the plastic condensate pipe, this is leaking out of the corner of the trunking and onto his floor. The server room is nice and cool and customer has said that he has not noticed any drop in performance of the a/c system just that it 'just started leaking a couple of days ago'.

I turned it off, replaced the insulation, checked the indoor filters which were clean, checked outdoor unit which is also nice and clean. Turned the system back on on Friday, set to 21C and said to customer give me a call on Tuesday to let me know what has happened.

He rung me this afternoon to say it is exactly the same and there is condensation on the insulation and water pipe

What have i missed? What would cause this? I can only think it is refrigerant issue (which is R410a by the way) and why has it only just happened when it has been ok for last 18 months?

Thanks

[chemi-cool]

Insulation should be at least 13 mm thick.

The usual insulation used with splits is only 6 mm, and its not enough.

Also check that the set point is not too low.

[goldpau]

thanks for post but i replaced the insulation and what i put back on was def 13mm - i understand your point about the thickness of the insulation but why has it been ok for 18 months and only now it has started being a problem?

[chemi-cool]

Was there any material on the insulation?
Is the insulation exact pipe size?
Was the pipe dry when you put the new insulation?

It sounds to me like ice in the indoor unit and arround the pipe under the insulation.

Insulation must be dry.

Did you check for lack of refrigerant?

[goldpau]

Answers in RED

Was there any material on the insulation? NO
Is the insulation exact pipe size? YES
Was the pipe dry when you put the new insulation? YES - fully dried it all out

It sounds to me like ice in the indoor unit and arround the pipe under the insulation. Have checked indoor unit and no ice, also no ice outside

Insulation must be dry. can confirm was dry when i put new on

Did you check for lack of refrigerant? Not yet, could this really cause the problem? As said didnt feel need to check refrigerant as system was cooling perfectly well and no ice on indoor unit - hence why i am confused

[paul_h]

If it's low on refrigerant, it could cause water leaks. Especially on an a/c running 24/7.
I've had unit's blowing water from the evap just because it's 100g short. It all depends on the design, the humidity, filter condition/fan speed etc.
Some units/conditions go from icing up to no cooling when slightly short. Others go to cooling still but excess moisture before they get to the icing up stage.
I wouldn't flap about if it's a server room and you want to get it done and not come back. Reclaim and weigh what you get, if the charge is not quite right, then find the leak with nitrogen and vac before weighing in new refrigerant to the manufacturers spec.

[AcidSlasher]

when your there next, put insulation on the plastic condensate drain pipe too. if the water running through it is really cold it will cause condensation to build up on the outside of the pipe. iv seen condensate drains that run through ceiling spaces cause enough build up of condensation on the outside of the pipe to drip down and ruin ceiling tiles.

[Brian_UK]

I second AcidSlasher, the condensate drain must also be insulated.

Also check for any airflow through the trunking which will bring in more moisture.

[paul_h]

I find the condensate drain to only be an issue if the water inside it is not flowing. The cold water has to be sitting around for a while inside the drain for any condensation to form on the outside. Especially in what is going to be a very dry enviroment (server room with a split running 24/7).
So if the drain flows freely that shouldn't be a problem. But I guess you could make sure the drain has a decent decline and water flows through it OK.

edit: Is there a condensate pump? Or am I misunderstanding you when you say the pipe duct goes across the wall and then up to the condenser and the water leak is out of the pipe duct corner going up?

[AcidSlasher]

the image i have in my head of the install from the way he described it is as follows:

the unit is mounted on an interior wall about 2 metres away from the exterior wall, the trunking runs across the interior wall from the unit then punches outside, THEN runs up to the outdoor unit. this would make the drain from the unit run horizontally, its possible it doesnt have any fall and would have water sitting in it as u said.

im going to have to disagree with you about condensation only forming on the pipe if water is sitting in it, to me condensation would form regardless, as long as the water chills the pipe down enough. what makes u say that? not saying your wrong, but im interested to know? we are all still learning things after all.

i figure if hes going out there anyway, he may as well throw some insulation on the drain pipe while hes there.

[paul_h]

The drain pipe is warmed by the ambient, the drain pipe has to fall below the dew point for condensation to occur on the outside of it. That requires a lot of chilled water sitting in it for a PVC pipe.
Good drains don't allow sitting water, hence don't have condensation forming on them because there's no sitting chilled water to lower the drain pipe to below dew point.
edit: My point was for all the cold water in the drain flowing out normally, the ambient is also warming the drain. So the condensate is chilling the pipe as you say, but ambient is warming the pipe. It takes a lot of sitting water to cool the pipe enough to produce PVC pipe sweating, and that only occurs with a poor flowing drain full of chilled water.
Nearly ever domestic wall, ducted and cassette split is not insulated, and they never have a problem unless the drain is blocked/restricted

[Prince Vaillant]

What type of insulation are you using? The best stuff is Armaflex as it is of a closed cell construction. www.pipelagging.com

[goldpau]

thanks for all the posts, acidslasher you are correct in how the system has been installed.

Ive used insulation from HRP (cant remember the brand) but never had a problem with it in the past.

Went back yesterday and checked the refrigerant, weighed it out and was short by 240g, pressure tested overnight and no drop whatsoever so replenished the system today with new 410a back to original charge - also insulated the water pipe

cant see any draught in the plastic trunking as the hole to the outside was well filled and the trunking was all siliconed closed.

waiting for customer to ring me on Monday to hopefully say all is well but cant work out why it is 240g short when there is no leak and also why it has been ok for last 18months - fingers crossed all is sorted now

will follow up with what happens

cheers all

Paul

[Gary]

The short answer is that condensate forms on any surface that is below dewpoint.

Either the surface temp needs to be higher or the dewpoint temp needs to be lower.

If the problem has not occurred in the past then one of these two factors has changed.

[sinewave]

but cant work out why it is 240g short when there is no leak and also why it has been ok for last 18months

cheers all

Paul

When leak/pressure testing did you check the valves on the condensor with the caps removed and the shraeder valve with no guages on it?

Most leaks occur there these days on newer 410a systems!

[setrad7791]

I'll tell you why..... All principles state that condensation can only occur when their is humidity in the air, so if the system is installed in a small server room and working correctly there should be a low humidity due to the moisture removal of the unit. Now if there is condensation on the pipework it has to be coming from an outside source..... my best guess would be the penetration through the room where the pipework exits, im guessing warm humid air is tracking down from the ceiling/wall cavity along the pipwork inside the trunking. Is the pentration sealed?

[icecube51]

The short answer is that condensate forms on any surface that is below dewpoint.

Either the surface temp needs to be higher or the dewpoint temp needs to be lower.

If the problem has not occurred in the past then one of these two factors has changed.

could agree more, its like clockwork.

Ice