Drain Pipe Design

[weeliang82]

Dear all forumers,

Do you know where I can find good website that provides proper guide on how to design drain pipe for air conditioning?

I needed to design drain pipe flow for 60 units of normal wall mounted split units for a budget hotel and I want to know on the alternative that I can have...

Thank you...

[multisync]

I have been told water runs downhill

Hope that helps..

[monkey spanners]

Hi Weeliang,

I don't know of any web sites for drains. But as Multisunc says gravity is your best option here if possible, pumps tend to be noisey and i would expect would not last long in a humid country such as Malaysia.

I would be looking to size any drain to suit the duty of the indoor units, i forget what the ratio is but i think in the UK where it is less humid it is 0.7L per KW of cooling. Check this for your country.
I would avoid running drains from units on a different levels into each other as if the drain blocks up the lowest unit will the leak water.
Would be worth getting a copy of the installation instructions for the proposed equipment and check what recomendations the manufacturers have also.

Jon :)

[nike123]

On projects like that I do it with PVC ø32mm and ø50mm pipes and as multisync said use natural ability of water to go downhill rather than use pumps.

[US Iceman]

Gravity drain is the only way to do this. My main concern with using pumps to transport condensate is the possibility of failure. Gravity draining is simple and very little maintenance requirements other than the occasional check to keep the drains open.

If you do a search for Manning Equation you will find a lot of hits that describe the calculation of open flow gravity drains.

Here are a few to get you started...

http://www.fsl.orst.edu/geowater/FX3/help/8_Hydraulic_Reference/Manning_s_Equation.htm

http://www.efm.leeds.ac.uk/CIVE/CIVE2400/OpenChannelHydraulics2.pdf

http://www.co.fort-bend.tx.us/upload/images/drainage_district/3_2.pdf

http://udel.edu/~inamdar/EGTE215/Open_channel.pdf

Essentially this is a section in the field of hydraulics. This is typically used for determining water flow capacity in open culverts or sewers. It also applies to piping. The essential concept is that the water will flow through the pipe, which is only partially full. The vapor space on top of the water in the pipe helps to equalize the pressures with the pipe.

It's an interesting topic and not one that has an easy answer other than doing some research and trial calculations.

Hope this helps you in your project.;)

[Brian_UK]

Assuming that each bedroom has a bathroom and each bedroom is having an AC unit then use a gravity drain connected to the bathroom drainage via water filled traps.

[weeliang82]

Thanks for all the prompt reply,

Yeah, I was thinking the same..to just connect the drain pipe of each of the fan coil unit to the bathroom drainage pipe in washroom (since each of the room have its own washroom). Seems to be more practical that way...

I was looking to connect all the drain pipe of the FCU and connect it to a main drainage pipe, but that seems unpractical, especially if the pipe is clogged in the future...

[multisync]

Thanks for all the prompt reply,

Yeah, I was thinking the same..to just connect the drain pipe of each of the fan coil unit to the bathroom drainage pipe in washroom (since each of the room have its own washroom). Seems to be more practical that way...

I was looking to connect all the drain pipe of the FCU and connect it to a main drainage pipe, but that seems unpractical, especially if the pipe is clogged in the future...

I wouldn't necessarily agree. Most large installs have their own dedicated drain running alongside. To use each room as a drian off will increase the install costs and be more intrusive to the room during maintenance and blockages.

If using in ceiling units we would always run our own drain to the outside. If using wall mounts then that will make things far more complicated and is dependant upon many things only a drawing/site visit could illuminate