Requirement of Insulation on Drainage piping Due to Condensate Drain

[Buildtech2]

I am currently working on hotel tower and our client is insisting to provide insulation on drainage piping to avoid possible condensation due to condensate drain. As per project specifications, the condensate drain pipe to be connected to the nearest floor drain. It is to be noted that condensate drain pipe is already insulated but when it discharges the condensate drain water from condensate drain pipe to the floor drain and thereafter into horizontal drainage / waste pipe, our client is expecting some condensation on floor drain and also on the horizontal waste pipe which is connected to the floor drain.

As per my understanding, if the air around the pipe is cooled below the dew point temperature, condensation can be expected on the waste pipe.So we should prevent the air around the pipe from dropping below the dew point temperature to prevent condensation.

The temperature related collected is as follows.
The ambient temperature in the ceiling where fan coil unit is located is 75 F DB / 61.1 F WB.
RH = 45 %
Humidity ratio = 58.4 grain/lb
Specific volume = 13.654 cu.ft./lb
Enthalpy = 27.13 btu/lb
Dew point temperature = 52.25 F
Condensate drain temperature is 53.6 F
Material for drainage piping is CPVC.
Appreciate, if anybody can provide me any hint to avoid insulation on drainage piping as it will create a huge cost impact on our project.

 

[EnergyProfessional]

the conditions of the air in the plenum could be different from infiltration etc.

in the end it doesn't matter what engineers think. the client insists, and pays for it. so make them happy and you are on the safe side.

 

[LittleInch]

So is the condensate coming from a cooling fan coil unit?

So fairly cold?

Or condensate from a condensing boiler?

Either way I really don't understand the issue here? If you do get condensation on the inside of the pipe, then it falls inside and keeps going or are you talking about external condensation on pipes within a ceiling void?

A drawing / sketch and a bit more description would help. You know exactly what you're looking at but the rest of us don't so we need a bit of background to describe the situation.

As it stands then it appears yes, you need to insulate the drain to stop drips of water from appearing and dripping onto the ceiling or the room occupants. Hotel guests don't like drips landing on them.

If you gather the condensate in a small vessel / large section of pipe set up as a sump and then heat it somehow you might not need to insulate, but it's a lot of effort.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Buildtech2]

It seems it did not provide any clear explanation about actual issue.
Condensate drain coming out of the fan coil unit will go the floor drain through condensate drain piping which is already insulated. From floor drain, it goes to the horizontal waste drainage pipe and finally goes down through drainage stack. Now client is asking to provide insulation to the horizontal waste drainage pipe and also to floor drain to avoid condensation within ceiling void as waste drainage piping is running in the ceiling void.

Fan coil units are located in the ceiling void of hotel guest rooms.

 

[mrev23]

Insulation isn't needed if you can count on the given values:
Dew point temperature = 52.25 F
Condensate drain temperature is 53.6 F

But, as cautioned by EnergyProfessional, the dew point temperature in the ceiling void is not controlled and might climb above the condensate drain temperature.

The cold condensate from the FCU can cool the piping downstream from the floor drain. The outside surface temperature of uninsulated drainage piping in the ceiling could drop below the dew point in the ceiling void. Moisture would condense from air in the ceiling void, drip on the ceiling, and damage the ceiling.

This statement implies some level of distrust in the dew point remaining lower than the condensate temperature: "It is to be noted that condensate drain pipe is already insulated."

And a caution about using CPVC pipe (the risks would seem to be relevant for any application, not just FP):

https://www.wheatland.com/wheatland-standard/cpvc-sprinkler-pipe-31-flavors-of-risk-1/

 

[EnergyProfessional]

You have to know the condensate spends some time in the trap and warms up as it flows. it isn't a really large flow velocity. The PVC pipe has some insulation value. So a smart engineer could calculate the pipe outside surface temperature at the location in question. If condensate starts out with 53.6°F, that pipe outside temperature could be close to 60°F.

But again, the owner gave you directions to apply insulation. Unless you can prove adding insulation creates a danger or code violation, you should do what the owner wants. If the owner wants pink insulation, they shall get pink insulation. It isn't the most ridiculous owner demand.

 

[PEDARRIN2]

Few thoughts.

1. Owner wants it so owner will accept cost. Nobody wants to sleep in a room that has spots on the ceiling.
2. Spending a lot of time engineering out of it instead just doing it.
3. Specify the insulation from the drain to the stack or next horizontal branch (served by fixtures that will likely mitigate any lower temperature fluids).

 

[Buildtech2]

Thanks everybody for your valuable inputs. Will share relevant calculations and conclusion.

 

[chicopee]

Condensation is a big problem in cold climate location. I remember the exhaust vent of an air hot furnace protruding from the wall of a storage room dripping condensate during cold weather. Extreme cold weather eventually froze the condensate totally blocking the vent line and the hot air furnace stopped working. The storage room got pretty cold but luckily none of the content got "frost bite". So we put insulation around the pipe and problem solved. Just make sure the insulation is rated for hot temperatures and is weather resistant.