Evaporative condenser´s liquid drain trap

Hi guys,

Everybody knows that it´s necessary a trap in the liquid drain evaporative condenser´s piping when there are more than one condenser operating in parallel.

We have a main run piping 2,5m far from the condensers.

What´s the better solution in your opinion: to make the trap as nearest as the main piping (trap with a small horizontal piping lenght) or the condenser (trap with with a big horizontal piping lenght)?

Best regards,

Volnei

Hi volnei,
doctors differ, patients die:D I would run the main liquid line feeding the receiver with a pitch to the receiver. Then run each of the condenser condensate lines with a pitch towards the main liquid line, trapping the individual condensate feeds as they enter the bottom of the main liquid line:)
Any other sugestion folks, as this is a bit of a grey area:confused:
Regards. Andy:)

Quote:

---

We have a main run piping 2,5m far from the condensers.

What´s the better solution in your opinion: to make the trap as nearest as the main piping (trap with a small horizontal piping lenght) or the condenser (trap with with a big horizontal piping lenght)?

---

I am having a little trouble picturing your choices, volnei, but I would think the less pipe the better, if that addresses your question.

I am assuming you are referring trapping that obviates the potential of liquid refrigerant logging in one condenser or the other. I would think any trap equivalent to the vertical depth of the condenser coils would suffice.

Quote:

---

doctors differ, patients die

---

Quote:

---

Any other sugestion folks, as this is a bit of a grey area

---

LOL Andy. It is more than a grey area. Liquid return line piping is a black hole, loaded with apparent contradictions.

Many manufacturers recommend that you size the liquid return line to permit sewer flow (insuring a layer of vapor above the gently sloped pipe to avoid vapor lock in the receiver, for example.

Then they go ahead and recommend traps. Some others (including ASHRAE) advise adding a receiver vent line to get around the first contradiction. Of course there are always check valves to play with.

I whacked my self on my head with this one in the old Fridgetech pages to no great satisfaction.

I think the simplest and shortest is the bestest. I have seen too many installations where the cures caused more problems than if all good advice was ignored in the first place.

Drop directly from the condensers to a level near their mounting surface, join the pipe to the main and be done with it. And yes, the receiver is ideally located below the condensers.

Could soneone post an informative link for me to peruse, if it is not inconvenient? I am entirely unfamiliar with this subject.

thanks in advance :)

Hi Herefishy,
sorry I tried to find the post on www.fridgetech.com , the one Dan mentioned, but to no avail:( :confused:
Maybe Marc could post an url to it.
Regards. Andy:(

Dang. I could have sworn it was on Fridgetech. I couldn't find it either. I know ASHRAE fundamentals and Carrier manuls deal with the theory as well as Stoecker's book. Also Hussmann manuals did. I could copy and fax pertinent pages, if anyone is interested.

If I recall how the discussion started, it was something like, what if you have two condensers piped in parallel, what tends to happen when all the fans cycle off in one condenser and all the fans in the other are running? Or what can you expect to happen when you have differently sized condensers piped in parallel?

The going theory was that you had to have a liquid seal of sufficient height to overcome any pressure drop differences between the condensers, or otherwise one would log with liquid while the other has insufficient condensing capacity to keep up, thus you lose the benefit of the combined condensers' capacity.

I seem to remember it was a busy debate. Now I am worrying in my dotage if I was imagining it all. I hate when that happens.:)

Here's something from Heatcraft. For what it is worth.

http://www.heatcraftrpd.com/Maintena...s/H-IM-43B.pdf

If you have some condensers in parellel, the liquid line got to be trapped individually. If not, you have the same pressure comming into the condensers, but if one of the condensers do not operate properly, and therefore have a very little pressure drop over the condenser, then the other condenser cannot have a bigger pressure drop (it cannot have a lower pressure comming out) and will therefore back liquid up in the coil, until it allmost work as bad as the other one.
Or look at it this way; if you have a equalising line from the reciever to the inlet to the condensers, then you have the same pressure in the inlet to the condensers as in the reciever. You have a pressure drop in the condenser and therefore a lower pressure than in the reciever. Hmm, If you have a trap, then there will be a build a liquid column before the trap to overcome the higher pressure in the reciever, no trap, then there will back liquid up in the reciever.
Saludos