code, as far as i know, is one or the other. We do both, secondary drain line should terminate in a conspicuous place so the homeowner can't help but notice it.

 

I'd personally go with the code: 2009 IRC M1411.3.1 Auxiliary and secondary drain systems. In addition to the requirements of section M1411.3, a secondary drain or auxiliary drain pan shall be required for each cooling or evaporator coil where damage to any building components will occur as a result of overflow from the equipment drain pan or stoppage in the condensate drain piping. Such piping shall maintain a minimum horizontal slope n the direction of discharge of not less than 1/8 unit vertical in 12 units horizontal (1% slope). Drain piping shall be a minimum of 3/4" nominal pipe size. One of the following methods shall be used:
there are 4 options plus you can use a water level monitoring device in the primary drain pan. Devices shall not be installed in the drain line. The options are basically a pan with conspicuous discharge, a drain from the aux. drain in the coil, a pan with a float switch and drain, or a wet switch in the aux. drain port.

The code calls for a switch to "shut off the equipment". There is debate over whether or not you can break 'y' vs. 'R' as some wish to leave the fan 'on'.

 

If its in the ceiling or attic, use a secondary drain pan. Float switch in primary and float switch in secondary, both wired in series to r with no batteries in the stat, so the customer know there is a problem.

 

i break y so if the coil is iced it will thaw by the time the customer realizes the temp isn't keeping up so i can do my job when i get there rather than waiting on ice to melt.

 

Installing drain line float switches has never failed me before and I'm a little suprised. Not that I'm aruging with the code or the reasoning, it's just an observation. I guess I'll start making sure these always go in the secondary on the coil.




Thanks fella, good insight and good thinking.





I sure do love this site and the wealth of information and opinions found here in such a short amount of time. If only my coworkers realized the amount of information that can be found here and it's ability to help them make themselves better techs.

 

+1 for breaking the Y connection. Customer will call for a running but no cool compliant. Ask customer if outdoor unit is running. Cycling of the R connection on a system powered thermostat could potentially damage the stat over time.

 

How does a clogged drain line equal an iced up coil?

 

Usually, in my neck of the woods, if the float switch has one off its bc its freezing up rather than clogged drain.

 

Here is how I look at it.

You are spending some time with family on Saturday afternoon. You are on call, but the temperatures are only in the low 80's, and you haven't had any calls, so you were thinking of taking the family out for dinner.

Scenario 1) Emergency drain pan with a float switch and no drain.

Customer that lives 30+ miles from you calls with no cooling, has guests over, needs you to come NOW.
You go out, its 130ºF in the attic, and you have to clear the simple primary drain trap clog, AND deal with several gallons of water.

Scenario 2) Emergency drain pan has a drain line, with secondary drain from coil piped into the emergency drain line, and moisture sensor in emergency pan to turn the system off if things get really bad.

Customer that lives 30+ miles from you calls because the water dripping from the emergency drain line over the back porch reminded them they need to call to schedule their regular PM service for sometime next week.


Now tell me which drain setup you would rather your customers have.

One says don't install a secondary drain on a drain pan because if the primary ever overflows or the coil ever freezes and then thaws and ends up in the secondary, the water will continue to drain for however long until homeowner finds this. Perhaps it's in a hard to reach or out of the way place and they never see it. Assuming the secondary drain works properly and the home owner never ventures to the attic, the secondary pan could potentially spend a lot of time acting as a primary.

So what if the secondary drain ends up acting as the primary for a period of time?
Run a drain line off the emergency pan, and pipe the coils secondary drain outlet into the the drain from the emergency pan, instead of just dumping it into the pan.
Put a moisture sensor in the emergency pan to shut the system off if water gets in the actual emergency drain pan, indicating something bad is happening.

 

Here is how I look at it.

You are spending some time with family on Saturday afternoon. You are on call, but the temperatures are only in the low 80's, and you haven't had any calls, so you were thinking of taking the family out for dinner.

Scenario 1) Emergency drain pan with a float switch and no drain.

Customer that lives 30+ miles from you calls with no cooling, has guests over, needs you to come NOW.
You go out, its 130ºF in the attic, and you have to clear the simple primary drain trap clog, AND deal with several gallons of water.

Scenario 2) Emergency drain pan has a drain line, with secondary drain from coil piped into the emergency drain line, and moisture sensor in emergency pan to turn the system off if things get really bad.

Customer that lives 30+ miles from you calls because the water dripping from the emergency drain line over the back porch reminded them they need to call to schedule their regular PM service for sometime next week.


Now tell me which drain setup you would rather your customers have.




So what if the secondary drain ends up acting as the primary for a period of time?
Run a drain line off the emergency pan, and pipe the coils secondary drain outlet into the the drain from the emergency pan, instead of just dumping it into the pan.
Put a moisture sensor in the emergency pan to shut the system off if water gets in the actual emergency drain pan, indicating something bad is happening.

Yep ^

 

I realize iced coils and clogged drains are two separate issues but they often coincide. Once the primary clogs with ice, it pees out the pan or the secondary. Now, while wet switches, floats and alarms are nice, just keep in mind that anything made by man can and will eventually fail. Having a gravity drain as backup makes the most sense to me. Mark makes a subtle point that is reflected in the code: a conspicuous discharge point. You should educate your customer where to look for this and how often to inspect it and what to do when it pees.

As for whether or not you break 'Y' vs. 'R' on a pan switch really depends upon what the emergency pan is there for. If it is just for cooling, then 'y' should be fine. If you have a condensing furnace, you'll need to break 'R'. If this is straight A/C then you could install a drain on the Aux off the coil but you wouldn't know it was technically overflowing unless your client observed the discharge. If you install a flow alarm on the Aux drain, you get the best of both worlds: functional non-mechanical drainage with equipment interruption to force notification of the owner but that entails a service call that day instead of maybe giving you a week or two as Mark suggested. Now, if you tie the alarm into a home automation system you can have it call you and tell you its sick.

On a little thread drift, when you encounter a clogged coil drain, do you ever examine the goo to see how much is dirt and soiling vs. algae? I mean, if your filtration is effective, why should you get enough dirt to clog a drain off a coil? Seems to me that would be important as you can sell adjustment/ improvement of the filtration. I see horrible filter racks and open slots all the time and I know its hurting the system when it clogs the coil. It can affect comfort delivered, system efficiency, airflow, delta T, humidification,SH/SC, combustion analysis and HX service life, etc.

Another thread drift: when you have an attic system with secondary pan and blown in insulation, do you protect the pan with some form of netting? I find a lot of these pans clogged with insulation. In cases with metal pans, I would recommend a wet switch such as a 'hockey puck' even if the pan has good gravity drainage. If you rely on a float switch, a pan can remain a pond of standing water for long periods, which can rust through rusting in water damage. A plastic pan of course doesn't have this concern.

 

On a little thread drift, when you encounter a clogged coil drain, do you ever examine the goo to see how much is dirt and soiling vs. algae?

Algae in the dark?

That goo that grows in the drain pan is good old fashioned bacterial bio-slime, or even slime mold.

It comes in a variety of colors, even pink!

 

No I don't inspect the goo, it usually looks like a big nasty rotten oyster. Most systems have a filter grill then the return duct leaks pretty good from there to the unit so that's where most of the nasty cones from. Most customers just want it fixed then for as little $$$ as possible. I always offer the option of better filtration but rarely do people go for the added expense unless its a new install. I've never seen netting over the aux pan, sounds like a good idea but again the added cost and time to do it renders it unlikely to be done in the real world. tge majority of people only care about now, not what might happen in the future.