No secondary (pan) drain in Attic Okay per builder

From the Realtor’s email today

"Please see the e-mail traffic below regarding the heat pump at ADDRESS, As you may recall, it did not have a secondary drain line from the pan in the attic to the outside. The owners referred the problem to their builder who looks to be saying a secondary drain line is not required because there is an electronic overflow device is installed on the unit (float switch?). The builder said below that it was installed to code.
I’m not an HVAC person, but this would be the first time I’ve heard of a pan with out an overflow drain.

Many thanks."

I know what [FONT=Comic Sans MS][size=2]International Residential Code see M1411.3; and Uniform Mechanical Code see 310.1-.5 say…

I really like this Barry response, however he doesn’t address the ‘float’ or ‘water level’ cutoff switch as a ‘secondary replacement’…

What I told her…

"[FONT=Comic Sans MS][size=2]High limit float switches can and do fail. When most things of an electrical nature fail, something stops, and it is usually immediately obvious that something is wrong. When a high limit switch fails, liquid goes where it is not supposed to. Often, it isn’t obvious until there is damage. That’s the problem with them and the reason they are installed as a back up to the back up.

Building codes are absolute minimum standards. All competent HVAC installers provide a primary, separate secondary and a float switch (I have all three on the AHU in my attic and the one under my elevated home) and the authorities having jurisdiction (doing the rough mechanical inspections) often miss things. People are only people.

Ask an HVAC Installer if it’s done correctly not the person responsible for paying to make it right… Go to the neighboring homes and see it they have them (separate secondary drain as well as a tertiary float switch). That they were omitted and overlooked in this home could be isolated occurrence or it could be the way the HVAC sub did them all and they were allowed (I doubt it, but I’m not infallible[FONT=Wingdings][/FONT]). :mrgreen:

Bottom Line-

[FONT=Verdana]Should the primary drain pipe ever clog without a separate secondary drain, water may overflow the drain pan and potentially damage the service platform, insulation, ceiling joists/plaster/sheetrock, and furnishings or flooring below. Repair by a licensed HVAC contractor is highly recommended.[/size][/FONT]

Whether any of my advice is followed or not, I simply make recommendations I feel are in the best interests of my clients."

I feel better, sorry for the long post…
BTW the house was a 2007 build :roll:

I disagree. The code says either a float switch, a pan drain, or both. Who are you to make up your own rules?

Personally, whenever I see a float switch, I test it to make sure it turns off the system. If it does, that’s good enough for me.

It isn’t best practice but as long as the float switch is installed properly it should cut the power to the unit before the pan overflows.

I recommend a secondary drain as an upgrade.

The code is not that ‘cut and dried’ when you read all 3 numbered items.

Would you live under the primary and only a float switch in your attic?

The reason I wrote it up as I did is because I’ve not seen it on a house under 5 years old in the last 5 years or so…

Do you wonder why? Better building practice comes to mind.

How do you ‘test’ the float switch, by the way?

Gotta go to bed now (wife just left) keep 'em coming…:mrgreen:

I raise the switch. If it doesn’t instantly cut off the blower or condenser, I put a multi-tool that I carry with me under it for a while and continue on with the attic inspection. If it doesn’t cut off the condenser or blower after 5 minutes or so, I write it up.

Call the building department and ask them if a seconday drain line is needed if there is a float swtich. If they say no, ask them what happens if the switch fails. If they are not enforcing it, then all you can do is recommend that one be installed for reasons already stated.

Some terminology corrections are needed in this thread, reference to secondary and safety drains commonly get misused by inspectors, builders etc.

The drain pipe “from a pan” is called a safety pan drain or safety drain.

The extra drain from the airhandler to the pan is called the secondary drain.

Sometimes the secondary drain runs outside over a window and sometimes the safety drain does.

I have seen both the primary and secondary running outside with a pan and float switch but have never seen all three pipes running outside.

My two attic systems use a microswitch type float switch, no pan drain.
Microswitches are very reliable when used in low voltage, low to zero use applications.
No water in the pans for 7 years on two systems.

The round type, magnetic? or something, not sure about the reliability of those.

Appears Joe that I am stalking you tonight (not really) let me ask this question I am full of question tonight being you did not answer my flue question I will ask this one. You stated if it does not cut off the blower or the condenser you write it up what if it just cuts off the blower and not the condenser or just the condenser and not the blower what then do you do.


Do you agree with the drain pipe terminology posted above?

I think its important, especially for this example:

System has a safety pan with no drain pipe and no float switch.
It also has the secondary port on the unit with the factory plug still present.

What if an inspector writes up “missing secondary drain”.
A contractor or handyman might just add the stub pipe from the unit to the pan and not even address the missing safety drain since all that was really written up was the missing secondary pipe.

If the condenser turns off, that will stop the production of condensate I believe. If the blower (entire system) turns off, then there is obviously no problem.

In the winter when I raise the switch, the furnace shuts down. In the summer when I raise the switch, sometimes only the condenser turns off (I have to walk outside to see). Perhaps if I waited long enough, the entire system would shut off; I don’t know.

You can usually tell by the sound (suction of the refrigerant) if the condenser turns off.

I saw two floats today on the split units, pointed them out and said they were ok.

I do not test secondary pans either as a regular service, and they have been known to fail also.

Barry is a carpentar and just makes some stuff up to sell papers.

I was just ragging you for your choice of words you made it sound as if it was alright if just one or the other cease to operate, I knew what you were talking about but others might not.

Yes it is very important to use the right terminology. I have seen the secondary drain line which is the high drain off of the evaporator connected to the drain on the safety pan and common to a noticeable area. It just depends on the AHJ what they want. I have one city I inspect in that does not require a drain on the safety pan if a safety switch is within the pan and two other city’s that require a drain on the pan reguardless if switch is used or not. Personally I think all drain pans should have a drain line installed but If they don’t and the AHJ does not require it I don’t make a big stink out of it just advise and move on.

Interesting points Charley, looking back on the floats I saw today, both A-Coils were in first floor closets.


You’re absolutely correct. I call your ‘safety drain’ the secondary drain (or simply pan drain) when its really a separate overflow drain (safety drain).

In the IRC referenced example it’s called both an “auxiliary pan drain” in method 1; an “overflow drain” in method 2; and a “separate drain line” in method 3.

Point taken, the message remains unchanged. I wouldn’t trust only a float switch above me.

This horse is dead…:mrgreen: