Thread: Furnace questions

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Originally Posted by Jeff Eastman

Picture A:

Does not the secondary drain line need to be p-traped and insulated?
No

And is the secondary drain line allowed to tie into the auxilary catch pan drain line?
Yes - its the same as if the secondary terminated in to the pan. Probably would keep water out of the pan, as well as subsequent corrosion, pan replacement, etc.

Picture B:

Is this satisfactory support for the elbow? I'd think the strap should be AT/UNDER the elbow, not south of it.
If the installation is stable, I wouldn't worry about it.

Picture C:

Is the elbow near the furnace suppose to be strapp supported? If so, how would that be accomplished?

Same as answer to B.

Originally Posted by Jeff Eastman

Picture A:

Does not the secondary drain line need to be p-traped and insulated?

Yes.

And is the secondary drain line allowed to tie into the auxilary catch pan drain line?

I would not do it that way, you want the secondary to drain into the auxiliary drain pan so the water will activate the shut off switch.

Picture B:

Is this satisfactory support for the elbow? I'd think the strap should be AT/UNDER the elbow, not south of it.

No and yes (to your two questions).

The vent should be supported in three axis: up/down, right/left, and frontward/backward - that strap is not addressing but half of one of those.

Picture C:

Is the elbow near the furnace suppose to be strapp supported? If so, how would that be accomplished?

Supported, but the 'how' depends on where, to what, and how far away that is connected to whatever it is connected to.

Yes... there should be a trap in the primary drain line. Does that unit have one?

I can't tell as it appears the insulation may be obstrusting my view of the trap.

There is still an issue with the styrofoam in the pan. Any of those little pellets become loose and will assist in providing an indoor waterfall (from the attic).

I never have like the placement of a unit on top of styrofoam...

rr

Why would the secondary drain pipe need a trap?

If the secondary gets plugged, the water will back up into the pan and activate the sensor - if one is installed.

Does not the secondary drain line need to be p-traped and insulated?

I have to admit that I have never seen the secondary line insulated before and I assume that is to keep down condensation on the exterior of the pipe. But that would also imply that there is condensate water draining into it. It does not have to be p-trapped as that drain shouldn’t be needed unless the primary fails or becomes clogged. I do not foresee a problem with either and would not report on it. However the secondary drain line is turned up so that it will not function as a backup drain and will not drain into the catch pan if it were to be needed. I would report on those items.


And is the secondary drain line allowed to tie into the auxilary catch pan drain line?

Richard said “And is the secondary drain line allowed to tie into the auxilary catch pan drain line? Yes - its the same as if the secondary terminated in to the pan. Probably would keep water out of the pan, as well as subsequent corrosion, pan replacement, etc.”

But it looks to me to be that the primary drain line is tied into the water catch pan drain line. That cannot be done as if the primary condensate drain line clogs or fails downstream so does the catch pan drain. There goes the ceiling below. I also do not see a trap on the primary drain line. It could be out of the picture.


Picture B:

Is this satisfactory support for the elbow? I'd think the strap should be AT/UNDER the elbow, not south of it.

As for as the straps, as long as it is secure it should be fine. Granted poor workmanship by the mechanical contractor and this could have been a lot better. I would check for stability and check the connections at each transition. If it moves, report on it. Don’t burn yourself.


Picture C:

Is the elbow near the furnace suppose to be strapp supported? If so, how would that be accomplished?

Same as Picture B. Its out of the picture but why couldn’t the elbow be eliminated and the flue pipe be run straight up to picture B elbow? BTW the elbow could be supported from underneath by bearing the elbow on a noncombustible material such as sheet metal bent and secured to the plywood.

Code is crystal clear on this. The secondary drain line is NOT allowed to be tied into the primary drain line.

This is from memory but gets the point across: The secondary drain line must drain to a separate and conspicuous location.

Conspicuous - meaning you will notice it when water comes out.

I do not recall code saying it has to be insulated, but if it terminates to a "conspicuous" location as required by code, it won't be draining long enough to sweat much.

The most conspicuous location I've seen is over the garage or front door - dropping down from the soffit.

Since it should terminate to daylight, no trap is needed.

Jerry and Richard -

You are not required to have a sensor switch AND a secondary drain line. You are required one or the other. Since there is a secondary drain line, I would assume there is NOT a sensor.

The secondary drain from the coil (not the emergency pan drain) should be trapped or you have a pipe leaking conditioned AIR. Priming the trap would be needed to make it work the 99% of the time the drain is not needed. I recommend mineral oil or equivilent.
I know Lennox tells you to trap both primary and secondary on at least some of their units. So it is at least sometimes a manufacturer requirement and common sense the rest of the time.

Originally Posted by Bruce Lunsford

You are not required to have a sensor switch AND a secondary drain line. You are required one or the other.

You are correct and I am aware of that, however, if you have an auxiliary drain pan AND a secondary drain line, the only water you will ever (never?) get in the auxiliary pan is from the unit overflowing, which is what the secondary drain line is there to prevent (you do not water overflowing into the unit and getting it all wet, you will ruin the unit and the insulation in the unit).

Since there is a secondary drain line, I would assume there is NOT a sensor.

Except that I can see the wires to it.

I'm assuming this is an attic installed unit with a drip pan underneath. These lines are for a/c condesation removal. The two lines should be separate, one for normal condesation run off from the coil area during the operation of the a/c system, the other from the drip pan is an emergency line. If water is coming out of the emergency line connected to the drip pan, than you have a unit leakage issue and it should be addressed.
I instruct my clients to monitor this line during the operation of a/c during the warmer months. If they were tied together you would lose a vital piece if info that tells a defect has occured. If in fact there is a leak in the system and it goes undetected, it would most likely manifest itself as a water stain to the interior finish below the unit.

Originally Posted by Phil Rubenstein

These lines are for a/c condesation removal. The two lines should be separate, one for normal condesation run off from the coil area during the operation of the a/c system, ...

Phil,

There 'is' a separate 'primary condensate drain line' which is trapped and insulated.

The two lines are: 1) top one is 'secondary' condensate drain line which ties into 2) the auxiliary drain pan drain line.

There is really nothing wrong with tying the last two together, except for:
- the secondary drain line is not trapped
- the secondary drain line (as routed) is not insulated (if this just was trapped and then drained to the auxiliary drain pan, it would not need to be insulated)
- the auxiliary pan drain line is not insulated (if the secondary condensate drain line did not run into this drain line, this would not need to be insulated)

- (while this is not really 'wrong', it is 'almost useless) the auxiliary drain pan is going to 'almost' never get water in it as the secondary condensate drain line is routed, and, in fact, is not even required with the secondary drain line routed that way - see M1411.3.1.2 below and visualize the drain line between the auxiliary pan and the secondary drain line as 'not being there', that the secondary drain line continues outside as the rest of that drain line (which would now need to be insulated) and ends at "a conspicuous point of disposal to alert occupants in the event of a stoppage of the primary drain." (as that drain line probably does).

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 in the direction of discharge of not less than 1/8 unit vertical in 12 units horizontal (1-percent slope). Drain piping shall be a minimum of 3/4-inch (19 mm) nominal pipe size. One of the following methods shall be used:
- 1. An auxiliary drain pan with a separate drain shall be installed under the coils on which condensation will occur. The auxiliary pan drain shall discharge to a conspicuous point of disposal to alert occupants in the event of a stoppage of the primary drain. The pan shall have a minimum depth of 1.5 inches (38 mm), shall not be less than 3 inches (76 mm) larger than the unit or the coil dimensions in width and length and shall be constructed of corrosion-resistant material. Metallic pans shall have a minimum thickness of not less than 0.0276-inch (0.7 mm) galvanized sheet metal. Nonmetallic pans shall have a minimum thickness of not less than 0.0625 inch (1.6 mm).
- 2. A separate overflow drain line shall be connected to the drain pan provided with the equipment. This overflow drain shall discharge to a conspicuous point of disposal to alert occupants in the event of a stoppage of the primary drain. The overflow drain line shall connect to the drain pan at a higher level than the primary drain connection.
- 3. An auxiliary drain pan without a separate drain line shall be installed under the coils on which condensate will occur. This pan shall be equipped with a water level detection device conforming to UL 508 that will shut off the equipment served prior to overflow of the pan. The auxiliary drain pan shall be constructed in accordance with Item 1 of this section.
- 4. A water level detection device conforming to UL 508 shall be provided that will shut off the equipment served in the event that the primary drain is blocked. The device shall be installed in the primary drain line, the overflow drain line or the equipment-supplied drain pan, located at a point higher than the primary drain line connection and below the overflow rim of such pan.

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