IMC Condensate Questions

[jar546]

A new commercial building is being fitted with high-efficiency fuel-burning appliances that produce condensate. The design includes a condensate drainage system that utilizes CPVC piping. The piping is planned to have a uniform diameter of 3/4 inch from the drain pan connection to the point of disposal. The system is also designed to include a condensate pump located in the attic space.

Based on IMC Section 307:

1. Is the chosen material (CPVC) for the condensate drainage system compliant with the requirements of [M]307.3 Drain pipe materials and sizes of the IMC?
2. Does the piping diameter comply with the minimum size requirements as per [M]307.3?
3. Considering the location of the condensate pump in the attic, what specific requirement must be adhered to as per 307.6 Condensate pumps to ensure proper safety and functionality?

 

[classicT]

A new commercial building is being fitted with high-efficiency fuel-burning appliances that produce condensate. The design includes a condensate drainage system that utilizes CPVC piping. The piping is planned to have a uniform diameter of 3/4 inch from the drain pan connection to the point of disposal. The system is also designed to include a condensate pump located in the attic space.

Based on IMC Section 307:

1. Is the chosen material (CPVC) for the condensate drainage system compliant with the requirements of [M]307.3 Drain pipe materials and sizes of the IMC?
2. Does the piping diameter comply with the minimum size requirements as per [M]307.3?
3. Considering the location of the condensate pump in the attic, what specific requirement must be adhered to as per 307.6 Condensate pumps to ensure proper safety and functionality?

I think I may be using a different year of the text, so code references may vary. Following answer is using the 2021.

1. Yes - see orange text in 307.2.2
2. For sizing, the applicable section is not 307.3 but is from 307.2.2 and its table. Cannot answer definitively, but it is unlikely if there are multiple systems. 3/4" is the minimum size, larger diameter required where equipment capacity exceeds 20-tons; pipe cannot decrease in size downstream. (See 307.2.2 red text)
3. Condensate pumps in an attic require connection to the appliance served that will shut the appliance down if the pump fails. (See green text in 307.3)

2021 IMC​

307.1 Fuel-Burning Appliances​

Liquid combustion by-products of condensing appliances shall be collected and discharged to an approved plumbing fixture or disposal area in accordance with the manufacturer's installation instructions. Condensate piping shall be of approved corrosion-resistant material and shall not be smaller than the drain connection on the appliance. Such piping shall maintain a minimum horizontal slope in the direction of discharge of not less than one-eighth unit vertical in 12 units horizontal (1-percent slope).

307.2.2 Drain Pipe Materials and Sizes​

Components of the condensate disposal system shall be ABS, cast iron, copper and copper alloy, CPVC, cross-linked polyethylene, galvanized steel, PE-RT, polyethylene, polypropylene, PVC or PVDF pipe or tubing. Components shall be selected for the pressure and temperature rating of the installation. Joints and connections shall be made in accordance with the applicable provisions of Chapter 7 of the International Plumbing Code relative to the material type. Condensate waste and drain line size shall be not less than 3/4-inch pipe size and shall not decrease in size from the drain pan connection to the place of condensate disposal. Where the drain pipes from more than one unit are manifolded together for condensate drainage, the pipe or tubing shall be sized in accordance with Table 307.2.2.

TABLE 307.2.2
CONDENSATE DRAIN SIZING​

EQUIPMENT CAPACITY	MINIMUM CONDENSATE PIPE DIAMETER
Up to 20 tons of refrigeration	3/4 inch
Over 20 tons to 40 tons of refrigeration	1 inch
Over 40 tons to 90 tons of refrigeration	11/4 inch
Over 90 tons to 125 tons of refrigeration	11/2 inch
Over 125 tons to 250 tons of refrigeration	2 inch

307.3 Condensate Pumps​

Condensate pumps located in uninhabitable spaces, such as attics and crawl spaces, shall be connected to the appliance or equipment served such that when the pump fails, the appliance or equipment will be prevented from operating. Pumps shall be installed in accordance with the manufacturer's instructions.

 

[klarenbeek]

Is the attic subject to freezing temperatures? If it is, the pump and associated piping can't be located in the attic or you will have a mess.

 

[classicT]

Is the attic subject to freezing temperatures? If it is, the pump and associated piping can't be located in the attic or you will have a mess.

You don't generate condensate at the interior heat exchange coil in winter. Condensate is generated on the cold-side of the coil where the coil temperature is lower than the dew point.

 

[klarenbeek]

You don't generate condensate at the interior heat exchange coil in winter. Condensate is generated on the cold-side of the coil where the coil temperature is lower than the dew point.

According to the OP, these are fuel burning appliances, not heat pumps. The condensate is generated in the secondary heat exchanger and the vent system. It typically drains back to to a trap internal in the appliance where it then leaves the appliance into the condensate drain system.

 

[classicT]

According to the OP, these are fuel burning appliances, not heat pumps. The condensate is generated in the secondary heat exchanger and the vent system. It typically drains back to to a trap internal in the appliance where it then leaves the appliance into the condensate drain system.

Ahh, yes... going back to the OP, fuel fired was specified. In that case, it would have to be a condensing type unit. Any condensate generated is from the combustion process.