Heat Trace or Dry-Pipe System for Loading Dock?

2/8/2021

We have a project that includes a 3,500 sqft unheated loading dock. We're in the initial design stages of the project.

Based on your experience would you recommend we specify a heat trace or dry pipe sprinkler system for the loading dock?

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6 Comments

Dan Wilder

2/8/2021 08:50:22 am

Personally, Dry system using Black Sch 40 and dry/N2 air supply for longevity. Using Sch 10 is also acceptable if needed, I would stay away from thinwall (Sch 7/Sch 30) if possible.

On just the cost difference between the wet/dry valves vs the heat trace & insulating puts the initial costing in favor of Dry (with a standard compressor). Let the owner decide if a dry air/N2 system is in their best long term interest for service (obviously this will add cost).

You're going to have the pipe install regardless, the pipe size increase for dry "shouldn't" be a major factor (not sure of the water supply). Having to go back over with heat tracing/insulation is additional labor not required on a standard dry system.

One other thought. While heat tracing is allowed per 13, make sure the MFG listing include all components of the system (specifically branch lines with sprinklers attached or on sprigs).

CJ Bonczyk

2/8/2021 09:41:54 am

I would use the dry system installation in this instance along with the same recommendations as Dan mentioned above. Heat tracing requires specific listing for branchlines, electronic supervision, and you have to be very careful with the install and how close the installation is to sprinklers. They can be very complex to very simple depending on the type that is purchased which will effect the reliability of the heat tracing like time-clock switches and the thermostat. Note that if the wet sprinkler system supplies an auxiliary dry pipe or preaction system, NFPA rules do not permit heat tracing in place of heated valve exposures that protect the dry pipe valve or to safeguard supply pipe from freezing.

Glenn Berger

2/8/2021 10:01:05 am

Recommend that a dry-pipe system with N2 to be used. Piping should be only Schedule 40 with cut groove or threaded fittings. Depending on the quantity of potential days below freezing temperatures will have an impact on the final decision.

Franck

2/8/2021 12:18:10 pm

Without any doubt : dry pipe system, for reliability.

Heat tracing add an additional chance of failure resulting in the freezing of you piping.

I have also seen many times heat tracing + insulation around the piping, resulting on obstruction to the upright sprinklers on the branch lines... (if more than 3 in. Diameter, the pipe needs to be considered as an obstruction... and a 1-1/4 in. pipe with insulation can become a 4 in. Pipe...

Michael Vangeli

2/8/2021 01:10:35 pm

While I agree with the comments on dry pipe, my question is where is the project? If you are in southern Florida or somewhere else that it normally does not get below freezing I'd look at the heat trace just because of the maintenance and installation savings. In my opinion it is easier to test and maintain the heat trace tape for places where it may only be needed a few times a year. There's plenty of published data on weather to help with the decision.

Stephen Keen

2/8/2021 03:08:05 pm

Trace heating and Lagging would be my choice.

- no costly maintenance for the dry valve / compressor
- no possible valve failure
- no delay in operation as the pipes are filled with water
- no valve space required
- no additional pipework
- no possibility of valve damage from loading vehicles

Also, you should never put an isolating valve in a system if it can be avoided.

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