David Richardson/NCI
Interior Hvac Diagram
David Richardson/NCI
If you know what to look for, a visual inspection provides clues to unsafe operation. It's never good for one package unit to exhaust into the economizer of an adjacent unit.
National Comfort Institute
Before you jump on the heat pump bashing bandwagon, look at your duct installation practices first.
Contracting Business/Kelly L Faloon
Ahr2023 Succession

Service Clinic: 15 Tips to Peak Performance in Steam Heating Systems

Dec. 1, 2007
With energy costs at record levels, efficiency is on the minds of homeowners, and contractors are being asked to bring utility bills down. Try this steam

With energy costs at record levels, efficiency is on the minds of homeowners, and contractors are being asked to bring utility bills down. Try this steam system checklist on your next “I can’t afford to heat my house” call.

For All Steam Systems:
Tip No. 1 — Make sure the boiler is clean.
The water in the boiler must be free of oil and impurities. They cause short cycling and wet steam. Either of these wastes energy. Look at the gauge glass for indicators. If the water bounces rapidly or violently, chances are its oil. The burner short cycling on and off from the low water cut-off is like city mileage in a car. If water is dripping down from the top of the gauge glass, the boiler is producing wet steam. Wet steam does not heat as well as dry steam, so the burner runs longer to satisfy the call for heat.

Tip No. 2 — Make sure main vents are installed and working properly. End of main vents have to be there to have even distribution of the steam along the main. Steam moves from the higher pressure in the boiler, to the lower pressure at the open air vent. The steam supply main is full of air at the start-up of each run cycle. That air has to be released from the pipe so steam can move freely to the last riser. The burner will be short cycling on the steam pressure operating control if there is no release of air from the main.

Tip No. 3 — Check the steam pressure control setting. It’s the simplest adjustment to make, but has a major effect on the system. Lower steam pressure costs less than higher steam pressure. Operate as low as possible for best efficiency.

Tip No. 4 — Check water line position. Normal water line position has a huge impact on the production of steam. If set too high, there is more water in the boiler than the burner is designed to heat. That results in longer run cycles and higher operating costs. If set too low, the burner will short cycle on the low water cut-off. That results in poor steam production and again, higher operating costs.

Tip No. 5 — Check the main vent(s) size. The bigger the opening is in the main vent, the faster the system will heat. The faster steam gets to the radiators, the less the burner runs. This also has the effect of making the system heat evenly. Steam should get from the first distribution main to the last distribution riser in no more than four minutes. Calculate the amount of air in the steam main, then install enough venting to pass that quantity in four minutes or less.

Tip No. 6 — Check near boiler piping for proper size and orientation. This has to be right to get dry steam. The early boiler manufacturers used large steam chests and large openings to produce dry steam. Modern boiler manufacturers use the piping around the boiler to dry out the steam. Undersized pipes create higher outlet velocities, which can carry water out of the boiler as wet steam. Follow the installation instructions for good performance. For best performance, move up a pipe size, or add a riser to slow steam velocity and distribute drier steam.

Tip No. 7 — Check the amount of combustion air that is available to the burner. The burner has to have enough air to fire optimally. This applies to any fossil fuel heating appliance.

Tip No. 8 — Perform a combustion analysis to fine tune the burner. Record the results so they can be compared at the next check. Prove to yourself and your customer that the burner is operating at peak efficiency.

Tip No. 9 — Insulate or re-insulate all the supply piping, including the near boiler piping. This may be the best investment to reduce the fuel bill. So many replacement jobs I go to do not have near boiler piping insulation. Any steam-carrying pipe should be insulated. This has been true for more than 100 years. It’s still true today.

For Systems Over 500,000 btu/hr:
Tip No. 10 — Install a boiler feed unit.
A steady water line equals peak performance. The larger the system, the more the impact will be.

Tip No. 11 — Install a cycle rate control that senses both outdoor temperature and return water temperature. They are not cheap, but they have a great payback. Add this to the efficiency strategy only to systems that are working correctly.

For One-pipe Systems:
Tip No. 12 — Make sure all radiator valves are fully open or closed.
Partially closed valves slow condensate return, leading to flooding problems.

Tip No. 13 — Replace all radiator vents throughout system with one common size vent. The same size port on each vent proportions the steam flow for even heating.

For Two-pipe Systems:
Tip No. 14 — Make sure all the radiator traps are working correctly.
If traps are failed open, steam is being wasted and the system will heat unevenly.

Tip No. 15 — Install thermostatic radiator valves on each radiator. They will balance the flow of steam similar to the metering systems, resulting in even heat and shorter run cycles.

Follow the order of the list and remember, peak performance starts with a clean boiler.