The Ultimate Boiler System Layout Tips

Midwest Machinery has sold and started up A TON of boilers to date.

In the last 10 years, high-efficiency, high turn-down boilers have become the gold standard. Just like a Ferrari, which needs the right fuel, brakes, tires, and equipment precisely tuned to run like a champ – so does your new boiler.

Conditions not met could result in tens of thousands of dollars LOST (we’ve seen it) on installation changes or repairs on the job site.

We’ve compiled the most useful tips to greatly reduce the amount of on-site changes you could incur when installing boilers:

1. If the water piping is larger than the boiler connection then a reducer can be used. Add union and isolation valves on ALL pipe connections – water and gas.

boiler isolation valve


2. On gas isolation valves, make sure they have test ports. This allows for much easier maintenance in the future.

boiler valve


3. All waterways must be filled, pressurized and completely purged of air before use. Consider adding an air separator to make this task easier.

air separator


4. When flushing the system, the boilers must be isolated. Flushing through a boiler can cause debris to clog the heat exchanger, resulting in boiler failure.

isolation during flush

5. The system expansion tank must be charged and connected to the point of lowest pressure in the system – before the system supply pumps. Boilers require adequate pressure for proper operation. Refer to the O&M for your specific boiler specs. Expansion tanks need to be air charged to the static pressure of the system on the water side. Shipping presets these days are insufficient for high efficiency boilers. Shipping pre-charge is normally 12 pounds. Most medium-mass boilers require 35 pounds.

system expansion tank


6. Install a temperature sensor on the water line to monitor temperatures. The boiler system cannot violate the “cold start” requirement or go below 130 degrees inlet temperature or the boiler will condense. Inlet temperatures must be kept above the minimum required in the manufacturer’s literature. This is very important on non-condensing boilers and it is important not to freeze on condensing boilers.

temp sensor


7. Verify there is sufficient load available for high fire of the Boiler. During startup, we have to operate the boiler at high fire to set the combustion rate. If the existing water is too hot, startup cannot be properly completed. On variable primary systems, the minimum flow should be sized for the minimum flow that a boiler requires for full fire. This is important for installations such as schools that have a night setback and a warm-up period before school starts in the morning. This is a time where the boiler is called to fire, but there is low load thus low flow available in the system.

base mounted pump


8. Allow sufficient height above the boiler for burner tube maintenance and annual cleaning on some boilers. Allow full unrestricted clearance to the back and all parts of the boiler. Without proper clearance around the boilers, maintenance becomes difficult which will affect the life of the boiler. The easier a product is to maintain, the higher the likelihood that it will be maintained.

boiler clearance


9. The boiler must be installed on a housekeeping pad equal to or larger than the footprint of the unit, made from non-combustible material. The height of the pad is very important on condensing boilers. The outlet for the condensate drain must be above the neutralizer connection so that there is sufficient fall from the boiler to the neutralizer. Likely, the neutralizer kit will be on the floor and not on the pad. If the neutralizer is too high, condensation will back up and cause increased pressure within the heat exchanger.

boiler concrete pad


10. The vent for the gas regulator must be per the manufacturer’s guidelines. With today’s very high efficient and low turn down boilers, stable gas pressure is crucial to the operation and boiler life. Regulators require properly sized vent lines to operate correctly. If the vent lines are too small, the diaphragm will not operate properly and gas pressure will become unstable. Each regulator must have its own vent line. Do not combine multiple regulator vents into 1 exhaust port.

boiler vent piping


11. Gas pressure reducing valve bleed and vent lines need to run from equipment jacket to outside of the equipment room as required by codes or manufacturers’ requirements.

dont combine vent lines


12. Controls – System sensor well must be installed so that the entire sensor is seeing the flow. If the sensor does not see the flow, it will detect temperature change slowly. This will result in the boiler overshooting set point and also taking longer to come on when the heat is required, i.e. boiler short cycling and inconsistent water temp. It’s better to put the sensor on the side vs. top of the pipe to avoid any air pockets.

boiler system sensor


13. Exhaust venting and air intake must be installed including any required drains and drain loops.

NOTE: The size and type of the venting material must meet manufacturer & code requirements for the specific venting category of the unit installed. Check the manual or consult with the factory for suggested vent terminations. Most of today’s high efficient boilers can utilize PVC, CPVC or Polypropylene. Flue temperatures are what determine the material that should be used. Traditionally, the flue temperature is related to the temperature of the water that enters the boiler. Max flue temperatures for these materials are as follows: PVC = 149°F, CPVC = 194°F, Polypropylene = 230°F Stainless Steel = 300°F. Improper air intake and flue sizes cause incorrect back pressure within the boiler. This leads to shortened life and sporadic firing. Think of trying to blow air through a 30’ long drinking straw!

vent drain


14. Permanent test ports need to be installed inside venting. Test ports are a commonly overlooked maintenance accessory. They are required for combustion analyzation. Any time a boiler is started up or serviced, a combustion analyzation is required to set the air/gas ratio proper combustion levels per manufacturer.

test port for boiler flue


15. Building Pressure – High efficient boilers operate optimally in a pressure neutral room.

make-up air


Is this EVERY possible tip and requirement? No. BUT, it’s the most common we’ve seen day in and day out. When these requirements aren’t met it costs everyone involved more time and money.

commercial boiler pre startup guide