The Ultimate Boiler System Layout Tips

midwest machinery boiler

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. Water connections made to the boiler must be made in full pipe diameter (no reduction from the header connection size). This may require a reducer at the unit connections.

HVAC boiler water connections


2. Use Union and isolation valves to the piping connections to the unit.

HVAC boiler isolation valve


3. All waterways must be filled, pressurized and completely purged of air.

HAVC boiler 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 failure.

HVAC boiler isolation valve


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. Expansion tanks need to be air charged to the static pressure of the system on the water side. Shipping presets are now insufficient for high-efficiency boilers.

HVAC boiler expansion tank


6. The system cannot violate the “cold start” requirement. Inlet temperatures must be kept above the minimum required in the manufacturer’s literature. This is very important on non-condensing boilers and is important to not freeze on condensing boilers.

HAVC boiler temperature sensor


7. Verify there is sufficient load available for high fire of the unit. On variable primary systems, 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.

HVAC boiler sized flow

8. Install clearances as specified in the manufacturer’s installation manual and all code requirements.

HVAC boiler clearance


9. 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.

HVAC boiler easy access


10. 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.

HVAC boiler oversized pad


11. Have a properly sized lock-up type gas pressure regulator (one for each boiler/water heater) installed per manufacturer’s requirement. Proper gas regulator sizing is very crucial. Improper sized regulators can cause sporadic operation to be dangerous and unreliable.

HVAC boiler pressure regulator

12. 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. Vent lines are commonly undersized. 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. With today’s very high-efficient and low turndown boilers, a stable gas pressure is crucial for operation and boiler life.

HVAC boiler vent lines

13. Controls – System sensor well must be installed so that the entire sensor is seeing flow. If the sensor does not see flow, it will detect temperature change slowly. This will result in the boiler overshooting set point and also taking longer to come on when heat is required, i.e. boiler short cycling and inconsistent water temp.

HVAC boiler flow sensor

14. 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 manufacturers & 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 = 149degF, CPVC = 194degF, Polypropylene = 230degF 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.

HVAC boiler exhaust vent drain

15. Permanent test ports need to be installed in 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.

HVAC boiler test port

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

HVAC boiler 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