Design & Heat Load

Boiler Board

Each home has its own unique heat load and the boiler system needs to be designed to meet those heating needs. Wilson HVAC Company has many size boiler board options available, however, to effectively meet the heating needs of each unique home, pole barn, addition, or new project, we need to know more specifics to properly address those heating needs. The cost varies for each boiler board. These depend greatly on the size of the area needing heat. Cost ranging from $ 3,500.00 on up depending on heat load and type of boiler such as the wood boiler design, electric boiler, or gas boiler design. This cost does not include the radiant "infloor" HePex tubing. We strongly suggest having a boiler and radiant heat certified HVAC technician to service and install all boiler systems.

For further information please send an email to Ken Wilson at

We will continue to bring more information to this website an appreciate feedback on what you're seeing or not seeing on this site. Below is a sample of how we layout a boiler board. With space in mind, we try to the piping close tight to fit onto a "half sheet" of plywood.

The piping design we use includes features such as auto fill valves, back flow preventers and isolation flange sets.To make the pumps easier to change, we design our boiler boards with isolation flanged kits (yellow tabs next to red pumps). We also have incorporated temperature gauges in the copper waterlines. We install and temperature gauge on both supply & return waterlines. Above you can see two round dial temperature gauges located on the lower left side of photo.

Flange Set Devices

The flange devices which adapt the circulators & pumps to the adjoining copper or steel piping can be threaded or "sweat" fittings. Sweat fittings are for soldering copper. These style fittings come with or without the valves built right into the flange housing. There are bolts that connect the flange to the pump as you can see in the photo above next to the red pump. Even though the isolation flange sets with "valve built in" are more expensive, it has been my experience that they should be used wherever a pump is placed in the piping system. This will drastically reduce the difficulty of servicing and changing the pump out if & when it goes bad and the expense upfront will payoff itself with just one service call to changeout pump without the isolation.

Back Flow Preventers

The back flow preventer is a type of check valve. It is standard installation and "code" in areas in Minnesota.

Auto Fill Valve

The Auto Fill Valve is another device that is installed in the water piping designed and will add water to the boiler system if/when the water level has fallen below safe equipment operating standards. The Auto Fill Valve is desinged to be left on at all times and will reduce the water inlet pressure (which is usually higher) to an acceptable minimum boiler pressure. I've found some local codes don't allow these auto fill valves.

Scenario #1

If the boiler were to leak anywhere in the whole water system, water damage
could result when the auto fill device had kept flowing water into the system.

Scenario #2

On the flipside, if the system pressure gets to low,
air can enter the system which will cause the pumps
not to be able to move the water and critical damage
to the designed system and its components could result.


There is a specific kind of antifreeze solution that is made to be used with boiler systems. It is designed to be added to the water to decrease the temperature at which the boiler water will start to freeze and rupture or become to thick to flow properly through the waterlines. Although this antifreeze solution may not be required by code, here in Minnesota I recommend its use although pure water will give off more heat than antifreeze protected water. The customer and contractor need to discuss both pros and cons.

Valves and Unions

Valves are devices that are installed in the system to either isolate other certain components for service and replacements or installed to control direction & flow of fluid. unions are devices that can be taken apart and minimize maintnenace and repair. Everyone of these valves or unions added into the design cost money but can drastically reduce labor in the future for service repairs and maintnenace on the system.

Air Eliminators

Air Eliminators are a device installed in various areas of the boiler piping design to help remove air from the system. I've found the most effective location is to install an air eliminator in the main boiler piping in the largest main piping above the boiler. Two Main Air Eliminator Types are Air Scoops and Microbubble Eliminators. Air Scoops are generally cheaper but are less effective and have to be strategically placed to be effective. Micorbubblers have become more available in recent years and literally scrub the air bubbles out of the water as it is pumped through this device. Microbubblers are not location sensitive, however I've had the best installing in a high point in the main boiler piping is best location. With the proper system piping design, this device can make the entire boiler purging automatic and maintain system free of air. There are other types of smaller air bleeder vents which can be placed in various areas of the piping however, with a properly designed layout, these extra vents shouldn't be needed. The exception to this my be that on a cast iron floor mounted boiler, sometimes "teeing" in a vleeder vent above the boiler where pressure relief valve is located, can be very effective at removing additional air especially on the initial fill.