Tankless Gas Water Heater

Tankless Gas Water Heater Systems are usually bigger compared to their electric counterparts, and are usually used to service multiple points of use simultaneously or as a whole house unit.

The image below describes a typical Gas Tankless Hot Water Heater. As can be seen, water is heated as it flows thru piping that runs around a burn chamber. Computer controls the fire’s size to heat the water to the desired temperature.

Natural Gas tankless water heater is very similar to Propane tankless water heater (LP Gas), and the differences are minor. Choosing between the two should be done according to the availability of Propane & Natural Gas where you live, and the type of piping already installed in your home.

Tankless gas hot water heater can be installed outdoor or indoor. An Indoor installation requires proper ventilation to dump the exhaust gas outside. Point-of-Use installation is almost never used.

There are two types of burner lighting systems. The older one uses a constantly burning pilot light, while the new models have an Intermittent Ignition Device (IID), which resembles the spark ignition device on some gas kitchen ranges and ovens.

Since a constantly burning pilot light wastes some energy, prefer a heater with an Intermittent Ignition Device.

Installation requirements consist of:

1. Electrical connection: a minimal electrical connection is required for the ignition system and control circuitry.
2. Proper gas-line: The big unit’s gas requirements may exceed that of your current system and may require a wider gas line to meet its needs.
3. Ventilation: Make sure that you purchase Category III stainless steel (UL1738 certified) venting for your instant gas water heater. Type B venting accessories are not acceptable.

Indoor Tankless Water HeaterIndoor Models:

The interior-mount units can be placed in any room, vent directly to the outside and have an integrated condensate collector. They also have a safety system that shuts down the unit in case of raised levels of carbon monoxide.

Indoor models further differentiate by their venting method, which refers to the way they supply the burner with fresh air while exhausting the flue gases outside:

Non-Direct Ventilation

In non-direct ventilation, a small internal electric fan or blower supplies combustion air intake from the location where the water heater is installed for efficient operation.

At the same time the fan pushes the flue gases to the outside when the unit is operated. Vertical or horizontal venting, which is determined by the direction of the piping as it leaves the unit is possible with this ventilation type.

Direct Ventilation

Tankless heaters with direct ventilation are sealed. Because of this, combustion air is supplied directly from the outside to the gas burner.

Two pipes or a split pipe are used, running from the water heater to a wall or the roof of a home. One pipe is used for fresh air intake, while the other is used for exhaust.

This type of venting should be located at least three feet away from windows and is often used in tight-fitting locations with limited ambient air.

Outdoor Tankless Water HeaterOutdoor Models:

The exterior-mount units do not need a venting system at all. In these models the exhaust vent is built into the front of the unit. That makes installation much easier and cheaper.

The outdoor models are designed to be weatherproof, and most of them incorporate freeze protection technology that will offer protection down to -30÷ F (-34÷ C). This will allow for outdoor installations in most climates.

Typically, outdoor models lack the carbon monoxide shutoff safety system.

In new constructions, homeowners often install two outdoor tankless units, one on either side of the house. They then split the plumbing to avoid long pipe runs.

Outdoor tankless water heaters can be placed in a specially designed metal box which can be recessed into the outer wall of your home. The front of the box can then be painted and textured to match your home’s exterior surface.