| Over the past 12 years, the preference of the | | | | vented units; which manufacturers have passed |
| gas space heater market has shifted drastically | | | | on to the consumer. |
| towards power vented gas space heaters and | | | | The U.S. Department of Energy's Energy Policy |
| away from gravity vented models. Most major | | | | Act of 2005 is the most recent blow to the |
| manufacturers are currently phasing out their | | | | gravity vented gas space heater market, which |
| gravity vented product line. There have been | | | | takes effect in August of 2008. The new codes, |
| many reasons for this shift: | | | | which are designed to reduce fuel consumption, |
| - 20% Better Fuel Efficiency. While fuel prices | | | | will further reduce demand for gravity vented gas |
| continue to skyrocket and manufacturing | | | | space heaters. Gravity vented units will require |
| methods become more efficient, the payback | | | | the following: |
| period for power vented units can no longer be a | | | | · Intermittent Ignition Device: The price |
| factor - there usually is no payback period. The | | | | premium for gravity vented units will increase |
| smaller diameter vent pipes and shorter horizontal | | | | with this additional cost. |
| runs associated with power vented units make | | | | · Automatic Vent Dampers: This |
| the installation less costly. Often times the upfront | | | | expensive addition is meant to open the vent |
| installation cost of a power vented unit is LESS | | | | system while gravity vented units are running and |
| than a gravity vented unit. Considering the lower | | | | close them when the units are off. This raises the |
| first cost and the lower operating cost, nobody | | | | total installation cost and increases the wiring |
| should choose gravity vented units in a new | | | | complexity and sequence of operations. |
| application. | | | | Per the requirements of the 2005 EPAct, owners |
| - Tighter Building Designs Combined With Lower | | | | who purchase a power vented unit will |
| Flue Gas Temperatures Create Venting Problems. | | | | simultaneously reap the benefits of: |
| When building construction was looser there was | | | | - Decreased equipment costs |
| more natural infiltration; this was ideal for the less | | | | - Decreased installation costs |
| efficient gravity vented unit that produces higher | | | | - Decreased wiring and sequence of operation |
| flue temperatures. With loose construction, there | | | | complexity |
| are rarely any venting problems. With tight | | | | - Decreased risk of nuisance lockouts, no-heat |
| construction, there are many venting problems. | | | | situations and manual resets |
| Flue temperatures have been reduced as the | | | | - Decreased risk of flue products spilling into area |
| thermal efficiencies have eclipsed 80%, nearly | | | | - Increased ability to overcome negative indoor air |
| eliminating the natural draft effect in modern vent | | | | pressure problems |
| systems. Along with the increased thermal | | | | - Increased equipment reliability |
| efficiency came negative indoor air pressure. | | | | - Increased equipment life expectancy |
| Other higher efficiency products such as boilers | | | | The following is a simple guide line for replacing a |
| and exhaust systems can create a negative | | | | gravity vented unit with a power vented gas |
| pressure in the space. Negative indoor pressure | | | | space heater unit. |
| plus cooler flue gasses results in poor venting, | | | | When replacing a single gravity vented unit with a |
| flame roll-out, increased condensation and | | | | power vented unit, it is important to comply with |
| corrosion inside the vent systems. This causes | | | | National Gas Code (NFPA 54) venting information. |
| premature failures of heat exchangers, vent | | | | When replacing a unit and determining if the vent |
| systems and burners. Often times flue gas would | | | | system is re-usable, the following article is |
| spill into the heated space. Blocked vent safety | | | | applicable. |
| switches (BVSS) became mandated by code to | | | | NFPA 54 - 2002, article 13.2.21: |
| protect users. Incidences of nuisance lockouts, | | | | (Quick overview - see article or details) Vent |
| no-heat situations and manual resets increased | | | | Connector Upsizing - Vent connections shall not be |
| drastically with the code-mandated blocked vent | | | | increased more than two sizes greater than the |
| safety switches (BVSS). | | | | listed appliance categorized vent diameter. |
| - Power Vented Units Are Less Expensive Than | | | | Items to review before using an existing system: |
| Gravity Vented Gas Space Heaters. As demand | | | | 1) Inspect vent systems prior to reusing to |
| for power vented units increased, while the | | | | ensure solid integrity. |
| demand for gravity vented units decreased, the | | | | 2) For multiple units, the vent systems must be |
| laws of economics took hold. With increased | | | | separated unless the unit venting conforms to |
| demand came longer production runs which | | | | common venting requirements listed in your |
| reduced set-up and overhead costs. The cost of | | | | manufacturer's installation literature. |
| purchasing components for the power vented | | | | If an existing gravity vented unit has been |
| units decreased as well. Furthermore, with the | | | | converted with a powered exhaust, review the |
| aforementioned increased efficiency and reliability, | | | | venting system to ensure that it meets the |
| the cost of manufacturer support in the form of | | | | venting requirements in your owner's manual and |
| service calls and warranty claims decreased. The | | | | article 13.2.21. |
| opposite effects increased the costs of gravity | | | | |