When homeowners are planning to purchase a replacement oven, there are a few simple questions you should be prepared to answer in order to get the correct oven for your application.
1. What efficiency do I want or need? (80%, 93% or 95%)
2. How will I vent the unit (vent pipe or PVC)?
3. Direction of air flow (up, down or horizontal)
Efficiency?
- The three basic options available on the market today are 80%, 93%, and 95%. It seems like a no-brainer to choose the most efficient unit. It would seem so, but the reality is that here you have some options to make.
- Conventional 80% gas ovens are vented with standardized metal vents and often require exhaust through the roof. The 80% oven is the lowest price in the oven market, but with that price comes the tradeoffs. The first and foremost thing is efficiency. An 80% efficient oven is just that, 80%. That means 20% of every fuel dollar you use to heat your home is lost through burnt exhaust.
- The 93% gas oven has become the oven of choice for most homeowners. One of the most attractive features of the entry-level high-efficiency oven is its ventilation flexibility. The 93% furnaces are called “Condensing Gas Furnaces”. Most have primary and secondary heat exchangers, which increase efficiency and allow these units to be vented with standard plumbing-type PVC plastic tubing, and they can be vented in a variety of configurations, including the ability to come out of a wall. side or basement foundation and vent directly into a horizontal run. This flexibility of not having to penetrate roofing materials is a breakthrough. The other notable advantage of the 93% efficient gas oven is the increased savings achieved. A 93% oven is approximately 14% more efficient than the standard 80% version. This can equate to significant savings, and while the high-efficiency 93% oven is on average 40% more expensive than the 80% models, the savings made can easily make up the difference in a short amount of time.
- The best option comes in the 95% and above gas oven models which, by description, appear to be only slightly more efficient than their 93% counterpart, but on a closer look, you will find that this group of ovens is in a class for themselves. . Ultra-high efficiency 95% gas ovens are often combined with variable speed fan drives, two-stage gas valves, and a host of other additions that not only make these ovens more efficient, but also more comfortable. , in addition to being almost silent in its operation. . Along with the 2% increase in base gas efficiency, two-stage gas operations allow the unit to amuse itself and fire at significantly reduced speed during marginal outside temperatures. This adds to the savings on energy bills. Variable speed fan impellers not only increase the comfort and efficiency of operation, but since they are programmed to “increase” and “decrease” during operating cycles, the normal airflow heard with the Conventional ventilation systems is greatly reduced. It is not uncommon for owners never to hear this unit work. These extended operating cycles and variable air flow also increase the efficiency of air conditioning systems that are operated in conjunction with these ovens. Pricing for these 95% optimal ovens can be 30-40% more than 93% for single-stage versions, but additional convenience and efficiency benefits must be considered.
Venting:
- As mentioned above, there are multiple options for venting your gas oven and knowing what you want or need is an integral part of choosing the oven.
- Metal or PVC? This choice is determined by the efficiency of the oven you choose and the limitations you have with your building structure. As noted above, 80% gas furnaces use standardized sheet metal vent piping and are typically vented through roof penetrations. In some cases, you may already have a vent that you want to use and your choice of oven may depend on that vent material. Furnaces that rated and rated 90% or more typically use PVC tubing to extract burnt gases. PVC vented ovens offer greater flexibility when venting, as in addition to ceiling-penetrated venting, these ovens can also be vented in horizontal directions, through side walls and basement foundations.
Air flow direction:
- This last piece of the oven choice puzzle is critical when choosing your oven. Here are some guidelines to help you decide.
- Upflow – This type of setup is often found in basement locations. Return air or inlet air from the upflow furnace will enter from the bottom and supply air will flow out from the top of the furnace and then into the ducts and vents above. This configuration can also be found in the same lava as the living space and then vented upwards and into the ceiling or floor registers in the rooms above.
- Downflow or Counterflow – This type of oven is exactly what it sounds like compared to upflow models. The return or inlet air is drawn through the top of the oven and out the bottom. This type of furnace is often found in main living areas and feeds vents on the floor and roof vents on lower levels. They can also be used in an attic where a downdraft scenario is needed.
- Horizontal – Often the upstream and downstream furnaces mentioned above can also be set in a horizontal position. To visualize this, think of the oven lying on its side. Rather than up or down, this configuration allows them to be positioned at one end and discharged at the other horizontally. This can be useful in attics that are too low to accommodate a free-standing oven. They are also used in basements or root cellars that have lower than average ceiling heights and cannot use the vertical oven.
If the above options seem confusing, speak with your heating and air conditioning expert before purchasing your next system. Most online HVAC stores have phone numbers to call or live support agents to help you make the right decisions for your home.