High Efficient Condensing Furnaces
Today’s latest furnaces are much different than the furnaces 30 years ago.
The biggest difference between standard or mid efficient furnaces and the newer High Efficient furnaces is the fact that they condense flue gases.
A little high school physics refresher. A btu is the amount of energy required to raise a pound of water one degree Fahrenheit.
It then takes another 970 BTU’s to take one pound of boiling water and turn it into steam.
When a pound of water condenses from steam back to water you also recover 970 BTU’s per pound of condensed steam. This is what makes condensing furnaces so efficient. Also recovered is heat for every degree the condensate drops.
On the old furnaces you would see in the winter steam coming out of the chimney on the roof in colder weather. One of the biggest by products of combustion in a furnace is water vapour. The newer furnaces recover this wasted heat by condensing the flue gases.. The furnace then exhausts out the side of the house through special plastic piping at a very low temperature.
Because the secondary heat exchanger condenses the flue gases it must be made of stainless steel. This is because the by products of the condensate make it slightly corrosive.
Also this is why you need a drain or a condensate pump to carry the condensate to a drain.
There are other differences to the older furnaces. A furnace must be sized big enough to heat your home at the coldest day of the year.
In Calgary we would figure -40. Some winters it doesn’t even get that cold but it does sometimes, so your furnace has to be big enough to handle that temperature.
Some newer furnaces have a two stage gas valve or a modulating gas valve. With a two stage it operates at lower btu’s most of the time, usually 70% but can kick in to 100% on the really cold days.
A modulating valve is even more efficient. It runs in increments anywhere from 40% up to 100% depending on the heating requirements.
When replacing an older furnace with a new high efficient the new one will be much lower BTU output. A 100,000 btu 60% efficient furnace basically outputs 60,000 btu. A new 60,000 btu 95% high efficient furnace outputs basically 57,000 btu’s. This is only 3000 btu’s less. There is a very good chance that this would be enough.
Most furnaces in were oversized back when gas prices were a lot lower. Also over the years a lot of homes have had their insulation, windows and doors upgraded. This can be determined with a heat loss calculation on your home during the quotation process.
With a modulating valve a 60,000 btu could run as low as only 24,000 BTU’s at 40% when little heat is required. Compare that to the old furnace running at 100,000 btu’s in the same situation. You do the math.
There is a lot of saving in natural gas consumption with new furnaces but there is also electrical savings.
Most of the newer high efficient furnaces go with a variable speed blower. This is a brushless direct current motor and it is a very efficient user of power. It also automatically ramps up to what is required to push the air through your ducting system. If your filter is plugged a little it will compensate.
A lot of people like to have their fan run all the time to make the air more evenly heated in your home. This is where you really realize significant savings. The Variable speed motor runs at a very low speed so you can’t even hear it. It moves the air around slightly just enough to make the air in your home more evenly heated. This saves you about 80% in power compared to running an older furnace blower full time.
Also you are going to see around a 35% saving in your heating bills if you currently have a 60% efficient furnace.
Now you add a new high tech thermostat into the mix. They are basically a small computer making the furnace even more efficient. There is even a thermostat available that you control from your I-phone or Smart Phone. It can even send you an email when your filter needs replacing or your furnace needs servicing. There is also an additional sensor you can add that can tell you if you have a flood in your furnace room. You can also control garage heaters and fireplaces from your smart phone.
Additionally you can also control your humidifier from your phone.
It is called Red Link Technology from Honeywell.