Need advice on a new oil furnace

November 8, 2006 10:53 AM

My husband and I are in the market for a new oil furnace. Help us make sure we get the right one.

We've never had to buy a furnace before. We've lived in our current house for 6 months and the furnace is working OK right now, but two different furnace guys who looked at it during inspection tell us that it's on its last legs. Since it's not totally dead yet, we've got a little time to do some good researching.

It's an oil furnace and we have hot water radiators throughout the house. Currently the entire house (except for a small addition the previous owners built) is on one thermostat. The addition has its own thermostat. Should we get more thermostats? One for upstairs, one for downstairs?

Also, our hot water is now heated somehow in the furnace. We don't have a hot water tank (that I can see). It's actually quite a mystery to me where our hot water comes from. Should we keep this type of system for our new furnace? Or should we get a normal hot water tank?

Are there any other options for furnaces we should ask about? My research on this is just beginning, but I wanted input from the hive mind to help me focus my research.

posted by SheIsMighty to home & garden (4 answers total)

Hey gang, the husband here - one detail to add to the hot water tank question - currently it's just the two of us in the house. We have a guest every once in awhile and hopefully will eventually have kids running around, but that's a little bit in the future yet. So short term, there's two of us using all the hot water. Near term, two of us and a couple of squealing babies.

Also, the current hot water heating system has so far only been taxed by the one time we tried running both of the house's showers at once. Other than that instance (and the fact that some of the hot water gets REALLY hot), the hot water's been good - it's just dependent on this ancient furnace.

Incidentally, even after talking to one of the heating guys, how hot water's created in this thing's a mystery to me too.
posted by Moondoggie at 12:02 PM on November 8, 2006

Here's a quick comparison of various home heating system technologies.

If you can comfortably cut off some areas of your house from general air circulation, and are then OK with having them heated to only a much lower temperature (like 55° F), then you might realize savings. But your actual savings would depend on how effective your insulation was between the colder areas and the warmer ones, how much area you're heating to a lower temp, and a lot of other factors. And if you have a radiator system, setting up a zoned heating system with a new furnace will call for installing some kind of distribution manifold for the hot water that circulates to heat your home now, to allow heated water to be metered out to the various zones you establish in the house, as various thermostats will regulate. This is usually far more practical in two or three story houses, where heat from the main floor will tend to rise, and upstairs bedrooms can usually be cut off during the day.

Your current hot water system is probably a hot water "coil" in the existing furnace. This is literally just a coil of tubing in your furnace's burner area through which water is directed for your furnace burner to heat. This means your furnace burner kicks on any time you demand hot water, even in summer. The main benefit is that you have "endless" hot water, but it's a pretty expensive way to get hot water at current oil prices, and it means you run the furnace burner year round, with a constant demand for oil. Depending on your hot water use patterns, and your area's electric or gas utility rates, you might find that a conventional water heater is a better deal in terms of operational costs, or not. You would have additional plumbing installation costs if you choose a separate water heater solution, and you'd lose a couple feet of floor space to the tank.

If your house has gas availability, you probably want to review the whole gas/oil/electric heating source debate, with figures from the various utilities and contractors. Oil and gas pricing is subject to big spikes, as we've seen in the last couple of years, so you have to put in your own sense of what the future holds for any energy source, particularly in New England. For the present, oil looks like the overall best bet for heating, but as you've seen, this can go topsy turvy pretty quickly.

If you are still living in Connecticut as your MeFi profile suggests, you may not be a candidate for alternative types of heating like conventional heat pumps [due to the severity of your winters] or geothermal heat pump systems, [due to the soil issues on your site]. But from an operational efficiency standpoint, heat pumps can be attractive, since they pull "free" heat from the environment. The tradeoff, particularly in geothermal heat pump systems, is the cost of drilling wells to tap geothermal heat, which in rocky New England, can be a considerable installation expense. Still you might want to investigate these systems with reputable contractors in your area. They can be an environmentally friendly solution going forward, if that makes a difference to you in justifying their greater installation costs. I couldn't find anything particular to programs in Connecticut, but in other areas of the country with similar climate, so called "duel fuel" heating programs have been implemented, which encourage people to install efficient heat pumps and oil or gas heating systems, for higher overall energy efficiency, by offering special reduced electric rates for "duel fuel" customers.

Modern oil furnaces can be very efficient devices, particularly if they are combined with new flue systems that scavenge exhaust heat to preheat inlet combustion air, or recover flue heat to living spaces. But those devices may cost extra, and require construction or modification of existing flue and vents, adding to total system cost. Be sure to discuss these features and cost alternatives with your contractor. And also be aware that if this is going to be your primary heating system, you need to understand if it will be possible to operate it, in the event electrical power is lost. Some older oil furnaces used to have emergency operation modes where the oil could gravity feed from the tank to the burner, and the burner could be manually lit for constant operation, keeping hot water convectively circulating to radiators, to keep the house from freezing during power outages. If your house doesn't have fireplaces or other backup heating means, you might want to discuss these situations, too. Many times, because of the reliance modern furnaces have on process monitoring electronics and ignition, they need electrical power to operate at all. So, you may need to have a small backup generator on hand to run your heating system during electrical blackouts.
posted by paulsc at 1:19 PM on November 8, 2006

The main benefit is that you have "endless" hot water, but it's a pretty expensive way to get hot water at current oil prices, and it means you run the furnace burner year round, with a constant demand for oil.

I believe tankless hot water heaters are often considered more energy efficient than hot water tanks.

The tradeoff, particularly in geothermal heat pump systems, is the cost of drilling wells to tap geothermal heat, which in rocky New England, can be a considerable installation expense.

It sounds like you don't plan on moving for a long time. If that is the case, this is certainly worth looking into. It isn't the kind of upgrade that earns a profit on resale though, so you are going to have to be able to claim several years of energy savings to make it economically viable.

Modern oil furnaces can be very efficient devices, particularly if they are combined with new flue systems that scavenge exhaust heat to preheat inlet combustion air, or recover flue heat to living spaces.

High efficiency furnaces are a lot more expensive, and it is often said that they don't last as long (from hearsay, maybe 10 years expected life instead of 20-30 years for a mid-efficiency?).
Basically, extracting heat from the flue gases cools the gases down. This allows water condensation that wouldn't happen if the flue gases were a lot hotter (hydro carbon plus oxygen means lots of water). Water leads to rust, which leads to parts wearing out.

I'm very much in favour of sound environmental decisions, but three expensive furnaces cause a lot of environmental impact too. Let your environmentalism show in your day to day behaviour - keep your house cooler - let economics determine what efficiency you should be buying.
Which is not to say high efficiency is a bad decision for you. I'm not even able to guess at the answer to that question. Just saying high efficiency isn't the panacea it sounds like.
posted by Chuckles at 7:24 PM on November 8, 2006

I meant to put a link to wikipedia on tankless hot water heaters.
posted by Chuckles at 7:26 PM on November 8, 2006