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Most efficient oil heat solution

Matt Culik | Posted in Mechanicals on

Need some help regarding best solution for oil-fired heating for my situation.

Here’s my situation:

Live in NJ. Been in this house for a year, and plan to stay here for a LONG time. Heat exchanger on old oil-fired furnace is cracked. Had an independent manual J done, and the heating load is 77K Btu. Current heating system is one zone for the entire house (3200 sqft). It worked well enough last year that I’d stick with one zone if that’s the best way to go given my design goals below.

My design goals, in priority order, are:

1. Efficiency – reduce energy consumption as much as possible to save $$$ (especially if/when oil prices go up again)
2. Low total cost of ownership – factoring in initial cost, maintenance costs, fuel costs, etc.
3. Comfort – obviously, but willing to make some sacrifices if necessary to save $$$
4. Longevity – I want a system that will last a LONG time provided I keep up with maintenance (which I will)
5. Low initial cost – I’m a buy once, cry once kind of person; would rather spend more $$$ initially (to a point, of course) to do it right

Here are the options I’m considering:

1. Replace existing furnace with a new oil-fired, right-sized furnace, with a heat pump coil on top to satisfy the load in the not-so-cold months of the heating season.
2. Same as option 1, but add zoning (whole house is currently one zone).
3. Install an oil-fired boiler and buffer tank, outdoor reset, hydronic air handler for the first floor (in basement, using existing ducts), and hydronic air handler for the second floor (in attic, using existing ducts). Possibly incorporate indirect hot water (vs. electric now). The hydronic air handlers will have heat pump coils on top, and my understanding is that the heat pump and hydronic systems can be run at the same time, allowing the heat pump to satisfy part of the overall heating load.

Which one would you pick, given my design goals?

Notes:
– Sticking with oil as the fossil fuel
– Sticking with forced air as distribution method, and not in a position to redo duct work

Thanks!

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Replies

  1. User avatar
    Dana Dorsett | | #1

    As outlined on that other forum,..

    That's an unusually high heat load for a decently tight & insulated 3200' house in NJ. A review of the particulars of the Manual-J, as well as a fuel use heat load calculation as a sanity check is in order.

    https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new

    Ducts & air handler in the attic will increase the actual load, unless the attic is converted to an unvented conditioned attic, with the insulation at the roof rather than the attic floor.

    Individual room hydronic fan coils won't drive air infiltration the way ducted systems do. Any new duct or recommissioned older ducts need to follow ACCA Manual-D, and room to room pressure differentials need to be verified to be under 3 pascals under all operating condition to limit air handler driven infiltration (which adds directly to the load when the air handler is running.)

    An oil fired water heater is inherently self buffering, cheaper than a boiler + indirect, and would be at least as efficient as an oil boiler + buffer tank. Study this document (compare system #6, the oil fired water heater to other options.)

    https://www.bnl.gov/isd/documents/41399.pdf

    With the fuel use heat load numbers to back up or disprove the Manual-J and your ZIP code (for weather data, including 99% outside design temp) we can then take a look at what sort of heat pump options might make sense.

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