Different kind of question from me. We're finally converting our own house in Piscataway from oil to gas: split-level, oil boiler with baseboard, hot water off a tankless coil in the boiler. Got three quotes and they disagree on the chimney.
Quote 1: new gas boiler and a new gas water heater, both into the chimney with a new liner.
Quote 2: high-efficiency boiler vented out the side wall in plastic, new water heater into the existing chimney, no liner.
Quote 3: high-efficiency boiler out the side wall, a separate sidewall-vented water heater, chimney not used at all.
Quote 2 is cheapest. Quote 1's guy says Quote 2 is going to cause problems. Who's right, and why does the chimney matter so much? Appreciate it. Kash told me to get more than one quote, so here we are. Still doing ride-alongs too, so this is half for the house and half for me.
Quote 1's guy is pointing at a real problem, kid. That old chimney was sized for an oil boiler sending a lot of hot exhaust up it. Take the boiler out, and a gas water heater alone in that big flue is what we call an orphaned water heater. Not enough heat to draft right, so the flue gas cools and condenses, and you get weak draft, moisture eating the masonry, and possibly exhaust spilling into the basement.
That's why conversions get a liner sized for whatever's left in the chimney, or take the chimney out of the picture like Quote 3. Quote 2 could be fine if they actually checked that chimney, so ask them exactly how. If the answer is "it'll be fine," that's a no.
And CO detectors on every floor, whoever you pick.
HVAC contractor, owner · 25 years · Middlesex County, NJ
Mentor
What I'd ask all three:
- Did you do a heat loss, or are you matching the old boiler's size? Old oil boilers are usually oversized
- Who removes or abandons the oil tank, and is it in the price?
- Who handles the gas service with the utility?
- What's the warranty on the installation, not just the equipment?
Thanks Ziggy, this is exactly what I needed. Going to ask Quote 2 how they checked the chimney.
edit: Quote 2 said they'd "see when they get there." Going with Quote 3.