Author Topic: 3-Part Question: Heat Pump, Gas Boiler, Flue Reline  (Read 2163 times)

TrulyStashin

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3-Part Question: Heat Pump, Gas Boiler, Flue Reline
« on: October 02, 2014, 08:54:08 AM »
My house (1963) has a gas boiler (2004) serving hot water baseboard radiators.  It also has a heat pump (2012).  When I had the heat pump installed, I opted to NOT include the auxiliary heat strip feature.  Auxiliary heat could be added later and I couldn't afford it then.  The system is set up so that the heat pump serves the house until it gets below 40 degrees, at which point, the boiler kicks in and takes over.  My gas bill spikes when that happens -- last winter my gas bill for Dec through March averaged a little over $200/ mo.  When the boiler is off, it is below $40/ mo (water heater and stove).  The electric bill averages $150, though admittedly, the heat pump is off Dec to March.

I had the boiler installed in 2004 when I converted from oil to gas.  I got the brand new boiler for $500, which is super cheap, but it is WAY oversized for the house and has proven to be unreliable.  Typically, it generates at least one service call each year at a cost of $300 - $500 each.  Every autumn, I set aside $ for this.  Amazing how a very mechanically simple appliance can find so many ways to break.  Anyway...

I just had the chimney flues inspected and got (expected) bad news.  The flue that serves the boiler and water heater absolutely must be relined.  It's a safety issue and I will do that ASAP.   

Option 1:  Reline the flue to serve both the boiler and water heater -- $1540

Option 2: Decommission the boiler and remove all the copper radiator pipes (sell for scrap).  Add auxiliary heat to the heat pump and heat the house with only the heat pump (common in my region).  Cost to reline flue for just the water heater is $900 ish.   I called the HVAC guy who installed the system and am waiting for a quote on adding the auxiliary heat system.

The cost to add the auxiliary heat might be lower if I can DIY it.  I'm pretty handy and have a good friend who is an electrician.  Is it feasible to DIY adding the auxiliary heat to an existing heat pump system?  If so, does anyone know of internet sites that sell these systems to consumers?

Any other thoughts/ opinions y'all have are welcome.  WWMD (What Would Mustachians Do?)

Bob W

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Re: 3-Part Question: Heat Pump, Gas Boiler, Flue Reline
« Reply #1 on: October 02, 2014, 09:54:44 AM »
Actually your heat pump will work fine to about 10 degrees.  I just becomes a little more inefficient under 40 degrees.  If you do add the heat strip remember to set it up to not kick in until 10 or 15 degrees.  Otherwise the heat strip is pricey to run.

You also should consider replacing your hot water heater instead of adding to the flu.  You could probably purchase a nice electric 40 gallon tank for $400.  It depends on if you have the power nearby to run it. 

Conversely you can buy a high efficiency gas hot water heater (tank or tankless)  that only requires a small pvc flu which you can run out the side of your house.  These babies are efficient! 

Here's some info on a tankless gas hot water heater ---

Running out of hot water will be a thing of the past! The 94% ultra-efficient, Rheem tankless H95 direct vent indoor series tankless water heater vents with standard PVC which is readily available at a lower cost and easy to install. These water heaters feature a built-in condensate neutralizer which reduces installation cost and time, plus industry-best low activation flow rates which provides more fixture options, especially low-flow faucets and shower heads. Enjoy your hot water with a 12-year heat exchanger, 5-year parts and 1-year labor limited warranty. Digital (UMC-117) remote control and 10 ft. of thermostat wire is included.

You could install that yourself or hire a pro. 

FYI,  My heat pump runs off of a well water system.  (pump and dump).   I do not have a heat coil or back up heat.  But my ground water is always 54 degrees. 

Freestater

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Re: 3-Part Question: Heat Pump, Gas Boiler, Flue Reline
« Reply #2 on: October 02, 2014, 10:01:58 AM »
What kind of desuperheater is your HVAC guy quoting you for?  I've never heard of a heat recovery system used when a heat pump is in heating mode.  In the summer, the condenser side of the unit can act as a water heater, but in the winter it's providing heat to the supply air.  Can you clarify where the waste heat is coming from in the winter? 

The fact that you're already paying more on a monthly basis for that oversized boiler, I'd say forget option #1.  That $1500 would be much better spent fixing insulation leaks and bringing your home closer to airtight levels, reducing your heating & cooling load.

TrulyStashin

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Re: 3-Part Question: Heat Pump, Gas Boiler, Flue Reline
« Reply #3 on: October 02, 2014, 11:18:16 AM »
Good news.  The HVAC guy was just here.  I've used his company for a decade and he is always good to me on pricing and he agreed to coordinate with an electrician-friend of mine. 

My electrician-friend will run a No. 6 wire from the panel to the air handler in the attic.  He's doing this for free.  All I have to do is pay for the supplies.  Once that is done, HVAC guy will add a 10k auxiliary heat coil for his cost + labor for a total of about $250.  He can also do the flue relining with a flexible metal 4" tube for the water heater.  He's going to call me back with the cost of that but it will be under $500, he said.

I'd love to take Bob Werner's advice and go with a new, tankless water heater.  But I scored an awesome deal on CL last year and scooped up a brand new 50 gallon gas water heater for $150.   So, I'll stick with that as the cost to replace it doesn't pencil out.

Right now, it looks like I can decommission the boiler, reline the flue, and add the auxiliary heat for a grand total of around $900.   There is a whole lot of copper piping for that radiator system.   It will be interesting to see how much it brings from the scrap yard.  I won't miss those stupid radiators, that's for sure.

Bob W

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Re: 3-Part Question: Heat Pump, Gas Boiler, Flue Reline
« Reply #4 on: October 02, 2014, 11:34:40 AM »
You're rocking!   Look up info on the heat pump temp for efficiency.  I believe it is a curve of efficiency.   I made the mistake of turning my heat coils on at 40 degrees one winter and it cost me dearly.  So I researched and found that it was better to wait until around 10-15 degrees with a heat pump.