Hydronic system overhaul

Discussion in 'Boiler Forum' started by onelostsoul, Apr 18, 2014.

  1. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Thanks for chiming in Badger (and the rest of the group as well).

    Regarding pellets:

    There are these guys one town over. Given the population density here, I am probably one degree of separation from the owner :)

    Not sure how I would work the pellet storage. The topology of the lot may get in the way. But I suspect that the major obstacle to a pellet boiler may be my wife.

    Regarding the mixed mini-split/ small mod-con solution - here is the scenario I imagine:

    1. Leave the Peerless in place as a back-up. Pull out the indirect tank. Add an Airgenerate hybrid electrical DHW heater. Add two Mitsubishi M-series. There are several things I like about this approach:
    1. I can add components ad-hoc (not need financing if I can stretch the project over a period of time).
    2. I can have the DHW heater installed next month and turn off the peerless for the next 6 months.
    3. The overall cost of the project is probably about 10K less than the benchmark ( Daikin Altherma with the Peerless as a backup)
    4. AC is there if needed
    HOWEVER. I lose my radiant floors until the Peerless kicks in. Profoundly sad

    Hence scenario 2:

    1. Replace the Peerless with a small mod-con. Which one? I requested a bid on installing the new Vitodens 200 (smallest one steps down to 19 kBTU and at the high end is still enough to cover my heat loss). Scratch the Airstream (hot water is now handled by the boiler). Yet the capex goes up and so does the opex.

    Price of electricity is currently at 17c/ kWhr. Set to raise shortly to 18c/ kWhr.

    Thoughts?
  2. Dana

    Dana In the trades

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    2,934
    Location:
    01609
    A Peerless that isn't running isn't burning any oil, and functions just fine as backup, provided it isn't one of those finicky old-school oil-boilers that develops issues at idle. Assuming your Peerless is running no more than 80% as-used efficiency due to oversizing and age (you'd be lucky to actually hit that) it delivers about 110,000 BTU per gallon. EIA data shows a 3-year average price of $3.80, so that means you've been paying about $34-35/MMBTU for heat.

    Propane, even when burned in a mod-con isn't sufficiently cheaper to operate than an electric boiler to easily rationalize the extra up-front cost. EIA data[/URL] shows propane averaging about $3.50/gallon in NH over the past 3 years. That's about 91,500 BTU source-fuel, burned in a 95% efficiency Vitotens delivers ~87,000BTU per gallon, or about $40.2/MMBTU. That's more that what's its costing to run the Peerless.

    An electric boiler delivers 3412 BTU/kwh, so it takes 110,000/3412= 32 kwh of power used in an electric boiler to deliver the same heat. So with 18 cent electricity it's like burning $5.76 oil in your existing setup, or about $57.8/MMBTU- more expensive heat to be sure, but a helvua lot cheaper up front & lower maintenance than a mod-con. It's still less than 50% more expensive than running with propane, and if it's going to be less than 10% of the total heat source (probably would be, if you're judicious about it), it won't much matter.

    A 10kw/ 34,000 BTU/hr electric boiler pretty much covers your entire heat load, and costs a bit less than a grand for the hardware for a no-frills version. Even a modulating 2-stager like the Electro EB-MA-10 runs about $1200 at web store pricing. If you'd be willing to forgo heating the whole shebang to 70F when it's -3F out or only wanted to cover your radiant zones you could go smaller, but having the capacity to be able to run all of your fin-tube zones if you had to as backup doesn't cost much. There isn't much point to going bigger than 10kw, assuming you can fire up the wood stove or one of the mini-splits (or leave the lights on) to cover the difference between 38K and 34K in the event that you really need to cover the full 38KBTU/hr when something is down.

    You clearly don't want to make the electric boiler your primary heating system, but with a floor thermostat keeping the radiant floors at say 72-73F and using heat pumps for keeping the rooms at temp, the electric boiler's output would be a pretty small fraction of the total heat, but a disproportional fraction of the bill, which is why you wouldn't crank the floor temps up to 76F unless you had to. A 73F floor in a 70F room is pretty comfortable- the floor would be emitting about 5 BTU per square foot of floor area into the room, and the ductless or woodstove or whatever could cover the rest (presumably the bulk) of the load at much much lower operating cost.

    A Mitsubishi M-series single-head version will deliver a COP of about 3.2 or better in your climate, sourcing an average 3.2 x 3412 BTU= 11,000 BTU/kwh. At 18 cents kwh that's $16.4/MMBTU, which is by far the cheaper source of heat, less than half the cost of heating oil burned in the Peerless, or propane in a Vitodens.

    According to the load spreadsheet you posted radiant zones comprise about 1/4 of your total heat load, and if used in conjunction with wood stoves or ductless would be sourcing less than 10% of the total heat at that higher price point, but could be as much as 1/3 of the total heating bill. If your radiant floors are fairly responsive (as opposed to slabs o' concrete) you may want to run them on a timer + floor T-stat to skimp for the hours that you're not actually using the space.

    Another aspect to a right-sized modulating 2-stage electric boiler is that you can micro-zone the hell out of the place without creating problems for the equipment, if you think you'd be using it for the rooms too remote from the mini-splits, and not merely "hail Mary" backup.
  3. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Interesting thought. I had completely ignored the electric boiler option because it is the most expensive one. However when we are looking at a backup, it becomes viable.

    Then my replacement scenario looks like this:

    Regarding the mixed mini-split/ small mod-con solution - here is the scenario I imagine:

    1. Leave the Peerless in place as a back-up. Pull out the indirect tank. Add an Airgenerate hybrid electrical DHW heater. Add two Mitsubishi M-series. There are several things I like about this approach:
    1. I can add components ad-hoc (not need financing if I can stretch the project over a period of time).
    2. I can have the DHW heater installed next month and turn off the peerless for the next 6 months.
    3. The overall cost of the project is probably about 10K less than the benchmark ( Daikin Altherma with the Peerless as a backup)
    4. AC is there if needed
    HOWEVER. I lose my radiant floors until the Peerless kicks in. Profoundly sad

    1. Replace the Peerless with say - a Hydroshark 3? Leaving the Airstream Airtap to handle the hot water at all times. Hydroshark serves to power the radiant and as a final backup (catch all for when I away -- skiing, perhaps :cool:)
  4. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,236
    Location:
    Maine
    To quote the guys from Shark Tank " I'm out "
  5. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Thanks for playing though. I really appreciate your time.
  6. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Just a quick update:

    Installed a 66 gal Airgenerate Airtap water heater over the weekend. Turned the oil boiler for the summer. First impressions - it is as quiet as advertised (which was the reason to get it - it is next to a sleeping space). I will post some data on electrical consumption once I have lived with it for a while.

    039.jpg

    Thank you all who participated in this thread and took time to help me.
  7. Dana

    Dana In the trades

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    Location:
    01609
    As a point of reference, was it hard to find the Ati-66 in stock locally/regionally, or did it need to be shipped from a remote (if still USA) location?
  8. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,236
    Location:
    Maine
    It's incorrectly piped
  9. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Tom - you are correct :)

    I will post the picture of what it looks after things were cleaned up. This picture was pretty much at a state where it enabled the kids to take showers.

    Dana - on your question - I had to have it shipped to NH. They have a decent distribution network in the NorthWest from what I have read. However, their presence in the NorthEast is non-existent. The reason I went with it was because of how quiet the compressor is. Which is true as advertised.
  10. nhmaster3015

    nhmaster3015 Master Plumber

    Messages:
    836
    Location:
    The granite state
    What do you do if it needs parts and service.
  11. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    I sit on the front stoop and cry like a little girl.
  12. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Here is what the installation looks like finished. The pump on the right side drives a hot water recirculating loop. This is plugged into a remote control operated outlet (outside the picture) which can be turned on and off from the bathroom with the remote. It is the most efficient way I could think of to operate the pump. It requires some training with the kids but I have purchased electrified dog-collars to speed this process along.

    install.jpg
  13. Reach4

    Reach4 Well-Known Member

    Messages:
    2,496
    Location:
    IL
    I think you might want to add a support for the pressure tank.
  14. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Thank you Reach - I will do this.
  15. nhmaster3015

    nhmaster3015 Master Plumber

    Messages:
    836
    Location:
    The granite state
    I hope you dropped the tempering valve down about a foot below the top of the tank or so. Otherwise, hot water sits on the element spring and weakens it prematurely.
  16. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Thanks - the tempering valve is out altogether. The hot water in the tank gets up to 125 degrees - not like the 150 degrees the old peerless produced. Simplified things.
  17. Dana

    Dana In the trades

    Messages:
    2,934
    Location:
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    Last edited: Jun 19, 2014
  18. onelostsoul

    onelostsoul New Member

    Messages:
    19
    Location:
    New Hampshire
    Thanks. I will fix this when I decide to sell the house.
    :)
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