A fireplace is a useful backup heat source that can fill the gap between your system capabilities and any extreme weather that happens along.

Many people like them for the ambiance of a fire, not to mention the useful heat output.

I installed a 60KBTU wood burner that can heat the entire home in the event of power loss or gas shortages. In case you are wondering, that is enough heat to warm up five hypothermic construction workers. We've had numerous opportunities to test it.

Posted By ICFHybrid on 28 Mar 2012 11:56 PM
A fireplace is a useful backup heat source that can fill the gap between your system capabilities and any extreme weather that happens along.

Many people like them for the ambiance of a fire, not to mention the useful heat output.

I installed a 60KBTU wood burner that can heat the entire home in the event of power loss or gas shortages. In case you are wondering, that is enough heat to warm up five hypothermic construction workers. We've had numerous opportunities to test it.

Unfortunately 80% of our customers don't have access to natural gas. Propane tank and lines only for a backup fire place? Adds costs and beats the purpose.

Posted By Dana1 on 28 Mar 2012 06:55 PM

Posted By docjenser on 28 Mar 2012 06:01 PM
Let me ask another question here. Let's say I have a typical setting, old house with energy improvements, or a new house, 2500 - 3000 SQF one story home, with a typical design temp of 0F and a 40 - 50kbtu/h heat loss. So an air sourced heat pump has a COP of 1.5 or 2.0 at that temperature and minimal overall capacity. How am I gonna get 50,000 BTU/h into the house? Strip heat?

Spend the money on getting the heat load down to under 36K with air sealing & insulation retrofits, and drop in a 3 ton Mr. Slim (or a Daikin Altherma, if you love cozy toes and are willing to pay extra for it).  It's usually less money than 4+ ton geo,  even as retrofit (but particularly cheaper on new-construction. )

For example, I live in a ~2400' mostly one story bungalow (~350' upstairs) built in 1923, with 1500' of semi conditioned basement that stays above 65F all winter to boot. This hows has KNOWN gaps in the insulation, and standard triple-track storms over the original double hungs for windows. Design temp here is +5F, but it clearly gets colder. I'm constrained by radiation & water temps to a maximum output of about 42-44KBTU/hr, yet this place sailed through -8F temperatures without losing ground during a cold snap last year.   When I moved in the heat load was probably pushing 50K @ 0F, but it's well under that now after blowing cellulose into the walls that were easiest to get to, air sealing the place  a bit, and insulating on the foundation walls & band joist.  Based on fuel use and boiler efficiency analysis its somewhere in the mid-30s @ 0F now.

The Mitsubishi H2i series are specified for full rated output at -15C/+4F, and similar sized Fujitsus & Daikins will put out similarly, even without being fully specified there.  (Some models have -20C output specs to refer to.)  The H2i models deliver over 70% of rated spec at -25C/-13F.  It doesn't take much baseboard to cover the difference if the mini-split covers the load a design temp of 0F, and you have the cold-snap of the decade at -10F.

I COULD be heating with a mini-split, but it wouldn't be dramatically cheaper than the current gas-fired system- there's no incentive to move that direction. But it's just not that tough or expensive to pull the heat load down, even WAY down in most houses.  A 50K heat load @ 0F on a house that size is either a leaky wind tunnel or a shack- my place isn't anything like super-insulated (not even current code-min!). If my heat load was even 40K @ 0F it would mean they're slipping me some sort of super-therm gas in those pipes, since that would imply my heat loads greater than the source-fuel BTUs that actually support the loads.

But I suppose it's cheaper to just buy some electric baseboards instead of air sealing and insulation...

I'm sure there are some real antiques out there where it's too difficult, expensive or even impossible to get the heat loads that low with some appropriate retrofits, and those are clearly not going to be the best candidates for ductless air source heating.

And, places with design temps around 0F aren't likely to hit an annual average COP greater than 2.5 too.  With bigger heat loads and lower temps the present-value economics start tipping toward geo ever more quickly, when the design condition heat load is over 3 tons, and design temps are in negative digits F.

I pulled the table on the largest Daikin (54 dodel, I believe 4.5 nominal tons, integrated values). While the COP around 0F is still around 2, the heat capacity now is around 25 KBTU/H.
You say that 50 KBTU/His too leaky, but with the newest New York State energy codes that is not unheard of for a 2800 sqf new build, single story house with somenicewindows. Even if I get it down to 40 KBTU/h, the 25 KBTU/H from the largest Daikin is not gonna heat the house. Now I get a cold snap....I hope you see my point.

Unfortunately 80% of our customers don't have access to natural gas. Propane tank and lines only for a backup fire place? Adds costs and beats the purpose.

My fireplace is a wood burner. Presumably, wood is widely available.

The nice thing about a fireplace is that many people want it for the ambiance. As such it is enjoyed under the heading of entertainment or even decoration. That way, it doesn't have to sit around waiting to do duty as backup heat, yet it still provides the fill-in for peak heating needs.

Posted By ICFHybrid on 29 Mar 2012 08:51 AM

The nice thing about a fireplace is that many people want it for the ambiance. As such it is enjoyed under the heading of entertainment or even decoration. That way, it doesn't have to sit around waiting to do duty as backup heat, yet it still provides the fill-in for peak heating needs.

What it wont do while it is "sitting around" is meet code as the automatic heat source to reach 68* in your home....so if load calcs say you are short (and the inspector actually enforces the code), you would require another mini-split or some electric baseboards etc.

Sorry to keep bringing up code, but some of us live in the real world of responsibility to the rules. You might also be shocked to learn that not everyone has an abundance of inexpensive lumber or the desire to tote it around.

Dana 1
"I COULD be heating with a mini-split, but it wouldn't be dramatically cheaper than the current gas-fired system- there's no incentive to move that direction. But it's just not that tough or expensive to pull the heat load down, even WAY down in most houses."

I'm not sure you would find a central minisplit compared in comfort to your gas boiler. Why would you replace an honest to goodness central heat plant and delivery system that could be easily zoned to give each room it's own thermostat reducing consumption.....for a nonducted poor delivery system? Mini splits have their place, but suggestion that it is a good fit in your home (compared to existing system) is silly.

so if load calcs say you are short (and the inspector actually enforces the code), you would require another mini-split or some electric baseboards etc.

I love it when the Political Commissars get going...... ;-)

When faced with a diligent inspector who wanted to dig down through the engineering manuals for the true rated output, I'd just show him some resistance heat.

I pulled the table on the largest Daikin (54 dodel, I believe 4.5 nominal tons, integrated values)

Not sure what unit that is rated at "54". I have a Daikin Altherma unit which is a central air to water unit rated at 54kBTU nominal, but it also has 6kW of resistance heat built in for the peak loads

Posted By ICFHybrid on 29 Mar 2012 09:50 AM 
I'd just show him some resistance heat.

Right on. Good to follow the rules.

Posted By ICFHybrid on 29 Mar 2012 08:51 AM
The nice thing about a fireplace is that many people want it for the ambiance.

Sounds great. What brand of automatic wood pump do you recommend?

Looby

Posted By docjenser on 29 Mar 2012 05:00 AM
Even if I get it down to 40 KBTU/h, the 25 KBTU/H from the largest
Daikin is not gonna heat the house. Now I get a cold snap....

Well, duh!!! That's why you shoulda built on Puget Sound.

Looby

Posted By joe.ami on 29 Mar 2012 09:20 AM

Posted By ICFHybrid on 29 Mar 2012 08:51 AM

The nice thing about a fireplace is that many people want it for the ambiance. As such it is enjoyed under the heading of entertainment or even decoration. That way, it doesn't have to sit around waiting to do duty as backup heat, yet it still provides the fill-in for peak heating needs.

What it wont do while it is "sitting around" is meet code as the automatic heat source to reach 68* in your home....so if load calcs say you are short (and the inspector actually enforces the code), you would require another mini-split or some electric baseboards etc.

Sorry to keep bringing up code, but some of us live in the real world of responsibility to the rules. You might also be shocked to learn that not everyone has an abundance of inexpensive lumber or the desire to tote it around.

Dana 1
"I COULD be heating with a mini-split, but it wouldn't be dramatically cheaper than the current gas-fired system- there's no incentive to move that direction. But it's just not that tough or expensive to pull the heat load down, even WAY down in most houses."

I'm not sure you would find a central minisplit compared in comfort to your gas boiler. Why would you replace an honest to goodness central heat plant and delivery system that could be easily zoned to give each room it's own thermostat reducing consumption.....for a nonducted poor delivery system? Mini splits have their place, but suggestion that it is a good fit in your home (compared to existing system) is silly.

I wasn't suggesting it was a great fit, just that it could handle the space heating load.  The boiler is also handling the domestic hot water, which is a separate consideration.

The Daikin Altherma would cut it simply retrofitted in to my current system, but my water temp requirements are still too high for optimal performance, and at the higher water temp/lower COP and power rates north of 15cents/kwh, the operating cost would be somewhat higher than with the current gas-fired setup.  For less than the price difference between an Altherma and 3-ton geo it might be possible to get there, but I haven't botherd to do the math on that- the operating cost delta between the gas fired system at the new-improved operating point would be negligible, and the money spent on the Altherma would be better spent on taking the heat load even lower.

In general, anybody on the gas-grid will have a tough time making a financial case for heating with ductless air-source, but anybody heating with oil, propane, or resistance electricity will usually have an easy time making the case, even as a partial-solution. 

On a deep energy retrofit project on a three-family building I've been advising on locally, the decision for going ductless rather than gas-fired wasn't simple- the building is on a gas main, and the service is hooked up to the building, but the heat loads @ design condition, were between 12-16KBTU/hr, with somewhat comparable cooling design loads.  Other solutions were assessed (hot water heater hydronic, mid-efficiency wall furnace + permanently-installed window-shaker AC, etc.) but in the end 3 1.5 ton Mitsubishis (with a few kw of resistance electric for backup) won out on the price/performance and operating costs of combined system, despite also going with condensing gas for the domestic hot water.  Average heating season COP is anticipated to be in the 2.5 range at a minimum for the lossiest unit, but it likely to be 2.7+ for the lower-loss units due to the modest oversizing. (Max output @ the local design temp of +5F on the 1.5 ton Mitsubshi MUZ-FE18NA is specified to be 21,600BTU/hr, and at -13F is estimated at ~15K. The -13F temp was last seen in this location only about 15 years ago, so it happens, but less than once/decade. Sub zero happens several times/decade.)

Electric baseboards are cheaply installed, code-compliant back up for when these systems don't meet 99%+ percentile loads, and have negligible impact on the net seasonal COP.   It's the average winter temps & sizing is what ultimately determines the average COP for air-to-air ductless, but with the air-to-water Altherma the water temp is also a big factor.  IIRC the published specs on the Altherma heating output are for 45C-50C water out, with a delta-T between 3-9C through the water side HX.  With slab radiant or WarmBoard, etc the water temp requirement @ 0C on a decently insulated house would typically be under 40C, sometimes under 35C which improves both net output and COP.  (NRT.Rob has real data on this, since he is heating his offices in Gardiner ME with one, where the outside design temp is about 0F, or maybe a bit under.)  Most places with 0F design temps have average January temps of ~20F, a temperature at which mini-splits are already pushing 3.0 for a mid-speed COP, but it's the low COP during the colder parts of the day/month that peels roughly a half-point off that for the seasonal average.  Oversizing by 25-50% buys a substantial part of that back though.

BTW: The rated capacity @ +17F for the 1.5 ton Mitsubishi is only ~11.5K, while it's max out at that temp is ~19.5K, a function of capacity loosses (but not COP losses) to defrost cycles. COP @ +17F==2.77. Average temp in this location= low to mid 20s.

Very little is given up in COP to defrost cycles, because both the heat of vaporization (965BTU / lb of frost) and heat of fusion (144BTU / lb of frost )were garnered high-COP, but only the heat of fusion is given back, but at an even higher, near double-digit COP by reversing the system into cooling mode for defrost. So while some power is used to give back that 144BTU/lb, the vast majority was heat already taken at the standard COP, and it's pretty much a wash.

The more grains H2O per lb of air the greater the losses to defrost. But at +5F the grains/lb of the air even at saturation so low that the time & energy spent in defrost at temps that low is miniscule compared to the total, and under most conditions it would be capable of putting out very near it's max output (which is HIGHER at +5F then at +17F.) I s'pose I'll be finding out next winter how well they really make out, but the (fairly experienced) installer is also confident that they'll more than meet the entire load at design temp, and on the lower loss unit it may even handle the -10F load.

What brand of automatic wood pump do you recommend?

Looby

An automatic wood pump? :-)

You city slickers sure can come up with some thigh slappers.

I use an axe.

And then, I carry it the old-fashioned way.

Does that axe-equipment carry an ASME label, so's it can meet code, huh, huh, HUH!? ;-)

But seriously, the notion that it takes a 4+ ton Altherma to meet a 25K heat load at 0F running a radiant slab is a bit silly. Both the output & COP at a given temp are determined by the required water temp. You get a lot more out of them with a low-temp slab than in the panel-radiator temps at which most Asian & European users will be using (and at which the specs were drawn.)

A 2.5 ton Mr. Slim (PUZ-HA30NHA, if you want to look it up) would support a 25K load @ 0F with margin to spare for half the money of any version of Altherma, if you can part with the cozy-toesies concept of radiant floors. (32K out @ +5F with a COP of ~1.5, 22.5K out @ ~ -13F breaking-even, installed cost under $10K, usualy under $8K.)

ICFHybrid, you spendthrift! Show the inspector an electric tankless. I paid $186 for a 10kW Stiebel Eltron on eBay.

ICFHybrid, you spendthrift!

What? My axe?!?

Oh, heh, heh, the Altherma. Yeah, well, it was all new and shiny when I ordered it and I thought I would be the first on the block to put one in service, but since then a number of folks have come by, looked at it and got their own in service first. They started building before me, though. That's my story and I'm sticking to it.

The unfortunate part about making comparisons is folks wish to interject little short cuts or pet designs. Now apparently used equipment as well.
Do you guys think maybe geo would be a little cheaper as well if we undersized it using solid fuel back up and used eqipment? Maybe ignored the code, industry standards and other sundries?

Actually, ICFHybrid, I meant that an electric tankless is less expensive than electric baseboards. Joe, my tankless was new in the box. Stiebel Eltron is the most popular brand in Germany and superior, my plumber told me, to Bosch.

Since it's only purpose is to meet code, and to maintain min temps on vacations that the sun should accomplish without it, I'd say it was $186 well spent, eh?

It appears that I overpaid: http://www.ebay.com/itm/Stiebel-Eltron-DHC-10-2-Tankless-Water-Heater-/260980644980?pt=LH_DefaultDomain_0&hash=item3cc3a89c74#ht_500wt_929