Recommended replacement for ancient oil-fired boiler ? Gas boiler? Heat pump?

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Tom Sawyer

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Oh yes indeed, keep your radiators. Unlike copper fin tube, radiators give you both radiant and convective heat and they will also give you a greater water mass which will allow you to run much lower return and supply temps too.
 

Dana

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Just had a follow-up call from the mini-split guys...

1 ton Goodman: $3,700 incl electrical
3/4 ton Fujitsu: $4,800

So quite a bit more than the prices you folks are seeing state-side...

The odds of any ~1000' house would have a heat load over 20,000BTU/hr @-3C (or even -10C) are pretty remote, provided there is glass in the windows, the doors actually close, and there's at least some insulation. The output of a pretty-good 3/4 ton mini-split @ -15C is typically around 10,000-11,000BTU/hr and considerably higher at -5C. A typical 1-ton puts out ~15,000 BTU/hr @ -10C (which could equal or exceed your actual heat load at -10C). You don't have to take the manufacturers' word for it (but you usually can), many will actually exceed spec on capacity, when bench-tested by third parties.

For doored off spaces with tiny heat loads, cove heaters (preferably with occupancy sensor cut out, not merely thermostat control) can make up quite a bit on the comfort end when being remote from the fully-heated spaces leads to a temperature sag. The last thing you want to do is put a 6000-9000 BTU head in a room with a design heat load of 1000BTU/hr, but you can reasonably put a 500W (1700 BTU/Hr) cove heater in there, which has huge comfort advantages over electric baseboard, and it'll be able to bring it up to temp at a reasonable rate without feeling like you're in the broiler, and can still be pretty comfortable when the room is still 3-5C below setpoint, since it's heating up the human occupants directly- sort of like sitting in the sunny window on a cold day.

The average COP of any decent mini-split will be about 3.2-3.5 in your climate, but round down to 3.0 if you're using cove heaters or baseboards for temperature balance. That means your $/MJ cost for heating with electricity get's divided by 3. A condensing boiler or hot water heater will probably average about 95% on the fuel, with another cost adder for the pumping power, but even ignoring the electricity use, multiply your gas $/MJ number by 0.95, then compare the numbers.

Your per MJ costs from your earlier post:

Gas: $0.0143/MJ
Electricity: $0.1034/kWh ($0.0287/MJ) - but will be increasing 20% over the next 2 years.

Condensing boiler or HW heater @ 95% efficiency: $0.0143/MB x 0.95= $0.0136/MJ


Ductless & cove heater averaging a COP of 3: $0.0287/3= $0.0097/MJ

That's 29% cheaper than the condensing gas option, but figuring it which will rise 20% to

.... (1.2 x $0.0097/MJ=) $0.0115/MJ...

...which is still 15% cheaper than heating with condensing gas at todays gas prices.

Goodman is now owned by Daikin (purchased within the last year). Daikin is the world-leader in variable-refrigerant volume HVAC, and you'd usually be paying a premium per-ton for a Daikin-nameplate mini-split, but it's not clear to me whether what's under the tin on the Goodman will be Daikin vs. somebody else's hardware, but I suspect it's nothing like the Daikin nameplate units. The rated heating output of their 1-ton is only 13,000BTU/hr bit on the low side compared to competitors' 1-tons, and comparable to the -10C output of the 3/4 ton Fujitsu AOU-9RLS2. (Would need the extended range output tables each to know for sure where the Goodman lives) A Daikin 1 ton puts out about 14-15K, a Daikin 3/4 ton puts out about 10K.

That's not to say that condensing gas won't be a realistic (and quite comfortable) option (and yes it DOES come with hot water heating included) but the installed cost will likely exceed $10K when you include low-temp radiation for what's now handled by electric baseboard, maybe a bit less if you went with a Vertex HW solution (tbd), and it'll cost more to operate. Even at the (truly) exorbitant $4800 quote for the 3/4 ton Fujitsu, a pair of them still under $10K, with enough left cash over for a few 300-700W cove heaters for temperature balancing as-needed.

But start with the room-by-room heat load, look at the big picture (including the hot water part), and I'm sure you'll figure it out.
 

American

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I regret removing our old cast iron coal (converted to oil) boiler and replacing it with a new oil fired boiler in 2007. If I had it to do over again, I'd have kept the old boiler and converted it back to coal. Yes, that means two to theree trips to the cellar and a couple of hour work per day to keep the house warm - would it be worth it? Of course all the heating contractors recommended we replace it. I wonder how much additional cash the boiler installer got when he sold our old boiler to the scrap yard. I had no idea how much heavy metal was hiding under the sheet metal box that housed the boiler until I saw him hauling pieces of it up the cellar steps - so heavy he could barely lift them. Alternatively, I'd have gone to gas as there are gas lines in the street here. But at that time, gas and oil cost the same.
 

Dana

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American: Scrap rates for cast iron hadn't peaked yet in 2007, a period where CLEAN shredded scrap STEEL was fetching ~$250-300/ton at the smelter or dock on the way to China (not the local scrap yard.) Even if it weighed a ton (and it might have) don't think for an instant that cast IRON fetched even as much as $50 at the scrap yard in that time frame.

Fig.2.JPG


In 2007 the retail residential price of natural gas in most of New England was still well under that of heating oil. Heating oil hasn't been cheaper than gas on a $/MMBTU basis in this region since back when natural gas prices spiked above the trend lines in 2002.

oil-season-peak.png


N3010MA3a.jpg


In 2007 heating oil was in the $2.50-3/gallon range (~$18-22/MMBTU, source energy) to natural gas peaked at ~$17/MCF (under $17/MMBTU). An 86% gas burner vs. an 86% oil burner would have still tipped in favor of the gas-burner, and a mod-con would have tipped HEAVILY in favor of the gas burner. Even an 82% efficiency gas burner would have had the slimmest edge over 86% oil at the very bottom of 2007 oil prices. The argument might have been made that there was little advantage to making the switch at that time, but it's simply not the case that the cost of oil & gas were truly the same- gas was cheaper, just not all that much cheaper.

Since 2004 heating with ductless mini-splits has been cheaper than heating with 86% efficiency heating oil in most of New England (and in cheaper local electric utilities it's been longer than that.) At the past 5-year average they are self-financing, paying for themselves in offset oil use in 3 years or less. (Show me a safe & legal investment with that type of after-tax return!) If you are on a gas main and there isn't a huge hook-up fee retrofitting a gas burner to the oil boiler is DEFINITELY cost effective. Otherwise, retrofitting a mini-split would be then next most cost effective strategy. Or, if you don't have air conditioning and are adding it, the upcharge for a heating + cooling mini-split is tiny, and always worth the up-charge as a hedge against gas price increases. During the shoulder seasons when it's 40F+ outside it's cheaper to heat with a mini-split than an 82% efficiency gas boiler due to the extreme efficiency of mini-splits at part load & temperate outdoor temp.

Even at dirt-cheap $/MMBTU source-energy coal prices, burning coal in a ~50% efficiency antique wouldn't have much economic rationale beyond the avoided first-cost of a new boiler. (And the spectre of carbon monoxide poisoning from using those low efficiency antique boilers wasn't just a bad dream either- it's the reason why people would sleep with the windows open even when it was -10F outside, and needed to put the radiator right under the window to keep from freezing even with the heat on.)
 

Tom Sawyer

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He probably made about 40 bucks on the scrap which weighed against the stress on his back muscles seems cheap lol

Your old beast, even converted back to coal would cost you way more to operate than your new boiler. Old boilers had passages large enou to throw a cat through, 800 to 1000 degree stack temperatures were the norm which means that generally, close to 1/2 of the fuels energy was going up the stack. There really is nothing good to say about old boilers except that they sure did last.
 

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After a long delay, time to get back at it!

Got a natural gas line installed and ready to go. Heavily leaning towards installing a Lochinvar WHN-055 Mod-Con boiler.

The problem is that I have an old house, carved up in to little rooms, that people like at different night-time temperatures. My son (who doesn't have a mm of fat on his body) likes it tropical, whereas my daughter likes her room cool.

Heat loss calcs (@26F/70F) for their rooms are 1,800 btu/h and 1,900 btu/h respectively. Going to use the existing oversized cast iron radiators in their rooms. Calcs show that 120F feed water should put out that much heat.

Given that the minimum firing rate of this boiler is 10,000 btu/h (and the total house heat loss is 21,100 btu/h), will it be a big problem running individual thermostats to their bedrooms (i.e. each on their own zone) because other zones will likely be calling at the same time?

Was planning on using a Grundfos Alpha (in AutoAdapt or delta-P mode) driving a 11 port manifold directly (with actuators on each zone). No buffer tank. No primary/secondary loop.

Am I asking for trouble??
 

Dana

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As long as all of the radiation is high-mass radiators, not fin-tube, you'll be OK micro-zoning it with a boiler that modulates down to 10K. There may be a few short-cycles over a season when the call for heat is from but one of the smaller zones, but the zone call overlap factor will be high.
 

Tom Sawyer

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Go with thermostatic valves at the radiators, constant circulation and no room thermostats.
 

JCH

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I was all ready to install a gas boiler/DHW/buffer tank system last year (driving new under-floor plates and existing cast iron radiators) but then realized there was still a lot of low-hanging fruit in terms of reducing my overall heat loss. I even got a natural gas feed installed, although it is currently unused. There are *no* air ducts in my house, just radiators and electric baseboards.

One year later, I have reduced our annual heat usage (annual kWh) by over 20% (down 40% from 3 years ago), with another 20%+ on the way once I add external insulation when I switch from exterior stucco to hardie-plank siding next year. Actual heating load is now 4.5kWh/C/day. At -5C design temp, that works out to 4.7kW or 16k btu/h.

Given the $10k+ cost of a new hydronic heating system, I thought it best to wait until things settled out.

** Have any air-to-water heat pumps arrived in the North American market? Looking at a max lift of 100F (120F water at -5C design temp). One day I'm hoping to be able to drive it with EV panels.

I know there are quite a few air-to-water options in Europe, but have not found much here. Anyone heard anything?

Thanks!
 
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Dana

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Daikin's Altherma modulating air-to-water units can handle your loads with ductless mini-split type efficiency (better than most of the systems available in Europe), as long as your peak water temp requirements aren't too high (and if that's 120F/50C that should be do-able, though 40C would be higher efficiency & capacity). They've been installed in nearby WA, so I'd assume it's at least remotely possible that you could find an installer willing to hook you up in Victoria.

Sanden's CO2-refrigerant combi-systems may be available in the US soon (pending safety-agency approvals), and have been installed in a few homes in that region as well. Most of their business is in commercial compressor systems. I haven't seen any publicity releases on them yet, but I've corresponded with a guy in Portland OR who is installing one in a certified PassiveHouse. The NEEA consortium of utilities in the US Pacific Northwest have put some of their systems through perfomance testing. You'd probably get there with one of those too.

If you have a basement to run some smaller ducts in, you can probably do OK heating the first floor with a 1-1.5 ton modulating Fujitsu mini-duct type mini-split, which would probably cost a lot less than an Altherma and would run about as efficiently. If it's more than one story it get's messy trying to figure out how to duct it while keeping the ducts & air handler completely inside the pressure & thermal boundary, but it may be possible. These mini-air handlers can fit in the top of a closet under the ceiling and serve 2-4 adjacent rooms without taking a lot of space, with very modest duct sizing for each room.
 
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JCH

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Thanks for the options Dana. The Altherma sounds great -- it'll only need 120F on the coldest days of the year (the historical all-time low in this neighbourhood is -7C/20F) and for keeping a DHW tank hot. As you know, more typical January temperatures here are in the 3-5C/37-41F range (which would only require 40C/105F boiler temps).

The plan is use all the existing cast-iron radiators (which were on one huge gravity- converted to circulator- zone) with a delta-P ECM circulator, a buffer tank, and a 11-zone header to cover off the 2-storey house plus basement. The buffer tank's temperature would be controlled by an outdoor reset controller and vary between 25C/80F and 50C/120F.

I was hoping to also use the same heat source to keep a DHW tank at 50C/120F+.

I'll definitely keep my eye on the Altherma's availability here (or in Port Angeles).

Cheers,
 

JCH

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Just taking a look at the Sanden equipment you mentioned. The 65C potential output (by using CO2 as a refrigerant) is certainly even more appealing than the Daikin's 50C limit when used for generating/maintaining DHW.

Hopefully by next year, both systems will be available here (or near here!).

Thanks again,
 

BadgerBoilerMN

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We rarely use 5/8' PEX except in snow melting applications. More often 3/8" PEX is used for light loads and 1/2" in all others. Cast iron radiators can be run in series if you know the heat loads and radiator output for each room. In most cases it is safer to home run each radiator back to a manifold.
 
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Dana

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Just taking a look at the Sanden equipment you mentioned. The 65C potential output (by using CO2 as a refrigerant) is certainly even more appealing than the Daikin's 50C limit when used for generating/maintaining DHW.

Hopefully by next year, both systems will be available here (or near here!).

Thanks again,

I've been hoping for over a decade for CO2 refrigerant equipment to be readily available in the US, and there have been several tantalizing near-misses. Sanyo had 4.5kw and 9kw combi-heating options being marketed in Europe about a decade ago, but the product line got canceled. Seems like it may still be possible to buy them, (or maybe not- some catalog listings never die) but it's not an actively supported product.

In most of the US the higher air-conditioning loads makes air-to-air a much higher volume market.

In Japan the "Eco-Cute" techology collaboration consortium has a fairly substantial number of residential scale domestic hot water offerings using CO2 refrigerant split heat pumps (Sanden is one of the consortium), some of which would be readily adaptable to hydronic heating applications. (The name is in English, but a multi-lingual pun: "kyu-to "means "bring/deliver/heat hot water" in Japanese. They're not exactly "cute", aesthetically speaking, but it was a good bit of marketing. :) ) Mayakawa is another Eco-Cute vendor that currently has operations in Canada, but it looks like they're targeting only commercial & industrial-scale applications. Several of the familiar Japanese heat pump vendors have Eco-Cute products, just not available on this continent.
 

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So if I were to install an Altherma / Sanden hydronic heat pump with a buffer tank (so I can micro-zone) plus DHW heating option, I'm assuming that I could install the heating/cooling version and use it to cool the buffer tank during the summer and feed that cooled water to fan-coil radiators on our second storey. (Here in Victoria our second storey reaches 28C/82F in the summer due to the numerous skylights that make the dull rainy winters bearable).

Correct?
 

Dana

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The Altherma has models with a cooling mode, but I don't think the Sanden does. (The short spec sheet doesn't indicate a cooling mode.) Sanden makes cooling equipment, but their small hot water heaters seem to be heating-only.
 

JCH

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Daikin's Altherma modulating air-to-water units can handle your loads with ductless mini-split type efficiency (better than most of the systems available in Europe), as long as your peak water temp requirements aren't too high (and if that's 120F/50C that should be do-able, though 40C would be higher efficiency & capacity). They've been installed in nearby WA, so I'd assume it's at least remotely possible that you could find an installer willing to hook you up in Victoria.

Sanden's CO2-refrigerant combi-systems may be available in the US soon (pending safety-agency approvals), and have been installed in a few homes in that region as well.

Re-opening an old thread because I've been patiently waiting for Air-to-Water Heat Pumps to become available here in Canada. In the meantime, the CAD/USD currency exchange rate has worsened almost 30%, meaning that the capital costs are significantly climbing...

I recall seeing that Altherma was pulling out of the market (correct me if I'm wrong). And Sanden is saying their systems will be available in Canada/US this spring.

Now I'm revisiting Dana's original suggestion of using a Polaris DHW tank to provide <120F water for radiant plus DHW. This would bring the capital costs of a Natural Gas solution down quite a bit (as it eliminates the separate buffer tank). The PR100-34-2NV Polaris is $4k CAD here vs. $4300 for a Lochinvar WHT-055 plus $1300 for a stainless steel Lochinvar 30 gallon buffer tank (which I've heard have leakage issues).

I've done a heat loss for every room and the existing cast-iron radiators are perfectly sized to handle the heating load at the coldest day (-10C) with 120F water. Was planning on continuously pumping water through them (via delta-P ECM circulator) with TRVs on each radiator.

Question: Is there a way to implement outdoor reset with the Polaris so that I can keep the water continuously circulating and maximize condensating efficiency? The Polaris's capacity (100kBTU/h) is way above my heating needs (18kBTU/h at design temp / 120F water) so it will be running short cycles.

If so, then how do you handle using it to supply DHW as well? I'm thinking that if I want both micro-zoned heating and DHW that I'm going to need separate tanks for each water temperature.

Appreciate your help!
 

Dana

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If you just set the storage temp for the Polaris to 120F it'll always be condensing, there is no need for outdoor reset to keep it condensing. With some modification to the controls to allow it a bigger temperature swing it's impossible to short-cycle it, due to it's high thermal mass.

Another mod-con possiblity to look at is the HTP UTF-80W. It's overkill at the high-fire end, but with a 10: 1 turn down it modulates down to about 7600 BTU/hr out at the low end. Set up correctly it would always be modulating in condensing mode in your climate.

There is another air-source heat pump out there that's very likely to be able to fill the bill, almost perfectly sized for your design water temp and load. The 2-ton Chilltrix CX30 reversible chiller is good for just about exactly 18,000 BTU/hr @ -10C outdoors with 120F water output:

http://www.chiltrix.com/chiller-technology.html

This is a modulating heat pump too. It's worth contacting them!
 

JCH

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Thanks! Just checked and my local wholesaler (Emco) does not carry either HTP nor Chilltrix products. :-( Have to see if I can find a local Canadian supplier.

Because I'm using the original (75 year old) cast iron radiators, am I correct in my assumption that they're not suitable for potable water and I'll therefore need 2 storage tanks? (one for DHW and one as a heating buffer tank)
 
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