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

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BadgerBoilerMN

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Buffer tanks are an indicator of a lazy mind, present company excepted.

I used to use a lot of Polaris water heater for combi service. But as you point out, they do not modulate, nor is there an option to change hysteresis. Not even a differential adjustment. Inexcusable. If you really want to see a water heater cycle, buy the Polaris in a 34 gallon and heat a two story SIP home with it! Still working great but the noise and the cycling doesn't add value.

Still, the built-in buffering is an invaluable bonus and the standing water a must for the filling of large tubs or other hi-demand peak loads.

The Phoenix will modulate and if matched up with the Taco XPB will not short-cycle.

Running the Polaris at 120°F is not considered safe by the Legionella scare crowd. But depending on the design temperature you will not have to worry much about condensing.

With old cast iron radiators a properly sized ModCon with an indirect fired water heater is really the only viable solution if NG is available.

NTI makes one of the best and import a great indirect and IBC, also Canadian, makes another boiler with a 10-1 turn-down. It is hard to short-cycle ModCon boilers driving cast iron radiators unless you ignore the EDR and heat loads altogether.
 

Dana

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Potable water is corrosive, and shouldn't be used in heating systems. To use a condensing hot water heater as the heat source requires isolating the system side from the potable side with a heat exchanger. The pumps on the potable side should be bronze or plastic, not iron. If using a hot water heater as the source it doesn't require any thermal buffering tank on the heating system side.

Depending on the total volume of water in the zones you may not need thermal buffer with the UTF-80 or a Chilltrix. Both will modulate down to a fairly low output. I'm not sure what the min-mod output of the Chilltrix is at +10C, or what it's nominal turn-down ratio is, but the UFT-80 can drop back to ~7600 BTU/hr out. If the smallest zone radiation has say, 100 lbs of water-equivalent thermal mass (including the iron's thermal mass) it takes 900 BTU to raise the temp of that water 5C. At 7600 BTU/hr that's 900/7600= 0.12 hours or 7.2 minutes, which is a reasonably long burn cycle for even a cast-iron boiler, let alone a low-mass modcon. I'd be very surprised if you needed a buffer to make the UFT-80 work given that you have cast iron radiators (rather than very low mass heat emitters such as fin-tube baseboard), no matter how small the zones are.
 

JCH

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Just found a source for HTP Versa Hydro locally -- the PHE130-55P is $8,000 CAD (!). So it would be cheaper to install a NG Boiler and a stainless steel indirect tank ($4k + $1.5k CAD) instead. The upside also being reduced cost when the tank eventually springs a leak.

Finally got a hold of John at Chiltrix -- they'll ship it up here to Canada -- not sure yet how much that'd be. The Chiltrix EC30 is $3.4k USD (=$4.7k CAD), so comparable to a Lochinvar WHN-055 boiler ($4.3k CAD) for capital costs. As per Dana's earlier post on this thread, operating costs of the Chiltrix (even at a COP of 2.5) would be lower than a NG boiler. The bonus is that some of the Chiltrix power could come from EV solar panels (and a local battery) down the road.

If the Chiltrix does what they claim it does, it's the great news I've been waiting for.

Currently digging through the Chiltrix literature to clarify how I'd configure it to drive:
- DHW, and
- cast-iron radiators + under-floor heating plates @ 120F max, plus
- possibly a cooling fan unit on our upper floor during the summer (while still using it to create DHW).

I'll check back in when I have a better idea of what's involved...
 

BadgerBoilerMN

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That road may be a long one.

I have a gas-fired condensing boiler, electric boiler and Fujitsu heat pump for the shop. No doubt that COP beats condensing boiler until your electric rates hit he 25 cents/kW range, but the boiler/indirect range is he safest in terms of payback, ROI and reliability.

A SS indirect will usually last 30 years.

I don't know anyone who has a Chilirix, let alone know how to install or service one. Then there is the cold weather performance. Remember that output and efficiency suffer when it gets below freezing making most air source heat pumps marginal choices in cold climates. Mine has falls off sharply when we hit the single digits.

God knows I like new things, but my pioneer days are dwindling.

As for design temperatures. This is tricky business in residential hydronic retrofit situations since you must start with a room-by-room heat load, measure EDR for that room and plot the ODR and design water temperature before you can match up a heat source.

Being slightly--ok a lot--less mathematically gifted than Dana, I use a dedicated Manual 'J' based software program for this task and you should too.
 

Dana

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In Victoria there's no real problem with cold temp operation in a location. With a 99% temperature bin of about -3C it's practically the Canadian Tropics. But the local technical support issue is real enough.

Chiltrix publishes output specs and efficiencies down to -25C (wet bulb) , a temp not seen in Victoria since the last ice age, but -10C happens maybe once per decade.

CX30-heating.jpg


heat-table.jpg


But designing a Chiltrix into the system is well beyond the design skill sets of most DIYers.
 

JCH

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I've already run room-by-room heat loss calcs for the house, plus cross-checked that against HDD vs actual consumption.

I spent a few months plowing through Siggy's original book (Modern Hydronic Heating) and did all the calculations to figure out the heat loss for each room and the required geometry of under-floor plates to get the heat flux required at a max design temp of 120F.

Last week, Siggy's latest book (Heating with Renewable Energy) arrived on my doorstep -- it has a great chapter on using chillers, both for heating and heating/cooling combi systems.

You're both right though -- when things go wrong (as they will at some point), having locally-sourced parts is huge. The (somewhat) reassuring part is that Chiltrix uses replaceable 3rd-party components in its boxes.
 

BadgerBoilerMN

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"But designing a Chiltrix into the system is well beyond the design skill sets of most DIYers."

More to the point; it is also beyond the skill set of "most" of the HVAC techs as well. This kind of thing will only work with an experienced and dedicated zealot behind the wheel.

They don't grow on trees.
 
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