Combi Boiler: Dunkirk vs Navien

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Chris Neffshade

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Hi,

My contractor has been going over options with me for combi boilers to install for baseboard hydronic in my house. He has been exploring different brands, and today he suggested Dunkirk. Previously Bosch and Navien were both the other options. I can find very little about Dunkirk online (and what I do find seems to be more bad than good) am wondering if anyone has any personal experience here.

His main reason for thinking about Dunkirk is that there would be more local support than the overseas companies. I don't know if that is really enough to be worth it though.
 

Dana

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What model numbers?

How many feet of baseboard (on each zone, if broken up into zones)?

Not all combi boilers are created equal, and the minimum fire output relative to the zone with the least amount of baseboard is important for figuring out if it's anything like an appropriate solution.

If the baseboard is so short that it'll short-cycle the combi boiler, tank type combi is often the better solution.

But let's run your radiation numbers against the models in question anyway, it doesn't take hard-math.

If the Dunkirk is the CCB-150 RUN AWAY (and find a different contractor for even bringing it up- seriously!) That thing requires expensive stainless steel exhaust venting, but worse, it only has a 3:1 turn down ratio, which would require a high rate of hot water flow for it to regulate temperature well. And since it's min-fire input is 50,000 BTU/hr (about 42,500 BTU/hr out) it's output at minimum fire would be near (or above) the actual heat loads of most houses- it will never modulate in space heating mode, and needs at least 70' of baseboard on any given zone to keep from cycling. There are very few houses (if any) where that would be an appropriate solution.
 
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Chris Neffshade

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As far as getting a properly sized unit I trust him and he has been sharing his design and calculations with me (final zoning is still under consideration depending on minimum boiler output etc). I am more interested in people's experience with the brand than anything.

In terms of models we are talking condensing for both. For Dunkirk it would be the Helix VLT and for Navien the NCB-E series
 

Dana

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The actual model numbers matter, since they don't all have the same min-fire output.

The Helix VLT series are not a combi boilers, they are mod-cons with stainless finned water-tube heat exchangers and ~5:1 turn down ratio. You'd need an indirect fired tank for domestic hot water. The smallest in the series (the- 50 ) has a decently low 10,000 BTU/hr in, which would be about 9500 BTU/hr out at minimum fire. The shortest amount of fin-tube baseboard it can run at condensing temps without cycling issues is about 45'.

The smallest NCB-E modulates down to about 12K-in 11.5K out, which would need about 55' of baseboard to not cycle at condensing temps. It might be a bit short on domestic hot water delivery. The bigger ones have better hot water delivery, but also higher min-fire output.

If US-made, US-support is important, consider going with HTP's UFT series, which have stainless fire-tube heat exchangers and 10:1 turn down ratios. The UFT-080W (also sold under a Westinghouse nameplate as the WBRUNG-080W) has enough high-fire output for 19 out of 20 homes in the US, but modulates down to 8000 BTU/hr in, ~7600 BTU/hr out, and can serve a ~35' baseboard zone at condensing temperatures without cycling. The lower-head heat exchanger means it can be pumped direct in most systems (no primary/secondary), saving on hydraulic separation plumbing and the extra pump. It's also designed with a separate port and internal control built-in for serving indirect hot water heaters. (They're relatively inexpensive too.)

Navien's NHB series mod-cons also have a 10:1 turn down ratio, and the NHB-80 is comparable to the UFT-80 on most characteristics (including price), except it has dual water tube heat exchangers, and is typically plumbed primary/secondary (using Navien's not-super-cheap manifolds). Setting it up for an indirect hot water heater would be comparable to setting up a Dunkirk VLT with an indirect ( not as convenient as the UFT.)
 

BadgerBoilerMN

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"Overseas companies" Really?

Like Honda, Toyota, or Mercedes?

Your contractor should have experience with the boiler he suggests. Who will work on the boiler should installation and commissioning not go as planned?

I have installed over a dozen different condensing boilers, foreign and domestic, but proper application and installation are critical, followed by local support. These are things best left to an educated installer/service provider.

I would find him first.
 
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Dana

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Overseas can't be trusted- you've heard about that overseas VW diesel, right? ;)
 

Zl700

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HTP UFT US Made?
Correction it's a Kiturami Korean manunafactured boiler and finished in the US.
Look at the exact cabinet and component characteristics of products offered by Laars, HTP, Triangle Tube, Noritz, Westinghouse (an HTP label) and some others. All Korean made products made by Kiturami and relabeled.

Now who do you trust?
 

Dana

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I was wondering just how much of that boiler was outsourced. (Thanks!) At least it isn't made by VW! :)

I looked, couldn't find a Triangle Tube with the same characteristics, but the Noritz Combi, UFT/Westinghouse and Laars Mascot series all sure look like the Kiturami Homsys:

19408_CA01_SUB.jpg


UFT_HTP_2.jpg
wbrung080w.jpg
FS-Noritz-Combi-Boiler-angle-right.jpg

Mascot-FT-Wall-Hung.jpg
 

Zl700

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Kiturami besides boilers and combis also makes a tankless water heater that many our labeling and adding to their lineups
 

Dana

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kurae?! Ara seo! (or however you latinize that... :) )

So, Kyungdong & Kiturami are duking it out for a piece the North American market using different tactics- love it!
 
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