Like I said, it's not an $800 upgrade once you account for the trim item reduction... pump downgrade, pump energy cost reduction (think $10/month in electricity), less piping, etc.

Your conversion is good but I'm not aware of anywhere in canada with a degree day count that low for a typical room temperature. in deg F you can't hit the northern border of the US without breaking 8,000 HDD/year. Are you in some crazy warm microclimate?

Aren't heating degree days standard for the room temperature of 18°C (65°F)? If you were to measure it relative to say 75°F, then we would be around 8200°F-days.

Our climate is mild, but sholdn't be much differant that Bellingham, Washington. What do you show for the Seattle area on your references?

I see 5500-6000 degree days at the washington border to canada on the coast. So I was wrong... there is one place you'd be under 8,000 at the border! Missed that little corner there.
5000-5500 for seattle itself.

that's raw yearly, not modified to eliminate summer days.

Vancouver & Bellingham have even fewer HDD than Seattle (more favorable moderating winds off the Pacific, with fewer/lower obstructing coastal mountains), but about 1-2F cooler design temp (for those days when the wind is coming out of the mountains.) Victoria & Nanaimo, has similar HDD to Vancouver but an even warmer design temps.

I'm not surprised it's under 30KBTU/hr peak- in a house like that it might even under 20K unless you have quite a bit of glazed area.

Thanks for confirming, I was getting worries that all the heat load calculations previously were wrong!

There's not much glazed area in the house, but there is a lot of exterior wall surface area with vaulted and 9ft ceilings. The biggest heat loss even with the HRV is from air exchanges.

So with a small heat load, high mass, and long cycles times: Stick with the original plan of DV hot water tank, or for the same cost switch to a DV Navien heater, or upgrade to the MC-50 for $800? (note: most the pumps and hardware are already purchased so no cost savings by downsizing further)

Sounds like you're in water heater land.

without knowing what you have it is hard to know if a switch to a tank makes sense. If you can return stuff, I would do that in most cases. But this case would be the "least horrible" for a navien as well if you are all set up for it already... but I do think it will end up costing you more in maintenance and electrical usage than the tank would.

Always my first point.

If you get professional help before you spend money, you will be money ahead. On line vendors rarely have the time or knowledge (present company accepted) to help the avid DIYer choose the right system for there particular situation (or location).

Tank-less water heaters misapplied for space heating, are false hope for the stingy or misinformed.

I should clarify, when I said pumps and hardware I mean the circulator pumps (grundfos superbrute), pex coils (Rehau) and distribution manifolds, connectors, etc.

The tank and venting have not been purchased, hence the question about application. Not everyone can afford a professional design, and this is a very simple system with low load. The professionals that I have talked to in this area have immediatly steered towards much to large and complex of system to meet our needs. It's not an apartment complex, it's just a small single family house.


Thanks for the input, It's looking like we might be better to go back to the original DV waer heater (which are also not rated for space heating), and hope to get 80% efficiency with long burns times.

Have you taken a look at the AO Smith Vertex 100? They are not cheap - 2 grand for the water heater available in LP or NatGas, but they are designed to do both DHW and Radiant floor heat.

-Rosalinda

Hi - I had a question regarding the layout of the main feed for a radiant sytem - i had trouble starting a new post....I wonder if you would be able to help me? I have to travel from my hot water source/furnace through 30 feet of a 4 foot crawl space (new construction) to my tubing feed/return panel (which has four loops of 300 feet each). I can either go the shortest easiest route but it would necessitate using four 90 degree bends, or I can travel an additional 10 feet and make a large loop through the joists, and only have two 90 degree elbows in my 3/4 inch white flexible main feed and return lines. Question: Is it any worse (will it hamper flow) to use the elbows? thanks claude stein

This question is for the experts that favor the mod/con boilers. Thoughts on the CH-180 instead of the NR-180? Has outdoor reset, made for domestic hot water and heating applications. I don't know how much it might cost more than the NR-180, but would that be a better fit in this case for better longevity, better efficiency, and lower cost than a mod/con?

Victor
www.ecobuilthome.ca
A 4350sqft Net Zero Energy initiative

"Not everyone can afford a professional design, and this is a very simple system with low load."

I disagree.

Every system I have redesigned or performed a factory start-up for, wasted at least $500.00 on materials or long term efficiency. It is not possible to design a system by blog. The best the layman can hope for is to learn the appropriate answers.

I am the ModCon zealot and still use a simple standard for choosing water heater or boiler. That being the balance of the load.

First, the available fuel.

Second, the heat load.

Third, the local factory/dealer support structure.

Long term investments require long term strategy.

Posted By BadgerBoilerMN on 24 Jan 2011 10:31 AM
"Not everyone can afford a professional design, and this is a very simple system with low load."

I disagree.

Every system I have redesigned or performed a factory start-up for, wasted at least $500.00 on materials or long term efficiency. It is not possible to design a system by blog. The best the layman can hope for is to learn the appropriate answers.

Yet the purpose of this forum is to enable the sharing of information between professionals and layman. This is not a professional only forum, so replying to every question with telling the poster to hire a pro to design may be a bit out of place.

I do appreciate your input, but disagree that with some help, many on the non-professional users of this forum should be able to design and build a good solid system.

Posted By vkykam on 23 Jan 2011 04:47 PM
This question is for the experts that favor the mod/con boilers. Thoughts on the CH-180 instead of the NR-180? Has outdoor reset, made for domestic hot water and heating applications. I don't know how much it might cost more than the NR-180, but would that be a better fit in this case for better longevity, better efficiency, and lower cost than a mod/con?

Victor
www.ecobuilthome.ca
A 4350sqft Net Zero Energy initiative

I asked our local rep about that, and his opinion was that there was not a lot of gain for the extra ~$700, unless you are actually running a combi system. The heat exchanger internals are the same, but it adds the domestic loop and the outdoor reset.