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Discussion Starter · #1 ·
I have yet to install a Viessmann boiler in the field, but there is a local Viessmann plant that offers Academy sessions which I plan to take this fall, however I've installed a few other brands of Mod-Cons - mostly IBC's, which are made in Vancouver, as well a a few electrics, and other gas boilers.

I might be buying my mom's house potentially which is a 3 bed/1 bath rancher, about 1100-1200 square feet potentially, with a crawl space and I'd like to retrofit radiant floors into it in the joist spaces (coined as "staple ups," but I'd use the Radaint Heat Transfer Plates by Rehau more than likely). The house currently has about a one year old Bradford White 40 gallon electric lowboy, but I'm sure I could find a new home for it.

I had an earlier idea to go with a simple Thermolec electric boiler for this application. But one night recently I decided to crunch the numbers with eletricity versus gas and suffice to say even with the 3rd lowest electricity rates in North America where I live, it's still pricey to heat with electricity.

Currently where I live it's $9.78 per gigajoule (950,000 BTU's) for gas, about $16.43 per gigajoule of electricity, and if you use over 1350 kilowatts every 2 monthes, you are charged $23.00 per gigajoule for every KW over that amount (one Gigajoule = 278 kilowatts roughly). So it's 1.6 to 2.3 times as much to heat with electricity if you assume 100% efficiency with both appliances, which is not the case, as most electrics are 100% but most mod-cons are 92-95% AFUE - with even higher efficiencies in low temps. But in a nutshell it almost makes some heat pumps not seem worth it, at least a air to water version, on colder days.

So I've dreamt up another solution - Viessmann makes a combi boiler which has a plate heat exchaner built in that modulates from 25,000 to 90,000-ish BTU's. The Boiler acts as both a boiler with a boiler supply/return, and a tankless (sort of) with the cold in/hot out through the brazed plate heat exchanger. According to the Viessmann specs, it will produce 2.1 GPM's at 128 degrees and that's with a 50 degree cold water inlet temp, which is reasonable for a 3 bed/1 bath rancher, but I have dreamt up another idea:

What if I did a Solar Domestic preheat tank upstream of the boiler, which would bring up the inlet temp of the domestic water fed to be heated by the boiler? This would in effect increase it's output and save $$$ obviously.

So I'm curious of a few things

1) What can you tell me about this particular Viessmann model if you've installed it?

2) Any thoughts about the set up I described?

3) Any Input on the Viessmann Vitodens 100, which is about half the price, which I could use with an indirect tank?
 

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Haven't gotten a chance to install the big V but I've worked with other combi units. The biggest problem with preheating with solar is what to do with all of that heat energy when no one is home or there is no dump zone. Sometimes the incoming water can be hotter than what the domestic side of the combi is supplying.

I've always had mixed feelings on the subject. I often wonder what the effect of all that hot water has on the flow switches and safeties. There are fusible links in the newer models that are one-time fuses. It's a little extreme since it's the last of three other safeties equipped, but the temperatures can get that high.



I've had success with the new Burnham combi. I believe the model number is the GC160. Good unit, IMHO.

As far as the solar end goes, and I know that space seems to be an issue for you, I love the dual coil storage tanks. Buderus comes to mind as well as others. It keeps the solar circuit independant of what's going on the boiler side and makes sure that you keep all of the necessary warranties and prevent that kind of heat moving through the coil.

Solar is great technology, but since I'm in the northeast, we don't get the chance to install too, too many of them. I'm sure that someone on this board has done a few more that I have so I'm interested to see other's ideas as well.
 

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Sounds like some really good ideas. What I have always done in the past is to talk with Viessmann directly.

Ask to talk to Stuart at the Langley branch, he travels alot but usually is more than willing to give advice on whatever questions you might have.

I have worked on some installations of Viessmanns, just lately a retrofit with a Vitodens 100, the installer did not do a proper job. Cheaped out and didnt pipe it properly.

To get all the energy efficiencies you HAVE to follow their piping diagrams. Most importantly is the low loss header.
 

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Discussion Starter · #4 ·
Hey SPH - did you take the Viessmann Academy courses? Also, who do you work for out of curiousity? Do you do a lot of heating or more plumbing?
 

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No I have not taken the Academy courses but I have wanted to, just hard to find the time. Just done the tour and talked to alot of people there. When we get a set of prints with a hydronic heating layout we can show them to Viessmann and they will engineer a system for it.

I work for Schubert Plumbing & Heating. You work for Integrity right?

We do more plumbing than heating in new construction. But we service alot of boilers and radiant systems.
 

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Discussion Starter · #6 ·
I work for Schubert Plumbing & Heating. You work for Integrity right?

Yup.

I'm in the same boat - but I think if I can remmeber it, I'm gonna try and do some of the Academy sessions in the fall.

And like you we prefer to do heating but we often win full mechanical jobs where we tend to do more plumbing than heating.
 

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Discussion Starter · #8 ·
do you do the HVAC as well?
Integrity does it all. When I started with the company about 2 1/2 years ago, we were mainly boilers/geo/radiant floors/plumbing with a small HVAC department that mainly did HRV's, bathroom fans, and the odd air handler. We recently picked up some very experienced Solace guys early last year and now our HVAC department is a force to be reckoned with and we're much more well rounded. Myself personally though I just do plumbing/hydronics. Our company actually has a few "departments" - PLumbing/Hydronics, Controls, Geothermal, and HVAC crews, as well as we have one dedicated service guy and I do some service myself as well although I've still got a lot to learn that way too (do you ever stop learning doing service though?). Some guys interchange between the 2 like the geo guys going into plumbing if they have a lull doing geo once in a while (which is rare) but generally it holds true.

Why aren't you a member of Teca?
 
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