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Planning new oil furnace and solar hot water installation

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Posted by LML999 on May 10, 2007, 5:20 pm
A few questions from a newbie (be gentle!)...

I live in New England, in a 45 year old house, original furnace.

I have a decent southern exposure, am thinking of including a solar
panel with my furnace replacement.

Considering the Weil-Mclain Ultra furnace. It's a cast iron unit, any
issues with it not running all summer?

Hot water will be indirect, heated as a zone off the WM.

My solar guy suggested a single large hot water tank, a 120 gallon
Vaughn, with dual heat exchangers, the lower one for solar heating,
the upper for indirect furnace heating if no solar is available.

Is this more efficient than running two separate tanks?

Also, a 120 gallon tank makes sense for thermal capture, but a lot for
DHW. Won't I be heating a lot of water and thermal mass in the winter
with my furnace?

SuperStor has an 80 gallon dual exchangers, still double the size my
oil guy recommended (family of 4, 2 teenagers...)

Thoughts appreciated.

Posted by Mark Schofield on May 10, 2007, 7:41 pm
Try posting this question on "the wall" at http://www.heatinghelp.com/ . It's
a site that has allot of professionals in the heating trades. With a boiler,
you might want to leave it on year round. When the indirect is heated by
solar, then the boiler will only come on to maintain it's low temp. But if
you get a run of cloudy weather, you'll need the boiler. Turning a boiler on
and off allot (cold start) might induce expansion and contraction which can
lead to cracks and leaks. I have a WM WTGO3 boiler with a tankless coil
which is fed with preheated hot water from solar. The boiler will run only
15 minutes (1/4 gallons) a day to maintain its low temperature setting. Be
careful about cold starting a boiler unless the manufacturer and your
contractor say it's OK. Washing machine, dishwasher, two teens (girls) might
use more hot water than you think. Good luck. post your decision.   Mark S

Posted by LML999 on May 10, 2007, 8:01 pm

Thanks. I called WM earlier today and asked this same question...their
technical support said that we should have no issue with turning off
the boiler for the summer.

I'm pretty much set on this configuration (WM Ultra, SuperStor 120
dual input, Apricus 30). Only major questions at this point are
whether I shut down the boiler completely in the summer, or leave it
on a setting below what solar normally provides, and the positioning
of the panel and the run of the pipes. I've got a tricky roof, with a
beautiful overhanging Norway maple tree. The tree shades much of the
house during the day, keeping it cool. I also have a nice portion of
roof that has exposure through most of the day. I will probably end up
putting the Apricus 30 on that portion of the roof somewhat optimized
for winter collection (slightly more upright).

Posted by Mark Schofield on May 10, 2007, 10:21 pm
 WM might say it's OK to shut it down for the summer and then bring it back
online for the heating season, with a slow warm-up. But if you need it to
assist with DHW when there's no sun for a few days, the on and off more than
once a year might be harmful. With a system that high-end, you'll probably
use an outdoor reset with summer lockout  to keep the boiler at minimum over
the summer with a call, if needed, for DHW. I put a Honeywell AQ 475 on
mine. Probably the Ultra has a control package built in. One large tank with
dual exchangers rather than two tanks will heat the indirect rather than
only feed the indirect with solar water when there is a draw for DHW. I'd
post a question on "The Wall" about turning the Ultra on and off for DHW if
the sun can't keep up with demand. What type of heating? Radiant, baseboard.
Nice to be able to put the whole system in at once. Viesmann also makes
integrated systems. Check their site for some more ideas.

Posted by nicksanspam on May 10, 2007, 11:03 pm

I doubt it.


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