# hot water system



## wg_bent (Aug 9, 2007)

I began looking at solar hot water system.  The installer I contacted said the first step would be to ditch the coil in furnace system I have now and move to a zone based system.  Easy enough... He also said that would improve the efficiency of the system I have now.  Are there any problems with doing that?  Just plug the in/out for the coil, and install zone and tank?  He estimated 2 grand for that, but I've installed zone's before... I consider that almost relaxing easy work. Will it improve the efficiency?


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## kevinlp (Aug 9, 2007)

I am thinking of solar water heating at some point in the future as well. We already have a 3 zone system off our boiler (upstairs hydronic forced air, downstairs baseboard, hot water storage tank -indirect?). Our roof is aligned east-west so we have a great position.

Let me know what you find out for costs.


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## thephotohound (Aug 9, 2007)

I, too, am doing my homework for a solar system... I'll be watching this thread closely. My house is facing east/west as well.

Re: the $2K to change the coil... that's not the whole system, is it? I thought the photovoltaic panels alone would be over $5K. Maybe I misunderstood.


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## Burn-1 (Aug 9, 2007)

TPH he's talking about swapping the tankless coil in his boiler for an indirect hot water heater which is an insulated tank that runs off a zone valve. I'm considering the same thinng and have received similar cost estimates. It's more efficient than a tankless coil. 

The indirect tanks are also nice because you can get one which will allow you to incorporate the solar heat exchanger in the system. Do a search for Vaughan or Rheem solar tanks and you'll see what I mean.


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## wg_bent (Aug 9, 2007)

Yes, that's what I'm talking about.

The other costs:

He quoted me a rough payback of 6-8 years.

The website was www.hvce.com

Average system cost was about 8600.00 for a 2 panel system. about 11,000 for a 3 panel system.  Tax credit of 4750 brings the 3 panel system cost to 6250.

He said the 2k for conversion from the coil in furnace to a tank off a zone was elegible for some tax credits because it's an efficiency upgrade, but he wasn't sure how much.

Thanks for the info on the tanks.  I have stubs off the furnace I installed already so I can add zones at will and the plumbing for a tank system would be really easy to install.


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## wg_bent (Aug 9, 2007)

I have to say though that browsing the internet... I see that a lot of systems are available for between 3 and 4 grand.  That's a lot less than 11 grand.  I'm wondering... does it require a pro installer to get the tax credit?  If not, the cost goes WAY down since I don't think they look that tough to install.


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## wg_bent (Aug 10, 2007)

One thing I found is that there are two tank systems and 1 tank systems.  Any input on which is better?

In a two tank system, the solar heats the water, then the DHW output goes into a second tank that is further heated by electric, gas, oil, wood (for  Eric) etc...  The single tank system has two coils.  The lower coil is the solar, the upper is the secondary connected to your other heat source.


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## thephotohound (Aug 10, 2007)

Interesting... I wonder what it would take (panels, that is) to provide hot water and HWBB for heating 1000 SF... any ideas?


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## cbrodsky (Aug 10, 2007)

Hi Warren -

You're more than welcome to stop by and check out our system sometime to get some ideas - even this weekend - we'll be around.  We had a different company do it:

http://www.ebmservices.com/

Jon Harkness is the person who handled our system.

The prices quoted were quite a bit less although it could vary from on install to another - $8600 for a 3-panel system w/120 gallon storage; I believe it was around $7300 for a 2-panel system w/80 gallon storage, but we thought the extra 15% cost for 50% more total output was worth it.  Based on the panel costs, it should only be about $1K per panel additional unless that third panel really complicates things.  I estimated that had I purchased the items myself, I would have been looking at $5-$6K buying over the internet for 2 or 3 panel system, so for labor, we paid about $2500 - but then you get tax credits that cut that cost almost in half.  I can assure you it was well worth $1250 actual out of pocket cost to have them install it 

I am suprised the other company is telling you to get rid of the tankless coil if you still leave your oil heat on for backup in the winter.  They are correct that a tankless is wasteful when you run the boiler all summer, and avoiding that is really where you save a lot - people who already have natural gas heaters have a much tougher payback argument.  But when your boiler is going to be on anyway, it is still the most cost effective way to get hot water.

Ours was installed with valving to run three different ways:

1.  Solar only, bypassing the tankless coil, with an internal electric backup element for shoulder seasons when boiler isn't on for heating purposes.  This is the most cost effective and simple way to extend your boiler shutdown period.  The cost of electric to finish off the heating is still much less than standby losses on the boiler.

2.  Solar tank feeding the tankless coil - in the winter, you get some partial preheating of the water which lowers the load on the furnace.

3.  Bypass solar tank and run exclusively on tankless coil - really only useful if you need to get into the solar tank.

Addressing a few other questions - the thermal stratification in the solar tanks works very well and better than I would have expected.  Two tanks is overkill IMHO.  We regularly see 50 degree differences in the bottom vs. top of the tank.  As you use hot water off the top, you draw in cold to the bottom, and when the solar system runs, it sends the heat to the low part of the tank.  If it's not hot enough by the time it's at the top, then you have an optional electric backup element that can finish it off.  Our tank has yet to get below 115 since April so I'm not sure when it'll actually be required - this past weekend, the tank hit 180 and maxed out so it'll be a while before that comes into play.  Also, keep in mind that 120 gallons of water at 150-180 degrees goes much much longer than a 60 gallon conventional water heater at 120 degrees.  You bleed off much less of the hot water to mix with cold to get up to the temperature you'd like to have at the tap.

The solar tanks also cost close to $1000 so that can be a big cost factor if you use two, while going from an 80 to 120 gallon tank is only about $100 more if I recall correctly.

-Colin


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## cbrodsky (Aug 10, 2007)

Since people were interested in cost, and more and more people are getting quotes, a few more details on credits below.  The numbers I quoted in my last post were prior to these credits which in NY, cut the price roughly in half.

Federal credit is 30%, maximum of $2K:

http://www.dsireusa.org/library/inc...tive_Code=US37F&State=Federal&currentpageid=1
***check for conflicts with AMT if you think you will be paying AMT***

New York State credit is additional 25% - limit of $5K (recently increased!)

http://www.dsireusa.org/library/inc...Code=NY03F&state=NY&CurrentPageID=1&RE=1&EE=0

Check your state:

http://www.dsireusa.org/index.cfm?EE=0&RE=1


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## Vtgent49 (Jan 18, 2008)

I have a DHW coil in my wood/oil boiler. Presently it preheats the DHW on the way to a gas HW heater. In the winter, the gas never runs, as the tank is fed HOT water. Also, this way the boiler is never fired just to heat HW. My boiler coil is seperate from the two zone heating water.

My present solar design, which I bought and will finish in the Spring, will be piped the same way. The solar will heat a coil in the bottom of the tank, but in the winter the preheated water will still be from the Boiler, so I won't care if there is 2 feet of snow on the collector plates. My tank is a Vaughn with electric back-up, which I hope to never use.

BTW, I don't think you want to plug an unused coil, as I've heard they can explode.


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