Trial & Error 'summer' burning

[ISeeDeadBTUs]

No call for space heating now, so I continue to wrestle with the best/easiest/least expensive way to provide DHW. I've no storage, so in the past I've tried the one-fire-a-day approach. Since the GW has no fan, this is a slow process when it involves 2 full HX. And I think it wasted wood. Since the GW was down all last summer, I simply burned oil. Much easier and painless - until fall comes and the tank needs refilling.

I've tried keeping a fire going by setting the aquastat back to 100, but sometimes the fires takes a V E R Y L O N G T I M E to restart when using this approach.

Currently I am having good success with a different approach.

I leave the GW aquastat set at 170, put one 8-12" Oak round in, and turn off the inside loop of the HX. This seems to work well. The fire doesn't go out because the damper opens more often. And the damper closes quicker because the indoor boiler is not robbing heat. Add to this the Bennie's of less heat in the boiler and DHW during the day, which minimizes the standby losses into the home.

Summer's far from over, but so far this approach is working the best of any. We shall see . . .

 

[mole]

Dead BTU's,
I've seen from your posts that you're a Seton style purist (against storage). That's where we all started out. But yout application - summer water heating- is just screaming for storage. Come to the dark side. You know you want to.

 

[ISeeDeadBTUs]

You're not as insightful as you think. I'm not against storage. I don't have storage currently.

Storage would increase standby losses into the residence during summer. THAT'S not happening!

I also try to consider payback. I'm currently thinking that PV on the roof with instant electric water heaters would be the best payback.

But my OP was about experimenting with the RMND unit.

Those that know everything can't benefit from anyone's experiance :smirk:

 

[jebatty]

"Summer?" - what a joke! Up to 5" of snow in the forecast for today and tonight. Still in "high burn" mode (well, almost).

 

[mikeyny]

Well, my tarm is in the basement without storage. On cool days and nites I have been building small fires to heat the DHW but once the weather stays warm I will be done. No need to add heat to an already warm house. I would like to build a amall burn chamber under an old gas or oil fired water heater and experiment with that someday. 80 gal of water over a small fire for about an hour a day might not be too bad.

 

[mole]

You're not as insightful as you think. I'm not against storage. I don't have storage currently.

Storage would increase standby losses into the residence during summer. THAT'S not happening!

I also try to consider payback. I'm currently thinking that PV on the roof with instant electric water heaters would be the best payback.

But my OP was about experimenting with the RMND unit.

Those that know everything can't benefit from anyone's experiance :smirk:

Sorry for offending you. Good luck with your photovoltaic hot water.

 

[woodsmaster]

You're not as insightful as you think. I'm not against storage. I don't have storage currently.

Storage would increase standby losses into the residence during summer. THAT'S not happening!

I also try to consider payback. I'm currently thinking that PV on the roof with instant electric water heaters would be the best payback.

But my OP was about experimenting with the RMND unit.

Those that know everything can't benefit from anyone's experiance :smirk:

I see lowes now has heat pump waterheaters for $1,500 . Don't Know how well they work but sounds like a good idea. Like anything new the price is sure to come down. I'm putting my storage in
a shed so I dont get the heat in the house in the summertime while I'm heating the dhw and pool,,, sure I'll lose a little heat to the outside but it's just wood and it grows on trees!

 

[mole]

Those heat pump water heaters are supposed to be real efficent. And in addition, they cool and dehumidify the basement. If you also pay to run a dehumidifier in the basement in the summer, which is expensive, you might kill two birds with one stone. And they qualify for an energy rebate too. I've been wrestling between that approach, solar hot water panels, and burning wood all summer. I opted to try burning wood for a summer before making any decisions.

 

[Ncountry]

I would like to build a amall burn chamber under an old gas or oil fired water heater and experiment with that someday. 80 gal of water over a small fire for about an hour a day might not be too bad.

Years ago in my "poor days" this is what I did. I used an old 50 gallon pressure tank .Stacked up 2 rows of stone,set tank on it's side on top, put 4' of 6" chimney up the back behind tank, ran garden hose to it and back to the basement. Voila! instant hot water heater .Worked like a charm until winter and then we were back to heating water in a kettle on top of the wood stove.No expansion tank either , amazing what you can get away with when you do not know any better. Although there was the occasional blown garden hose.

 

[mikeyny]

WOODMASTER.
My wood grows on trees too but so do the blisters on my fingers from cuttin haulin and splitin

 

[Hunderliggur]

"I’m currently thinking that PV on the roof with instant electric water heaters would be the best payback."

At about $5.00/watt for PV Electric and batteries, PLUS installation, and the electric instant water heaters, PV is a VERY expensive way to heat water. One of the BEST solar applications is DHW. I don't know what yor family size is, but 32sf of collectors with an 80 gallon tank worked 99% for a family of two for 2 years here (only30A electric service so no electric backup). If you don't want to run your boiler then solar hot water is the way to go.

Either way, PV and instant electric or Solar DHW system, both are probably more $ than adding well insulated storage to your in place boiler system. And you can also cancel the summer gym membership and split so hot water wood instead!

 

[jebatty]

Northern MN "tried" summer in April, found the "error" in that it was too warm, and snow again in the forecast for today. The home fire is burning brightly.

 

[in hot water]

consider solar thermal, in your area you should see a 50% SF solar fraction across the year with a panel or two. Figure 1- 1.5 gallon of solar tank per square foot of collector. Solar thermal has an efficiency up to 60%, PV has about a 15%.

Federal tax incentive is still 30%, many state and local programs add to that.

hr

 

[ISeeDeadBTUs]

I understand your formula, hr, but . . . if I go solar DHW, all I have is hot water. If I go PV, I have my electric (or at least a portion thereof) and I can use that same electric to heat my DHW. I grant you that heating the water with vac tubes would be more efficient, but not as cost effective as installing one system versus two.

Thoughts?

 

[Gooserider]

I understand your formula, hr, but . . . if I go solar DHW, all I have is hot water. If I go PV, I have my electric (or at least a portion thereof) and I can use that same electric to heat my DHW. I grant you that heating the water with vac tubes would be more efficient, but not as cost effective as installing one system versus two.

Thoughts?

Try running numbers w/ flat plates instead of vac-tube collectors... IMHO vac-tubes are overpriced and don't offer any real advantages over flatplates...

Secondly, look at all your collector siting options - PV requires 100% unobstructed sun, as any shade on any part of a PV string will kill most of that string's output. OTOH, shade on a flat plate system only hurts output in an amount ~ equal to the % of shade...

When we looked at our southeast facing roof, with a tall chimney on the south end, we found that about 50% would not have worked for PV as the chimney cast a sundial finger style shadow over that end, only 5-10% shade which is no big deal for flatplate DHW, but deadly for PV - thus it would have worked out for us that the best setup would have been about 50% flat plate and 50% PV - of course all such stuff is now on hold till I figure out how the new lifestyle works...

Gooserider

 

[in hot water]

You need to crunch all the numbers. Most electric HW tanks run a 4500W element. I suppose you could downsize to 2500W, and wait longer for the recovery. What do you pay for a KWH from the utility, what is the installed price of 3000W or so of PV. Does your utility buy excess? Life expectancy of the array, etc.

I agree with Goose, PV arrays need a good straight shot at the sun to be efficient, a tracker ideally to face them across a solar day of 5-6 hours.

Thermal is a bit more forgiving regarding siting. Most families use hot water on a daily basis. 40- 50 gallons for a small family should be enough. I suspect $6,000 or less would buy a two panel 60 gallon, quality solar system. Deduct 30% and any other incentives, maybe get down to under 4,000. Many states get you to about 50% covered by various incentives. Payback should be under 10 years and the system should last 20- 30 easily if you buy quality stuff.

"The stars may lie, but the numbers never do," crunch them with your own data.

Solar arrays can grow over the years and contribute to the heating load also.

Everyone needs to read Tom Lane's "Lessons Learned" book and especially the way he explains "can you afford to purchase a SDHW system"

hr