# Water heater insert / boiler mod for P61/45/38

Posted By nate vignola, Jan 27, 2013 at 8:28 PM

1. #26

### Bioburner Moderator Staff Member

Aug 4, 2012
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Yes you need a pretty good temperature differential to make the water heater exchanger work. Takes about 5 degrees of heat out.

2. #27

### brack86svo Member

Jan 18, 2013
89
12
Loc:
Central PA
I think you're the only one on here I've seen running a Crosslink kit. I've checked out a couple of your threads hoping you posted some pictures of the coil insert, just so I could get some ideas.

Do you heat your house and DHW with your kit? Does your stove run constantly if so?

3. #28

### nate vignola New Member

Jan 27, 2013
29
8
I've wondered what the BTU rating is on a Crosslink type system. Is there a lot of creosote build up on the coils? I've wondered if there was since the coils are a low temp. I remember the build up as being a problem with earlier wood boilers and the stainless tubes and having to chisel off the junk.

4. #29

### nate vignola New Member

Jan 27, 2013
29
8
There are several variables that need to be nailed down, but for the most part, electric water heaters are 100% efficient. If you know how many gallons are heated, or how many KWH's are used, it's a quick calculation.

In my case, I use ~ 1000gallons/week. I have a standard water meter at the front of the water heating system that I take a recording every few weeks, along with the KWH's used by the element in the electric water heater, (if it engages - which it doesn't).

So- 1000 gallons/week at 8.3#/gallon, and and average rise of 75F (might be a bit more this time of year), it would equate to 1000x8.3x75=622500 Btu's/week, at 100% efficiency. 1 KWH is ~3400 btu's. A btu is defined as a the amount of energy required to heat 1# of water, 1degree F.

Take the current electric rate and figure out how much of the year could have water heated by pellets. On average, payback should be 3 years or less. Most boilers mods primarily benefit from pellet energy on the margin ->The electrical energy consumed by the pellet stove does not increase proportionately to the heat energy absorbed by the insert, only an increased consumption of wood pellets is realized. I mean the fans don't spin any faster, just the feed rate just increases.

My home is ~4000sq ft and I use a P61 and an Accentra FP insert to keep warm. During the non heating months, I use solar to heat my water.

To me, the bigger cost savings is the where the heating dollar travels. If I use pellets, the dollar stays local. If I use oil, it's not staying local for sure.

Regards,
Nate

5. #30

### Bioburner Moderator Staff Member

Aug 4, 2012
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Ive only had ash build up that I brush off when I do the AM stove check and the PM fueling. I used a plastic bottle brush for a couple weeks till I found a steel brush that worked. Wish I could remember where I got the brush as it will be shot by seasons end. Wood boilers have a complete pile of issues as they run a wild ride of temperatures and incomplete combustion and burning wood at 2 to 3 times the moisture. Where there is smoke there is poor combustion.

6. #31

agreed!

7. #32

### SmokeyTheBear Minister of Fire

Nov 10, 2008
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Well I do believe that with 315 million plus people in the US and by definition some 157 million plus being below normal intelligence the lawyers have plenty of potential class action victims.

Me thinks I'll find a way to get a hangnail and sue all of the deep pockets.

8. #33

### Bioburner Moderator Staff Member

Aug 4, 2012
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Darwin Theory has been negated by a good medical system, only to be sued by the idots they save.

9. #34

### SmokeyTheBear Minister of Fire

Nov 10, 2008
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Standish, ME
Actually Darwin didn't directly address this aspect. Strictly survival.

10. #35

### Bioburner Moderator Staff Member

Aug 4, 2012
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Man survived not by being strong but by being smarter. Take the smart away and they won't survive unless by being supported.My two cents as I watch them fish someone out of a frozen lake they tried cross in a car with two kids strapped in the back. Yes booze is involved.

11. #36

### SmokeyTheBear Minister of Fire

Nov 10, 2008
13,363
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Loc:
Standish, ME
Not always, the urge to eat can overcome a lot of what is out there in the wild.

12. #37

### Bioburner Moderator Staff Member

Aug 4, 2012
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Update on car in lake. The young girl died

13. #38

### nate vignola New Member

Jan 27, 2013
29
8
Attached are pictures as promised. The main assembly that replaces the glass is 1/2" plate aluminum milled out to receive the copper water jacket. The rods are also aluminum bolted through the aluminum plate, backed by another 1/4" aluminum plate. The material science behind it is that the aluminum plate will have a much lower chance of breaking, as compared to the ceramic glass. I included a few thermal images of the insert running and also a view of the fire.

smoke show likes this.
14. #39

### brack86svo Member

Jan 18, 2013
89
12
Loc:
Central PA
That's impresive looking. As someone else has voiced a concern, not seeing the fire would make adjustments difficult. What kind of heat transfer are you seeing? The one I made, with running the stove as high as the manufacturer will recommend steadily, I see a 15* rise. That really varies based on the volume of water, yours may flow more volume then mine does but, it will give everyone a rough idea.

15. #40

### DexterDay Guest

Looks good. Im impressed. Lots of Sq inches for exchange.

I won't be installing one, but interested in hearing more about the system.

smoke show likes this.
16. #41

### Bioburner Moderator Staff Member

Aug 4, 2012
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I like the glow of the fire coming up the basement stairwell at night. Even if the fire is on low and I can't hear a fan I still know we're being kept warm by the soft moving glow at night. You still have to set the fuel to keep the fuel from overflowing the pot but probably run and take a quick look to adjust.

17. #42

### nate vignola New Member

Jan 27, 2013
29
8
At 1GPM, the stove will create 18K btu's flat out-full throttle, 36 degree rise. With normal settings (stove mode 5, high fan, feed 4 and a flow of 2GPM) about a 10 degree rise, or 10K btu's/hr. The stove doesn't have an adjustment outside of the feed rate, so I adjust it based on the amount of ash on the burn pot.
A few of the main design ideas- 1. no traps for steam, 2. a small finite liquid reservoir (5-10gallons), and 3. no water 'in' the stove, and 4.had to be reversible.

Steam is the #1 hazard, so using the drain back tank accomplishes 1 and 2 provided that the pipes are installed so that there are no air traps. The aluminum structure absorbs the heat and transfers the gain to the copper water jacket, externally - 3. Since this adapter is bolt-in, there isn't a permanent change to the stove. If the stove is re-sold or re-purposed (It could happen), take the exchanger out and put the glass back into the stove-4.

The way this is designed, worse case is that I come home and find 10 gallons of water on the concrete floor. Probably would be seen first as a weep / drip since the water jacket is brazed together. If anything a crack could develop and the water level in the tank would drop over time.

There isn't a way for steam/pressure to be created, and even if steam was created, it's not contained to create an explosion hazard since there are no check valves or any mechanical stoppers on the feed/return lines, all lines are vented to atmosphere at the drain back tank. The reservoir is a limited quantity and if a leak or full failure occurred, there wouldn't be huge mess, as compared to connecting the water jacket to boiler feed. If the water jacket was internal to the stove and it failed, that would be a real black mess to clean up and could potentially trash the stove.

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18. #43

### brack86svo Member

Jan 18, 2013
89
12
Loc:
Central PA
The only problem I see, is you limit yourself to stoves that don't require you to see the flame to know how it's running. What is your estimated price on these units?

19. #44

Jan 18, 2013
89
12
Loc:
Central PA
20. #45

### Bioburner Moderator Staff Member

Aug 4, 2012
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Loc:
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Maybe I make a oven for the door of my garage Harman. Harman pot pie? Harman ribs. Harman pot roast. Harman pecan pie. I have got to go make breakfast. Pigs in a blanket.

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21. #46

### nate vignola New Member

Jan 27, 2013
29
8
Yes it does pigeon hole the insert to a limited brand and models, right now. Other brands can be fitted by changing the plate structure. I haven't worked with other brands,but if this one takes off, then others would be fitted, or if someone wanted one built, I'd build a custom unit / work it out.

Since a payback period is usually 3 years, depending on the DHW consumed by the user, and other materials needed, I'd price it at \$850 for the insert itself and see how it goes. The total conversion could be as much as \$1600 with the tank, pumps, controllers etc, but there are avenues to minimize the expense. There are other ways to adapt it and other functions, such as heating a jacuzzi, assist the baseboard heat by heating the return leg to the boiler, etc.

In my area, a used functioning harman runs \$1800-\$2000. To me, it's not as much about the savings, but where the heating dollar goes.

22. #47

### nate vignola New Member

Jan 27, 2013
29
8
Good writeup- Did you consider copper? Much higher transfer ability than stainless or sched 40. Copper is around 380, stainless at 16, and sched 40/iron is about 80. Might be worth the shot. Maybe if you can find a tankless water heater coil at the scrap yard, it could work.

23. #48

### brack86svo Member

Jan 18, 2013
89
12
Loc:
Central PA
I had considered it. Everything I had read about using copper said it would crack over time being exposed to direct flame. I figured stainless would hold up and have no corrosion.

24. #49

### Bioburner Moderator Staff Member

Aug 4, 2012
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Loc:
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You would have holes in the copper in no time from all the products of fire. Think of the copper battery cables and how fast they turn with copper sulfate and thats without heat.

25. #50

### nate vignola New Member

Jan 27, 2013
29
8
The sodium in the fuel wouldn't help too much either. Forgot about the oxides and ion exchanges for the acidic conditions. really thick copper would be cost prohibitive and brutal to work with.