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Joined on October 26, 2011

Last Post on November 13, 2013

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clogged heat exchanger

@ November 13, 2013 8:50 PM in clogged heat exchanger

I’m installing some insulated lines from my outdoor wood furnace into a SuperStor Ultra 60 gallon indirect fired hot water tank which serves as a heat exchanger for the baseboard heat in the house. I got the old lines off the inlet/outlet for the heat exchanger on the tank, and noticed a ridiculous amount of black build up (lime?) inside the heat exchanger (my index finger barely fit inside the 1” outlet). The tank is 10 – 12 years old, the owners manual for the tank says the heat exchanger coil is cupronickel. I’d really like to flush it if that’s feasible. What could I safely flush through that type of alloy that would still remove the deposits? I still have the old pex lines and the old pump from the wood burner handy so it would be a quick set up for the flush as long as the pex can withstand whatever solution I use, at least for the duration of the flush. Any advice would be greatly appreciated.

Open system

@ August 20, 2013 12:29 PM in pipe ID and flow/BTUs

No O2 barrier because it's not a closed system - I can stare right down the top vent of the stove into the water. So it's not a true "boiler". Since Oxygen can already enter the system there, I'm assuming O2 barrier on the pex wouldn't make a whole lot of difference?


@ August 19, 2013 10:18 PM in pipe ID and flow/BTUs

Thanks for all the comments posted. I will be going with the 1 1/4". I actually got hold of a friend of mine who is, quite literally, a rocket scientist. Turns out that fluid mechanics - and hence hydronics -  is right up his alley. He ran the numbers on my system and confirmed that 1 1/4" is a better choice. His numbers weren't quite the same, but then again he had the benefit of gathering some additional information from me. Bottom line, very few circulator choices would get me even remotely close to the gpm I need with the 1" ID, but 1 1/4" opened up several options.

Next, I need to find 1 1/4" ID pex for the shorter run in the house. I don't need oxygen barrier nor insulation on the pex (I will wrap it myself), so I'm just looking for plain old 1 1/4" pex that is rated for 200 degrees. Will this be hard to find? Would anyone like to recommend manufacturers?


@ August 14, 2013 10:49 PM in pipe ID and flow/BTUs

but as long as you're punching numbers, the final measurement for the new line is 90 foot (65 foot was a bad estimate with a tape before I dug the trench), plus add that to the 30 feet inside, for a total of 120 feet each way.

The Superstor doesn't carry any of the BTUs for the garage, just the house.

You're right, we have a lot of heat loss in the house and garage. My buddy estimated I needed 130,000 btu's/hour on our coldest days to heat the house alone.

An extra 1/4" worth it? Sounds like it might. For example, that's extra electricity spent running a bigger pump - electricity isn't free either. 

By the way...

@ August 14, 2013 10:15 PM in pipe ID and flow/BTUs

you guys are scaring me. I called the PexFlex distributor today and ordered 90 feet of 32mm/1" ID dual pex for pick up 3 hours from here on Friday. It's probably already cut and ready for me. The wife had already expressed her concern at the $1200 price tag and the 1 1/4" costs 6 bucks a foot more. Without someone on the ground here to advise otherwise, I estimated that the 1" ID could get enough BTUs to the house to be worth the investment. Past winters, the wood furnace could hold the house at temp as long as outside temps stayed 27 or 28 degrees or higher with calm wind. Really cold days, lots of wind, the gas boiler did half the work. I figured insulated pex without the heat loss plus bumping from 3/4 to 1" ID, based on Zman's numbers, even if they weren't right on, I would at least be doubling the btus I'm currently getting.
It's possible that the PexFlex hasn't been cut off the reel yet and if I call first thing in the morning MAYBE I can still spring for the 1 1/4" ID...if absolutely necessary (?). You guys impress the heck out of me with your knowledge and I really appreciate the input, just pulling out my hair not having the professional background to make the right decision.

So, not understanding the head loss numbers, MY question of the day is: is the extra $540 and an angry wife worth the 1 1/4"?


@ August 14, 2013 9:59 PM in pipe ID and flow/BTUs

60 gallon. The wood burner holds 290. What about running the wood furnace to a plate exchanger then into the Supersor, which holds the water until called for - would that be considered a "buffer"? What is the advantage?

Rochester NY

@ August 14, 2013 9:48 PM in pipe ID and flow/BTUs

...and doesn't the Superstor tank count as a "buffer"? Water from the wood burner heats water in the Superstor, thermostat kicks on, circulator pulls water from the Superstor to heat the baseboards.

I agree...

@ August 14, 2013 9:16 PM in pipe ID and flow/BTUs

"Doing so requires a more in depth analysis of the system, but that may well be a worthwhile investment right now."
I agree 100% - if I only knew who to call in my area I'd gladly pay to have an expert come out and tell me exactly where I stand and what I need.  What level of expertise is required for that kind of analysis? Should any decent home heating professional in the yellow pages have that kind of knowledge? Last guy who came out to service my gas boiler didn't want anything to do with figuring out the wood stove. How would I go about searching for a hydronics expert in my area?

Also, I will never need to move all 225000 btus on that one pump. A separate pump moves water to a radiant floor system in the garage from the same furnace and keeps up nicely - garage is nice and cozy. I'm guessing from what I've read that the house itself requires maybe half that.

1" / gpm?

@ August 14, 2013 5:20 PM in pipe ID and flow/BTUs

As much as I'd like to go with larger pipe, the cost of bumping up to 1 1/4" is prohibitive (almost $20/foot). 1" ID Pex-Flex (actual ID is 32 mm, slightly over 1") is more in my price range, and will still be a significant improvement over the 3/4" ID pex in the system now. Keep in mind I don't have to move all the BTUs at my disposal since the wood furnace also heats the garage on a separate pump / loop. So...
The PexFlex distributor recommends a Taco 0014 pump for my application, with 32 mm ID pex. Not sure if it matters but each way there is about 125 feet of line from the furnace to the heat exchanger. How would I calculate my gpm with this pump? And once I establish what my ∆T is with the new setup, how do I calculate the BTUs being transferred to the house? Thanks again.


@ August 8, 2013 9:53 PM in pipe ID and flow/BTUs

Thanks for the replies. It's clear that I need to go with the Logstor product, minimally the 1" ID, 1 1/4" ID even better. Thanks for the link SWEI, that's very good material. If you can't tell I want to do this job right, and sometimes that means learning on a steep curve. I'm in the middle of reading it now and plan on printing it along with responses to this post and passing it on to my friend before we tweak the system.
Can you clarify by what you meant by mixing on the distribution side? I interpret that as "cooling down" the output by mixing it with return flow. Why would that be necessary? We actually installed a mixing valve in the garage last year so we could run the wood burner higher than 130 degrees without damaging the concrete in the garage. Believe it or not, the previous owner who installed the system was running 130 degree water into the house but had the gas boiler thermostat set at 212 - in other words, the gas boiler was heating the water in the wood burner!
I was already planning on running conduit, not sure what a messenger is but I assume it's a wire that can be used to fish other wires through at a later point (again my inexperience shines through). As for mass, the Superstor is 60 gallons, the woodburner holds 290 gallons.
One concern I have if I keep the Superstor tank in the system but increase btus to the house, is how hot I can heat the water in the Superstor. The past two seasons water temp in the Superstor maxed at 150 degrees (that's as hot as I could get it, and only in between cycles would it reach this high). With more gpm, more btus, and less heat loss to the ground, how high can I heat the Superstor? 180 degrees? Seems to me I remember trying to contact the manufacturer in the past with no luck to get an answer to that question. I do know the warranty states that heating water above 150 qualifies as commercial status as opposed to residential and compromises the warranty.

pipe ID and flow/BTUs

@ August 7, 2013 11:16 PM in pipe ID and flow/BTUs

I have a 2550 square foot farmhouse. The house came with an outdoor wood furnace that is rated at 225,000 BTU/hour maximum output. 180 degree water pumps from the woodburner through ¾ inch pex tubing into the basement over a 65 foot run. Once the water enters the basement, it flows through another 30 foot run of ¾” pex tubing before entering a SuperStor Ultra indirect fired hot water heater. Water from the woodburner runs through the heat exchanger in the Superstor, thereby heating the water in the Superstor which then heats the house via baseboard heat. As a side note, the water from the Superstor actually flows through a gas fired boiler first before heading upstairs, with the boiler acting as a backup for the house if the wood furnace can’t keep up with demand. However, for our purposes let’s ignore the gas boiler because my goal is for the wood furnace to meet the full demand of the house.
There are a few problems with this set-up, which I inherited from the previous homeowner. First of all, the underground pex tubes are leaching a ridiculous amount of heat into the ground, to the tune of 15 degrees over the course of the run into the house. As a result, I am in the middle of installing insulated pex lines, either Thermopex or Logstor Pex-Flex, on the underground run to the house. Based on the manufacturers rating I am expecting heat loss after install to be 1 or 2 degrees total – a dramatic improvement. However, after spending two days digging, replacing one broken septic pipe, one underground gutter pipe, and tunneling under a sidewalk, I want to make sure I do this absolutely right the first time. Here’s my dilemma:
Thermopex uses ¾” ID pex tubing. Pex-Flex uses a true 1” ID. By all accounts, Pex-Flex is a slightly better product, even though documented Thermopex failures are extremely rare. A buddy of mine is a heating/cooling professional and will be helping me make my final connections in the basement, but he won’t be free until September. Meanwhile, I have an open trench and a wife who wants her gardens back, so I need to make a decision between the two products this week and get the pex buried in the ground. The big question is, is it worth the extra 3 dollars a foot for Pex-Flex, and the extra hour drive to the dealer, to increase the size of my pex from ¾” to 1”? I’m tempted to go with the larger Pex-Flex so I can get more BTUs into the house quicker, but if I do so, then I will need to replace the two 30 foot runs in the basement with either copper pipe or a true 1” non-insulated pex, and I don’t know pricing on these materials. I also don’t know how much more BTU’s the larger ID will give me. Predictably, the Thermopex dealer says the 1/4" difference in ID isn't a big deal and the Pex-Flex dealer uses the larger ID as a selling point. To throw another wild card in the mix, I’m fairly certain the SuperStor setup isn’t ideal: currently, the heat exchanger in the SuperStor can’t keep up with demand, so we may end up going with another type of heat exchanger once my buddy takes a look at everything and tweaks the system. (He mentioned a steel plate heat exchanger and the outdoor wood burner manufacturer included info on “Flatplate” company products in the owner’s manual). Then again, once I’m running 180 degree water into the house with the insulated pex instead of 165, maybe the SuperStor setup will be sufficient.
I’d appreciate any advice on this. I just don’t have the knowledge to run the formulas to see what I really need in terms of volume/flow/btu’s. A few more pieces of information that might help:
·        Although we blew in insulation, the house is not very efficient in terms of heat loss (old drafty farm house).
·        The wood burner is a done deal – too much money into refabbing it last year so it stays as the primary source of heat regardless.
·        Right now I’m using Taco pump model 007-F5, 1/25th HP .71 amp 3250 RPM (I don’t know what the gpm’s are with this pump)
·        The woodburner also heats a radiant floor setup in my 4 car garage, so I’m close to the maximum square footage this furnace is rated for (3800 square foot total house and garage, I think my model is rated for 4k or 4500)
·        As of right now I’m leaning heavily towards buying the Pex-Flex and having the dealer install fittings for 1” copper onto it (Pex-Flex takes special fittings), I figure that way in the short term we can just use an additional fitting to temporarily step back down to ¾” for the basement run or later on go with 1”. That is, unless I have 20 guys on here telling me I’m crazy because there’s no way I’ll ever need the extra ¼” and ¾” will be sufficient in all applications.



Mixing valve

@ December 6, 2011 10:24 PM in Mixing valve

I'm hoping this falls under the category of "controls". I've posted a few times on the wall and the feedback has been helpful, but although we're getting closer to a solution, I've got one last stumbling block. Short version: my wife and I moved into our house last March and inherited an outdoor wood boiler that supplements a gas boiler in the house and heats a 4 car garage via radiant floor heat. The former homeowner ran the water temp at 130 for both loops - the problem being, at that temp, they were actually robbing heat from the gas boiler in the house. Now I'm trying to get a mixing valve installed for the garage so I can run the wood boiler at 180 for the house, and mix down water temp for the garage so I don't damage the concrete. We had a contractor come out and although he seemed knowledgeable, his plan "A" was to tap into the cold water feed in the garage and mix this with water from the boiler to bring the water down to temp. We were going to go ahead with that plan until I realized a big problem: under this "open" system we'd be introducing new water into the system each time the thermostat kicked on, which would eventually overflow the boiler. On my own, I've done some research and I've read about mixing valves that take the water which has already circulated through the loop, and mix this cooler water with hotter water from the boiler, thus keeping the overall system "closed", which is what I need. It seems to me that this is a more sophisticated type of control, and so probably will cost more - but how much?  The original estimate for plan "A" was well under $1000, how much more can I expect for this type of control? Several thousand? Because at a certain point, it makes more sense to just isolate the garage loop, fill it with glycol, drain the toilet in the garage and shut off the cold water rather than break the bank so I can have a warm garage. The contractor was going to do some research of his own and get back to me, but I feel like I need a better knowledge base to make a decision here. Thanks for any replies, we've spent two months trying to get this squared away before the cold weather hit, and from the looks of the weather forecast, I think winter is finally here.Reply Edit


@ December 6, 2011 10:03 PM in max water temp for concrete

Thanks...looks like the mixing valve is the way to go.  I have some questions about that I'm listing in a second post - the contractor seems a little uncertain about my application.


@ December 6, 2011 10:03 PM in max water temp for concrete

Thanks...looks like the mixing valve is the way to go.  I have some questions about that I'm listing in a second post - the contractor seems a little uncertain about my application.

max water temp for concrete

@ December 2, 2011 10:18 PM in max water temp for concrete

My wife and I moved into our house last March and inherited an outdoor wood boiler that supplements a gas boiler in the house and heats a 4 car garage via radiant floor heat. The former homeowner ran the water temp at 130 for both loops - the problem being, at that temp, they were actually robbing heat from the gas boiler in the house. So I turned off the garage pump temporarily and I've been running the wood burner at 180 degrees, the result being a major improvement in the house. However, everything I'm reading says radiant floor systems shouldn't run water temps above 130 or there's a risk of damaging the concrete. I'm trying to get a mixing valve installed for the garage so I can run the wood boiler at 180 and mix down water temp for the garage, but the contractor I talked to said the high water temp might not make a difference if the concrete didn't contain fiber mesh. He said regular concrete with rebar would probably be ok, but fiber mesh would break down. I haven't got hold of the former homeowner yet to see what kind of concrete he poured, but if it didn't contain fiber mesh, what do you think? It would be a heck of a lot easier to skip the mixing valve and just run at the higher temperature. Sure, I'd like my play area warm but it's just a garage so it's hard to justify the added expense if it's not absolutely necessary.


@ November 2, 2011 9:50 PM in Smith boiler question

I've got a heating guy coming out next week. Thanks for the input, I'll steer clear of plumbing the water directly into the boiler from the wood burner, although I wish there was a better way to make good use of the wood burner to heat the house. The installation guide that came with the outdoor burner does have a diagram showing how to tie into the gas boiler - what kind of problems can this lead to?

Turns out...

@ October 29, 2011 11:32 PM in Smith boiler question

Turns out, upon closer examination, the hot water from the outdoor wood burner runs into a single wall "heat exchanger" in the tank pictured above, and does virtually nothing to heat the water on the way to the gas boiler anyways. I watched a full cycle of the Smith boiler with the outdoor pump turned off, then turned the outdoor pump on and let it pump 150 degree water through the exchanger for at least a couple hours before watching another cycle of the gas boiler. In both cases, when the thermostat kicked on the result was the same. The water temp had fallen to 130 degrees, and it took equally long to climb back up to where it peaked around 210. I've got a diagram from the manufacturer showing how to plumb the outdoor boiler directly into an existing indoor boiler, but unfortunately I'm still having trouble convincing somebody around here to take my money. I live in the Rochester, NY area by the way - if anyone knows someone nearby who could tackle this, please let me know. Thanks.

Mixing valve?

@ October 27, 2011 8:48 PM in Smith boiler question

Thanks Tim.
I finally got hold of a guy I know who's in the heating business. He said the same thing - 180 degrees is too hot and will ruin the concrete. He mentioned a "mixing valve" that might allow me to run water to the concrete at one temp, water in to the house at another. Like I mentioned, the frustrating thing is, there's nobody in the area who services these outdoor boilers, and I don't have the experience to install something like that myself. I'm hoping he'll be able to help out - do you have any experience with mixing valves? Is it a quick install? What else does it involve other than simple plumbing? I'm assuming another thermostat would have to tie in to keep the water at a specific temperature?

Smith boiler question

@ October 26, 2011 9:18 PM in Smith boiler question

Simple question:
 Can I adjust the temperature at which my gas boiler kicks on? I'd like to lower it from where it currently is (presumably around 185 because I have baseboard heat) to around 170. I can't find any obvious control for this on my boiler.

Complicated explanation:
I just bought a house last March with a Smith GB100 gas boiler. I'm not sure how old it is, though it looks to be fairly new. The house also has an outdoor wood fired boiler that heats a garage with radiant floor heat and "supplements" the indoor heat: pex tubing from the wood burner runs into the "hot water tank" (not sure if that's the correct terminology here) located next to the boiler in the basement. The wood furnace also supplements a separate hot water tank for domestic hot water, but that is in a completely different loop.
The former homeowners told us that they kept the outdoor wood furnace water temp around 130 degrees. Talking to other people with outdoor wood "boilers", that seems low - I'm told that a 160 to 180 range is more common. Not only that, but a buddy of mine told me that baseboard heat is usually set around 180 to 185 degrees. If that's the case, then unless I keep the outdoor wood furnace hotter than the lowest temperature the water in the indoor boiler naturally hits between cycles, won't the wood burner actually pull heat from the gas boiler and cost me higher gas bills? The way I see it, without the wood burner in the loop, the indoor boiler will kick on to heat the house, then between cycles the temperature in the tank might fall to "x" degrees. When the thermostat in the house kicks the indoor boiler back on, it only has to heat the water back up to 185 from "x" degrees and maintain it there during the cycle until the house heats back up. But with the wood burner in the loop, that 185 degree water is flowing back outside into a furnace that's set for a lower temperature, and so the wood burner actually becomes a heat sink, doesn't it?

My goal is to keep the indoor gas from coming on as little as possible when I'm burning wood, so given the above, what I'd like to do is keep the wood burner around 170 degrees, and drop the temperature that the gas boiler kicks on to about the same. I read in the online literature that the current Smith G series kicks on the gas burners when the temp. falls 15 degrees below the cut out point for the burners. But can I adjust this setting on the gas boiler? I see no control that would allow me to adjust this.

Any help or advice here would be greatly appreciated. None of the heating companies around here want anything to do with servicing the outdoor boiler, and they don't seem to have any experience with this kind of set up. I do have a company coming out on Nov. 10 for standard maintenance of the gas boiler, but I'll be firing up the wood boiler this weekend, as the temperature here is expected to fall into the 30s. Thanks for your help.