[Christian Nelson]

Wow, gave me homework already!

So, where did you get your copy of Slant Fin heat loss estimator? I'm assuming you're referring to the Hydronic Explorer program.

I downloaded it off their site, I think yeah, it's called the hydronic explorer program, I did this a while ago, so I am not sure I can get all the facts straight, my bookkeeping is haphazard at best!

Now that your into the thick of winter, what is your assessment of your combo-hydronic system? Is it delivering heat to your home as you had hoped it would? What kinds of things would you do different? What did you do that was really right?

Well, it's easily keeping the house at 70 degrees, at least on the main floor, it feels comfortable upstairs, but I haven't taken the time to check with a thermometer. Outside temp was in the teens, and around zero F for a couple weeks, but is now up to the lows in the teens, highs in the twenties.

What I did wrong.. Well, biggest one was not using oxygen barrier PEX for my infloor loops, and between base board radiators. I've worn out a couple of pumps due to corrosion in 3 years of use. I am not going to be able to pull the runs out of the concrete, so I am planning on replacing my pumps with bronze as they fail, and maybe trying to find a nontoxic corrosion inhibitor to add to the water. Another bad move was I trusted a solder joint that was blind, I saw it flow, and assumed it wen all the way around. Of course, it was right above the new boiler I installed this year, and it didn't leak until a few weeks after I had it all going great. It leaked on to the controller board, and burned it up before I discovered the issue. I ended up buying a new board for $400 (after I finally found a place willing to sell it to me) so ALWAYS check all the way around your solder joint. Get a mirror if you have to.

Do you know what the 'degree days' are in your area?

I have that info somewhere in my house, I could probably look it up, but it's pretty tundra-ish. Think near Canada, and not on the coast. I am near the Twin cities of MN, I am just across the border in Wisconsin.

How well is your place insulated?

Well, not at all initially. Empty walls, except for the north side, they blew in some loose fiberglass that seems to be doing absolutely nothing! I have slowly been fixing that. This whole project began with me deciding to jack up the house, and redo the basement. It used to be half basement, and half crawlspace. Every winter, the house would settle funny, and half the doors would'nt open and close properly. This has been happening since it was built I am sure. I was never able to keep the floors, or the rooms over the crawlspace warm, no matter what I did. It had an outdoor wood boiler when I moved here, and I was chopping wood all summer just to feed that thing. No furnace back up when I moved in. I had to monkey with the old oil burning furnace just so I could leave for a couple days in the winter. The wood boiler didn't work out, if I didn't stoke it every 5 hours, the thing would go through wood like crazy, and never really warm the house. My wife didn't like hefting the 3 foot long logs into the thing, and I am gone for about 12 hours every day at work. So, we bit the bullet, jacked the house up, it ended up being 3 feet higher out of the ground, and a much nicer clean full basement under neath. This project has taken about 4 years, and I hope I never do this again in my lifetime! I did most of the work myself, with my dad's help. We hired the heavy lifting out, lifting the house, digging it out, and the cement work, but I laid out the PEX myself, and everything else.

Can you share details regarding your hydronic floor layout? Did you use a 'wet system' or a 'dry system'?

My hydronic floor layout is pretty simple, I have a mixing valve that keeps it under 120 F, and I ran 4 loops on top of 2 inches of rigid foam under 4 inches of concrete in the basement. I didn't bother with auto switching manifolds, since a boiler operator at the college I work at said if I went with the simple mini ball valves, once I found the sweet spot, I would be able to just leave them there, and the system would be pretty consistent. I also put 3 loops under the wood floor on the 1st floor, with the heat spreader plates crewed right to the bottom side of the floor. I then put the reflective bubble insulation under them, to keep the heat going up. eventually I intend to fill the joist spaces with insulation as well. I put a pump after the mixing valve, that is activated by a thermostatic switch in the basement. I placed the pump after the mixing valve, because when the system was an "open" system (I was still using the wood boiler that first year) the mixing valve would cause the water to bypass the loop all together if the water temp was above 120. Not sure what you mean by wet system, or dry system. There' water flowing in the PEX tubing, but I don't think that's what you are referring to.

More details of the radiators?

Radiators, are just some generic baseboards I bought through Grainger. High efficiency, I used the calculations from the slant fin software to size the heat runs. Ended up with two loops, one for the main floor, and one for the 2nd floor. I almost forgot the 3rd loop is the in floor. When I did this, I converted the whole system to a closed loop, with expansion tank. I used a big well expansion tank, as my boiler consultant told me you can't be too big, but you can be too small. So I found that a well one is HUGE, and actually cheaper, if you can afford the real estate on your floor. they dot he same job. I use pumps, no valves to switch my loops on and off. Original boiler I put in was an old Trianco Heatmaker, I got for $50, and replaced the burner, and pump, and igniter, and it was ready to go. I had to open up the controller board because it had cold solder joints, and I needed to resolder the joints. Unfortunately, I had to dial it way back (operating temp on it was 210, way too hot for my PEX runs between baseboards) with an Aquastat, and I think it was running VERY inefficiently. Basically I was forcing it to short cycle all the time. I thought about putting in a massive storage tank, and things like that, but decided ultimately to replace it with a high efficiency boiler. The old one kept the house nice and toasty, but it sucked the fuel down, around 900 gallons of propane from October to December of 2008. I really have nothing to compare it to, besides this new boiler though, so I don't know if that was better than the bajillion truck loads of wood I was putting through it before all this.

The reason I'm so curious is that I'm about to put one in my place in a few weeks, and I'd appreciate any advice you have.

I found the slant fin calculations for heat run size, and boiler size to be spot on. I was honest about my lack of insulation, and set it to have the water temp at 140. So far it was exactly right. We will see as I improve my insulation how it may change..

Yeah, doing it on your own forces you to be a combination of scientist, a grunt worker, a pirate and a revolutionary.

Lots of stress too, when your kids have red hands and faces from it being 50 degrees in the house, because you screwed something up, and your wife not saying anything, but you KNOW what she's thinking..

Well, using a heat pump as a secondary heat source makes pretty good sense. If your are using a commercial air-source heat pump, you should be able to geat a COP of around 2.5 or better. I haven't to build an air source heat pump so I'm not so sure what a DIY could achieve... most likely 2.5 or a bit less. My experiments with water-source heat pumps indicate that a COP of 3.5 is a reasonable expectation. Anyway, if you pencil the conversions out, you'll see that either approach should be more efficient than propane.

Well, that was why this caught my eye so quickly, was it was a water to water system. I want to directly heat the storage tank, from the ground loops. 130, even 90 degrees would be enough, if the solar isn't keeping up. I am thinking about still running the baseboards off the boiler, and splitting off the infloor stuff off the solar/heatpump augmented system. Maybe running a third infloor zone on the 2nd floor. I figure, I should be able to run exclusively off solar for most of the fall and spring, and it should keep the boiler from firing as much in the winter. The heat pump shouldn't be even needed much, other than a few days of the year, which is why a cheap old window AC unit would be just the thing.