Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: slimchance on November 22, 2017, 12:04:24 PM
-
I have a Hardy H2, heating the concrete floor of a 40x60 shop/house combo. I have an 8 circuit, manual flow control manifold, I would like to add a thermostat to my system so that it will shut off my pump when my in-house temp gets to a certain point, then the pump will come back on when needed. The floor holds the heat very well, but is seems like I need to slow down my burn cycles. I have my aquastat turned down to 160 from 170. The aqua stat turns the blower on/off. I have most of my manifold valves just slightly turned, feeding as little as 0.2 GPM per circut. As it is now, water entering my manifold is about 155 degrees, and exits the manifold at about 85 degrees. It seems like it is all I can do to get a 12 hour burn, but yet I really don't need all of the the heat it is providing the floor. I'm just looking for suggestions. Currently, with very little cold weather so far, "garage" temp has been around 72 degrees and the "living" space has been around 74 degrees. Wife likes the temps, but I feel like I could slow my burns down and save some wood.
-
Woowwwww. You are going to have a problem with the concrete soon if you don't stop heating the floor with 160 degree water. The radiant system Needs a tempering valve on it. It needs 80-90 degree input temps. Please head over to radianttec.com and read their information on radiant heating.
-
Oh and you shouldn't be running your minimum boiler temp below 160. You shouldn't have boiler return temps less than 30 degrees from when they left the boiler. Temps below 140 entering a boiler cause condensation on the inside of the firebox which mixes with ash to create and acid and eat the metal.
-
I doubt condensation would harm a 304 SS Hardy- but, yes it definitely needs tempered down water feeding the floor..way way too hot. Wood consumption should drop, temp swings stabilize, and you protect the concrete.
-
But I'm.forgetting you asked about a thermostat... Yes, the stat can start and stop the pump using a relay. A 90-340 or 90-370 would work.
-
Oh dear. My advice, put a 40 plate exchanger in the boiler loop near the manifolds and close up the radiant side of the exchanger so it is a separate, closed system with its own air separator, expansion tank, mixing valve, and pump while the boiler loop continues to circulate constantly, keeping the plate hot at all times. That new pump would be controlled by a wall thermostat and you could adjust flow output between the house and shop portions using the flowmeters on the manifold if you wanted the house a bit warmer. I just did this for a customer a couple days ago as he had a similar consumption issue and REALLY hot floors. Spoke with him this afternoon to see how it was going and he said he was going to hug me next time he sees me. Supposedly wood consumption is cut in half, AND his forced air coil is actually useful for the first time in 11 years since the floor isn't robbing 98% of the heat. Totally redefined his entire heating system with $450 worth of parts. Definitely something to think about. Boiler water in a slab is never a good idea. A few folks out there will use a 4 way mixing valve or an injection pump to run their floors, but the cost of that mess ends up being just as high or higher than just doing it right the first time, plus a closed system keeps oxidation out of the floor loops which plugs them up over time, and the typical 12psi a closed system runs at is far easier on the pump to circulate instead of "pushing" like they do in an open system, raising efficiency
-
I would tend to agree Eldon on the condensation but I had a hardy H4 that I ran for 4 years. It was 23 years old when I took it out of service. When I bought it used in 2011 it was missing a good portion of the bottom of the boiler floor in the firebox. I could only assume that it was from sitting every summer without a cap on the chimney and rain water getting in and mixing with the ash to create the acid and eating the floor away. This is just my theory though
-
Still coming out of a flat plate without a mixer could still be too hot. Done a lot direct out of boiler with a mixer that worked great. Pressurization with a flat plat can help you with air bleeding but I try to stay away from all the extra equipment when I can. Just my opinion.
-
I was thinking the same thing, mixing temp down would need to be done even with a flat plate? Maybe I missed something.
Interesting Honda. Wet ashes aren't good..
-
I assume you're both referring to my comment. If so, yes- you both missed something. Mixing valve was mentioned and is necessary for proper radiant slab operation. I figured since Honda already commented on the target water temps, I'd leave that part out
-
Out of curiosity gentlemen, when you pipe a 3 way into the boiler loop to serve a floor, what happens to flow in that loop when the zone valve for the floor opens? 8 loops for example, 2400 sq ft, average insulation, we're looking at 4-6 GPM necessary to properly heat said floor with tempered water. The typical 1" PEX underground can only carry 7 GPM total, so you have 1-3 GPM or 10-30k BTU left in your main loop. Mama's doing laundry and needs some hot water or all 4 kids run through the shower; there goes whatever was left. Then your forced air calls or the unit heater in the garage calls; oh dang, there's nothing left, why not? It'd be different if a radiant floor only ran for 5 minutes like forced air does, but with proper water temps a floor will run for several hours straight, robbing 2/3 of your available BTU. Being separated with a plate, that floor only uses its own water to heat and passes it through the exchanger to heat it instead of physically using the boiler's water to circulate through the floor. This maintains a constant 7 GPM through the boiler loop regardless of load, and allows it to replenish several times faster while still keeping everything satisfied. I specialize in radiant floors and have yet to see an atmospheric system perform anything like a closed when there are other things in the loop. It's not that I'm closed minded, I really would like to see an atmospheric system prosper to simplify the installation process but the fact is that it doesn't. Even if the floor is the only thing in that loop, a guy still needs a 4 way mixer or at least a 3 way zone valve plus a 3 way mixer to get flow without deadheading the boiler pump right? Perhaps I'm missing something but of the dozens I've swapped to closed, exactly zero of them performed worth a crap the other way and I can't see how they could
-
If the radiant is setup as a secondary loop, it can't deadhead the main loop. Only 3 way thermostatic valve and pump is needed.
-
Completely overlooked that, thanks. Still doesn't fix the rest of the problems though. Even set up as a P/S, you're still taking 4-6 of your 7 GPM from the primary loop in the aforementioned scenario. Say it's 10 or 12 loops even, you have nothing left. 100% of your boiler water goes through the floor. For the extra $225 upfront, I see absolutely no reason to potentially double your wood consumption and have a poor performing heating system UNLESS there is nothing else being served. Even then, I certainly wouldn't want oxidized boiler water in my inaccessible slab but to each their own. Just trying to get a grasp on why people do this
-
Thanks for all the information, looks like I have missed a few steps in my system design. What will happen to my concrete with current setup?
-
wreckit87, the way you setup a radiant system makes sense to me and I am following along on your points. I've never done radiant anything so far, so I really don't know much about them. Your point about robbing the flow from the main loop makes perfect sense and whenever I do radiant floors in my house, I'll certainly be using a closed loop with a plate exchanger and a mixing valve.
-
Radianttec.com has lots of good info opunder their resource page. Just overlook the info about them trying to push their products.
-
wreckit87, don't follow you about using a 3-way zone valve in a infloor set up. I never do that. am I missing something?
-
wreckit87, don't follow you about using a 3-way zone valve in a infloor set up. I never do that. am I missing something?
Let's say your boiler loop runs through the house, hypothetically hitting a DHW plate exchanger first, then a forced air coil, then catch the radiant basement floor on the way out. If using the main boiler pump to circulate everything, including the radiant, there is no way to direct 2/3 of your water out the branch of the tee and through the floor when the straight shot back to the boiler is free for the taking as the head loss in any floor is more than a straight run to the boiler. In this situation, you'd need a 3 way zone valve to direct all flow through the floor while the main loop gets nothing but 60-80 degree floor return water; we know how good that is for the boiler. That's how most of the clowns out here do it anyway, which slows down the primary boiler loop to whatever GPM can be shoved through the floor loops. Another option being a 4 way mixer to keep both the floor temps and boiler return temps at a happy(ish) medium, but the cost of that mixer is considerably higher than closing the system. A secondary zone pump for the floor in addition to the primary boiler loop pump is an option that I overlooked at first and RSI corrected me, which would eliminate the need for a 3 way ZV. That's how I see it anyway.
-
Thanks for all the information, looks like I have missed a few steps in my system design. What will happen to my concrete with current setup?
First off, running high temp water throws a HUGE amount of heat into the concrete, which we know is a very big heat sink. A wall thermostat, which most folks use, will satisfy when the air temp reaches the setpoint. When that happens however, the slab is usually too hot to stand on which in turn continues to radiate heat into the room well after the pump stops, and overshoots the setpoint. Let's say setpoint is 70, but the air temp gets up to 75 because the slab is so hot. After this, it may take 18 hours to get the air temp back down to 68 or wherever the stat kicks the pump back on- at that point, the slab is cold again and you start all over. You want the water to be the bare minimum temperature. If it circulated constantly but maintained air temp would actually be the most efficient system possible, which is almost achievable with the use of outdoor reset. A typical floor runs 90-110 degree water depending on load and desired air temp. This keeps a more constant slab temp which keeps a more constant air temp. Also, the constant hot/cold cycles of running high temp water destroys concrete and cracks the piss out of it.
-
Yes, I just use two tees close together with a mixer and a pump. Less restriction on main line than a flat plat. It's all on a secondary loop. Just had never heard of or conceived how you used a zone valve in a infloor setup. Hate them zone valves anyway. Try to avoid them.
Slimchance, you probably won't hurt your Hardy but it's going to burn a lot of wood dumping direct in floor and it's not good for your floor. Cheapest and easy way out is a mixer and second pump. Put the secondary pump on a stat. Do your garage the same way. Have a stat for each. Using a flat plat will work too but is more involved. Sounds like you are doing this yourself and the simpler the better?
-
I think we all agree the floor loops need to be mixed down to approx. 80-100℉ and hydraulically separated from the main loop either using a flat plate or close tees (or some other method)? The floor loop flow shouldn't affect the primary loop flow. With close tees the secondary loop can recirculate some water if needed. With the mixed down temps the close tees are only sipping off 1/4 of the gpm of the main loop in comparison to the floor loops. Most floor water gets recirculated and never hits the main loop. If it's the last load on the primary loop it won't affect the other loads like DHW or fan coils.
I've always used a secondary loop pulling through the mixing valve. Using a three way zone valve and using the main loop pump would choke flow as wreckit said and the mixing valve needs equal pressure on hot and cold inlets which it won't have pushing in the hot.
And I don't say any of this to argue, I just love hashing hydronics. :) Hope you guys understand.
-
I like this guy! ^^^^ I hope I'm not coming across as a jackwagon by being stern and asking silly questions- I have no intention of starting an argument either. The main thing I'm trying to push with radiant is to keep the oxidation and sediment out of the slab, which is present in an atmospheric system regardless of how much you filter your fluid. Your available BTU will transfer more efficiently as a closed system as well. I mean, you can keep your truck on the road by just changing the oil and not the filter, but is it right? It'll keep you moving for now and work okay, but after awhile the filter plugs with shavings and you spin bearings. Same thing happens in radiant floors. Does atmospheric radiant work? Absolutely. Is it as efficient or bulletproof as pressurized radiant? Not so much. There is a reason every radiant designer in the world specs oxy-barrier tubing- because a correct system should be oxy-free. You buy the pump and mixer anyway to run it atmospheric, what's another $225 for a plate exchanger, air separator, expansion tank, and relief valve to have a worry free system that'll outlive you? Minimal upfront investment to have a proper heating system over one that just works in my opinion, but it's merely that: an opinion. My local plumbers have made me a lot of money over the years by installing poorly designed systems, so I'm really okay with the job security ;)
-
I like this guy! ^^^^ I hope I'm not coming across as a jackwagon by being stern and asking silly questions- I have no intention of starting an argument either. The main thing I'm trying to push with radiant is to keep the oxidation and sediment out of the slab, which is present in an atmospheric system regardless of how much you filter your fluid. Your available BTU will transfer more efficiently as a closed system as well. I mean, you can keep your truck on the road by just changing the oil and not the filter, but is it right? It'll keep you moving for now and work okay, but after awhile the filter plugs with shavings and you spin bearings. Same thing happens in radiant floors. Does atmospheric radiant work? Absolutely. Is it as efficient or bulletproof as pressurized radiant? Not so much. There is a reason every radiant designer in the world specs oxy-barrier tubing- because a correct system should be oxy-free. You buy the pump and mixer anyway to run it atmospheric, what's another $225 for a plate exchanger, air separator, expansion tank, and relief valve to have a worry free system that'll outlive you? Minimal upfront investment to have a proper heating system over one that just works in my opinion, but it's merely that: an opinion. My local plumbers have made me a lot of money over the years by installing poorly designed systems, so I'm really okay with the job security ;)
thanks, that makes sense. I enjoy the discussion. :thumbup: