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New home and virgin to wood boilers (17 Posts)
New home and virgin to wood boilersI recently purchased a ranch style home with approximately 2500 sq ft 1st floor and 2500 sq ft basement. It has 2 Lennox furnaces in the attic (1 for each floor).
I can put a 20x20 inch heat exchanger on the intake side of each furnace and it's about 30 feet down to where my pex would be coming through the basement wall.
My boiler is a mahoning 200 multi fuel and specs at 150,000 btu. It is going to be 150 feet from the house and I was planning two 1 1/4" supply lines and two 1 1/4 return lines to the house. When it enters the house I was planning a manifold then taking seperate 1 1/4 lines to each furnace and also supplying a 20 plate exchanger to the hot water tank off the manifold. Any suggestions?
The posterI am also considering wrapping the pex with the low e insulation snd putting inside the corrugated pipe my self or going with the pex incased in foam inside of the corrugated pipe? Any thoughts on pump sizes as well here are pics of the two that came with the unit
There's quite a bit more to this than picking the right pipe sizeI'd suggest a thorough review of http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_10_us.pdf before you begin.
http://www.mahoningoutdoorfurnaces.com/index.php/products/coal-or-wood-burning looks like an open system? Not sure. You need to know, as there are critical design implications.
Start with a heat loss calculation on the house and a proper system design. I highly doubt it will require four pipes to the boiler.
ReplyI was told that 1" pex could only supply 80000 btu so since I needed 80000 btu for the first floor and 80000 btu for the second floor they suggested 2 supply lines of inch and a quarter. It is a non pressurized system
How couldyou possibly need the same amount of BTU's for and above grade story with windows and doors as you need for a basement of the same square footage with no windows and doors!
Think about that for a second!
Take SWEI's advice and do a heatloss on the the building and read that Idronics issue he posted. It will save you a ton of money in the long run and keep you comfortable in the meantime.
Most Outdoor Wood Stove dealers don't know much of anything about Hydronics.
People on here do.
ReplyYeah I've found that the salesmen want to oversize you on the boilers and they aren't to familiar with pipe sizes,flow rates and btu's.
Personally I want to do it right the first time and not waste money on unnecessary stuff. I can tell the people on here are pretty educated and that's why I posted my situation ( myself on the other hand am just a handyman trying to save a buck)
I purchased the boiler used at a great price and plan on doing the whole show myself
Alsosee here , http://www.caleffi.info/webinars/ . Scroll down to renewable sources in archive and view the webinar as given by John Siegenthaler . It will certainly help . A room by room heat loss should be performed for this home also to determine what really needs to happen in regards to interaction between the indoor stuff and the outdoor boiler .You didn't get what you didn't pay for and it will never be what you thought it wouldThis post was edited by an admin on February 9, 2014 12:50 PM.
Reply to RichI will definately watch the webinar and research that site. The house is currently all electric forced air with heat pumps so if I can just get everything out of this boiler I can then it will help out tremendously with the electric bill. My expectations going into this project is that the boiler is undersized but like I said I got a great deal and as long as everything else is installed correctly I can always upsize the boiler later. Like I said it was a really great deal so I actually got just what I thought I was getting ;)
Probablynot undersized . Even if the house is leaky as hell you are probably oversized . Hell even de rating the output to 75% you still have 45 BTU per sq ft at your disposal . Like Harvey and I stated , perform the heat loss and include all walls , doors , windows that are exterior and the R values . That basement if it is mostly below grade is already pretty well insulated as far as Earth goes . I recently designed a home in Kittanning , not far from you that is roughly the same size and the heat loss was only 78,000 at negative seven degrees outdoor temp and indoor temp of 68 . Point is that I think you will be surprised at what those calcs tell you . You may even end up with free Domestic hot water during the winter monthsYou didn't get what you didn't pay for and it will never be what you thought it would
Supply and returnSo would there be a benefit to running two supply's and two returns or can I accomplish the same objective with just 1 supply and 1 return in 1 1/4"? I just thought using dual lines I would be sending it there and back faster so it would have less heat loss
1set of one and one quarter inch S&R should be quite sufficient . Don't buy anything else urged by a salesman yet .You may have shown up here just in time to avoid disaster .You didn't get what you didn't pay for and it will never be what you thought it wouldThis post was edited by an admin on February 9, 2014 12:55 PM.
First things first.Before you purchase anything or start thinking about pipe sizes and such, do a heatloss calculation. If you have a smartphone or Ipad, here is a good one.
Size matterson so many levels. Once you complete the heat loss calculation, you will likely find that the boiler produces more heat than your house will need on the coldest day of the year. This will lead you towards a buffer tank and some additional controls. Running the boiler at a 30ºF ∆T will cut your flow requirement to 10 GPM.
One of the many factors you need to consider is how much wood the firebox holds. Wood boilers work best when they are run at full output, burning the entire load as hot and as quickly as possible. When they are throttled back by choking off the air supply, their efficiency drops and they smoke like the dickens. Your job is to find a place to park those BTUs while they are being made, which will increase comfort and reduce your workload.
I would also recommend looking at your emitter system. Fancoils are OK, but you may be able to add radiators or even underfloor heat to the ground floor of the house without too much work. Either would be a worthwhile investment if you plan to stay in the house for a long time, or if resale values in the area reflect the added value of radiant heat.
Ranch on low side lotThe lower level of the house only has two buried walls. It has two huge garage doors on the south side and the west side has two large windows,2 doors, and a large set of sliders. The house is 30 years old and all windows need updated. It is however very well insulated and all brick. You were talking about storing the btu's? It thought if the water goes back hot then you will conserve wood?
Storing BTUsrequires some kind of thermal mass -- a tank of water is usually the least expensive and almost always the easiest to control.
Sending hot water back to the boiler will merely increase the temperature of the 200+ gallons of water the boiler holds. Depending on the design, the boiler may react to that by choking off its air intake, which will starve out the fire and dramatically reduce the combustion efficiency. This in turn can coat both flue passages and pipes with creosote. Creosote reduces efficiency further, and when enough of it builds up, can cause catastrophic fires. The answer to all of this is an external buffer tank, which should be located in the basement or a utility room rather than outdoors. The size of the tank is determined by the boiler firebox capacity, the heat load of the house, and the type and dryness of the fuel used plus the temperature required by the distribution system. Fan coils require hotter water than radiators or floor tubing do, which has the effect of increasing the required tank capacity. You can order coils designed for lower temperature water, but they will cost more and (depending on the design of the coil) they may restrict airflow to a point where your existing supply fans do not work properly. The buffer tank needs proper controls on its output, the boiler needs either a thermic loading valve or a properly controlled electric mixing valve in order to prevent flue gas condensation from destroying it. All of these bits and pieces are interconnected -- a proper design will ensure you get the performance and comfort you are hoping for.This post was edited by an admin on February 9, 2014 4:55 PM.
Wood Boiler MisConceptionsWe sell and install outdoor wood boilers as well as all other forms of hydronics and HVAC. I have one at my house.
Most ODWB people range anywhere from clueless to being real fountains of misinformation. You've been effected by this blight on our industry. Many are good folks, but selling ODWBs is usually a second line of business and they have no training or experience in hydronics. For that matter, most HVAC contractors don't.
You've gotten some good info from the men on here already. Let me add some things based on what you've stated and what I run into regularly with ODWBs:
1. You don't place the hydronic coil in the return air duct; it goes in the supply, downstream from the AHU. No min distance, just enough to transition, not more than a 30* angle. If you place it in the return, you're gonna be buying fan motors and maybe compressors also depending on how the controls are setup.
2. You can NOT control the system from two thermostats correctly. I know, all the ODWB manufacturers give that stupid diagram. If you want all kinds of issues, go ahead and use it, but when it comes compressor time, remember my warning.
3. There's no way you need 160k btu's to heat your house. I doubt if you'd need 125k, but a heat loss calc. needs to be done.
4. A single set of 1 1/4" lines will be more than sufficient as long as your not setting the ODWB hundreds of feet away from the house.
5. Pressurization is an issue with the AHUs being in the attic. It takes 1 psi to lift water 2.31 feet. It also takes pressure to remove and keep air out of the system. If your attic is 20 feet above the water level of the ODWB, then you'd need about 9 psi to lift the water that high and you'd have 0 psi in the attic. Add another 5 psi to keep positive pressure in the attic and were looking at approximately 15 psi needed at the lowest level. But, your ODWB is unpressurized and directly opened to the atmosphere. This means you're gonna need a heat exchanger or a buffer tank with a coil to isolate the unpressurized ODWB from the pressurized side on the house. Don't let the ODWB know it all's convince you that the "pump" creates the pressure to over-come this. We use circulators, not pumps. Circulators do not create pressure in the system; the only create a slight pressure differential between supply and return. The do NOT create static fill pressure. That's the job of the fill valve connected to the pressurized potable water system of your house. That's one of several ancillary components that you'll need.
6. Do NOT use plumbing PEX for this system; it absorbs oxygen at the molecular level and oxygen is the enemy of any hydronic system. You need to use a PEX that has an 02 barrier. Rehau's underground piping has this, but it's difficult to bend.
7. Circulators are sized base on the gpm needed and the friction head loss of the piping. Gpm is based upon the amount of btu's needed at a given delta T. So, you need a heat loss calc to determine how many btu's you need in order to determine how many gpm you need to size the circ's.
These are some of the major and most frequent ares of mis-installation that I run into on ODWBs that need not occur. Yes, it costs more to do it right - but not in the long run! I have people right now begging me to come correct the problems with their ODWBs that someone created by tring to cut corners and do it on the cheap. Like the man said "You pay me now or pay me later". Do it wrong, and you'll pay a lot more than doing it right to begin.
You can send me a PM if you want further assistance.Bob Boan
You can choose to do what you want, but you cannot choose the consequences.
LIKE. LIKE LIKE LIKELike like like........
Pay the cheap price now, and you will end up paying more later.
Very good post Mr. ironman.
The OWB market is 90% false advertising claims and unqualified installers. It doesn't have to be like that, but the manufacturers choose to circumvent code and not requiring licensed installers. Despite what they might claim. The one giant loop that feeds multiple heat exchangers, and runs 24/7 with a "pump" big enough to run big commercial applications is the norm.
Very difficult market to educate, but when one has there system revamped and then they use half the wood. Only then does that one customer now know...... Rarely does one calculate all the time and expense for the wood supply. Somehow they always say its free.....