outdoor boiler

mrwood

we are working on a job to rework a house with steam heat. The radiators are steam only and the boiler and piping are being removed by the homeowner due to there age and leaks. the homeowner has found cast iron radiators to match the existing locations, and we are pressure testing these before install. the replacement boiler is an outdoor gassification boiler, piped into the house and through a plate to plate heat exchanger to isolate from indoor pressurised system. the homeowner wants to seperate the house into three zones, basically one for each floor. We plan on zoning with a circulator and manifold to each zone, each one having to pass through the plate to plate, maybe as primary/secondary. Any diagrams for doing this so we don't miss something obvious? The boiler is modulating and we are not using buffer tanks, and no back up boiler for now(budget), maybe add a gas modulating unit later, the system will also be full of glycol.

hot_rod

Highly

recommend a buffer/ separator 120 gallon tank at the very least. Look for one with multiple taps so it is both a hydraulic separator and the buffer.



it is almost impossible to run a wood fired boiler efficiently without some buffer capacity. They just don't respond quickly.



I am suspicious of an outdoor "gasification" style that is non-pressurized?? Sounds like an OWF with a marketing spin?? True gasification boilers are usually high quality steel construction, running them as an open system would be a disaster.



Maybe the outdoor part has glycol and that is what a HX separation is used?

mrwood

Gasifier

Heatmasters G series, a stainless construction (409) boiler. EPA tested out at 78% overall and carries a phase 2 tag for emissions. The boiler itself buffers about 265 gallons capacity and we found the modulating Siemens control to be very responsive due to induced draft, boiler maintains temperature -constant circulating to plate exchanger. We are separating indoor/outdoor with the plate for antifreeze and pressure/non pressure due to the boiler being non pressure. We traditionally don't have this many loops to radiators (20) so this many manifolds are usually not joined. We are just looking for ideas on closely spaced tees or setting up primary/secondary loops off the plate for best flow, we are in the 200,000 btu range at max heat load, (loss not radiators).

Ironman

Moose Antler

You might try the moose antler manifold. The heat exchanger would replace the boiler in the diagram. You could also add another set of closely spaced tees for connection of a boiler. Put them in the manifold downstream of the HX Tees. That way whatever amount of heat that the HX provides would be pumped into the boiler when its circ is energized from a heat call. If the water entering the boiler is hot enough, then it won't fire.



Size the manifold to keep the velocity in it near 2 fps. to prevent hydraulic interference. You can also use individual zone circ's in lieu of the manifold circ and zone valves which are shown.

mrwood

Right on

This is something like we were thinking, with check valves at each pump. Strap style aqua stat making the decision between letting the back up come on based on supply temp of outdoor boiler. I will try to figure approx flow at full load, 3- grundfos up 15-42 pumps pushing to rads with about a average of 120' of 3/4 pex round trip.

mrwood

Wood boiler piping

Just found your old post with the primary secondary on multiple zones

mrwood

Flow

Looks like we are in the 28 gpm with all three zones calling, as low as 8 gpm with one zone, how do you feel about 1 1/2 antler for low flows, as it looks like we taper off to 1" to maintain velocity at that flow

Ironman

2"

Probably be better with a 2"" header. 1 1/2" carries about 22 gpm, @ 4 FPS. You want it large enough at full flow not to have any interference between zones.

hot_rod

a few other ideas

what size is the boiler? What is the heat load?



If it is the 210,000 X 78% you have 163,000 to move. So 16 gpm will do that.



The largest unit is 350,000 x 78% = 273,000 around 27 gpm.



You will need some large tube to move that load from the OWF to the home.



Inside, if it is the 200K you could use an indirect tank with a 1-1/2" coil. Those brands will move 200K easily.



Or a buffer tank with an external HX, but that requires one more pump.



In either the tank is the separator, and air eliminator, and some additional storage.



A back up boiler, if it is a low pressure drop, like cast iron, could tie into the headers.

mrwood

load

the maximum load with all zones will be 200000 loss (not rad capacity) we are using the G400, not for capacity but for load time that will go 12 hours, and since ratings are for oak and not lesser wood. we are using urecon dual pex, 26-99 pump, charts out around 14GPM, about 30 delta at plate x, I like the napkin picture. I was just looking for alternatives , sometimes people come up with great ideas i have not seen or have forgot about over the years. I appreciate the comments. i agree on the 2'' manifold, our velocity is just low when we have one or two zones on, thats why i mentioned 1 1/2.

hot_rod

I run a gasifier

and I have found they really need to be run hot and full speed ahead to get anywhere near that efficiency number. If they are oversized to the load, they idle, smolder, and creasote a lot!



I know folks try to up size for extended burn times, but... it's rare to be at design load for weeks or even days at a time. An oversized wood burner can be a handful to manage.



The large water capacity will help somewhat, but once that capacity is heated to 180, it will still cycle, and idle.



You have maybe been to the "boiler room" at hearth website, lots of hands on experience over there with all types of wood burning boilers and OWF.



By far the biggest mistake is undersizing the lines from the boiler in. It really is worth the $$ to use the correct tube size. Those lines need to be sized to move all the energy out of the boiler. If in fact it has a 273K output at 78%, size to that. Someday you may chose to add additional buffer inside.



The best place to store energy is in the un-burned wood The next best is in a well insulated tank within the heated envelop. Outdoor, even in an insulated shed, not so good.

mrwood

Agree

I agree, we have found outputs to be well under rated capacity when you use everyday wood, oak around here gets logged and sold, not burnt, and farmers use fence row wood mostly, hackberry and other low btu. Also remember modulating air cuts down on cycles, and loading to match load always helps shorten idle times. We always shoot for 12 hours, it is a good balance. What brand are you currently using?

mrwood

Greenhouse

We are also slightly oversized due to possibly another load added from another transfer line for small greenhouse later.

hot_rod

tradeoffs

I have an EKO, Euro brand. Like most Euro brands it has a small firebox and small water capacity as they are generally installed indoors. So a buffer is crucial to smooth, clean operation. With good seasoned oak, maybe a 4 hour burn. I have installed EKO, Atmos, PK Pyro and Tarm gasifiers. Also Hardy, WoodMaster, Central, and Aquatherm OWF.



Most often the OWF with large fireboxes get packed with green and wet wood around here. With that fuel source studies show a 35- 40% efficiency. Small amounts of heat energy are transfered to the load, mostly smoke pollution to the down-winders My OWF neighbors burn 6-12 cords of wood, I burn 3 for about the same heat load.



I'm not sure what the true definition of a gasifier is, my experience is a ceramic lined secondary burn chamber with 1200F temperatures to get to 70- 80% efficiencies.

mrwood

At dealer

I was an aqua therm dealer as my wood boiler line when they started, when bill and the others were looking into new products. I still run an Eco 345 here at home. They sold some euro boilers and had terrible trouble and leed times out of them. Greenwood tech was sold by my friend and they had terrible luck with them also, and no product support, then they claimed they epwere going bankrupt and quit answering the phone. Any way AT standard will make 50 to 60 % some times of year! other times 30 % like you say. We picked up heatmaster about 6 or 7 years ago and have good support and product. AT rubbed me wrong on a few jobs due to mistakes on there part and you are selling against yourself since they will bid radiant jobs and sell out the door. Here in indiana when the rules changed we needed product and heatmasterss has come through. As far as a gasifier, you hit it pretty close, we also add that the wood is heated by the fire so the flammable gasses escape, pass through the coals and are ignited creating a very intense burn and also burning off most resins (creosote makers). We see different brands we install for others but they change every year it seems. EPA certification has had a bearing on this I believe, so now wild claims have to be verified. Hopefully it has brought honesty to the market.

mrwood

Wood

If 6-12 cords scares you I burnt 52 rick in one year once, heating house, barn, 2 car garage and 21,000 gallon swimming pool. That's about 26 cord. Now that I am not 20 and flexible i use about 12 cord a year, burning sawmill waste in the summer for the pool so no splitting or carrying.

hot_rod

I remember

talking with Dave, Bill, and Bob when they tried to build that stainless steel Omega boiler. They learned a lot about building a wood fired stainless boiler, it's not so easy. I thought they would be better hooking up with a good Euro manufacturer. Maybe they were a few years too early.



There are hunderds of gasification boiler in Europe. I think most of Austria builds wood and pellet boilers. High quality, well engineered stuff, Germany and Switzerland also.



I've just never seen OWF gasification boilers in my travels over there. They chuckle when you describe an OWF to them.



I did see a rather large round bale burner that claimed high efficiencies. That would be ideal here in Missouri, for the poultry barns. plenty of round bales sitting in fields rotting away.



Only a controled burn test , performed by a qualified lab would convince me of efficiency numbers. There are some pretty wild efficiency claims in the solid fuel burner industry.



Somebody has a new emissions tester for solid fuel equipment, i think it was at the recent fireplace expo in DC. That would tell a lot about how efficient the unit is burning.

mrwood

Changes

Dave's kids have also joined him and at last talk I believe they were talking about selling out or adding partners as a believe his health was failing. Bill moved on to another job, still with nuclear engineering I think. He gave me a great calculator for pex and flow rates in an exell deal I still use for rough pump sizing. We received a 345 from them that had no taper in the threads of the welded bungs, and they simply said oops,I thought we got those fixed, then I was stuck trying to make all the threaded connections stop leaking. they were really nice people,just had growing pains I thought. Hopefully they can adapt to the market and be successfull. I also found out later they were having their boilers built by a company that they did not control, and they eventually became a competitor.