OWB plumbing question

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Joe is the wood burner you are going to use a pressureized or non pressure unit? The reason I ask is that i have a Harmon wood boiler that is hooked directly to the gas boiler in the house. It is set up with a bypass system that runs 24/7, it opens allowing water to go from house to wood boiler then back to the gas unit. The system has two pumps one on the wood unit and one on the gas unit with two zones in the house and one in the garage.
 
hanniedog said:
Joe is the wood burner you are going to use a pressureized or non pressure unit? The reason I ask is that i have a Harmon wood boiler that is hooked directly to the gas boiler in the house. It is set up with a bypass system that runs 24/7, it opens allowing water to go from house to wood boiler then back to the gas unit. The system has two pumps one on the wood unit and one on the gas unit with two zones in the house and one in the garage.
Click to expand...

Not sure if it is pressurized or not, but the pumps I'm looking at are all good for 125+ psi.
 
Being an indoor unit I betting is designed for a closed system just like your present oil boiler is. As for pressure my system has 12 psi or less. If it is a closed type unit you can plumb it directly into you present system. Thus getting rid of the heat exchangers.
 
hanniedog said:
Being an indoor unit I betting is designed for a closed system just like your present oil boiler is. As for pressure my system has 12 psi or less. If it is a closed type unit you can plumb it directly into you present system. Thus getting rid of the heat exchangers.
Click to expand...

How would I plumb that? I need it set up so that if the temp gets down on the wood boiler (fire out etc), the oil kicks in and takes care of business.
 
joecool85 said:
You mean like this: http://www.energysavingsusa.net/catalog/item/1603486/1049385.htm ?

I have a feeling folks are less likely to do that due to the fact that OWBs tend to be a bit smokey as it is since people frequently install "too large" of a btu boiler to help on load times (long load times, larger firebox). This makes it smokey on warm days when it isn't working very hard, damping the fire down to a smolder. If you turn down the temp in warm weather, its going to smoke even worse because it'll be damping the fire down so hard.
Click to expand...

I would tie in the ODR to my boiler aquastat. When the outdoor temp. is 40 deg. or above, I change the setpiont on my CB to 165 deg., which will still carry the shop/house HX's, use less wood. I was on track to cut my wood usage about 20% before the last major cold snap came thru. Of couurse. it's ppricey, mainly used for gas condensing boilers, where ODR works beautifully.

joecool85 said:
How would I plumb that? I need it set up so that if the temp gets down on the wood boiler (fire out etc), the oil kicks in and takes care of business.
Click to expand...

First Joe, congrats on doing your homework on this! You will be pleased when everything finally comes together, and works properly, because you took the time to do things right the first time...as far as Grundfos pumps are concerned, they work well, just make sure that you can get parts easily, or keep a spare pump around in case of a failure. If your boiler was used in a pressurized system, you can pipe it direct, possibly using a 2-stage stat, or separate stats. Not sure of your supply/return pipe sizes, you can divert water flow from one to the other via zone valves, or 3-way valves, or do it manually, with a dual-action aquastat for control, depending again on how fancy you want to get with it...
 
mtfallsmikey said:
First Joe, congrats on doing your homework on this! You will be pleased when everything finally comes together, and works properly, because you took the time to do things right the first time...as far as Grundfos pumps are concerned, they work well, just make sure that you can get parts easily, or keep a spare pump around in case of a failure. If your boiler was used in a pressurized system, you can pipe it direct, possibly using a 2-stage stat, or separate stats. Not sure of your supply/return pipe sizes, you can divert water flow from one to the other via zone valves, or 3-way valves, or do it manually, with a dual-action aquastat for control, depending again on how fancy you want to get with it...
Click to expand...

Thanks, I always try to do my homework before getting involved in a big project.

I'm still thinking 30 plate heat exchanger tied to the 1 1/4" supply line on the oil burner would make the most sense. That way if I spring a leak somewhere, it's only affecting either the indoor portion, or the outdoor portion, not the whole system. I'm ok with the added cost, and efficiency wise it seems to be pretty reasonable as well.
 
joecool85 said:
Thanks, I always try to do my homework before getting involved in a big project.

I'm still thinking 30 plate heat exchanger tied to the 1 1/4" supply line on the oil burner would make the most sense. That way if I spring a leak somewhere, it's only affecting either the indoor portion, or the outdoor portion, not the whole system. I'm ok with the added cost, and efficiency wise it seems to be pretty reasonable as well.
Click to expand...

That's what I would do...make sure flow rate, BTU output, head are in the range.
 
mtfallsmikey said:
That's what I would do...make sure flow rate, BTU output, head are in the range.
Click to expand...

Looks like I'm going to build my system to handle 120,000 btu even though my house as it stands maxes out at 40,000 btu plus dhw.

The pump I've selected is good for 14gpm max at 5' of head (which is what I will have), or 140,000 btu at 20 degrees F delta T.

Not sure on heat exchanger yet, but pretty sure I'm going to go with a plate style one. A 20 plate should do it just fine, rated at 80,000 btu, but the price doesn't seem to be much more for a 30 plate (rated at 120,000 btu) so I will probably go that route.

**edit**
I had read somewhere that you normally get 4,000 btu per plate on heat exchangers, but obviously it will be different depending on gpm, material and size of each plate.

Anyway, looks like a 20 plate with 1" connectors would be right up my alley (I'd just have to step it down from 1 1/4" from the boiler with an adapter from the steel pipe). It says it's good for 128,000 btu (probably at 215F water, but still should be good for 100,000+ btu at 180F water).

http://www.houseneeds.com/shop/heat...rs/mischeatexchangers/heatexchangerbuyage.asp
 
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My internal boiler was pressurized. I just valved out the make-up water to it. My aquastat inside is set at 120. If my outdoor boiler is unattended for an emergency, the lp boiler will kick on to keep the system warm. Not heat exchanger, one pump internally that only runs when the house calls for heat. cheap, and reliable.

I installed a ball valve on each side, so both systems can be isolated if problems were to rise. When its early in the fall and spring time I set my outside boiler at 150, when its cold 185.
 
Any ideas on how to increase burn time on this bad boy? I've been reading online and it appears that most folks get 2-3 hours with split wood, 4 hours or so with unsplit rounds...I'd like to at least get 6-8 hours so I can get an overnight burn without the oil kicking in. If I can't, oh well, it's a freebie, but still it would be nice.

I have a couple thoughts though. It only has a 17" wide x 21" tall firebox at 22" tall...seems small compared to newer units. This one was made in May of 1978. Maybe thats all we can get is 4 hours out of it?

My second thought is that it only has a 50 gallon water jacket, seems most units now have 150-200 as a minimum. Maybe I could add a hot water storage tank to it and even though it would only actually burn for 4 hours, I would have heat for 8?

My house has a design btu draw of 40,000btu/hr, so on average it would be half that. If I want 4 hours of 20,000btu/hr, I would need 80,000btu/hr storage. With a 20 degree delta T, running the storage tank at 160/180, that would mean I would need a 500 gallon tank. My basement isn't super large, and storage tanks are kinda pricey, so I'm not exactly fond of that option. I could go with an old 30 gallon water heater, which would give me an amazing 4,800btu/hr of backup...aka - a little less than 15 minutes of heat after the fire goes out.

Couple other ideas, I'm not including the 50 gallons IN the boiler jacket, so that would give me 40 minutes of heat after the fire goes out if I add the 30 gallon tank, call it 30 minutes if it's super cold out. AND the oil will kick in if the fire runs out, so it's not like I'd be without heat. I could set a little beeper to alert me when the temp in the boiler drops below say...150F or so. Wake up and feed the boiler at night.

Or for now we could just stoke it at night, let it go out and have the oil kick in during the early morning hours till we wake up. We'd still save a lot of oil and for now it would be "ok." Eventually we will upgrade the boiler anyway, and maybe we could add a 500+ gallon heat storage tank at some point.


I now get why outdoor wood boilers make so many folks happy with their giant fireboxes and 200 gallon (32,000btu/hr) water jackets as heat reserve.
 
Also, I didn't happen to think to check (or really, know hot to check), but I wonder if this doesn't have an automatic draft control...is that possible? Or would it just boiler over all the time?
 
I had a 70"s model indoor stove you talk of originally. It sat in the basement next to the lp boiler. The lp pump would run to circulate the water when the wood boiler got to hot. It would cook you out of the house.
 
I'm kinda thinking about plumbing this direct, no heat exchanger. A couple guys have mentioned it now, and I checked and this boiler is made to be pressurized anyway.

So, this is what I have now:

Oil boiler, two zones plus a separate coil for DHW. Each zone has a pump, DHW coil doesn't, the water just flows through it when you are running it.

K, so - how do I plumb in my wood boiler? Keeping in mind it will be 30' from the house. I'm also thinking about adding a 200 gallon storage tank.

No need to worry about DHW, I can figure that one out later.
 
My original in house wood-boiler system was sized to run with the existing system. It worked with an expansion tank and pressure relief (safety)valve. It was sized properly to fit the system. I think that if your intentions are run it pressurized, you need to get with someone in your area that deals with boilers. It should be properly set-up and tested, so you don't have an explosion.

When I speak of my newer outdoor wood boiler system, it is de-pressurized.
 
getting back to the electricity cost of running a circulator 24/7, keep in mind that although you are adding this circ., you are eliminating the device that fires your inside boiler, i know typical oil fired furnaces use a transformer that can draw quite a bit, not sure on lp though. just a thought!
 
Ok, been doing more research and I'm thinking about doing a direct tie-in with my current system.

Looks like I'd need to use a Watts ET60 or similar expansion tank to allow for a little over 6 gallons expansion.

This is what I'm thinking of plumbing:

attachment.php


**edit** I didn't feel like changing the image, but I'd take out my check valves.
 
You will need some type of zone valve and aquastat to seperate your wood boiler hot in and cold return. Which is good because you can use that valve to control when your fossil boiler needs to kick on so you won`t be heating the wood boiler from your fossil boiler.
 

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