Add on boiler install

[paddock]

I'm looking for some help getting this thing installed. I have a Kerr TW2000 wood boiler that I plan on connecting to my existing oil boiler. I've been reading about series versus parallel setups. I also want my domestic hot water heated with the wood boiler. Here's where I'm confused.

- I have a DHW coil in the oil boiler, do I need a second in the wood boiler?
- Do I need a second pump to circulate the water between both units? Why do some setups have this?
- I'd will probably connect a switch to the oil boiler so that I can turn it off when I'm at home and use strictly wood, but when I'm away I want to switch to oil and remove the wood boiler from the system completely, maybe have a bypass in there somewhere???

Here's a diagram I quickly made using MS paint. Anyone want to finish it?

Thanks,

Mike

 

[WoodNotOil]

I assume the Kerr is not a gasifier (doesn't appear to be from a quick search I did). With that said, a series hookup may be okay in this situation as there will most likely be periods where the oil has to burn anyway each day (unless you will be home to fill it every 3 hours or so - just a guess) With a series hookup you would have the WB ouput Tee in on the OB return just after the zone returns. The WB return would Tee in between the OB output before the zone circ. There would need to be a circ on the WB return line hooked to an aquastat so it runs whenever the WB is up to temp. Hooked up in series you will not need an additional DHW coil as the OB will remain hot at all times.

The only problem with series is that the zone return water mixes with the WB hot water and reduces available temp while any zone is running. This becomes a real problem only if multiple zones run for long periods of time. Assuming your house is well insulated, this won't be too much of an issue. The way around that is to use a primary/secondary piping with a primary loop or a hydro separator. You can get an idea of that from the sticky.

 

[paddock]

Like this?????

 

[WoodNotOil]

You got it. That is the way a series hookup works. Put an aquastat like the L6006 (strap-on or in a well) to control the WB circ. Keep the WB at around 180 and set the OB to high of 150ish and low of 140ish and it should work seemlessly with the oil taking over when the fire goes out.

As I said above the only drawback is the mixing, but that may not be that much of an issue for you if your house is well insulated.

 

[paddock]

Sounds Good!! That's sort of what I had in mind.

But what happens when both circ's are running at the same time. Which way will the water flow?

Thanks.

 

[WoodNotOil]

Both ways proportionately to the size and gpm of each pump. Having a single zone pump will mean less competition for heat from WB which is good.

 

[Paso]

I was just curious what is the best advantage of the series hook up compared to running the hot water out of the Wood boiler into the cold return of the oil burner ( as shown ) versus having the oil burners return line suck from the return line of the Oil burner return. ( as opposed to pulling from the hot on top of oil burner as in diagram.

Nice illustrations by the way. Curious minds want to know

 

[paddock]

Is this what your talking about Paso?

 

[Paso]

Yes My thinking was the oil burner woulnd't start until the fire in the wood boiler went out. Saving that costly oil

 

[Hydronics]

Pipe the wood supply to the oil boiler supply & the wood return to the oil return. This works well. Be sure the zone(s) circulator is on the load side of the tee for the wood boiler though (tee in between oil boiler and circulator).
When no zones are calling the flow will actually be backwards through the oil boiler -this will maintain oil boiler temp for your tankless domestic coil.

 

[WoodNotOil]

Pipe the wood supply to the oil boiler supply & the wood return to the oil return. This works well. Be sure the zone(s) circulator is on the load side of the tee for the wood boiler though (tee in between oil boiler and circulator).
When no zones are calling the flow will actually be backwards through the oil boiler -this will maintain oil boiler temp for your tankless domestic coil.

Would that avoid the mixing issue?

 

[paddock]

Pipe the wood supply to the oil boiler supply & the wood return to the oil return. This works well. Be sure the zone(s) circulator is on the load side of the tee for the wood boiler though (tee in between oil boiler and circulator).
When no zones are calling the flow will actually be backwards through the oil boiler -this will maintain oil boiler temp for your tankless domestic coil.

That sounds interesting, but can't seem to picture how it would work. Where should the circulator be?

 

[WoodNotOil]

circ would still be on the WB return.

 

[Hydronics]

You'll need another circulator in addition to the one in your last drawing on the supply or return of the wood boiler. Return is preferable. Control it by an aquastat in wood boiler well or clamp on to supply.

 

[rjanw01]

I am a complete newbie to this and trying to cut down on my oil costs (roughly 500-600 per month @ 2.05 per gallon). I was looking at the Kerr TW2000 and Biasi 4 section indoor wood boiler. I would have 3 zones with a poorly insulated house at this point in time. I have access to loads and loads of wood and figure I can pretty much see a return on the boiler the first full winter of using it with a great savings to follow. This savings would in return be put in as insulation in the future remodel I have planned.

Reading your posts, I see that the "series" has been well covered with a draw back of return zone water mixing and reducing overall temp or has that been resolved in the replies 8 thru 13? Is this the same with a parallel installation? What is a parallel installation?

 

[WoodNotOil]

I am a complete newbie to this and trying to cut down on my oil costs (roughly 500-600 per month @ 2.05 per gallon). I was looking at the Kerr TW2000 and Biasi 4 section indoor wood boiler. I would have 3 zones with a poorly insulated house at this point in time. I have access to loads and loads of wood and figure I can pretty much see a return on the boiler the first full winter of using it with a great savings to follow. This savings would in return be put in as insulation in the future remodel I have planned.

Reading your posts, I see that the "series" has been well covered with a draw back of return zone water mixing and reducing overall temp or has that been resolved in the replies 8 thru 13? Is this the same with a parallel installation? What is a parallel installation?

I think that the piping suggested in 8-13 would probably work well and seems to address the mixing problem. I might even give it a shot before taking the drastic action of redoing everything. It is kind of a parallel/series hybrid as the water flows directly to zones if they are calling (parallel) and if not it reverses through the OB (series).

 

[Hydronics]

Piping as shown in drawing 11 with the additional circulator mentioned in 13 is a parallel system (the supplies and returns are connected).

 

[paddock]

Piping as shown in drawing 11 with the additional circulator mentioned in 13 is a parallel system (the supplies and returns are connected).

I'm getting ready to install this now. And I plan to piping it according to drawing 11 with an additional circulator. But I'm wondering about my domestic hot water when the zones are calling for heat. Should I install a coil in the wood boiler as well?

 

[GKG-MO]

My boiler is piped the same as figure 11, works good. I would consider another aquastat for overheat protection so if the boiler would get to say 200* one of the zones would open to lower the temp.

 

[GKG-MO]

Sorry, Double post.

 

[GKG-MO]

Just 1 more observation. Shouldn't the Zone circulator be on the return side of the OB? Maybe not but that's how mine is.

 

[paddock]

GKG,

I don't think it matters where the circulator is. Do you get DHW from form your system? If so, how is it setup?

 

[wil lanfear]

Piping as shown in drawing 11 with the additional circulator mentioned in 13 is a parallel system (the supplies and returns are connected).

I'm getting ready to install this now. And I plan to piping it according to drawing 11 with an additional circulator. But I'm wondering about my domestic hot water when the zones are calling for heat. Should I install a coil in the wood boiler as well?

I have my pellet boiler piped exactly like drawing 11, using a circulator as mentioned in 13, its located on the pellet boiler return. I also have an aquastat located in the oil boiler which controls this circulator starting and stopping.

I do have a coil in the pellet boiler, probably don't need it though, the circulator between the two boilers keeps the water in both boilers the same temp.

 

[GKG-MO]

Sorry, No DHW. I would like to add it in the future but just wanted to get it installed this year. I don't know how your DHW coil works but I can tell you the water in the OB stays between 140 and 175. The WB is set at 140 to 180.
I was told by a friend that does heating installs for a living to keep the circulator on the return side to limit the amount of heat it sees. I'm not saying that it matters but that's what I was told so that's how I did it.