Suggestions wanted

bill nye_3

Suggestions wanted (or at least considered) Long story , I hooked up a wood boiler for a friend about five years ago. It is an outside boiler and I did not want to mix the water with the system water so I used an eighty gallon indirect water heater as a heat exchanger. The system was a gravity circulation system from the teens or twenties. A Burnham V34 boiler with circulators was installed in the early 1980's. The house is  not insulated and the home owner does not want to compromise the plaster or craftsman style wood trim or siding.



So, to get to the point. They do deep setback and will not change habits. When the thermostat calls for heat so much cold system water returns it causes the oil burner to start. Some other plumber rigged some hokey switch so he could shut off the burner while the wood was going. But now people are away from home and oil burner can't be switched on an off.



 My thought was to disconnect the oil boiler from the loop, tie the main together and use two closely space tees to protect the boiler from all the cold system water on a call for heat. I am probably not doing such a good job trying to explain this. I put the guy off for a year or two but now he wants me to do something next week. Every summer I put him off and fall arrives and then it is too late. 

Snowmelt

Central boiler

I would think some kind of aquastat has to be used when the temp goes below 140 that means no more wood in the wood boiler and the oil boiler comes on. I would use a flate plat hex instead of a full indirect water heater.

Harvey Ramer

Solution

Put the system on constant circulation with ODR and put a fake thermostat on the wall.



Harvey

Jamie Hall

I don't blame the man

for not wanting to compromise the plaster and trim and siding and all -- I face exactly the same consideration here (although I have an additional headache -- this place is a museum, and National Register and all that -- so even if I wanted to...).



But it couldn't be a worse setup for deep setbacks.



Not only are gravity systems really bad at recovering from deep setbacks -- they were never meant to do that -- but the deep setbacks are, whether your client realises it or not, very hard on the plaster and woodwork.  Never mind any furniture, paintings, musical instruments (pianos, in particular, react very badly), and what have you.  But you probably can't convince him.



I like Harvey's idea. 



It seems to me that what is needed is to sort of reverse the thinking.  Make that oil burner your base heat -- the floor of the setback --on an ODR with constant circulation, and use the wood burner to lift the place out of the setback, or to hold it warm if and when there are people there to fire it.

bill nye_3

primary -secondary

 I dug out my books "to get learned up" on this stuff again. Pumping away and primary -secondary made easy. I found my notes from a Dan Holohan seminar on 8-24-05 in New London, Ct. Back before the economy fell apart.

hot_rod

P/S may not

protect the oil boiler from cold operating conditions without a temperature sensing, and responding logic.



What about a three way themostatic mix valve on the oil boiler? A 3 way is a simple, effective, non - electric option.

bill nye_3

What I have learned

I asked a lot of people a lot of questions , no one seemed to have an answer. Chris from Winnelson stepped up to the plate. We did a heat loss, I surveyed all of the radiators and looked them up in Dan's EDR book.  Most of the numbers seem pretty good. I used slant fin's hydronic explorer and I was a little "light" on my load. Chris redid it an fudged a few factors I wasn't aware of so worst case at 0° F it is about at 90,000 btuh. So I only need about 9gpm through the system.



The wood boiler is about 100 feet away from the 80gallon indirect so 200 feet round trip + 50% for friction fittings and check valves you got 300x .04 = 12 ft of head + some more for the coil in the indirect. 1" pex both ways



So the wood fired water boiler had a 3/4" tapping and a 007 pump. Today I tied three 3/4" tapping's together and put in a 0014 . The 0014 came with the boiler and I wasn't aware of it.  Tomorrow I will tie three 3/4" returns together. Easier said than done in very limited space.



The indirect heater was circulated through the oil boiler the way it was always done. Into the return and out of the supply. I am going to pipe the heating system return into the 80 gallon indirect, just like a buffer tank, and then into the boiler return. We will see if it works. Customer "Will Not " give up tankless coils so out door reset may be hard to accomplish. I may do Honeywell that plugs into the new aquastat or a tekmar 256 .



Whattayathink?

Ironman

Primary Loop

I would connect the house piping to form a primary loop and then use two sets of closely spaced Tees to inject into it. Moving from return to supply, the first set would be from the indirect that's connected to the wood boiler. The second set would be from the oil boiler into the loop. This way the wood boiler would supply whatever heat it could and then the oil boiler would kick in if the wood boiler is not producing enough. You could use a strap on aquastat or ETC to hold the oil burner off if the wood is producing enough heat.



I concur with HR that some form of thermal protection for the oil boiler would be prudent.



Obviously, your biggest obstacle is your thick-skulled customer who won't listen to his pro. Setback on a gravity system is totally counter-productive. It's using more fuel and also sacrificing comfort. Not to mention the thermal stress it's imposing on the boiler.



Another issue with ODWBs is that most are slow to recover, especially when hit with a dump load like your facing when that system comes out of setback. The more buffer that you can add to the wood boiler, the better it will handle the dump load and the more efficient it will burn.



I like Harvey's solution best.

bill nye_3

Prim/sec piping

One of my biggest obstacles and the reason I am looking for help is the piping arrangement. I can not seem to get my head around how I can tie it together. My Imagineering skills are not working well on this one. The piping leaves the boiler in two directions . Two supply and two return. The supply main decreases in size toward the end of the main. The last radiator( both sides of house ) is the end of the supply and also the beginning of the return.

In my first post I may have stated money wasn't going to be a problem, well now it  is. The cost of plumbing supplies is crazy. $25-30 and up for one 1-1/2" or 1-1/4" copper fitting ! I will try to at least get some outdoor reset as much as the tankless coils will allow.

Thanks for listening. If I can get a camera I will try to post a picture.

Zman

Suggestion

The way I see it you have 2 problems.

The first problem is inadequate flow to the OWB. I agree that 9 gpm should be your target. Assuming that your indirect has fairly low resistance (not an amtrol) here is about what you will see:

Taco 007                4.4gpm

Taco 0014              6.63gpm

Taco 0013              8.34gpm

Grundfos 26-99    7.8gpm



The other problem is the piping/control arrangement.

Since the boilers are piped in series, when either is firing, it is wasting heat through the other. If you don't have glycol in the outdoor boiler, you may need this setup to prevent the outdoor boiler from freezing when on vacation and the OWB is not firing. If you don't need to keep the outdoor boiler warm using the indoor boiler, it would be pretty simple to install an aquastat and a DT/DT relay that would only allow the indoor boiler to fire if the outdoor boiler is cold. You would simultaneously turn on the indoor boiler and turn off the circ to the outdoor boiler. Problem solved...

Zman

Freeze protection

If it turns out you need freeze protection, You could have a seperate control that would turn the OWB circ back on if the water drops below 50 degrees and then off of it goes over say 70 degrees. If this was wired in parallel with the other control, it would give freeze protection without wasting as much heat or confusing the primary control into thinking the  OW boiler if firing.

bill nye_3

money spent

Personally I don't think that I would have dropped all the big coin on this outdoor woodstove and related piping. The home owner is a good friend and I got involved after everything was in place. I do not have any electrical  wires that can communicate between the two boilers. I found out today that the boiler had two 1-1/4" tapping's. I spent a lot of time manifolding the 3/4" tapping's together. But I would have had to drain 400 + gallons of water with expensive additives. So, I guess it was justified.

I read the directions today for the first time. The wood boiler people do not want the return temperature to fall below 150° F for extended periods . So I think the 0014 @ 6.6 gpm isn't such a bad thing. It came with the boiler incase you used a shell and tube heat exchanger. Those little pumps are $$$. If I do outdoor reset I won't need high temperatures most of the season and I won't get the huge system dump load when the t-stat calls.



I would have spent all that money on insulation , windows and doors, a good boiler , out door reset , and an indirect water heater.

bill nye_3

Pictures

I will try to borrow a camera and post a picture or two.

SWEI

I'm guessing that

the 1" PEX is already buried?  Just wanted to makes sure that wasn't still an option.  I'm not a big fan of big pumps whenever I can find a way to make use of a small one.