Boiler plumbing design

Years ago I bought a wood fired boiler to be plumbed in with the existing oil fired boiler. The company I bought the boiler from desgined the dual plumbing job and the additional electrical controls. To make a long story short, their design did not work for beans. Since then I have re-plumbed the boiler and re-wired it, it worked better, but not the way it should. I have a new design on paper and was wondering if I posted it on here would someone on here be willing to look at it and give it their blessing or suggest changes so it would work.

 

Always willing to look... go ahead and post it...

 

This drawing just shows the basic plumbing layout. The return line has the 4 zone valves on it, by opening one valve and closing two you can bypass the wood boiler and just run oil or gas. Or by closing one valve and opening two you can run the wood boiler and have the controls of the oil boiler distribute the hot water to the zones as needed. Maybe I ought to have run a pipe from the wood boiler to the expansion tank also.

This drawing shows the electrical part of the system. I don’t have the zones wiring drawn. The L6006A-1145 Honeywell Aqua stat sits on the wood boiler. When the temperature in the wood boiler reaches 140 degrees it turns power on to the oil boiler controls. The oil boiler has all the thermostat and zone valves wired to it. When powered up the oil boiler will run thinking it has a fire in it. There is a switch between the controls and the burner gun, that is turned off when you don’t want to have oil back-up. That switch can be turned on when you go to bed or on vacation. The switch on top of the controls should be turned on also when going away for weekend or vacation.

My main question is will the oil boiler controls run the pump and open the zone valves when the burner gun is not firing if the controls don’t detect a flame. And if so is there a way around this? The burner gun on this boiler doen not have seperate wires going from a photo eye to the boiler controls. Is there some other problems in this system that I am not seeing.

I am not a HVAC person, I just know enough to be a little dangerous.

 

Hi Jerome,

This would be my preferred way to pipe that set-up.

Jerome.pdf
As for controls, set up the oil boilers aquastat to be lower than what the wood boiler would normally put out.
Set the wood boiler to start the pump at say 160 or so, and that will kick on the boiler circ and inject it's flow into the system loop.
If the water supplied to the oil fired boiler is higher than the aquastat's setpoint plus the differential the burner will not fire. It will take a bit of play to getthe setting where you want them. Be cautiuos about boiler minimum water temps for both.

You zone controls "should" function propely but I don't see where you describe what they are, but generally they dont need the burner on to work, actually they call the burner.

Good Luck

 

Is the wood boiler system open to atmosphere, if so you'll need a heat exchanger somewhere in the system.

 

Now there is a good point, good to see someone mention that

 

Jerome, I think you should give us some specifics... like the MAKE and MODEL of each boiler.

I do NOT like the idea of having to open and close valves and switch switches all the time... way too much room for operator error...

Can you say KABOOM?

The preferred method IMHO is to pipe the wood boiler in parallel with the oil/gas boiler, with a heat exchanger if needed. All the controls should be automated so that there is no chance of a mishap, and proper safety precautions taken.

Example: What happens if you've got a nice wood fire going, and the power goes out?

 

I thought a closed system uses an expansion tank and an open system did not need one.

 

NJ Trooper I was hopeing you would reply, The wood boiler is a Buderus, model 02.40-6. The oil boiler is a Burnham with a Wayne oil gun M-SR, model A1250. The controls are Honeywell aquastat- protecto relay R8182E R8182F.

The way my current system is plumbed and wired you open and close no valves and switch no switches. It does not work like it should and I want to change it.

Kaboom is not in my vocabualry, sounds like a big diaster.

I am not sure what a parallel system is, it is currently plumbed similar to what TO Heating posted in his pdf. I have two pumps, eight zone valves, and eight thermostats. It does not work right and I want to change it.

What happens if you have a nice fire and the power goes out? You turn on the exhaust fan in the boiler room. You then open the loading door and with tongs you remove wood and carry it outside away from buildings. If there is a hot bed of coals you take the ash shovel and shovel the red coals into a metal bucket and with gloves on you carry the bucket outside the house. I have done that once before.

To Heating wanted to see how I plan to wire the zone valves in. I did not know there was more than one way to wire zone valves for an oil boiler. Here is the drawing.



This last picture is of the current system that does not work properly. Whichever boiler is fireing the other boiler is just as hot because whichever circulating pump is running, water is also going into the boiler that is not fireing. That in turn confuses the boilers. The confusion is caused by the aquastat on the wood boiler that switches power back and forth depending on what temperature the wood boiler is at. That is why I want one pump and one set of zone valves.

 

I think this is either the same, or very similar to yours...

http://www.buderus.us/files/20100122...0618151-01.pdf

Take a look at figure 47

Consider some of the manufacturer recommended installation details.

 

more importantly, an open system admits a lot of oxygen...
There is an expansion tank in the diagram.

 

Look into a Taco ZVC404 for your zone valves.
Cleans up the wiring and gives indicator lights.
Has a dry contact for the boiler, and another the you can switch line voltage for a system circ.

 

What is a taco zvc404? Are they zone valves or zone circulating pumps? I don't have access to information on this product. Don't know what you mean by cleans up the wireing and gives you indicator lights.
What do you mean by you can switch line voltage for a system circuit?

 

I do not fully understand the manufactures installation details

 

You must learn how to use Google!

 

true, but a large number of wood boilers ARE open systems, and designed for that. Thus the need for the heat exchanger to keep the open side open, and the closed side closed.

 

I did the google thing and found the ZVC 404 to be a zone valve controller. looks fairly simple to wire up.

I am familar with Honeywell zone valve wiring so I might stay with them.

It dawned on me today that I can wire my existing oil boiler the way that I want to wire it after I re-plumb it. By doing so I will find out if the system will work as I want it to before I go to all the work of the re-plumb job. The current plumbing system will not work real great but by being careful I will find out what I want to know.
Thanks for the suggestions and help you did give

 

NJ Trooper, I looked at the buderus installation examples and electrical connection schemes a little more and feel I better understand them now. I do have a couple of questions though.

I googled shunt pump and read a little about shunt pumps, it looks like pump #3 would be a benefit to the system. Would just need to know what size pump to use and the correct flow control valve to use. Shunt pump #4 pumps to a storage tank, what is this storage tank for and where would the return lines go back in if there is one?

If I understand the symbols correctly ther are two flow control valves one upstream of a shunt pump #3 and another downstream of the heating pump #2. Would these valves be just a valve with a flapper in them or something different.


I don't think you need it but here is the electrical also

 

This diagram does have a 'dump zone', but what I don't see is a 'power fail' dump zone.

P3 is set up to circulate through the woody when the 160° aquastat is below setpoint, assuring flow through the boiler as it was coming up to temp, and P4 would turn on when above that setpoint.

I'm not sure where the optional storage tank would return! It is what it says, a large tank to be used as a storage 'battery'... and logic would tell us that there must be some way to discharge and recharge it... so I would guess that it would return to the return... I notice that they say NO CHECK VALVE... I believe this is so that it could flow BOTH directions... from the supply to the tank when recharging, and the reverse when discharging... but then that would indicate that there be something that turn P4 OFF at some point, and I don't see that.

Could be any flow-check valve... or a pump with internal flow check.

P3 would be a small-ish pump, wouldn't need a ton of flow... an 007 or a 15-58 would probably be fine.