Replacing Boiler and Adding Storage

[nbroyer]

Hello,

Currently I have an old Franks Philip wood boiler supplementing my propane boiler. The configuration is shown in the current_boiler.jpg attached image. It works okay, but it idles a lot and I have to cut my firewood 12". I also do not have a boiler protection bypass loop and I know my dump zone doesn't work well. This summer I purchased a used EKO 25 with all the controls and a 500 gallon storage tank. The location of the ports in the tank aren't ideal. They are shown in tank.jpg. The tank is in the opposite direction of the load, as shown in boiler_unconnected_tank.jpg. I know I could just loop from the wood boiler to the tank and then have a separate loop from the tank to the load, but I would like to be able to heat the load directly from the wood boiler if the house is calling for heat and the wood boiler is up to temp. What's the best way to accomplish this with my setup?

Thanks in advance,
Nathan

 

[leon]

Hello Nathan,

The first thing I would like you to do is invest in two paper backs Pumping Away and Classic Hydronics.
These two paper back books are a great reference for hydronic heating and of all types.

You need to do a lot of plumbing repair to make your system work for you the right way.

Purchase these two paper backs and then you will see how to do this properly as they have a wealth of
information that Dan Holohan has written for both the plumbing novice and the professional plumber alike.

 

[velvetfoot]

I am totally no expert, and don't even have a wood boiler but I'll chime in anyway.

I think you're thinking of a two-pipe versus a four-pipe system. Bob Rohr posts a link to a publication that goes into this, I think. Plus there is stuff as stickies at the top of the forum.

The way I look at it, you want to have the zones have first crack at the hot water coming off the boiler. Note, I think you probably should put in a bypass (boiler protection) valve.

I think you could just extend the supply and return lines from the wood boiler, along with appropriate check valves, over to the tank, and add a pump just for the zones. Two lines: supply to top and return to bottom of tank. Then when the wood boiler is running and a zone calls for heat, some goes to the zone and the rest goes to the tank. When all zones call for heat at same time, most of the water off the boiler goes right to the zones and anything left over goes to the tank.

The flow in those line extensions in bi-directional. When charging, the flow in the line hooked into the existing supply line to the top of the tank goes to the tank. When running on the tank, it flows the opposite direction. Same thing for the return extension going to the bottom of the tank. This reverse flow is I think why you need a pump for the zones as well pump for each boiler.

You should get one of those fancy constant pressure pumps, or whatever they're called, for the zones, that adapts to how many zones are on.

They make things called loading groups or something like that, that are specifically for loading up the tank. Expensive. May or may not be worth it, I don't know.

You're gonna need a bigger expansion tank, you know.

That's my take, LOL.

 

[nbroyer]

Hi Leon,

Thanks for the advice. I don't have those books, but I have read many excerpts on his website that have been helpful.

Velvetfoot,

I appreciate the response. I've seen Bob's link that discusses the two vs four pipe system into the tank. I may have misunderstood, but I was under the impression that for the two pipe system the T's needed to be as close to the tank as possible. If this isn't the case, this would make things much simpler than I imagined.

I will have a boiler protection loop with the new boiler. I also have a large expansion tank that came with the new boiler and tank.

Thanks,
Nathan

 

[Bob Rohr]

Here is a link to the Idronics that explains the various buffer tank piping options.

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_17_na.pdf

Yes the tees should be close to the tank, or that header pipe needs to be generously sized to keep pressure drop as low as possible.

 

[nbroyer]

Hi Bob,

Thanks for the link and clarifying what's needed for the two pipe scenario. I have 1-1/4" pipe going from the wood boiler to the load, currently. If I were to tee off above the new wood boiler, what size pipe would I need from the tee to the tank to keep the pressure drop as low as possible? Would this be your recommendation in my situation, or do you think it's better to tee off close to the tank? I would use more material teeing close to the tank, but the larger header pipe needed to tee above the boiler may be costly?

Thanks again,
Nathan

 

[nbroyer]

Hoping to rejuvenate this thread. I'm looking to do this immediately (actually hoped to have it done by now), so any help is really appreciated. Thanks!

 

[Nofossil]

I'd agree with other posts that suggest that you have some replumbing to do to get it right. Like so many things, it's not like there's one perfect solution, but you do need boiler protection and anything you can do to promote stratification in storage will help. Mostly tha means keeps flow rates as low as you can and still get the job done.

If you can approximate the schematic below you'll be in pretty good shape. You can use tees in and out of storage (the two pipe instead of the four pipe solution) because of the way your storage connections enter the tank.



In this design all circulators have flow-checks. Ideally the wood circ and especially the load circ are variable speed - a Grundfos Alpha would be a perfect load circ if you have zone valve that provide some restriction, and a Taco Viridian set up to maintain a target wood boiler outlet temp would be great as a wood boiler circ.