Mandatory reading

It certainly does bear repeating. Thanks. So many of the questions that come up on the Boiler Room and the Hearth Room arise from a fundamental misunderstanding of the efficient burning of wood. Not surprising because most people understand wood burning from a camp fire or open air fireplace. Forum pros, contributors and lurkers should take this article to heart and follow its expert advice. Many questions on moisture content, seasoning wood, is storage needed, and gasser or not are answered. Of course, contrary choices may be made, but hopefully they can be made based more on facts and less on misinformation or lack of knowledge.

Seems like sticky material - maybe it could be linked in one?

piping my storage tank this week. noticed that in there storage diagram they put the expansion tank on the zone side of storage. ???? why that placement?

8nrider said:

piping my storage tank this week. noticed that in there storage diagram they put the expansion tank on the zone side of storage. ???? why that placement?

Click to expand...

One thing about that set up is if you happen to let your storage cool down ,it would take a long time to get usable heat off your boiler.
HD.

The theory of how the whole system is set up is to me a standard for all to follow. To ansswer the useable heat question, the simple fix would be to have the house distribution tee'd in right at the boilers entrance to the thermal storage. In my system, as soon as my boiler circulator turns on (based on boiler controler set temp), I have useable heat, there is a little bit of hydraulic separation that is lost, but with an injection mixing, the pump regulates itself, and doesnt stress the temp control as a mixing valve would. A simple swing check, or a integral check in a pump fixes this.

8nrider said:

piping my storage tank this week. noticed that in there storage diagram they put the expansion tank on the zone side of storage. ???? why that placement?

Click to expand...

This expansion tank on the zone side of storage became very clear to me this weekend after letting my storage temperature deplete to a level lower than usual.I had no pressure on the zone side yet still had plenty of pressure the boiler side of the storage.Since my boiler was cold my TRV was preventing expansion water to reach the zone side and since the storage is 660 gal. and the boiler is only 20 gal. I can see the importance of having the expansion tank on the zone side where the effects of expansion and contraction are much greater.Your boiler side will still be able to accept water from the expansion tank all the way down to the temp of the TRV which should still allow plenty of pressure for the next fire.

Yes indeed. Storage is highly desirable and arguably necessary for systems with an archetypal downdraft wood gasifier boiler. And gasification boilers need dry wood, and they need return temperature protection.

As for the system presented, anyone considering it as a model for their own system should be aware of a few things.

First power-failure heat-dump is accomplished with a state-of-the-art return temperature control module that incorporates a low-resistance back-flow preventer flap that allows convection flow in the event of power-failure. But then there's a conventional angled swing-check up top. This defeats the benefit of the low-resistance flap. And since they call it a back-flow preventer because it prevents back-flow, the check-valve up top is not needed to begin with.

And as shown, the system serves low temperature emitters exclusively, and only supplies some of the DHW load incidentally. As such the design doesn't need maintenance of stratification as a design goal. If you want to supply some baseboard, or a water-to-air HX, or if you want to supply all of your DHW needs with higher-temperature water, then a design that preserves stratification would be necessary.

The outdoor reset switch-over logic is necessitated by the all-mixed all-the-time design. This is a brilliant use of complexity to overcome a design shortcoming. With proper maintenance of stratification all you need is an aquastat, since with stratification either top of storage is hot or it isn't.

As for DWH, since the design seems to assume that the storage tank is inside the dwelling, current best-practice would be simply to immerse a tankless coil [ironically] into the top of the storage tank using a port provided for that purpose.

Others have complained that injecting hot water from one end of the storage tank and pulling in from the opposite end would delay unacceptably the availability of hot water when the wood boiler is re-fired. Since there's not a lot of water at the top of the tank, the arrangement shown would allow hot water to float right across the top of the tank reasonably fast. Then again, teeing the load line into the line from the boiler after it goes into storage similar to as seen in 'Simplest' would work even better with no downside.

--ewd

Well thats good! I was worried about how long it would take to get usable heat off my 150 gal. primary buffer tank. Cant wait should have it fired up by next weekend.
HD.

Transitions, Part 2 is now available online at

http://www.pmmag.com/Articles/Column/BNP_GUID_9-5-2006_A_10000000000001131109

Thanks Steve,I was eagerly waiting for that.