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Nofossil

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In the spirit of 'Questions That Ought To Be Frequently Asked' (QTOTBFA?) here are a few things I wish I'd known before embarking on the wood boiler journey. I made some of these mistakes, but some I avoided through blind luck. These are in no particular order, and are just my own observations. Anyone else have additions?

1) If you do a sidearm or any other DHW heating scheme that could result in unsafe temperatures, use a tempering valve (Honeywell AM101 works nicely) to protect hot water users from scalding.

2) Closed systems are closed to protect the boiler and pumps from corrosion. Fresh water or water exposed to air introduces dissolved oxygen. Flushing your system increases corrosion.

3) Circulators want to be installed with the motor shaft horizontal.

4) If you have a gasifier, you need dry wood. Wood doesn't dry until it's cut, split, and stacked. It takes at least a year minimum under ideal conditions to get wood dry enough.

5) With a wood boiler (especially with storage), plan lots of extra baseboard so that you can heat with cooler water.

6) Radiant heat is great. Increases the amount of usable heat that you can get from storage.

7) Use solar to heat your DHW first, rather than heating storage. Dump any extra heat to storage.

8) If you can do it, you really want your storage indoors.

9) If you can do it, pressurized storage is preferable.

10) Getting air out of your system is a pain. Get a good boiler room trap - Spirovent is good but expensive. Put vents at the high points of all loops, preferably at the point where the water starts heading back down.

11) If you have an open tank, you'll wish you had more coil surface area.

12) Indirect DHW tanks are an excellent companion to a wood boiler.

13) Sidearms are an excellent invention, especially if you don't have an indirect tank. However, see #1 above.

14) Thermosiphoning is your friend and enemy. Think very carefully about where intentional thermosiphoning might help, as well as where unintentional thermosiphoning might hurt, Any time hot water is in a location below cooler water, there's an opportunity for this to happen.

15) Install valves to isolate components for servicing / replacement. Use gate valves. Ball valves are easier to open and close, but they are more prone to develop unserviceable stem leaks. Replacing a valve is a real pain - you often don't have any way to isolate it....
 
nofossil said:
15) Install valves to isolate components for servicing / replacement. Use gate valves. Ball valves are easier to open and close, but they are more prone to develop unserviceable stem leaks. Replacing a valve is a real pain - you often don't have any way to isolate it....

Agreed on everything except this. Gate valves are far more likely to leak. And they often leak through the valve, eliminating the purpose of having an isolation valve.

The stem on a ball valve can be tightened just as easily as on a gate valve. You might have to loosen the nut holding the handle, first, but that's no big deal. And the stem can be re-packed on any quality valve, regardless of type.

Joe
 
BrownianHeatingTech said:
And the stem can be re-packed on any quality valve, regardless of type.

Joe

'Quality' might be the issue here. I had a ball valve that absolutely could not be repacked - a non-repairable valve is a Bad Thing.

Don't tell me you don't have any additional words of wisdom?
 
nofossil said:
BrownianHeatingTech said:
And the stem can be re-packed on any quality valve, regardless of type.
'Quality' might be the issue here. I had a ball valve that absolutely could not be repacked - a non-repairable valve is a Bad Thing.

Don't tell me you don't have any additional words of wisdom?

Use only quality valves and other components. :) If in doubt, ask here, search the web, and look things over carefully to see if they are well-made and repairable. As you said, replacing components is not much fun, particularly in the case of valves.

In that vein... install unions in convenient locations to allow for replacement of components. In general, look for ways to make maintenance easier. Anything mechanical can fail, and you don't want to spend three hours on a half-hour job, because you put an item 2" too close to a neighboring item, and couldn't easily get at the bolts/screws/whatever that you needed to. Pay attention not just to the minimum clearances in the manuals, but also to the recommended clearances for service - anywhere there is a difference, you know that's an area you might be crouching to try and work, so consider going even better than the recommendations.

I'd also add that putting a mixing valve on your domestic hot water tank is always a good idea, even without a sidearm. They are required in some areas. Expansion tanks are also required in some areas (DHW expansion tanks are different from heating system tanks). Having the mixing valve installed allows for superheating the tank, which can give longer run times.

I'd amend 9 to say that pressurized storage is preferable on smaller systems, and unpressurized on larger systems. I wouldn't realistically consider pressurized storage above 1000 gallons, except for certain commercial applications.

I'd amend 6 to note that radiators are not quite as good as in-floor radiant, but they are better than baseboard, in most cases.

In new construction or in cases where the existing system is being removed, I'd note that electric is a very legitimate backup heat source (mostly for forced-air systems). If it will only be used on rare occasions, the cost per kw is not important, and the lower installation cost can make the system more affordable, or allow for investment in other areas where a few extra dollars can make major improvements (like variable-speed pumps, for one example, or more insulation, for another).

Joe
 
I would add for any boiler system, check pH of the water even if you don't check anything else. Acidic water (ph less than 7) is a real corrosion producer. Swimming pool supply places have litmus paper to check pH, as do some health food stores. Desirable pH is 8-9.
 
I agree with BrownianHeatingTech.... Gate valves suck...... I have a brand new one (Mueller to boot!) on my tank that had a slow drip from the day it was new when shut off....... (Through the valve, not the handle)

I've reused many ball valves in my project.... A couple leaked around the packing... Tighten it up just a tad and good as new.....

And they SHUT OFF all the way....
 
How about...

Protecting the boiler from cold return water with a mixing valve on the return.

Keep flue temps at or above 300F to protect from condensing flue gasses.
 
Perhaps an obvious question, but from a relative beginner...

What, in #12, is an indirect DHW tank? I've got a tarm 40 coming, with storage. My current setup is oil with perhaps a 100 gallon hot water tank on a seperate loop. What's my best approach to sensible heating for DHW? Should I get the DHW coil in the Tarm, or just go with electric on-demand. My hot water demands are far-spread in my house, and can be considerable, as I run a B&B;on weekends (but not at all busy during the winter months.

Any comments would be greatly appreciated.

Thanks
 
All excellent suggestions and observations.

I'd add getting a stack temp thermometer so that you can see what your boiler is actually doing.

And maybe because it's one of the few things I'm good at, I'd suggest accumulating more wood than you think you'll burn in any given season.
 
penfrydd said:
Perhaps an obvious question, but from a relative beginner...

What, in #12, is an indirect DHW tank? I've got a tarm 40 coming, with storage. My current setup is oil with perhaps a 100 gallon hot water tank on a seperate loop. What's my best approach to sensible heating for DHW? Should I get the DHW coil in the Tarm, or just go with electric on-demand. My hot water demands are far-spread in my house, and can be considerable, as I run a B&B;on weekends (but not at all busy during the winter months.

Any comments would be greatly appreciated.

Thanks

If your hot water is a zone loop off of your heating system, then my guess is that it might be an indirect unit. They usually have a coil inside of them for transferring heat from the hydronic system to the potable DHW tank. If not, there are flat plate hx's and side arms that can do that for you in your new setup.

If you are running with storage, it might not make sense to have a coil in the Tarm, as there will be periods when it is not hot. However, you could preheat the water in a coil before it goes into the tank, minimizing the amount the tank zone/loop has to run.

What type of storage are you getting? Is it from Tarm?
 
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