Thermal Storage and Outdoor Reset

[BoiledOver]

When charging storage, the initial thought (in the beginning of gasser ownership) would be a one lap charge. That proved to be counter productive in my case. Excessive and conflicting on/off cycles of the blower and circulator proved to be less efficient. Two laps works quite well.

Drawing from storage demanded a one lap depletion, without ODR. With the use of ODR it now matches the charging strategy of a two lap rotation. As you can see from the following image and a little math, the total btu's used is right around a quarter million at the temps shown in a 14-1/2 hour period. For the Eko 25, a recharge of that amount is an easy ride. At double that, say a half million btu's, takes twice the time and attention to accomplish. Add the additional factor of bringing the boiler temp up to charging temps means for a 6 to 8 hour procedure which includes several reloads. So, I may rethink the charging theory again.

On the house side, ODR is giving favorable results. @Sparky The indoor feedback has so far been what I would expect. It shows best during the solar gains when it is closes the storage from the supply mix. On the other end, in frigid temps with strong winds, it did not keep up as well. What did work was to shift the reset ratio up for the cold snap. Immediately after installing the ODR control, I gave it a 1:1.4 curve from considering the house side of the system. After some trial and error, it is now at 1:1.43. During the cold stuff, 1:1.48 worked pretty good. Armatur doesn't include a decimal point on the LK 110 unit. A person could also bump the entire curve up by whatever degrees necessary to get the same result. Either way would require a reprogram when weather conditions level out.

 

[maple1]

Without ODR here, my charges are 2 laps and my discharges are usually 3 laps. Depending how far I charge & discharge.

 

[salecker]

If you guys are calling separate firings laps...
I do one firing a day,and draw from that for the rest of the day.
-40C temp the fire gets lit at 1 pm and gets shut off at 11 pm
-30C temp the fire gets lit at 3 pm and gets shut off at 11 pm
-20C temp the fire gets lit at 5 pm and gets shut off at 11 pm
And the firing times drop off as the temps warm up.We take our storage to close to 190F but are limited by the boiler shutoff which begins the idling phase at around 187F
That is the normal routine that our boiler goes through.No fancy resets and i have pumps that run continuously feeding the house,and the plate HX so my storage never stops moving.I don't know if the pimps were controlled by thermostats if i would get more millage from storage.
I had plans of trying to tweak the system for better results,but seeing it works pretty damn good the tweaking dropped down the list of things to do and hasn't moved back up.

 

[nhtreehouse]

Without ODR here, my charges are 2 laps and my discharges are usually 3 laps. Depending how far I charge & discharge.

Hey maple, Just wondering what the temperatures of the tank are for the charging and discharging laps? So far, my system is more or less a single lap each way, so I'd like to hear how your setup works. I understand you have regular fin tube emitter, so how far can you take storage down for a typical house load?

 

[nhtreehouse]

Definitely not suggesting your piping is wrong, just telling you what I have gong on here. If I were to apply to way my system is piped to your picture I would tell you that the vertical return to the 3 way valve would be teed before it hits the boiler flow. The thinking being the return water will get "sucked up" to the mix valve and the "boiler flow" will take the path of least resistance heading straight back to the boiler. I got the book "Plumbing Away" but honestly only looked at the pictures so please take anything I write with a grain of salt.

Actually, I think there is something amiss in how I plumbed it. At least with the current operating conditions. May be some minor re-plumbing in store this summer. In the middle of another full burn with some more instrumentation to try and deduce what is really happening.

 

[maple1]

Hey maple, Just wondering what the temperatures of the tank are for the charging and discharging laps? So far, my system is more or less a single lap each way, so I'd like to hear how your setup works. I understand you have regular fin tube emitter, so how far can you take storage down for a typical house load?

Charging usually starts at 120/130-140. I just lit a fire, after getting in from being out all day. Storage showing 125/135.

Loading unit governs my laps - keeping 140/160-165 boiler return/supply for the first lap. Which is actually say 120/160 storage supply/return. Or 125/160 today. The upper might go to 165 - usually does.

Second lap begins when storage gets to 160-165 throughout, i.e. once the thermocline gets to the bottom. I usually don't do a full second lap, so typically see 165/185 when done burning. As fire goes out but while loading unit still circulates while boiler cools, they even out to more like 180/170. Temps measured at 1/4 & 3/4 of storage height.

Drawing from storage they go something like 165/185, to 145/160, back down to 120/135. Give or take. I do have ordinary fin tube, but I guess quite a bit of it. Seems they oversized when it was designed & installed 21 years ago. Or it was designed at a more common sense (to me, now) design supply temp of say 165 vs. 180. That stuff was all voodoo when we built & I paid like no attention to it at the time, just let them do their thing.

 

[nhtreehouse]

That stuff was all voodoo when we built & I paid like no attention to it at the time, just let them do their thing.

Love that voodoo. There are some great stories in Dan Holohan's books about service guys putting in baseboard everywhere they can. They would first oversize the boiler, then install radiation to match the over-sized boiler. When Dan challenged them on why so much baseboard, they replied "gotta match the radiation to the boiler." He had a particularly funny picture of an inside corner with like 6" of baseboard on each leg.

Back to the topic at hand. My place didn't have any radiation in it at all, so I went with what was fairly easy to retrofit and had the lowest possible supply temps. Obviously some form of a radiant panel will work with the lowest supply water temps, but destroying all the floors/walls/ceilings wasn't really in the cards. So I went with over-sized panel rads.

One of the thoughts I've had on ODR is it should, in theory, lower your underground losses, as you are sending lower temperature water underground, and heat loss via conduction is proportional to T. Do folks think I have that wrong? For maple1, this isn't an issue, as the boiler, storage, and heat distribution piping is indoors. TCaldwell mixes down in his boilerhouse, JohnDolz has his system in the basement where both boiler and storage losses are recovered inside of the building envelope. salecker has the boiler in an external building, I don't know about the OP, BoiledOver.

I know some folks might think this is splitting hairs, but I'm guessing my standby losses + underground losses are not insignificant. I still have more work to do insulating piping in the boilerhouse, and insulation on the tank. Scrutinizing the Logstor data sheets, underground losses for the supply pipe alone are in the region of 20-25 BTU/HR for each linear foot underground, when supplied with 180 degree water.

Underground losses definitely were a factor in my choice to cut in an ODR mixer in the boilerhouse.