I'm lost... Gasifier/Tank controls please?

Really good question. Eager to hear the answer on that

Welcome to the Boiler Room, Kevin.

I'm sure hot rod/master of sparks has some good stuff on that.

You might want to check out nofossil's very informative website:

http://www.nofossil.org/

Nofo is deep into controls, and other Alpha Geek pursuits.

Tarm will also put together a complete control diagram for you if you ask.

I haven't done the primary/secondary approach, but I think the basic issues are the same:

1) The storage tank can act as a heat load, and probably wants to be charged with top-to-bottom flow

2) The storage tank can be a heat source, and wants to be discharged with bottom-to-top flow

3) The storage tank may be inactive, either because there's no heat available for it, or there's no demand that it should supply.

4) There must be some system-level decision about the role of the storage tank.

In my case, I designed my system so that there's never more than one active heat source - wood, storage, or oil. The decision is based on outlet temperature. If the wood boiler is hot enough, it's the source. If not, storage is the source if it's hot enough. Failing that, oil is the source. I use a computer, but you could make those decisions with aquastats and relays.

In my case, each heat source has its own circulator. If that source is active and there's demand, the circulator runs.

Kevin O. Pulver said:

Hey guys,
This is my first day here and I haven't found my way around yet.
I do hydronic radiant heating but am installing my first gasifier for a customer.
It's a Tarm SP60 with 965 gallon tank.
I'm doing the primary/secondary piping like Hot Rod showed in another thread, but I don't know exactly how the storage tank circulator is controlled.
There's probably a thread here somewhere if I could find it. I'll post photos of all this when it's done. Thanks in advance.
Kevin

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Hey Kevin! Good to see you here. The first question I would ask is how you want the circ for the storage tank to run in the first place. Will you be extracting heat from it directly or via the primary loop?

Heaterman AKA S Ebels on the Wall

A differential control works well. A solar control is another name for it. tekmar, Resol, Heliodyne, dozens of them out there now. The Resols will even control the boiler and have variable speed output relays on some models.

Install the "collector" sensor on the primary loop downstream from your heating loads. The tank sensor midway on the storage. Anytime the boiler loop is warmer than the tank temperature, that fires the buffer tank circ. You can play with the settings, typically 10- 15 on the differential on, maybe 8 for the off. So the buffer gets charges anytime the heating, possibly DHW loads are being satisfied.

My boiler to primary loop circ is run by the 140F stat and control located on my ECO boiler. It's a cheap thermodisc sitting on the top of the boiler under the jacket. It works well for a 7 dollar control

So now the boiler only feeds the loop if it is 140f or more. The buffer circ runs when the loop is hot enough to suppply all the loads and has additional btus.

The zone circs run on a call for heat, of course. With concrete floor radiant and no high temperature requirements I can pull that buffer down to about 90F. so a 180- 90 range gets me a lot of storage "capacitence"

Mike "hydronic Mike" from tekmar planned out this this logic, and sent a schematic for me a few years back using all tekmar 155 differential controls. tekmar had 2 new solar controls on display at the CIPHEX show last week. maybe they have a dual delta t control available now to handle two functions from one control?

I did see controls in Europe that can handle solar, wood back up, buffer function, and even outdoor reset from one box. Data logging and internet connections also.

hr

master of sparks said:

I did see controls in Europe that can handle solar, wood back up, buffer function, and even outdoor reset from one box. Data logging and internet connections also.

hr

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Dang! I'm not the only one doing that?

They're copying you !!

A couple more solar differential controllers are the Goldline GL-30 and Steca TR301U. The Goldline is the more flexible of the two. You can find them on Ebay for around $100.

Kevin O. Pulver said:

Thanks guys,
I still don't understand for sure how the floor gets prioritized/satisfied before the storage tank starts sucking up the BTUS.
I'm doing primary/secondary with Variable Speed Injection feeding 3 zones in the concrete floor, and one high temp baseboard zone coming off the primary.
It's much like the drawing Hot rod had here somewhere. Any more explanation would be appreciated.
Kevin

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In a nutshell the storage system should be the last set of closely spaced tees on the primary loop. If the water returning from the primary heat loads is hotter than the storage tank the controller will turn the storage circulator on.

Kevin O. Pulver said:

NOW, what turns the tank circulator back on when the fire has gone out and the tank now becomes our heat source?

Click to expand...

Mine becomes the heat source when the boiler relay signals it is out of fuel or I shut it down manually. The pump is then uncoupled from the controller, a four way valve reverses flow and the pump runs when there is a demand for heat. All of the control is analog handled automatically through relays.

I think this Caleffi iSolar3 controller may be the ticket. It has 2 differential functions, priority and variable speed function. It has 10 pre-programed "arrangements" but you can also build custom programs. It comes with 4 sensors and has a pre-wired power cord.

I have a sample but haven't had a chance to install and try it for a dual set up. Find info about it at the Caleffi site.

It should watch and prioritize the heat load, and only charge the tank after heat is finished. It should keep that buffer circ running until it falls below the setpoint you program. In other words the lowest possible temperature you can send to the floor.

A 3 way motorized valve tied to outdoor reset would be sweet. It would assure you could drive that buffer down to the lowest possible useable temperature. Possibly within a few degrees of the min floor temperature, maybe as low as 76- 78f.

The Taco mix valve would be ideal for that. I've seen it done with the Viessmann mixer also.

hr

Here is a sweet little control and distribution logic a friend a Radiant Engineering shared, Siggy CADed it out.. It happens to be a solar drain back concept but could be wood fired, or backed up too.

The logic is this. Two delta t, aka differential or solar controls. Pick a brand they all do the same function. I like the new digital that store and share more info and have data screens. Easier to see, and log what is going on.

In this case one controller runs the solar input, simple enough.

The second delta t controller runs three way divertor valve.

A 3 way motorized mixing valve Taco, tekmar, Viesmann,a few others is run by an outdoor reset control function.

The "storage" sensor for the second delta t controller goes down stream of the 3 way motorized mixing valve. the "collector" sensor at the top of the storage. It POWERS the 3 way divertor valve at the storage tank. This allows that storage to be pulled down to the lowest possible temperatue. Based on outdoor reset, of course.

For solar you really, really, want to drag that tank temperature as low as possible every day to present the coolest possible temperature to the array the next morning. The cooler the return to the collector, the higher their efficiency and better their payback

The upper DHW preheat coil also adds to the draw down potential of the tank.

Same for any boiler really, the cooler the return the higher the efficiency. It's ALWAYS a delta t game.

In this drawing the backup boiler is a small water capacity electric boiler. As such it could pipe right through without much loss. If it were a larger as a fired, or wood boiler I'd primary secondary it into the loop.

The delta t control may have a function to "call on" the back up heater, most do.

I'd guess a contractor could buy the brains to this system for 5- 600 bucks. That Resol control may handle two of the three functions from one box.

Notice the way DHW is generated with a pre-heat coil in the solar tank, up high in the stratification, with an instantanous to back up. No standby losses, and the potential to "valve out" the instantanous in the summer. A LISTED anti scald valve at the DHW supplier is a MUST. ASSE 1017 point of distribution valve. Caleffi of course

Make sense?

hr

Sure, any VS control will run that portion of the system. With any injection mix there will be some "blending" going on at those closely spaced tees. . You may not pull the tank quite as low, but it functions the same. What attracted me to this is a simple, single circ powered system. The power consumption is the circ and a few 120 or 24 v ZVs and controls.

Without the electric boiler, of course, this would appeal to "off griders"

hr