power outage -full head

[Jersey Bill]

It finally happened. I have absolutely no provisions for this event. I have talked about it, read about it, designed it for others, but done nothing on my system.
I went to bed early last night, about 10:00 p.m. because of a busy day today. We are pouring a slab for a masonry heater, concrete @ 8:00 am. Any way at 11, I hear the alarm beeping because the power failed. I loaded the boiler full before bed, so the boiler was cranking when the power went out. When I got into the boiler room with my flashlight (the battery emergency backup light is on the floor, not installed) the boiler supply was at 230, the return was @ 210. System pressure was @ 25 PSI. I hung around for a while, things appeared stable so I went back to bed.
At 3:00 I woke up to a funny smell. Still no power. Both temp. gauges were over scale, they max. out @ 245. I thought that I should get some feed water in to the system, so I filled a bucket from the drain to let some hot water out. Eventually the pressure started to drop to get down to the fill pressure @ 20. Then the boiler blowoff pops. Sprays the boiler room with water and fills it with steam. I was splattered, pretty wet, but not burned. Had to be a pretty funny scene, from the outside, I was in my pajamas.
Now the primary loop temp. gauge was reading cool, there was no water in the pipe. I could hear water popping in the boiler, then it blew again.
That lasted another 5 seconds, and I thought that I had to get some water into the boiler. I got some hoses and connected the boiler drain up to the slop sink faucet. The trick here was to have a female-female hose connector. I did. Then I slowly bled cold water into the bottom of the boiler. The system pressure started to go up so I connected the primary loop drain to a hose and put in in the sink to drain. I balanced the flow so the system pressure stabilized and the boiler temp. started to drop.
When the boiler got down to 150, I shut off the water. The system was stable, so I prepared for a power up, killed the house main CB and went back to bed. At 6:00 I switched on the main house CB and everything came to life. I opened up the air and the boiler fired right up from fuel still inside. Damage? so far some insulation melted off the pipes, thats it. I am lucky !

What can I say that I learned from this event? I just confirmed Murphy's law- If it Can happen, it Will happen. ( and it did)
I have to plan for the next event like this, and installing the emergency light isn't a bad idea either.

 

[atlarge54]

I have an el cheapo 400w inverter $20 at Menards and two large marine batteries which spend the summer on the water and winter in my crawl space. If I'm home and the power goes out I just plug in the pumps. My system doesn't need overheat protection so no big deal if I'm gone. You'll need something with an automatic transfer switch. A friend of mine has an automatic system for his corn burner, seems like he paid $500 not inc. battery. I'd say you were pretty lucky for the most part. Ain't free heat great? LOL

 

[stee6043]

I can't believe you went back to bed with 230 and 25psi showing on the gauge! Holy smokes...you are wayyyyy more relaxed and trusting than I am....

 

[Medman]

I'd like more detail on your PLC system - I have seen those GE fanuc units for sale relatively cheap.
Do you have more info on the system, including inputs, outputs, etc?

 

[Jersey Bill]

Its more complicated than just putting the wood boiler on a ups. Since its primary-secondary, circulating the water through the wood boiler alone wont take away the heat. And, I need to modify the controls so that the fan goes off in an outage while the pump is on the ups. The shotgun method to fix this problem is to put the whole boiler system on a UPS. I would need about 2 kw.

Clearly I shouldn't have gone back to bed. I should have started the cold water enema right then. But it still took 4 hours for the temp to go from 230 to 260. Hindsight is 20/20. If the outage was shorter or I had less fuel in the boiler when the power went out I would have been fine.

For the PLC, of the folks that have programmable controllers, everyone has their favorite. I happen to be more familiar with the Fanuc 90/30, although I work with Alllen Bradley and Siemens also. There is stuff for cheap on Ebay, and I have bought plenty of stuff there, but sometimes what I need isn't on ebay. Medman, did you want to see my control drawings , or info on the Fanuc 90/30? They have any input or output card that you might need.

 

[Medman]

The Fanuc 90/30 looks interesting because of cost and availability on eBay and elsewhere. My experience with PLC's is limited to AB, and that from some years ago. However I am not afraid to get something up and running here. I would like to know which modules are for temp input, whether converters fot thermocouples are necessary, etc.
This would be a winter project for me to get running, as I can already see the need for a more sophisticated and programmable control system than the semi-automated system used now. I am just finishing install and I already have five relays installed. A PLC would simplify things for me.

I have also seen PLC's from other companies on eBay, but I am unsure about aquiring temps on these units. Some are overkill for my application. Since my experience with PLC's is limited, I don't even know at this point what I really need. I would appreciate any guidance you could give, especially about programming software - ease of use, availability, etc.

 

[Jersey Bill]

Medman,
dont let the tail wag the dog. To decide on any control system, you need to start from the system. Create a sequence of operations.
here is an example:
if the living room stat calls for heat, close the demand relay, and open the zone valve
if the outdoor temp is below 20, turn on the baseboard zone valve
if the loop water is greater that the storage tank temp, and above 180, then shift the valve to divert water into the storage tank.
if the storage tank is enabled and the loop is cooler than the tank then shift the reversing valve so the loop water enters from the bottom.

Going to a programmable controller is a big step. I have the AB software because a company that I work for paid for the license. That software is about $1k, plus updates. The GE (PC) software called Prophecy Machine Edition, is about $800.
The benefit from an industrial controller is that there is a large installed customer base, with plenty of folks that can program, maintain, troubleshoot.

I just did a design for a friend of mine. I chose to use a Siemens S7-200 because it was less expensive than the GE fanuc 90/30. . The 90/30 is a workhorse and is overkill for a house. They have all the card i/o types that you need- thermocouples, relay outputs analog, whatever. The PLC was expensive, but his system has a wood boiler, gas boiler, storage tank, so by the time I added up the price for many many tekmar controllers to do the job, I got the PLC with a small color touchscreen for less, and it does far more.

 

[Medman]

Thanks for the info. I already have the logic sequences worked out, I did them for the relay controls. As I was laying them out, I was thinking the whole time that this would be so much easier to control with a PLC. I have been looking at units that are lower in cost and come with software. Some I have seen but know nothing about are Eaton (Cutler-Hammer), IDEC, Crouzet, even Panasonic.
As you say, the advantage of industrial controls is that there is a larger knowledge base.

 

[overshot]

You can try Automation Direct - stuff is cheap and the software is free up to 100 words

 

[rickh1001]

After reading Jersey's experience, I just ordered a Tripp Lite 750W inverter/charger. I will hook it up with a couple of marine batteries. I am running an EKO 60, with 500 gal pressurized storage, so simply keeping the primary circ going for a few hours will be enough to absorb the heat from even a full load. I could hook up one or two of the zone circulators (Taco 007's) in addition, if I want to be sure of getting rid of any heat.

There are basically two failure modes for my system - a power outage, and a failed primary circulator.

I already had the second happen. A few days after its initial startup, I filled the chamber to the brim with wood for its nightly burn. Shortly thereafter, it blew the 2A fuse on the controller. I realized I was in a tough spot, since I had no spare fuses (dumb) and a full load of wood just starting up. I managed to pull out much of the top of the load, and with gloves even managed to get out some of the charred, smoldering pieces, stinking and smoking up the cellar. I threw them out in the driveway, where they burned like a little bonfire. I still had quite a bit of wood in the chamber however. I found a similar fuse in the back of a piece of electronic equipment I had lying around, and it too blew. It turns out the new Taco circulator had seized up due to a motor bearing failure (factory defect). I had hoped the Eko would thermosyphon, but the internal check valve on the circ presented too much resistance. Anyway, I baby sat it, shutting off all the air, and still watching the temp climb up above the limit. I lucked out, and while it overheated, it wasn't too bad, and didn't melt the sensor or anything.

While the inverter/charger will solve the power outage risk, there is still the problem of a failed circulator. I am thinking about creating a small secondary loop using another circulator, tapping off of the 1/2" pipe above the boiler where I have the low water cutoff mounted. It could come on with an aquastat set at a high temp mounted on the top boiler supply pipe, and could run off the same inverter/charger. In the event of a failure of the primary circulator, it should move enough water through the storage tank to prevent boil-over. This is all nothing more than a fancy dump zone, but it seems simple enough, and should work.

If I have another emergency like this, I am not sure if it is best to let the Eko boiler over and run dry, or to try to slowly introduce some water into it. It seems the shock of the cold water would be more damaging than letting it go way over temp dry, even though it would need new temperature sensors afterwards.

 

[stee6043]

We all know that there is an emergency cooling coil on our EKO's. Has anyone who's had a burned out circ or a power failure ever thought to send some cold water through the 3/4" pipes on either side of the EKO? Seems like this is what it was designed for, right? I myself have an APC UPS but that won't help with a busted circ...

 

[rickh1001]

Stee6043,

I thought of that, and it still is a good approach. The only problem is see is the need to either tie it into the boiler water circuit, or to have its own little loop that would have to be supplied. Plus, I am not sure how much heat it would remove from the boiler.

It seems to me, for my setup at least, that it is simpler to supply a spare circulator, piped in parallel to the existing 1.5" primary piping. Like a spare tire, it would only be needed if the main circulator failed, and the boiler started to overtemp. I was also wondering if the alarm or some other signal on the existing controller could be used to kick in the auxilliary circulator upon overtemp. The necessary power will be handled by the inverter/battery or regular electric, so the Eko controller will stay running. All I need is a signal to start up the auxilliary circ if the boiler goes over, say 205F.

I hadn't thought all that much about this type of redundancy when I was first installing the boiler. However, when the boiler is running flat out, with a deep bed of coals and more wood on top, it is almost scary to think of how much heat energy is sitting there in the firebox. If I am present, I can always change out the circulator quickly enough to avoid a crisis, but if I am away, there would be one heck of a lot of heat to get dissipated. That's why they have pressure relief valves, but I hate to think of what the damage to the boiler might be.

 

[ManiacPD]

I hear you on this one. We lost power this past Sunday evening. Just stoked the boiler, same as you. I checked the temp and it was 205. I shut my draft as tight as I could and went to find the generator.

Took me about 10 minutes to get the generator out (it was buried from all the summer projects) and hooked up. Came back and it was 215 but the circulator was running and things settled down. I guess when it's loaded with wood there's no time to mess around.

Needless to say I was sweating and it was 20 degrees out with 40mph gusts...

 

[Jersey Bill]

After some time to digest the events, here is what I came up with.
My number 1 question was why didn't the boiler blowoff sooner. I think that my expansion tank is pretty large, its a 60V. The tank had enough capacity to absorb the expansion of the water in the boiler going up to 230 deg, and above. The increase in water temperature caused convection circulation from the boiler, through the primary (uncirculating) loop and into the system. An 80 gallon pressure storage tank is nearby and it heated up enough to melt the insulation off the pipes. The really hot water also heated up the domestic water indirect heater, and heated piping as far as 15 feet away from the boiler.
Why did the boiler blowoff? Because I did the wrong thing. I tried to get fresh, cool water into the system by lowering the pressure. It was at 25 psi, my fill pressure is at 12 psi. Lowering the pressure caused the water to boil. It would have been fine if i did nothing.
What did I do right? Back feeding cold water into the boiler drain was the key, and I set up a water bleed in the system to prevent the pressure from rising. This refilled the boiler with water and brought the heat away without electricity. Also, I never opened the fire doors. I have a chimney fire stick that might have put the fire out. Opening a door could cause a flashback when the fire is oxygen deprived. It would have filled the boiler room with smoke- yuck.
What would I do next time? Maybe nothing. If the outage is less than 4 hours my system can handle it. Maybe after an hour I can crank up my generator to let the wood boiler burn down, or fire it back up. The problem with the generator is that its big and loud. I think that its a 5 kw, probably enough for the whole house normal activity, no ac. I think running it at night is pushing my luck with the neighbors. A fuel cell would be ideal. If money only grew on trees......

 

[Eric Johnson]

I think it's much better to feed cold water into the boiler than let it go dry. If you lose the water in the jacket, all kinds of bad things will happen to the steel and welds. With water present, it's not going to get over 300 degrees, which is not all that hot as far as the steel is concerned.

 

[Duetech]

In the case of a power outage on my EKO40 I can close the secondary and primary air. Primary is basically irrelevant but secondary air is very important because the secondary air inlets act as draft feed tubes and with the secondary air closed I can essentially starve the fire of oxygen. I have a generator but some times things don't always work as intended so my first step is to be sure the air is closed. Knowing if you can shut down the fire will go a long way in preventing an over heat situation from getting out of hand.

 

[timberr]

I am just hours away from finishing my system, with any luck the 3 valve's I am waiting for will show up tomorrow and I will be filling the system Saturday and gasifying! I have been contemplating the same problem. I was thinking about about running a "T" on the supply side (before the circ pump) and putting a Taco zone valve that when it losses power it OPEN's. I would have a run of baseboard to dissipate heat then return it to the return side of the boiler with a flow check to insure under normal operation there wouldn't be any conflict. I like this because it would not involve any power and should work without my being their.

My question has been, how much baseboard would be needed? I am new to this, I have gotten a lot of good info from you folks how about it, realistically how much baseboard would one need for a Eko 25?

 

[hayrack]

An automag would solve power out overheat problems. They are closed with power and open on loss of power. They should be put into the zone you want to heat during a power outage. I believe in Maine it is code for a solid fuel installation. I have one hooked into my main floor zone and it has worked great for 8 yrs. There is never water on the floor from the relief valve blowing off.

 

[peakbagger]

Some general info on how well a boiler can survive a no water event on an industrial scale. The pulp and paper industry uses a boiler to recycle left over pulping chemicals for reuse in making pulp. Its called a recovery boiler. The boiler design is somewhat standard except that there is a tank of molten chemicals in the bottom of the boiler (known as smelt) after the organics are burned off. This smelt at the bottom of the boiler is very hot, think lava, if the boiler springs a tube leak, the water from the leak can occasionally make it down to the smelt bed where it rapidly vaporizes and expands in volume by a substantial amount. The resultant of this is a smelt/water explosion, and its usually a multimillion dollar event as the boiler panels usually blow out sidewards for several stories of the boiler. Folks have been killed over the years, by these events.

Needless to say, the owners and operators of these boilers, do not want to experience a smelt water reaction and have banded together over the years to come up with a way of preventing them. On the preventative side, they do extensive yearly testing and maintenance, but ultimately if a leak occurs, the entire boiler is drained dry as fast as possible, generally in a matter of a few minutes. The boiler that I was familiar with was a 850 PSI /825 degree F unit running at 380,000 pounds of steam per hour. It went through at least one of these emergency drains and came back up with no other leaks except the one that caused the problem in the first place. Note that the standard rule of thumb that each rapid drain event was equal to one year of service life.

On a completely different scale my, old Burnham SFB wood boiler, was equipped with a safety relief that would trip a couple of PSI less than the main safety, it is piped directly into the combustion zone of the boiler. I hope it never goes off, but it would put out the fire pretty quickly.

 

[rickh1001]

Eric,

In regards to having water present in the boiler, I would agree. However, I had one event soon after I installed my EKO 60, where the primary circulator failed, and I had an overheat. I pulled the wood out of the chamber, and got through it, but I worried about letting cold replacement water in, and shocking the HX tubing and welds. I introduced some water very slowly over an hour or so. However, I am not sure in another emergency, whether it would be better to just let things go and run dry, or to let water in slowly, even though I could hear it boiling and steaming as it entered the hot boiler.

Since the first event, I have added a deep-cycle marine battery and a 750W inverter running the EKO60 and circ, which should be enough to take it through a load of wood, if I were away in a power failure (I have 500 gal of storage, so I am assuming I could absorb/dissipate the heat if the primary circ continued running, even without the zones pulling heat out).

If the circulator itself failed, then there would be an overheat situation for sure, assuming the worst case of a full firebox and my being away. I am thinking about putting a thermosyphon loop in with an automag, but until then, I am assuming (hoping?) that the unit would blow off steam via the relief valve as the replacement water came in, and generally would survive an unattended event like that.

These are two distinctly different events. If the circ failed, an automag valve would not kick in, and an overheat would occur. The second is the power outage, which is easiest to contend with, using an inverter/battery combination. It only needs to run for probably 4-6 hours to burn down any wood in the chamber.

I would suppose there is some kind of circuit that could be built, that would allow an emergency signal from the EKO to kick the automag in, even with power on, if the boiler alarm indicated an overheat, plus have the automag simply kick in when the power fails. The inverter/battery wasn't that expensive, so I at least have half the problem solved, but the failed primary circulator problem still exists, and I am still thinking about how best to solve that. I suppose in the end, since the HX on the EKO is steel rather than cast (?? - is this correct?) then excessive heat would not be any worse than the weld temperatures of the joints. Still, it would be nice not to shock the system with cold water entry, I would think.

 

[timberr]

boilerman,

The downside to a battery / inverter setup is you assume you are going to be around. I have a backup generator but I need to drag it out of the garage, start it up and hook it up to the transfer switch. I am sure I can accomplish this without any serious overheat event.

What I am worried about is in a cold snap such as this one I would like to be able to keep my 25 running and head to work, if power goes out I can reasonably be confident that the boiler will have some protection. Usually when we do loose power it is for less then 2 hrs. I am covered in the event of Circ. failure with a aqua stat hooked to the boiler if it trips it opens my first floor zone as a heat dump.