Dealing with Power Outages with a Hand Fired System

Matt328

I have a hand fired coal boiler that we are really happy with for the most part. Shake it down, coal in twice a day and ashes out once a week or so and it's rock solid, house is 72 degrees (a little warm, but we have small children) even when its 15 below outside.

This weekend has been a rough one thought with a power outage that started around 2am. By 5am, without the circulator pumps, my boiler was in Chernobyl mode, >240 degrees and hovering around 30 psi, just below the release valve's threshold. We have a private well, so no power, no water service to cool the boiler down. So I dumped the fire and opened the boiler drain to release the steam to avoid damaging anything. Normally it sits around 180 degrees and 18 psi. We sat around the gas fireplace until the power came back on around noon, at which point I drained and recharged the expansion tank (old style bladder-less), refilled the boiler and built a fire. An hour later, the power goes out again. In preparation, I closed off all the air to the fire, and monitored the temps closely. It didn't take long for it to creep up again and I decided to dump the fire again at 220 degrees.

This all was a huge messy pain. First question is does it sound like I'm over firing? I try to target around 180 degrees, and on milder days it might creep up and activate the dump zone, and that keeps it from going over 190. How long should a hand fed coal fired boiler be able to keep itself under control with a power loss to the circulator pumps?

Second question is dependent on the first one I guess, if I'm not over firing and if the system is dependent on circulator pumps to keep it from overheating, I'm thinking about setting up a battery backup by wiring my circulator pumps, and possibly my well pump through an inverter/charger that is backed by a few deep cycle marine batteries. Is this a common thing to do, or is it completely unnecessary because I'm over firing?

GroundUp

Don't you have a powered damper that closes on loss of power? Or a NO zone valve of some sort on your dump zone that would automatically open and dump on loss of power?

STEVEusaPA

Why don't you get a small generator to run the well pump and circulator pumps?
Or a slightly bigger one, transfer switch, to run the essentials.
Maybe even an electric on. Something to run long enough so you can kill the fire and run the dump.

Fred

You have a gas fireplace. Why not just install a gas powered whole house generator ? They are a little pricy but they have come down in cost and probably don't use much more gas to run than the fireplace, with a lot more benefit and a lot less worry.

Jamie Hall

You've discovered the fun part of coal (or wood) heat. I would very much suggest a generator to power things when the lights go out. Size? Figure out what you want to have powered and go with that. Doesn't have to be automatic -- but it does have to have a properly wired transfer switch. Don't skimp on that.

The deep cycle batteries and a big enough inverter are another possibility -- but a generator is a lot more flexible.

The other thing: make sure your pressure relief valve is operating and reliable. Hopefully it is also arranged to go somewhere where the steam won't upset things. From time to time in the nature of things any solid fuel fired boiler is going to build excess temperature and pressure. It's in the nature of the beast. A reliable way to relieve excess pressure in a controlled way is very useful.

EBEBRATT-Ed

@Matt328

I don't think your overfiring. But if the boiler is firing and and the pumps can't move any water the boiler will overheat.

Water will move by gravity.

I don't know what your piping looks like but if you have any flo check valve in your system they can be manually opened.

If you have any zone valves they can usually be opened manually.

The above two thing will get you some (but probably not a lot) of circulation.

If it was my house I would pipe in some bypasses with manual valves that you could open when you loose power. I would bypass any flo checks (unless you can manually open them and bypass the pumps as well

I am sure if the power went out you could kill the fire or damper it down and the gravity circulation would get rid of enough heat so you wouldn't have to dump the boiler.

Other than that it's a generator or a back up system. Circ pumps don't take much power.

You could probably put an inverter in you car and run an extension cord in to power a pump. Pumps only take a couple of amps

ratio

What about a gravity-circulated dump loop with a power closed spring open valve?

Matt328

GroundUp said:

Don't you have a powered damper that closes on loss of power? Or a NO zone valve of some sort on your dump zone that would automatically open and dump on loss of power?

The only damper I have is connected to a mechanical actuator that rises and falls corresponding to the water temperature, it's adjusted currently to close completely around 170 degrees. I suspect I'm leaking draft through the oil gun attached to the back of the boiler. As for my dump zone, it has no failsafe, it is wired to an aquastat that overrides the thermostat input for the circulation pump at 190 degrees. My system has individual circulation pumps on one side of the boiler, and B&G Flo-Control valves on the other side. I haven't looked at them closely beyond identifying them, do they have a way to bypass and force them open?

@STEVEusaPA and @Fred We have kicked around the idea of a generator, but our power outages have been few and far enough between that we didn't want to spend the money. From some initial research, an inverter/charger setup could be done for around $700. A generator to run a few other things would be great, but they are orders of magnitude more expensive.

@Jamie Hall I had thought about routing the release valve's output somewhere else than just the direct 90 degree turn it makes down into the floor. I don't have any drains accessible from the boiler room, would i have any issues just routing it outside? That would have saved quite a bit of headache and mess at 5am this morning. I could have just popped that open, shut up all my draft and went back to bed. I could put a 25 psi valve in, like I said it was sitting right at 30 psi which is what the current release valve is rated for, but the temp was reading over 240 and things did not look or sound like it was within any safe operating range.

Also, a few have mentioned dampering the fire down to help control temps, but I think I might have an issue there since under normal operating, the damper is completely closed, like I said above it opens when the temp gets lower and closes once it comes back up again. With the damper completely closed, a fire will sit and smolder for days before going out. I had a fire going during the second outage today, and with everything closed up it still climbed from 170 to 220 in about 2 hours.

Is that normal, or is draft leaking in through the oil gun something I should look into addressing?

mattmia2

Most separate flow checks have a knob or lever on them to manually open them(the ones built in to pumps usually don't).

A generator big enough to run a couple hundred watts of pumps and controls is inexpensive, although a large ups with an external battery could do it too. The ~2000 w generator may not be able to start a refrigerator compressor or other moderate sized motors.

If the boiler is above boiling at atmospheric pressure, it is going to flash to steam and be pretty dangerous when you release it. the discharge has to be somewhere visible so you will notice it.

It sounds like if it took 2 hours to get to 220 with the fire damped all the way, if you could open the flow checks it would stay under control with gravity flow.

It might be worth it to remove the flow check on the dump zone and replace it with a zone valve that is normally open so it needs power to close and will open the dump zone automatically if you lose power. You would have to work out logic that is opposite the current aquastat, maybe either an opposite logic terminal on the aquastat or a relay. A 120v coil valve could help simplify it.

ChrisJ

One of the reasons my dad stopped using the 4kw generator I ended up with was, though it did start his well pump it didn't like it. It's rated 5kw surge 4kw continuous.

Just something to keep in mind.

Jamie Hall

For a safety backup... I think I might be inclined to also install a temperature and pressure sensitive safety valve in addition to your existing pressure safety valve. The are not expensive. They open at 210, and if you had one routed outside (no valves, minimum 1 inch pipe please!) it would safely release pressure before your system boiled -- which would eliminate the risk @mattmia2 pointed out (which is quite real) since you couldn't build pressure. Site it so it can't actually empty the boiler...

I doubt that you are overfiring. However, as you have noted, even a very small draught will keep a coal fire going quite happily for quite some time.

On the whole, I'd go for a generator. And, since you have a well pump (and it would be nice to keep it going) I'd go for one big enough to do that -- comfortably. As @ChrisJ noted, the starting surge on a well pump is significant (as it is for any big motor) and even if the generator can just barely handle the surge, the voltage will drop and that will make the pump motor unhappy. Cedric's home is a farm, so our requirements are a bit different -- but our 16KW generators are none too big.

retiredguy

You could install a separate pump piped and valved to run around the existing pump set up. Operation could be by a battery/inverter system, a low voltage battery powered pump or a plug and socket extension cord for direct connection from a dedicated small portable generator.If you really want to get your "thinking cap", you could install a dedicated gravity flow hot water radiator in the main area of the house to be used only when the power is off. You may not want a large Cast iron rad in any room but it only a suggestion. You could add a manual release valve, piped to the outside, to dump the excess pressure/temperature water. You did not say if you are burning hard or soft coal but that should not make a difference. You are probably not over-firing the boiler, that is the nature of the coal. When the power goes off the coal fire does not go out. I would find a solution that I could accept.

Lard

I had to do a backup system for the blower on my wood-fired scorched air add-on furnace for the same reason (overheating, burning crap off of heat exchanger and setting off smoke detectors).

I used a normally-closed relay (coil direct to mains) in-line with a thermodisc mounted on the plenum to enable a small 12v ~400cfm blower from an RV furnace in the event of an outage. The damper has a solenoid that drops and slams it shut. A couple golf cart batteries run it for a long time.

The same strategy could be used with an inverter, auxiliary circulator, and separate aquastat to send heat to a dump zone. A timer to exercise the auxiliary pump once in a while would be a good idea too to reduce the chance of the pump seizing up when idle. A wet-rotor pump takes less juice than a blower, so it would run a long time on a couple batteries.

wesPA

I also have a hand fired coal boiler at my house, it injects into a 119 gal storage tank. My house loop mixes out of the tank. On power outages, I am usually able to damper back the fire and have enough gravity circulation to keep things from overheating. I do not have a check valve in my house circulator, though, and have cast iron radiation . Also, I target 160-165 degree temps, to allow for a little more room. You are leaking air in somewhere if you have fire for a day with the damper closed!

Solid_Fuel_Man

What would you like to run with this backup system?

1. Boiler circulators only?
2. Well pump too?
3. Lights refrigerator too?
4. Basically hole house?

These answers will dictate the best answer.

Matt328

We're thinking a backup system would have to run boiler circulators only. Given that, I think an inverter/charger and batteries running the circulators would be sufficient.

For domestic water, I keep (2) 7 gallon plastic containers filled all the time, along with a few cases of bottled water in the basement. We have a 100 gallon propane tank that supplies the kitchen stove and a fireplace, so we can still cook hot meals when the power is out. All of this should get us by for a few days, which is all I'm aiming for at this point in time.

Jon_blaney

A small portable generator can be fitted to run on propane. I would go that way if I had propane.

ChrisJ

Jon_blaney said:

A small portable generator can be fitted to run on propane. I would go that way if I had propane.

Keep in mind, if you take a gasoline generator and modify it to run on LPG it will produce less power than it does on gasoline. I wouldn't be surprised at 30% less.

PerryHolzman

I purchased some used industrial battery back up pure sign wave inverters and have my boiler system plugged into it. It can power my boiler and monoflow T circulating pump for a minimum of 2 days (and closer to 4 days when the batteries are new).

I do have to change batteries about every 5 years.

System is totally automatic. Power goes out... Boiler and circulating pump just keep running with no attention from me. Power comes back on and the back up auto switches to 120 V AC, and also recharges the batteries (may take a day or so if drained).

I wish you well with this,

Perry

PerryHolzman

I'm posting some additional information based on some messaging with one of the members on this site:

Refurbished industrial UPS systems are available from multiple internet vendors. Double conversion - Pure sine wave output are the more expensive items... but will totally protect your boiler (or other device); and the good ones auto switch between line current and batteries (these take the line current, convert it to near DC, then reinvert it into pure sign wave output - protecting your equipment from surges; or take DC from the batteries and invert it into pure sine wave output).

For extended run times you want a base unit that allows connecting additional batteries as most UPS's are only designed for less than 15 minutes of power just to allow other backup power to come online or orderly shutdown of a system (and these systems often have appropriate computer wiring so that computer (or other electronic system) will commence an orderly shutdown in the case of a power outage lasting more than a very limited amount of time.

About a decade ago I purchased 2 Liebert GXT2 1000 VA 120V base units for my CPAP and computer, and 1 Liebert GXT2-2000 VA 120V base unit for my Viesmann Vitodens 200 6-24 boiler and Taco 007-F5 monoflow system circulator (primary/secondary with Low Loss Header).

I have 4 battery packs added to the GXT2-2000 for multi-day house heating operation with loss of power (the maximum allowed). I have 2 battery packs on the CPAP UPS (for all night + operation of the CPAP and heated humidifier).

In Lieberts GXT2 case you need to program the number of additional battery packs (and other voltage/cycle/alarm features) with a 9 pin serial cable and software that you could download from Liebert (it also helps to have an ancient laptop that you can use that has a 9 pin serial cable output).

I am not wedded to Liebert. That was the equipment that worked and was available when I was looking for it about a decade ago. Other manufactures make similar equipment; and the more modern units are not going to need a 9 pin serial cable to program them.

Unfortunately, while it appears that the Liebert GXT3 and GTX4 are the direct desendents of the GXT2... as double conversion pure sign wave output units... It appears based on my initial research that the 120V models do not have the capability for additional battery packs to be added. However, I am sure that Liebert would have such equipment (likely another model number). Finding it used/refurbished may take some looking (of course their are vendors who will sell you the appropriate new equipment).

Key pieces of advice:

1) Know how much power your system uses (and needs for startup as motors often require a surge current). Ensure that you have a large enough unit (general rule of thumb: your VA rating needs to be 50% higher than normal run current).

2) Study the manufactures manual and determine how long "new" batteries will likely last, and how much time additional batteries will add. Figure old batteries will only last 1/2 or perhaps 1/3 of that.

3) When buying Used/Refurbished be sure that you get the heavy cable that connects the battery pack to the base unit or the preceding battery. Some places require you to purchase this separately.

4) Be sure to understand if you need a special cable and software to program the base unit for additional battery packs; and get it.

5) The batteries do degrade with time and have to be replaced. Almost all companies selling refurbished UPS units also sell replacement battery pack kits for both the base unit and the additional battery packs.

You may also purchase batteries directly from www.atbatt.com and other vendors.

6) To assemble a total package you may end up buying equipment from more than one internet vendor. Perhaps you get the base unit you need from one vendor, and the additional battery packs from another. Spend some time and do some shopping and research.

Also, contact the internet vendors and tell them what you are tyring to do.... The good ones will help you assemble a system that works well from the equipment they have.

I hope this helps all, and I wish you the best...

Perry

mattmia2

Tripplite and Eaton both make 120v dual conversion UPSs with connectors for additional external battery packs.

You still may be better off with a 12 vdc dedicated backup pump, I think that the inverter is going to waste far more power than what the pump draws with the inefficiency of the inverter being the limiting factor in your run time.

Induction motors typically need 5-10x their running power to start which usually makes running anything other than small motors off a UPS impractical, the locked rotor current will be part of the rating of better motor.

Usually the external battery pack cables are some version of Anderson power poles so fabricating a cable isn't difficult if you need to or if you want to use flooded cell batteries instead of an SLA pack from the manufacturer(but you need to have a way to vent flooded cell batteries outside because they release hydrogen when charging)

hot_rod

I too would go with a backup power source, no piping changes, automatic switch, and possibly sized to keep the boiler and pump running

Upgrade to ECM pumps to cut power by 1/2

12v DC circs are expensive and not many sizes available. The B& G Ecocirc DC Strong what I use on off grid solar

mattmia2

I wonder what the efficiency difference between the pure sine and sawtooth inverters is. A transistor is pretty efficient driven at saturation and cutoff but if you have to drive it in its linear region to make a sine wave it loses a lot of efficiency.

Leonard

Looking at supplying 120 or 120/240. VAC.....

Just to power circulators and relays I;m guessing <500 watts would do it , so maybe small <1kw gen to start the circulator motors. Generally you assume starting power requirement is ~2X running power.

12VDC sine wave inverter can easily supply this, but need some bigger bats or running car to supply it. Problem is if you run car a long time it's engine is so large it will consume a lot of fuel even at ~no-load compared to a small generator engine. Plus car alternators max out at 1kw, if continuously run at 1kw it's diodes will cook and eventually die in few months (old Chevys) . Just like they do if you have an old weak car bat, that constantly sucks down 40 amps( they do)_

Wells take a LOT of power to start, typically need 5kw gen as a min.

Older 1800 rpm Onan gens can easily start wells. The newer generjunk stuff is 3600 rpm LOUD screamers and light weight doesn't like starting wells, need higher kw gen. Again issue is as go larger kw gen ( ei double it then engine no-load fuel consumption also doubles.

My 7kw 7NHM ONan gen uses gasolione @ .4GPHno-load and 1.3 GPH @full load

Whole house gen might be 12-20kw , will drink double the fuel at no-load as a gen 1/2 it's kw rating. If your out for 1 week your wallet will notice this. My 7kw gen drinks .4 gph gasoline at no-load, in 1 week thats $150 for gas just at no-load

On propane an Onan 6.5kw gen typically makes 6.3 kw and burns ~ 10% more GPH than when on gasoline. (Propane has less energy per gal than gasoline). Converstion to propane from gasoline is simple. Can drill the carb, or put adapter before carb, or add a "snokle tube " down the carb venturie

some info on fuel consumption of some Onan gens
https://www.smokstak.com/forum/threads/fuel-consumption-of-some-onans.190155/#post-1608454

Solid_Fuel_Man

Remember that we are talking either perminant split capacitor (PSC) or ECM motors here guys. The inrush is nill. And at worst the circulators (typical 007) draws 90 watts tops.

Heck I have a cheapo $30 400watt modified sine wave inverter that will run my entire wood system (one 0015, and one 0010). It makes the motors sound awful though! I just tried it once before I bought my propane generator.

Leonard

modified sine wave = some version of square wave.

Picked up a bunch of computer APC 1kw UPS units. They output a modifed square wave = 15% THD.

Connect them to 12VDC bat, push a button on front and they will start up and provide 120VAC.

Before I got my 7kw gen I planed on using 4kw UPS I picked up to run my oil furnace, needed 48 VDC though...4 cars running---high gasoline bill

square waves makes motors run hot, and likely Noisy

PerryHolzman

An advantage of having an installed UPS system with adequate battery packs is that my boiler and calculator pump operate for days in a power outage without any action from anybody. I travel away from home periodically. There have been power outages when my wife and I have been away. If you are depending on a generator that someone has to start... etc... your house and system could freeze before you get home.

Also, UPS systems tend to be much more reliable than "auto start" generators.

However, to each their own...

Have a great day,

Perry

ChrisJ

PerryHolzman said:

An advantage of having an installed UPS system with adequate battery packs is that my boiler and calculator pump operate for days in a power outage without any action from anybody. I travel away from home periodically. There have been power outages when my wife and I have been away. If you are depending on a generator that someone has to start... etc... your house and system could freeze before you get home.

Also, UPS systems tend to be much more reliable than "auto start" generators.

However, to each their own...

Have a great day,

Perry

With @Leonard unless it's an old Onan generator it's garbage. It doesn't matter if it does the job, or if it's reliable.

Leonard

Automatic bat start gens (ei Onan RV) with automatic transfer switches are commonly available. Whole house automatic switches (100-200 amp) cost a bit though, furnace only (<30 amp) might be cheap to make.

UPS could be more reliable than gen , IF you don't periodically run gen to exercise it, as they recommend you do (carbs plug up from ethanol gas). But then again bats also get weak and die with age. Everything needs maintenance if you expect it to be reliable.

For most battery backed UPS systems the problem is need a LARGE group of $$$$ batterys to have enough run time. And they have to be replaced periodically $$$$$ ( maybe every ~ 10 years) .

In this case of ~150 watt demand from circulator and controls a UPS would draw at least ~ 13 amps @ 12VDC. Given a typical larger car bat ( 50 amp-hr) that's only ~ < 4 hour max run before bat is dead. However it's likley UPS will shut down on low bat voltage before that, suspect at 1-2 hours max. So you likely would want a 48+ VDC bat bank and/or some VERY large bats$$$$$$

I have an old Onan gen primarily to run my old oil furnace for heat. I figure it's cheaper than batteries. Plus if outage lasts 1 week like my neighbors had ( huge ice storm), then I can go out and buy more gasoline, big city here. Bats only store X hours of energy, then your out.

Given all this trouble I'ld look at trying to modifiy the heating system so it at least automatically protects itself, if not heats house without a circultor (if that's possible, I'm not a heating guy)