# boiler overheating due to power outage



## Jeremy Bellegarde (Nov 24, 2013)

I came home today to find the power out, I had just had a used wood boiler installed in my basement. when the power goes out I have a spring valve that opens and allows the water to gravity feed through the biggest zone in my house. the temp is usually no higher than 190 when powered up and running. im not sure how long the power was out when I got home but the temp was at 215 deg...is that to warm? what can I do to prevent damage to my boiler if the power goes out and im not home to start the generator? any info would be greatly appreciated! thanks


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## webbie (Nov 24, 2013)

Pressure usually increases with temperature, so at 215 many boilers may be ready to blow their pressure relief valves.

First thing, make sure your PR valve is piped to somewhere so that when it goes off, it does not hurt anyone or muck up the area where you may have to get to.

In terms of more fail-safe power outage schemes, there are probably a few that people here can suggest. Many boilers in Europe used a domestic hot water coil (coil immersed in the boiler) and ran some cold water through it and then down a drain on overheat. Of course, if you have well water this won't do either!

You could add another overheat zone right near the boiler (with a rise) and even power it with a circulator that only turned on when the power went out. A big UPS and some basic relays could serve this function.


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## JP11 (Nov 24, 2013)

Add an auto switch and a whole home generator.



Sorry.. easy to spend someone else's money.

JP


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## Briquetmaker (Nov 24, 2013)

Search this forum for battery backup. There is a lot there. I believe this is a must do if you are leaving your boiler unattended with a nice roaring fire. I'm in the process of doing this myself. I am going to run 5 circulators and the boiler fan on a 1500 watt Aims power inverter. The battery, or batteries is the tough choice, big $$ to run a couple of hours.


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## maple1 (Nov 24, 2013)

What was your pressure when the temp was 215?

I don't think you were quite in the danger zone - but you were getting close. My old one saw temps over 220 before - it had a draft door that went wonkey when you were least expecting & wanting it to. Was it making any noises - that sounded a bit like boiling water?

Was the zone in your house that you have the dump plumbed to warmer than usual and above the thermostat setpoint? If so sounds like it was doing its job - you might want to consider plumbing in another NO zone valve & dump zone overhead somewhere, just for peace of mind. Redundancy is a very good thing when it comes to something like that. Maybe also setting your hi-temp aquastat setting back 5° or so.


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## Bad Wolf (Nov 24, 2013)

I have a set up with a Xantrex Prosine SW 600 inverter with the relay also by Xantrex. If the inverter is on and the power goes out the relay automatically switches to the inverter from house current.  The only problem is that when on the inverter draws 600 mAh or 7.2 watts from the battery. Over time that will run them down. I only turn it on when there is a storm coming, but that doesn't help with random outages.
I used to have two deep discharge batteries(200 amphr)  that would run the Tarm for about 8 hours. Now I have an 1800 amp hour bank that will run things for 2-3 days.


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## mustash29 (Nov 24, 2013)

What does your pressure usually run.....and how high was it today?

Maybe a simple thing would be to add another spring valve to the next largest zone so it can assist with dumping the heat load from the boiler, or add a dedicated dump zone in the boiler room.

What kind of boiler?  Is it an old school or simple unit with a blower, Sampson type firing control, etc?

Make sure the gaskets on the doors & such are in good condition and tight.  Make sure when power is lost that your draft door / damper, etc closes properly.  Some of the simpler type boilers had the ability to supply a bit of minimal draft (pilot air) to keep the fire barely going.  Couple that with a power outage and the strong winds we are having (strong draft) and you could be making more BTU's than you want in that senario.

Everyone around here is SO helpfull, great site.  If you can provide a little more info (pics, make / model info, etc) someone around here is knowledgable enough to pinpoint the best solution.


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## Briquetmaker (Nov 25, 2013)

Bad Wolf said:


> I have a set up with a Xantrex Prosine SW 600 inverter with the relay also by Xantrex. If the inverter is on and the power goes out the relay automatically switches to the inverter from house current.  The only problem is that when on the inverter draws 600 mAh or 7.2 watts from the battery. Over time that will run them down. I only turn it on when there is a storm coming, but that doesn't help with random outages.
> I used to have two deep discharge batteries(200 amphr)  that would run the Tarm for about 8 hours. Now I have an 1800 amp hour bank that will run things for 2-3 days.



Bad Wolf, Can you give me a little input how your battery bank is set up? I do get spotty outages but doesn't take much to knock it out for days.


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## Fred61 (Nov 25, 2013)

I have a 1500 watt pure sine wave inverter with built-in charger and automatic switch that activates when power drops out. I purchased it from these guys but I don't see mine on the page. I have it hooked up to my three deep cycle motorhome batteries that normally spend the winter in my basement anyway. I had originally tried a modified wave inverter (much cheaper) but when I turned it on for the first time I panicked when I heard the circulators humming and the controller led's  scrolling. I immediately replaced it with the pure sine wave unit. It switched almost instantly.

http://www.theinverterstore.com/pure-sine-inverters-off-grid.html?gclid=CN3D0O-YgbsCFe3m7AodLkMADw

Since I installed the inverter I have installed a whole house standby generator so I basically don't need but don't ask me if it's for sale. Seems like a nice tool to have around.


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## Bad Wolf (Nov 26, 2013)

Briquetmaker, they were replacing the UPS for our computer room at work and the batteries still had some life in them. The original set up was 138 batteries in 48 volt banks, I got 18 4 volt batteries at 300 amps each.  I put them together into 6 banks of 3 each for 12 volts.  I got the racks also so they are in 3 shelves, I made up a bunch of cables and linked everything together.
Its way oversized but I wanted something that would keep the boiler going if the power went out in the middle of the night or I was at work. I have no desire to get out of a warm bed at 2 in the morning during a snow storm to fire up one of the generators.
Once I'm up I have a 2000 watt inverter generator that will run for 9-10 hours on a gallon of gas.
About once a month I'll throw the charger on it.  According to the readout its usually still at 85-90% after a month.  I wanted to put it on a solar panel but according to the guys over at windsun.com I'd need a $800 set up just to keep them charged.


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## mole (Nov 26, 2013)

I know that inverters work well for some people, just not me, I guess.  I have gone through 3  different brands of inverter-chargers since 2006 at $300- $600 each. They've all died the same death- They stopped switching the boiler back to line voltage when the power is restored, so they run the boiler off of the batteries until the batteries are dead. The first inverter destroyed my Taco 007 too.  The last one was a pure sine inverter from the inverter store. They all made it past the 1 yr waranty though!!  For the last year plus, I've been on "manual backup switching" for power fialures, meaning I run down into the basement like an idiot shot out of a cannon to try to plug in the inverter before the 30psi popoff blows. Too stressful, and not wife friendly for the occasions when I'm travelling. This fall I finally reconfigured my piping and pumps.  I installed a $240 Laing Ecocirc 12V pump with flowcheck  in parallel with a Taco 3 speed 00R IFC.  I had read about it on a thread here a couple years ago.  I'm installing a relay that will turn on the ecocirc when the power fails and the supply water is over 150F( aquastat).  I'm just finishing up my wiring, hooking up the relay this week.  A small trickle charger will keep the batteries charged.   It was an expensive and time consuming changeover, but, as they say, insanity is doing the same thing over and over and expecting different results.


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## flyingcow (Nov 26, 2013)

I am assuming your boiler is in the basement, with the overheat zone above it? I understand thinking you need to hook up battery back ups, but those fail too. Automag on the dump zone is pretty reliable. 

A "fun" time is getting your boiler roaring, in a good full hot burn, than shut the breakers off to the heating system. And watch to see how the zone handles the gravity feed. IMO,it's something everyone should do. It can be a little nerve racking, but let it do it's thing. Do you have Baseboard heat? Or something else? Obviously you should feel the heat gravity feeding thru the system. 


My boiler is next door, on the same level as my house. I have fin tube hanging up high on a wall, in the boiler room. About %25 of my boiler output, with an automag. I did "test" it out.


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## Jeremy Bellegarde (Dec 3, 2013)

sorry it took me so long to reply...I have baseboard heat. the boiler has an automag or spring valve in the system so when the power goes out it allows it to gravity feed. I have a 1987 franks piping indoor boiler. it usually runs at 180-190 deg, and 20 psi. when I came home to no power it was at 215 and 24-26 psi. it will blow at 30 psi. the baseboard was warm and the pipe upstream of the automag was very hot. so im assuming it was working. just didn't know if I should look into a different backup system or if what I have is going to be enough without doing any damage to my system. thanks for all the input


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## 700renegade (Dec 3, 2013)

Jeremy, it sounds like your system with the automag is performing just fine.  To be sure I'd take the advice given above and run another test on purpose while you are there to monitor the whole event and could restore the power if something is about to get out of hand. 

No need to do more if it passes a test a second time.


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## maple1 (Dec 4, 2013)

How many zones in your house, and are they all hooked up to your automag?

You could maybe tie in another zone to it, if you're still looking for improvements that can be made.

We have a two-storey, I have the 2 upstairs zones plumbed into my dump valve. They flow pretty good once the flow gets going (except when they get airlocked, duh), but the downstairs zones don't flow a whole lot when I manually open them. I will be running my loading unit through a UPS in the future for added redundancy once I get things sorted for it.


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