Running the furnace fan from a generator

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jacob
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Running the furnace fan from a generator

Post by jacob »

I've developed some concern over an extended (1+ days) power outage over the winter. So far, so good, but ...

We have a fancy forced air furnace. The installer routed electricity to a junction box next to the furnace and the furnace is then plugged into that (110V sockets). The furnace is (as far as I know) only controlled from a digital thermostat upstairs that runs on AA batteries.

Questions:

1) As far as I understand I would need a generator that can supply real sine wave electricity to avoid ruining the controller board in the furnace(?)
2) The interwebs speak of the need for the furnace to be grounded. Now, generators don't come with a ground spike, so ... how does that work? Are we just talking about a floating ground? I presume that the furnace plug would be connected to the chassis of the furnace?!
3) My main concern is not really freezing personally as it is having the water pipes freeze and crack. I highly suspect that the pipes going to the bathroom run at least partway through the outwalls (uninsulated as far as I know). A more reasonable plan than spending $$$$ on a genset that will only be used for few hours, maybe, I could just let the water trickle. The concern then would be that if the electric power is out, maybe the pumps that drive the water pressure would be out too. (No water towers around here as far as I know.)

OTCW
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Re: Running the furnace fan from a generator

Post by OTCW »

In the case of an electric pump only municipal system in your area, the water trickle would work until the pumps lost power and the system depressurized (this would happen with water towers too, it would just take longer). At that point you'd want a way to drain your plumbing so the accumulated water didn't freeze and burst pipes. Don't know your topography, but it is possible your lines would drain back to the mains and it would take care of itself. Unless you have a backflow device or check valve.

Anyway, locate the lowest faucet and see if you can drain your system from it, if not look for a spot to install one that would do so.

Toska2
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Re: Running the furnace fan from a generator

Post by Toska2 »

There's only two water towers serving a town of 30k in northern Michigan. I never seen one without. In any case, public utilities are required to have a generator and 2-3 days of fuel. In the case of power outages, the general public won't use as much water for bathing or washing. Meaning they have an excess at that time.The major issue is the artic air after the storm. This could cause city pipes or the leads to houses to freeze. Water trickling will work until then.

If you wanted to use a cheaper generator then you could use pipe heat strips. I question the overall cost savings as you already have a furnace that has lower amp draw.

Why not get social capital by sharing a sine generator between neighbors? They might have one or be in need.

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Ego
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Re: Running the furnace fan from a generator

Post by Ego »

I've drained the building a few times to do plumbing repairs as some fixtures did not have angle stops. I would second this as the low/no-tech, no cost solution. Shut off the water at the curb. Open the lowest water tap until it drains. (caution: Check the water heater)

After you figure out the solution, type it up in a big bright laminated poster and attach it to the shut off tool then hang them in a prominent place. You never know who might be home when it happens. Also, this kind of thing shows future buyers that you are a conscientious seller.

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OTCW
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Re: Running the furnace fan from a generator

Post by OTCW »

Good point on the water heater. You can burn up the electric element if you power it on without filling/purging the air properly first if it gets drained.

jacob
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Re: Running the furnace fan from a generator

Post by jacob »

Our water comes in at the lowest point (out of the floor) of the basement which is 6' under ground, well below the frost line. It immediately tracks up to a pipe that runs under the basement ceiling joists; then down again to the basement sink where I think the system can be almost fully drained. I don't know what the angle is going to the street shut-off. In any case, the limited-information solution would be to open the lowest faucet to a trickle along with the highest/wall faucets. That'll keep things going as long as the city pressure is on. Once that is gone, everything should drain to the level of the lowest faucet which is below the frost line.

I had already figured that I'd be lending out the genset to neighbors for a couple of hours at a time to keep everybody from destroying their pipes not sleeping for 48 hours, but I think the new plan is just to make the rounds draining people's systems instead. I hadn't thought of doing that, duh! Ditto, draining/refilling the water heater.

I also really like the poster idea. Homes should come with instructions plastered everywhere. It's much easier than having to experientally learn ungooglable information the hard way.

Conclusion: No genset. But laminated poster on wall about the drainage strategy. $1000+ saved. Thanks :mrgreen:

Laura Ingalls
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Re: Running the furnace fan from a generator

Post by Laura Ingalls »

Having weathered quite a few power disruptions over the years I am not sure pipe draining is the solution. First, they mostly don't happen in extreme cold. Second unless you live in a drafty barn you are going to be super cold in your house before the pipes freeze. We had an ice storm in 2013 that left us with intermittent power for six days (three day with zero power and three more on and off). The house got down to 48°F at one point but the pipes never froze. Our respite was the garage and the wood stove in it. I suspect that even the nordic Jacob would be froze out before his pipes.

It is also going to take awhile to accomplish and invariably the power will go on as soon as you finish.

Riggerjack
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Re: Running the furnace fan from a generator

Post by Riggerjack »

Should you decide to go with a generator, no worries about sine wave AC. Generators generate sine wave. The only time you should worry about your AC signal is when you are using INVERTERS to generate AC from DC. This would happen when trying to use alternative energy/batteries.

A few generator safety notes. Go to your electrical meter, look down. There should be a 6 gauge bare copper wire, that leads to your grounding rods. sometimes the grounding rods are buried a few inches below the surface. This is the ground you want to attach to.

If you google around, you will see people hardwiring their generators into their house wiring. Some choose to do this in a pretty simple manner, with just a pigtail to an outdoor outlet. The problem is that voltage is not limited to your home, it goes out on your entrance cable, and shocks the linemen working on restoring power. These linemen usually have plenty of other work, so rather than chase out the source of the problem, they will usually just go find someone else's problem to fix. Areas with "Hot Wires", are remembered by line crews, and get put off to the end future of storm repairs. FYI.

There is a way around this. A transfer switch will shut off your main breaker, and feed generator AC into your house. It will be set up so that only the utility power or your generator power can be tied your wiring, but not both. This will keep you code compliant. These can get very fancy, with automatic transfers switches that will start your generator when power goes out, and shut it down when power is back.

Yes, you could just flip your main breaker yourself, but if you forget, there can be long term consequences beyond just doing a non code compliant modification.

Oh, and always turn off the breaker to your water heater before draining it.

workathome
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Re: Running the furnace fan from a generator

Post by workathome »

I would be interested to know what generator setup you chose, if you go that route.

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Sclass
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Re: Running the furnace fan from a generator

Post by Sclass »

Not to nit pick but if you buy the cheapest generator you can find (why would I get that idea :lol: ?) you may get something that has a modified sine wave. Some of the little sub kilowatt ones have really raunchy waveforms.

My ears perked up on this one because I sold a line of chemical analysis tools that people would take to the outback. After laying out $100k for a system they'd buy the cheapest generator or inverter. It caused all kinds of problems in the early years before I got serious about power conditioning.

workathome
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Re: Running the furnace fan from a generator

Post by workathome »

This video seemed to be a decent overview:

https://www.youtube.com/watch?v=lkbBt8hv8mQ

lilacorchid
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Re: Running the furnace fan from a generator

Post by lilacorchid »

Your pipes won't freeze overnight. I can't count the number of 2AM furnace calls my husband received with people convinced that their house would be an ice brick by morning. So you can calm your neighbours too. ;)

JamesR
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Re: Running the furnace fan from a generator

Post by JamesR »

jacob wrote:I highly suspect that the pipes going to the bathroom run at least partway through the outwalls (uninsulated as far as I know).
How about cutting open the drywall and taking a peak? Naturally you'll have to patch & paint it after, but could be worth it? :lol:

If you cut out a square drywall, then later to patch it just add a piece of wood behind the hole and screw into it with both the installed drywall and the cutout piece, and then just goop & sand & paint again.

sky
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Re: Running the furnace fan from a generator

Post by sky »

Municipal water will continue to have pressure even if electric power fails.

If your pipes are through uninsulated walls, you may get frozen pipes even if your house is heated, especially when the wind is striking the wall with pipes in it. It might be worthwhile to replumb the pipe inside of the insulated area.

You can let the water drip to prevent freezing.

If your area has frequent electric power outages, consider an alternate heat source, such as a woodstove or kerosene heater.

OTCW
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Re: Running the furnace fan from a generator

Post by OTCW »

Not always. It depends on the system. I've worked with probably over a hundred municipal water sytems in my career. They can be very different. Some have enough storage to last for days, some only hours, and some have none. Some have backup generators and others don't. Live at a high point, and you run out first, while someone a mile away, may have water until the power comes back on. Some systems have excess storage in certain areas and not enough in others. Generators at some pump stations but not others. Lots and lots of variables.

I lived in one place where the main pumping station caught on fire. Water was out for a week. Middle of the Summer, so no freeze worries, but that was just happenstance.

IlliniDave
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Re: Running the furnace fan from a generator

Post by IlliniDave »

Riggerjack pretty much covered re generators. Another side note is that over time without an artificial heat source your basement could wind up as the warmest place in your house, as the ground becomes a relative heat source. IIRC at your latitude the ground temperature is around 45*F, maybe a little warmer. That's more true if the basement isn't finished, and of course, isn't drafty. So I'd think that draining the system via the utility sink in the basement would be more than enough.

Growing up slightly north of you, issues due to freezing pipes were rare. In the south they are relatively common as water pipes often run below uninsulated/unheated crawl spaces and in outer walls. Are you sure you bathroom pipes run through a wall and don't come up through the floor near but inside the wall? (that's how they run in my parents house which I suspect is a similar vintage to yours).

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Ego
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Re: Running the furnace fan from a generator

Post by Ego »

jacob wrote:Homes should come with instructions plastered everywhere. It's much easier than having to experientally learn ungooglable information the hard way.
Every time I find myself struggling to figure out how something works, I make a poster and plaster it to my "Systems Wall" in the basement.

Image

The hundred year old elevator and the boiler for the steam radiators are both constant puzzles that I have not even started to document and I've got a convoluted Yed schematic of the electrical system that is a mess. I find that plumbing and appliance issues are solved quicker and cheaper if I tell the repair person the make/model of the faucet or refrigerator before they arrive so that is something I plan to add to the wall. Often, I can avoid the time and expense of having them go back out to retrieve the part.

Also, we kept all of the paint hidden away in the basement where the tenants couldn't get it. I made little cups full of the various paints we use in the building and put them in the laundry where the tenants have access. Now if they ding a wall, they'll fix it. A few of the really nice tenants who care for the building will periodically wander around with the paint, touching up the walls. Gotta love Millennials!

Image

While this may not seem like something useful for a homeowner, I find that having simple screw top cups rather than a messy can of paint and throwaway children's art paintbrush rather than expensive painters brushes that need to be cleaned, makes me more likely to touchup a wall.

workathome
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Re: Running the furnace fan from a generator

Post by workathome »

So looks like I'll just pay an electrician to install a transfer switch (sounded like it would be ~$300) and pick-up a high-quality Honda inverter generator. The total cost will be about $2,500 but would provide heat and basic requirements. I will be using some credit card points for Home Depot gift cards (see "credit card churning") to pay for most of the generator instead of airplane tickets since I don't travel much anyway.

Unlike Jacob, I am more concerned with my two children about actually keeping the heat running for health and comfort if there were power-outages, grid failures, the end of the world, etc.

There are much cheaper generators, but it seems like they may be shoddy and unreliable and the Honda should keep some resale value, plus be capable of running continuously for longer emergency / power-out situations.

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