MilliVolt Gas Furnace with Steam Radiators worked through the storm archived

We have the mini-volt type furnace and are grateful we at least had heat. Highly recommend this set up if your furnaces can be retrofitted.

milli volt systems are no longer made since they use a pilot light.

True enough - like most gas water heaters, some steam boilers have a pilot light that is lit all of the time. The small amount of heat from the pilot light is detected by a thermocouple that converts this heat energy into a small voltage signal. If this small voltage is present, your boiler gets the signal to turn on the gas.

The wiring in our system is very simple: Thermocouple -> Thermostat -> Water float switch -> Over-pressure switch -> Gas valve. So if the pilot is lit, the thermostat says it's too cold, there is water in the boiler and the boiler is not overpressured, then the circuit is complete and the gas comes on.

If the thermostat says it's too warm, or if the water level in the boiler goes too low, or if the boiler is over-pressured or if the pilot light goes out, then the circuit is open and the gas valve will not open.

Having the pilot light lit all of the time is viewed as a waste of energy. So newer systems require a power supply (e.g. your home's electrical power) to spark the boiler to life.

Over the years we've had a number of offers (from plumbers, PSE&G etc.) to "upgrade" our millivolt system to a more modern and efficient powered system but we have not done so.

http://forum.maplewoodonline.com/vc/discussion/comment/2093114#Comment_2093114

When we got a new boiler in our previous house (in the early 1990s, I think), we got a millivolt system like that. When we moved to our current house it had an ancient oil burner that DID require electricity for the pump. Later, when the oil burner died, we converted to gas and I asked for another millivolt type system and that's when I learned that they are no longer code-compliant.

I wonder what the relative hazards of gasoline generator use is compared to pilot-light based heating systems? (especially coupled with all the "gerry-rigging" that folks did to use their heaters after Sandy)

I still have a pilot light on my gas water heater, so we had hot water for the duration. Are those no longer allowed either?

sac said:

I still have a pilot light on my gas water heater, so we had hot water for the duration. Are those no longer allowed either?

Those are okay. I just had a new gas water heater installed today, and it will work without electricity.

We really need a professional to fully explain this but:

The house power is not used to ignite the gas but is generally needed to open the main gas valve within the system. I have no idea why Millivoltage systems are not common (except I've learned that if they are disassembled to be "field serviced" they will often leak) however the use of a pilot light is not the issue as actually almost all of the gas furnaces and hot water heaters around here use a pilot light.

In a gas furnace as the pilot light heats up the thermocouple (composed of two types of metal which via a reaction between the two metals produces a small amount of electricity) and when it gets hot enough from the pilot, it sends that electrical signal to open the gas valve via a solenoid operated by a 24 volt transformer (the transformer is what reduces your 120 house power). The solenoid (something that becomes a magnet when enough power is sent to it) to open the gas (main) valve and is the chief reason why the house power via the transformer is needed. In other words you need power to operate the gate keeper of the main gas burner jets.

In a millivolt system instead of a single thermocouple and a transformer there is a thing called the "thermopile generator" (actually composed of several thermocouples) that when heated by the pilot creates enough "mini" voltage all by itself to open/run the burner side of the valve.

The water heaters don't need power because they rely on water level/pressure to function. (Somebody else can explain this).

Some more-modern furnaces also have a complete electrical ignition instead of a pilot light but I'm guessing that there aren't that many around here.

So, exactly what is it about millivolt systems that has caused them to no longer be code-compliant?

I'm guessing that it could be that normally they were not as reliable in shutting off as the newer systems (that is when power is available of course) or difficult to safely service?

millivolt systems require a standing pilot, that is no longer code.

Pete, my (and most boilers I have noticed, -I'm not a professional) locally "non-millvolt" (thermocouple 24v transformer only) system and new hot water heater both have a standing pilot. Can you describe what the difference would be as you say?

It was still possible for manufacturers to manufacture heating systems with standing pilots until very recently, I would think they might still be available in warehouses.

Why water heaters are allowed to have a pilot light - I don't know. Im going to guess its because hot water is used 12 months of the year and the heat from the pilot light goes up the flue andis captured and stored in the tank, so its not nearly as inefficient as a boiler or furnace with a pilot light, so pilots for hot water were not eliminated. FYI - On demand hot water systems don't have a pilot light.

peteglider said:

FYI - On demand hot water systems don't have a pilot light.

Most on demand hot water systems don't have pilot lights ... the one we installed in our house in Philly did.

Boilers with electronic ignition do not use a pilot light. They light the burner similar to amodernstove or oven - you can hear the electronic igniter spark ("click click click") when firing. There is no pilot light.

Pilot lights used to occasionally go out. A non-lighted pilot light is essentially a gas leak. People re-lighting a pilot light without properly ventilating the area first go boom.

That's why pilot lights were replaced with electronic ignition.

A working thermocouple will prevent a gas leak if the pilot goes out. If the pilot light goes out, the thermocouple temperature falls, causing the voltage across the thermocouple to drop and the valve to close.

I'd be curious about other's experience about the electronic "intermittent" ignition as to it's service life and ease to replace when fails (a thermocouple is one of the few easy and cheap parts to replace).

Meanwhile, I have to note the irony that the one person I know with an "on demand" hot water system during our recent Sandy struggles was of course left without even the luxury of being able to take a hot shower (for a while there I thought I was going to live in mine like Kramer) and the one couple that I know down the street who have an old millivolt boiler system were the envy of the neighborhood (even though I suspect they have never even glanced at it in all the years they've lived there).

It seems that the newer such systems get, the more we become overly dependent on utility power that we can't depend on.

Meanwhile, I know a dude out in Milford who for years has pretty much heated his entire (smallish) home strictly with a wood stove all winter! He was laughing his azz-off through all this (of course he also doesn't even have a TV which I find downright uncivilized!)

I wish we mere citizens could have the choice of pilot light or electronic ignition for our boilers. I'll bet somebody made a lot of money dictating these stupid electronic ignition systems.

wnb said:

I wish we mere citizens could have the choice of pilot light or electronic ignition for our boilers. I'll bet somebody made a lot of money dictating these stupid electronic ignition systems.

The cynic in me would say that it was mostly a marketing decision and had very little to do with energy conservation and/or safety and the legislation was most likely drafted by the manufacturers and installers lobbying groups. It seems that many older systems while they can be more inefficient to some degree actually last much longer and are made to a higher quality standard and also are easier to repair. In general newer systems seem unnecessarily complex with several high price parts that seem to have short shelf lives and conk out more regularly than some of the older units. But that is all conjecture and hearsay so pay no mind.

I hear ya CapnMarko.

I don't think you are being unduly cynical. I think you're being keenly observant.

We've got an "inefficient" refrigerator that is at LEAST thirty years old, -working 24/7 all those years without a lick of trouble.

Oh well, when the Zombie apocalypse comes we'll all be scavenging junkyards and reading handbooks to make old things work.

peteglider said:

millivolt systems require a standing pilot, that is no longer code.

When did the township outlaw gas furnace pilot lights? When we got a new furnace 22 months ago (Burnham Independence 7), Gateway gave us a choice of going with a model with pilot light or with an electronic ignition. Are you telling me the code changed since then?

The codes eliminating millivolt heating systems is National Fuel Gas Code, not a local thing.

Millivolt boilers were never a good idea. It only seems like they were when our power goes out.

Modern boilers have safety controls that can not be a part of a millivolt (0.75-volt, 750 mV) circuit.

If there is a problem with your chimney which restricts or prohibits the outbound flow of carbon monoxide produced by the boiler from your home, a millivolt boiler won't sense the problem and shut the flame as will a 24-volt system's Spill Switch.

If the boiler is full of soot and a flame or excessive heat should find its way out the front of the boiler, a mV boiler won't automatically turn off like a 24V boiler will by its Flame Roll-Out Switch.

A mV boiler can't replenish is own water level without an external power source.

A mV boiler can't have an Automatic Vent Damper to keep the heat it produces in the house instead of letting it rise wastefully out of the chimney.

A mV boiler can't make hot water for your Indirect Water Heater or your Maplewood Room or basement radiators.

Most mV boilers can't be externally operated or turned off by a remote switch at the top of the stairs if there is a safety problem.

The powerpile generator can not produce enough power to flow through and operate these devices.

You're right to think mV systems and just about anything using a standing pilot is an easier circuit to diagnose and repair than one that uses an intermittent (spark or hot surface) ignition system, but we use them for good reasons: they are safer and they use less fuel and it's about time the U.S. get on par with the rest of the world in its quest for safety and efficiency when using carbon-based fuel-burning appliances.
Europe has taken care of this many years ago and they have 1 carbon monoxide incident to our 5, annually.

1955 Chevys are much cooler and easier to fix than your 2011 Honda Pilot, but do you want to drive your kids around in a car with an unpadded, sheet-metal dashboard and no headrests because one or two days a year you get to drive it a car show? Think about it.

We do the extra work to maintain our mV furnace including annual inspection and maintenance by our plumber. We don't mind refilling the water as needed, flushing the boiler monthly, etc. Our plumbers love the system and told us when we bought our house ten years ago that it could really last a long time if well maintained.

We also have CO detectors on every floor so not worried in that department either.

Thanks for the info MP!

Good points about the intermittent system but I'm curious if you can you tell us if that means that any new boiler installed needs to have an intermittent system by code? -Are all pilot systems out?

Meanwhile, I can't resist saying that my Dad drove us around in Corvairs for 13 years. -Thankfully that wasn't an unlucky number.

" Millivolt boilers were never a good idea. It only seems like they were when our power goes out."

I've suspected that this was the case.... However, the industry can be faulted, I think,for failing to compensate for the loss of resiliency. When phones moved from POTS to VoIP, battery backups were incorporated to compensate for the power outage issue. But for boilers, users are ended up having to jury rig after market or home grown solutions, many of which re-introduce problems and risks into the system, bypass safety controls, etc.

Is there some sort-of (for lack of a better word) "standard" back-up power system (that comes as an option?) with the modern boilers? After all, -safety should also include keeping the family warm during a major prolonged power outage where crews have to come from Mississippi to fix the lines days or weeks later.

Personally I don't like the idea of relying on a generator as a back-up power source. First of all you have to get and feed it gas with all the problems that that can entail. It requires the correct weight oil, you have to store the freakin' thing and take care of it at least as well as a lawn mower so that it works when you need it. It is one more thing to break down -Plus the proven potential theft during use times.

To wnb's point it seems like poor product design that homeowners should potentially have to jury-rig something with Marine batteries and power inverters or hard-wire and fuss with a generator (the way I did recently).

We all saw near anarchy break out in a hurry recently. During that time I loaned heavy chains to two neighbors so they could lock-up their generators and long gas lines appeared overnight both for cars and "walkers" with gas cans for their gens.

In other words: intermittent and/or pilot 24 volt systems "seem like a good idea" until the utility power goes off (again) and you and your kids are in a house with 2 feet of snow outside and the temperature is 22 degrees or lower.

I don't think there's a feasible way to easily have some sort of built in power back up for central heating systems. most require energy for the thermostats, control systems, igniters, blowers or pumps, etc.

but how about alternate heat sources - wood or pellet stove, fireplace insert, portable or permanent propane heaters, NG gas heaters, etc.? Those are self contained and among them there are probably options that work for everyone.

to be frank, one could argue that refrigerators, stoves, water pumps (for those who have wells), all are mission critical to a household as well. (some might add laundry, too ;-) )

I read yesterday that about 3% of homes have generators of some kind now. I bet when 99.5% of the homes were built around here, it was essentially 0%, except for commercial buildings. I suspect a lot of electricians will now be asking homeowners about their interest in installing transfer switches of some kind when they replace panels, make electrical upgrades, etc. and that it may even be expected with new home builds.

My old milivolt system had it's own vent damper - thermostatically controlled, not electric.

I don't mind manually filling my boiler because I don't trust and don't want an automatic feed. I have seen the damage done by those things when things go wrong and no one is around to monitor the problem.

It did have an emergency switch at the top of the stairs that worked.

And I always had heat when the power went out. Now when the power goes out I'm SOL. And the power is going out more and more, and longer and longer. One week out of heat and power is disgraceful.

There has to be a better solution to whatever problem prompted this new regulation.

mrmaplewood -- the main "problem" is energy efficiency. from a little reading, a standing pilot light wastes something like $14/month of energy.

A standing pilot light doesn't waste much of anything in the winter. It helps keep the boiler warm. In the summer the utility bills me a minimum charge which the pilot light and my gas range and barbeque never exceed. Where does that $14 number come from?

Well, I do know some people that have Marine battery backups for sump-pumps which I would think would require more juice than a boiler. I don't think that a boiler really draws much which I presume is why it has a transformer to knock it down (although I think I'm going to investigate).

I wouldn't suggest a battery/inverter system to run forever but even just a couple cycles a day for a few days during really cold weather could make a huge difference.

Personally, during the recent outage I was quite content with just having heat and hot water (the back porch became our fridge once the temp dropped). Loss of lights and other stuff was a perfectly acceptable life-style change (ya know, for a while until it wasn't).

More research is required!

NizhoniGrrrl said:

We do the extra work to maintain our mV furnace including annual inspection and maintenance by our plumber. We don't mind refilling the water as needed, flushing the boiler monthly, etc. Our plumbers love the system and told us when we bought our house ten years ago that it could really last a long time if well maintained.

We also have CO detectors on every floor so not worried in that department either.

I love posts like this. It's the window into how people think that just because their boiler isn't actively leaking or on fire that's it's a good thing to have in the house.

When a boiler reaches 20 years of age, it's a piece of crap. I don't care what your oil company says, or your plumber who hasn't the faintest idea how to gauge efficiency or maintain or pipe it properly.