Any millivolt system boilers still available?

Old_Steam · January 26

I have an old Pennsylvania Furnace Company boiler from the early 1960's still running fine. But due to age and condition, I know at some point I have to get something new. It is a millivolt system. I want to replace it with another millivolt system so I will still have heat in a blackout. Do they make modern millivolt system steam boilers today that dont have a need for any transformers?

Steamhead · January 26

No. Millivolt systems no longer meet energy-efficiency requirements.

EdTheHeaterMan · January 26

https://forum.heatinghelp.com/discussion/comment/1884191#Comment_1884191

Agree

But that does not mean that you can't get those old style parts brand new in the box and put them on the boiler after the job has been inspected. A steam boiler is the easiest piece of equipment to do that to. There are no circulators or zone valves involved. Just a high limit pressure control and a mechanical LWCO will make the minimum safety requirements You wont have the auto vent damper and electronic ignition but you will also not have frozen pipes during a power failure.

ratio · January 26

There are 24 VAC inverters available that will keep a gas valve open for a goodly while now too. More complicated, and there's the whole battery maintenance thing too, but it'll definitely keep the heat on until you can get the generator started and plugged in.

hot_rod · January 26

These power stations come in many sized. You could run a 24V system for days, maybe weeks with a large enough pack. Very handy for camping, tailgating and other remote uses.

I power lights and chargers and a small fridge in my camper for 4 days with a mid sized unit.

mattmia2 · January 26

https://forum.heatinghelp.com/discussion/comment/1884243#Comment_1884243

What are the idle losses of that inverter, if the inverter is on but has no load? When I have run salvaged ~1kw UPSs to power something like a cable modem with a pots bridge it seemed like the power to the load was negligible compared to the quiescent current of the inverter. Is that still a problem with these, if you want to power a small load for a long period of time you have to frankenstein a big battery in to a tiny ups.

hot_rod · January 26

Idle consumption varies based on the model ad size of the inverter. A few online sites test and publish that data for various brands and models.

Screenshot 2026-01-26 at 11.02.08 AM.png

I keep mine plugged into a 200W PV array on my camper, or at home into a wall charger. So it is always up to speed for power needs.

Or convert you boiler to DC volt, and switch off the inverter

mattmia2 · January 26

wouldn't converting it to dc be the same effort as converting it to millivolt?:)

EBEBRATT-Ed · January 26

I think a power station as @hot_rod mentioned is the best bet to keep a boiler on. No sense hacking in some millivolt controls.

The pressure control, LWCO and thermostat would have to be millivolt rated

kcopp · January 26

This is what I have my System hooked into if I lose power.

I just have a pigtail that I can plug into this.

M18 CARRY-ON 3600W/1800W Power Supply | Milwaukee Tool

hot_rod · 5:11AM

I guess it comes down to how often the OP has blackouts, how long they last, how much power the boiler needs, and how much $$ they want to spend on a back up system.

I imagine hacking a new boiler, converting the control would void warranty and put any failure liability on the hacker

Any millivolt system boilers still available?

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