[Half-Inch Stud]

So we have really enjoyed our Cast Iron Radiator heat. Mysteriously comfortable up until this past week. Then not so good; Bedroom too hot while House being held at 70F on the Main Floor. Dry like desert tortoise, and 1-sheet was a plenty.

Well today i inspected the 1950s gas furnace and found it running the water to 225F and 25 PSI. !!!! Instinctively went into it and found the Water Jacket Mercury Switch had Sprung to that high setting due to the Lock tension Thumbscrew losing tightness. Well i rotated the Jacket Temp setting down until it ckicked off. That was 150F. So locked it tight.

Turns out the Furnace resorted to the emergency trip circuit (another thermo switch in the Furnace set an apparent 225F or higher) for cycling the gas on/off. PHEW; averted a calamity.

Sits and thinks; what does the Internet say? "140-170F" on many blogs. Okaaay. So this is a PSA to check your Circulating Water Temp, and also keep the PSI safe too.

[dataway]

A few more degrees and you might have ended 1/4" Stud

[Shiny]

Thanks for the warning, glad the backup control kicked in before you reincarnated as a roasted brussel sprout.

[BTCS]

What's the relief valve set at on that unit?

[Half-Inch Stud]

3" Cast Iron Pipes don't appear to have a relief valve,

Well called the Gas Service guy (not heard back) because the gas still stays on too long as the water temp goes to 250Fs ( ridiculous ). Seems the thermo switch is electrically stuck "on" while the thermo-mechanical makes a nice click. I'm going in!

Added a photo, but not gonna wait around to snap it at the peak. Looks like the Delta IV Heavy in there (normal). Update: Snapped a Peak photo; 240F is where it shut off when i re-tuned the Thermo down from 160 to 130F. Me thinkin the Thermo is not close to displayed value anymore. Gonna add that photo

[Half-Inch Stud]

Here is the Thermo switch which goes into the Water Jacket. Found it sprung loose at 220F. Set it to 160F but still ran hot. Now set to 130F and guess i babysit this to see how hot it goes befor shutoff.

Looks like 4"-5" Iron reduces to 2.5" Iron pipe. Don't got wrenches for this type of pipe, and better not ever need them.

[Half-Inch Stud]

Removed the Thermoswitch and it looks to be a good design. Does have the strength to press/click the Switch, but is 40F off of Cal (at room temp). Good to know.

Gonna button it up.

[Half-Inch Stud]

Front Plackard. Built to last a couple hundred years. Furnace guy never called back, I left a Message.

[BTCS]

Talking about the boiler not the radiator. Label plate says you're rated max is 25 psig steam and 50 HW? I'd find the safety relief and ensure its not scaled-up if your running with an unreliable aquastat or pressure control.

[Shiny]

Originally Posted by Half-Inch Stud

Front Plackard. Built to last a couple hundred years. Furnace guy never called back, I left a Message.

Please forgive me but I can't resist...


You sure nobody swapped that ID plate? Those rivets don't look factory to me...



And yes, that thermostat looks like it was built like a tank. Why do you think it would lose 40 degrees calibration? Is the bimetallic coil corroded or was solder used as a mechanical connection and then creeped/relaxed or ??? If the calibration changed because the coil relaxed I'm not sure I'd be calling it a good design, but hey..

There's some serious nostalgia in that thing but geeeshhhh.. I'd say you are lucky the contacts in that switch are still working.

[Half-Inch Stud]

Originally Posted by BTCS

Talking about the boiler not the radiator. Label plate says you're rated max is 25 psig steam and 50 HW? I'd find the safety relief and ensure its not scaled-up if your running with an unreliable aquastat or pressure control.

I looked; nothing. In fact the public water comes through a copper pipe and Regulator, then converts to Iron for Automatic fill for Top-Off if some one goes around to bleed the upstairs radiators. A lot of cast iron radiators in this home....1919 home.

[bluebandit]

Most boiler reliefs are set at 30 psi. Some older units have no relief, they have one mounted inline with the water feed valve. Normal pressure is around 12 psi. Have you had the expansion tank drained lately.

[Tom Vaught]

I have a 4 zone hot water system, over the years I have had all 4 of the same water controllers replaced. There Are more modern (newer) designs but the old ones ARE built like a tank. Typically they drain the water and cut out the old unit and install the pipe and new unit in the system. Mine developed water leaks after 40 years.

In your case the control circuit for the device apparently failed.

The other thing is do you have all of the air out of the system?
Many times when the control fails over time the valve lets air into the system and less water and more air makes the water temp thru the system much hotter.

Tom V.

[Half-Inch Stud]

Originally Posted by Shiny

Please forgive me but I can't resist...
You sure nobody swapped that ID plate? Those rivets don't look factory to me...

And yes, that thermostat looks like it was built like a tank. Why do you think it would lose 40 degrees calibration? Is the bimetallic coil corroded or was solder used as a mechanical connection and then creeped/relaxed or ??? If the calibration changed because the coil relaxed I'm not sure I'd be calling it a good design, but hey..

There's some serious nostalgia in that thing but geeeshhhh.. I'd say you are lucky the contacts in that switch are still working.

I figure there was friction for where the swingarm pivoted on the centershaft, maybe dug a groove. Also the switch might have increased in Click pressure, just a wee. No corrosion but i could figure some fatigue or bimetal strain relief occured.

The system is holding Temp as usual 70 inside, 29 Outside. Temps to 180 then shuts the gas.
Cleaned-up the gauges; Temp gauge needle seems flakey, so would enjoy a replacement.

Here's a photo of the Furnaces: Coal (water and exhaust disabled) on left, Auger all there but not shown in photo. Natural gas on right..

[bluebandit]

In your last photos there is a relief valve right after the feed regulator on the supply line. If you have a temp gun shoot the outlet pipes to compare to the gauge

[Half-Inch Stud]

Originally Posted by bluebandit

In your last photos there is a relief valve right after the feed regulator on the supply line. If you have a temp gun shoot the outlet pipes to compare to the gauge

Oh thaaaat! Yea there is a relief valve on the water feed side which goes into the return. Never a drop seen.

I never had the expansion tank drained. However the radiators seems restored because none of them show any leak or rust stains. So i figure the tank was done at that time...whenever that was.

[dataway]

Wonderful equipment ... being ex-Navy machinist mate I would find it very hard to replace that with a modern system. I'd have glossy white lagging on all the hot pipes, copper and brass all polished and a clip-board with log sheets

[Shiny]

Originally Posted by Half-Inch Stud

I figure there was friction for where the swingarm pivoted on the centershaft, maybe dug a groove. Also the switch might have increased in Click pressure, just a wee. No corrosion but i could figure some fatigue or bimetal strain relief occured.

Thanks for the insight. The coiled strip seems an opportunity for residual stress that could relax over time but gotta admire the old-school mechanical approach. I'm still amazed the switch still works and overall, that the entire system still works.

My son texted me yesterday, fuming because his cell-phone battery won't hold a charge right when he paid it off. Device failure is a marketing conspiracy in his mind. I should tell him two cans and a string would last longer.

[Half-Inch Stud]

Originally Posted by Tom Vaught

I have a 4 zone hot water system, over the years I have had all 4 of the same water controllers replaced. There Are more modern (newer) designs but the old ones ARE built like a tank. Typically they drain the water and cut out the old unit and install the pipe and new unit in the system. Mine developed water leaks after 40 years.

In your case the control circuit for the device apparently failed.

The other thing is do you have all of the air out of the system?
Many times when the control fails over time the valve lets air into the system and less water and more air makes the water temp thru the system much hotter. Tom V.

Air is probably mostly out.
Temp control circuit locking Thumbscrew lost torque, so it sprung up in temp and couldn't press cluck switch.

Thank God there are no Zone Valves: grew up with those, and the 1st 2 home i bought had them: designed to fail in the electric coil. Then later the inlinw water switch button corrodes out.

The Cast Iron Radiator system has a Cast Tee for each radiator pipe ( in and out). a pair od Tees can be 3' apart on the 2.5" Main flow, and flow still occurs to the Radiator. no moving parts so flow must be encouraged by an internal flow divider huh.

[4dblnkldude]

Originally Posted by dataway

Wonderful equipment ... being ex-Navy machinist mate I would find it very hard to replace that with a modern system. I'd have glossy white lagging on all the hot pipes, copper and brass all polished and a clip-board with log sheets

LOL awesome post!! Car guys can appreciate anything old...even boilers.