Diagnosis and repair details for electric residential steam bath generator:
This article series describes in detail how, with help from the manufacturer we diagnosed and repaired a new but troubled installation of a residential steam generator in the shower of an existing home.
We explain what went wrong, what trouble it caused, and how steam generator problems with small residential steam generators might be diagnosed and repaired.
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The trouble we describe: no steam, water at steam head, error messages at the control, is laid entirely at my own feet as the purchasor and contracting-installer of the equipment.
Bottom line: I took my eyes off of the worker with the hammer drill! The rest is in the details.
Any mechanical system installation that varies from what the manufacturer intended includes a risk that you make a mistake. Having spent nearly 50 years diagnosing problems at buildings and their mechanicals systems I can but emphasize that even if nothing could possibly go wrong, something can and often will.
The property owners tested the new Mr. Steam® generator installation and found it working perfectly after the initial installation. For a few days.
The steam shower, whose enclosing safety glass window and doors were "on order" was sealed for testing using a plastic tarp.
At that time, pending completion of the weather-enclosure the generator, when not in use, was protected by a plastic tarp and was kept successfully dry. Besides, it never rained during that test period.
Above: the steam generator control circuit board indicator lights are showing that the unit has power and that it has been properly filled with water.
Then our sheet-metal crew returned to install the weatherproof cover over the steam generator. Thinking that we had plenty of working space, we made a fatal error: we failed to double-check that one of the mounting screws for the steam generator cover might pierce a pipe or an electrical cable.
The site screw drilled pilot holes and screwed the new cover box to the wall. It was a beautiful installation shown at page top and in other photos here.
Above, photos showing the location of the steambath generator cover mounting screw that was suspect, and photographs of the control cable conduit during installation showing the area that might be pierced by the cover screw.
Above: the steam generator during installation, yellow oval marks area thorough which the control cable conduit passes up the wall to the wall-mounted steam control.
The owners tested the steam generator that evening. It failed to operate. Steam was not generated and the wall control displayed two error messages.
The wall control power button and temperature control buttons gave no response.
Err2 was followed by H2O - the unit was not sensing that it had sufficient water.
Error codes are explained in Mr. STEAM GENERATOR MS90EC1 INSTALLATION MANUAL [PDF] where you can read that Err2 means it thinks the circuit board override-test button has been pressed for more than 5 minutes, suggesting a problem with the control or its cover.
H2O - a warning shown at the start of this article, means that the system is not detecting sufficient water - the manual lists several possible causes.
Was the problem a misadjusted water pressure regulator, a bad water control valve in the steam generator, or something else?
The green light indicates that the steambath generator has electrical power. Notice that the yellow WTR (water) and red HTR (heater) lights are not lit.
Above: to the left of the control circuit board you'll see the purple wire connected to a water level sensor probe for the steam generator.
Particularly if the system is being fed hard water, mineral deposits accumulating on the probe's sensor tip can interfere with the ability of the sensor to properly measure water level.
Some water level sensor probe models can be cleaned, others must be replaced if scaling trouble is found.
Behind the sensor probe is the black connector power switch for incoming 240VAC.
We checked the pressure gauge at the pressure regulator and re-adjusted the regulator to be sure we had about 20 psi of incoming water. That made no difference.
Then the wall control went completely dark, refusing to respond to the on-off switch nor its other controls.
Suspecting that a cover mounting screw might have cut the control wires between the wall control and the steam generator's circuit board we tried the on-board over-ride button on the circuit board.
If all else is working this test will give 5-10 minutes of steam generation.
The test cycle using the over-ride button (red arrow in our photo above) resulted in cool water running continuously out of the steam head (photo below).
Did this mean that a water control solenoid in the steam generator was broken?
Probably not. If the solenoid fails you should see either no water or water running continuously regardless of whether the unit has electrical power or not.
Watch out: being careless when drilling and mounting anything along the route of piping or electrical control cables that have been routed within a wall cavity risks causing serious damage to the equipment.
In a wood-framed building wiring is normally protected by steel plates if it passes close to the surface of a wall stud.
But in Mexico a common construction method builds out of solid concrete or out of adobe. After walls and ceilings have been constructed it is common practice to cut grooves in the wall surface for pipes or wires.
After pipes or wires have been installed they are plastered-over. Once the building has been painted, the exact path of these pipes or wires may be impossible to see.
Special thanks to the P.R., Mr. Steam's technical support representative who patiently guided us through the trouble symptoms and recommended the necessary repair parts for this steam generator repair work.
Readers who need help with the selection, installation, or repair of their own Mr. Steam steambath generator should contact the company directly at
Mr. Steam: Sussman Automatic Corporation, 43-20 34th Street, Long Island City NY 11101 USA Tel: 1 800 76 STEAM, or 9410 S. La Cienega Blvd., Inglewood CA 90301 USA, Tel: 1 800 72 STEAM, Tel: 1-800-707-2862 [USA] Website: https://www.steamsaunabath.com/ Email: Sales: Sales@SteamSaunaBath.com Service: Service@SteamSaunaBath.com
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DOEs ANYONE KNOW THE PROPER SETTING FOR A HONEYWELL PA-404-A 1009 PRESTROL CONTROL FOR A WEIL-MCLANE STEAM BOILER - Rick 9/11/11
Rick the exact pressure needed varies by installation but in a low pressure residential steam system the pressure range is usually between 0.2 and 0.4 psi.
what's the term they call the 2 steam pipes that form an H above a steam boiler. in other words the pipes from both sides of the burner connected together?THANKS,Walter - 9/25/11
Walter: sorry we couldn't give an instant reply; sometimes the volume of reader questions is considerable and takes some time to get thorough.
I am guessing you are referring to the steam header or manifold piping that allows steam to enter more than one steam supply line or riser.
A second piping configuration that will be along side, not above, the boiler is the Hartford loop - a loop of piping sort of like an upside down trap that prevents water from siphoning out of the boiler should there be a leak in the condensate return line.
Wow, what a great web site. I am trying to identify a vessel on the side of an old National steam boiler/furnace. It is about 12-18" tall, about 8" diameter and is attached to a manifold in the side that is about 12" off the floor. It is heavily rusted. The boiler is an old coal fired converted to oil. Can I send you photos? Thanks, Stephen firstname.lastname@example.org or strentsch 10/4/11
sure Mr. Strentsch,
use the CONTACT link found at page top, left, or bottom to see our email and send along some sharp photos and we'll be glad to take a look
I blow the system down regularly and then make up the water in the sight glass. However I seem to be using significantly more water then years past whereas I'd top the sight glass every couple of weeks in the past compared to every other day now. What do you think the problem is? - Tom C 10.27.11
Tom C: a common reason for increased water consumption in a steam heating system is one or more radiator steam vents that are not closing properly. Check also for a leak in the condensate return line.
I’m happy to have found this website. I’m getting back into heating and cooling and need to prepare for higher license. Question: Is there a DVD collection you recommended as an additional studying tool? I see that Harold J. Frost, Frederick M. Steingress, Daryl R. Walker’s collection is close to 600.00 which is very steep for my pocket. Would you happen to know of a website or cheap place I can buy such DVD or a CD? If not these guys than another author is ok. Thanks for the feedback. Kym 11/23/11
Kym if you are looking specifically for information on steam heating I'd pick up any of Dan Holihan's books on steam heat. He's the best.
The HomeServ tech just left after installing a new auto water feeder, and the PSI gauge on my steam heater is off the chart, over 30 PSI. I shut it down and called HomeServ and they said leave it on and they'll come in the morning. How do I lower the PSI myself so I can leave it on tonight and my little kids (two with strep) don't freeze? Thanks! 2/22/2012
Watch out: If the PSI gauge is showing abnormal pressure and the gauge itself is working properly the system is unsafe and should be shut down. Call someone else and fire that tech - from your description the system sounds unsafe
I HAVE AN OIL BURNER HOT WATER SYSTEM MY EXPANSION IS DRIPPING WATER OUT THE AIR VALVE STEM AT THE BOTTOM OF THE TANK SHOULD I REPAIR OR REPLACE - Mike S 10/12/12
Mike, an air valve stem is replaceable, I would tr that first. Check also for abnormal system pressure ( an unsafe condition). But if the internal bladder of the tank has burst - another explanation for finding water at the air pressure adjustment valve, then most likely you need to replace the tank. You'll know this condition because the tank will become waterlogged, heavy, and ultimately the boiler TP valve will drip (another unsafe condition).
I have a one pipe steam system. My dining room radiator air vent was just replaced because the old one was leaking profusely (damaged my floors). The porch radiator air vent was also replaced because of too much steam condensation in the room, but now the open/close valve is leaking at the base. The radiator upstairs in middle bedroom is banging and clanking. The pipe that runs along the basement ceiling (finished basement) also bangs when the heat is coming on. My plumber cannot really give me an answer. Any suggestions would be appreciated. Thanks p Rita 11/21/12
If you search InspectApedia for
BANGING STEAM PIPES
you can read about the diagnosis & cure of this problem
About the leaking valve - unfortunately that means you need another service call.
cleaned on a vav [?] system is leaking close the cilanod [solenoid ? -Ed] valve need to be replaced- Anon 11/23/12
See RELIEF VALVE LEAKS for procedures to diagnose and fix leaky TP relief valves.
Pressure on gas steam boiler was rising far too high, so high that the pressure relief valve released twice when it hit 15 psi (as it was supposed to do). Good buddy who really knows his stuff checked everything from pressure valve to pressuretrol. Nothing . He then checked "pigtail" and found blockage .Problem solved!! - Ken 11/24/12
Thanks for this note it may help other readers
My building uses steam heaters. I have no control over the heat in my unit because the thermostat is controlled by my landlord/owner who lives above me. However I have a small 1 bedroom with two heating units so even with all of the windows open, it can still get very hot. Is it okay for me to completely close the "open/close" black knob valves on my units or will that cause problems for the whole system? My landlord had previously told me not to touch the valves... Emily 12/10/12
Yes if the radiator control knob is not jammed or frozen you can try closing it partly or fully; radiator control knobs are intended to be a homeowner-resident-operator control. But if the knob is not easy to turn, don't force it as you might end up with a leak.
I have 2 yr. Boiler. It hisses like venting steam off and on loudly. Seems like when heat comes on venting starts until off. -Mr. Ed 12/28/12
Steam boilers include steam valves that hiss; we need more details.
I am having a pressure problem and it looks like one of my relief valve is leaking or letting the pressure out would this keep my boiler from running. It seems to be shutting off and I need to set the pressure all the time. is it as simple as changing the valve and resetting the Pressure? Rick 1/3/2013
See RELIEF VALVE LEAKS for procedures to diagnose and fix leaky TP relief valves.
II have a pressure of 28 psi and water is coming out of my return how can i lower the water pressure from my steam American standard boiler - Ronald 1/13/2013
Watch out: If your heater is a residential steam heating system it is operating at an abnormally high temperature and is unsafe. Turn the system off immediately and call your heating service company.
If your heater were a residential hot water heating boiler (hydronic heat) its pressure might be close to the upper end of normal operating pressure - and the leak at the valve could be due to a valve problem or to any of quite a few other causes. See RELIEF VALVE LEAKS for procedures to diagnose and fix leaky TP relief valves. See the links just below for information on how the steam heating system pressure is controlled and set.
(Mar 23, 2013) home able said:
Oil-fired steam boiler was functioning properly upto two weeks ago, now doesn't fully run to designated temperature on thermostat (digital). It will stop a degree or 2 short of desired setting even though thermostat says boiler is running. Why?
I'm not sure what's happening with your system. IN general the gauges are not lab grade precise. It's possible that your gauge or its sensor port are debris clogged. Try tapping gently on the gauge to see if the needle moves. Also watch the gauge to see its reading throughout the operating cycle.
(Apr 1, 2013) Luis said:
I have a gas bolier which continues to overflow. The sight glass floods even some pipes that run though the floor ang o up the wall with a steam trap a gauges at the to of the pipes. I called a company but they have not been able to find the problem.
Luis if the steam boiler keeps overflowing, or flooding, most likely the water feeder is out of order.
(june 19, 2014) anonymous said:
I have hot water baseboard system boiler in my crawlspace (.Basement) im thinking about replacing the boiler with a horizontal warm air furnace adams furnace. I keep getting freeze ups and they are very difficult to repair. The furnace adams make is supposed to be 95 percent efficient. Plus the fact there are no pipes to freeze is the warm air furnace the way to go? Thanks paul
You're commenting about hot water and hot air heat on a steam heat article - so this may be a bit confusing to other readers, but in general, conversion to another heating method is fine if you can bear the expense; each heating type has its pros and cons so IMO there is not a single "right" answer. Keep in mind that when you change from steam heat or hot water heat to forced warm air heat, your costs are much greater than just the heater itself as you have to install a heat delivery system : air ducts and registers. That can be convenient in some building designs and quite costly in others.
(Oct 16, 2014) Antonio said:
I just installed a 299 MBH gas fired steam boiler and connected to an existing system serving the second floor of an office building, approx floor area is 2,600 sq ft.
Existing EDR calculated as approx 900 sq. ft. The boiler started up successfully yesterday and I have been testing it ever since. Everything seems to be working fine. My question is what would be the right pressuretrol settings: I am using 1 psi cut-in and 1 psi differential and everything seems all right, but I may be missing something, maybe the boiler could work more efficiently with a lower or higher cut in pressure.
(Dec 15, 2014) Kevin M said:
I have a gas-fired steam boiler that has worked flawlessly since its installation six years ago. Suddenly it is overfilling. I let out several extra gallons a day to reduce the level in the sight glass. Should I replace the automatic feed? It is attached to the hot water heater, unlike previous installation I have had in other houses where it is connected to the cold water line. I sit possible that excess pressure from the expansion in the hot water supply line is forcing water past the automatic feed? What could cause this condition?
Over-filling of a heating boiler is indeed usually a problem with the automatic water feeder, more rarely leaks into the boiler from a tankless coil.
(Feb 15, 2015) Beverly Streeter said:
I live in a 16 unit apt complex. What make the heat clan and banging?
See the banging pipe diagnostic and repair suggestions at BANGING HEATING PIPES RADIATORS
(Apr 9, 2015) george said:
steam boiler heater runs for about 15 minutes then it cuts out
George I'm stuck on this one with no onsite data; could be related to heating of components, clogging of a filter, I dunno. It's time for an onsite heating service tech.
DO NOT keep pushing a re-set button. That's unsafe.
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