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1980s HB Smith/Dunkirk Series G210 Boiler Questions

MussSyke Member Posts: 4
edited February 2022 in Strictly Steam
Hello Everyone,

My first post. In October, I bought a great new old house in Maryland, with a 2-pipe steam boiler/radiator system. I am an Engineer, but I know next to nothing about boilers, except for what I have researched recently. I have watched a lot of excellent YouTube videos narrated by Dan Holohan, but I’m probably not watching them in the correct order for a beginner. As you can imagine, it drives me nuts to not know everything about a system in my own house.

Now that my first heating season is almost over, some of my more basic questions are becoming more urgent, because I need to know what to do with this system in the off season and I also figure that would be the time to make any improvements if possible. I will attach some pictures. Here is my first round of questions (I know some may be too basic, but understand that I am researching as much as possible as time permits):

1) Does anyone have a user manual for the G210 series or a similar series? Know where I can find one? That would be first on my wish list.

2) How do I turn this off? How do I turn it on? And what do I do with it over the summer? It seems that the previous owner never really turned it off, and I could see it boiling sometimes when the heat wasn’t on before the heating season. The neighbor, who is apparently an old pro at boilers, made it sound like it’s better to leave it on all year, but that sounds…wasteful. I saw some article about putting some chemicals in if you leave it “wet”, or what to do if you want to leave it “dry”, but I don’t even know how to turn it back on if I turn it off. One of the pictures attached is of the pilot light switch. (There are instructions for on/off on the side of the boiler, but I’m just a little concerned it won’t work or that I shouldn’t do it anyway).

3) I have this cool looking old thermostat from 1924. It heats just fine to about 70 degrees if you turn it down to about 55, but there are no still-working advanced features whatsoever (it has a clock and you can do night/day, but I don’t think that part still works). Any recommendations on a thermostat designed specifically for boilers? My gut tells me thermostats designed for forced air wouldn’t be satisfactory.

That said, I do have two heat pumps with resistor packs on two separate modern thermostats. Should I see about integrating all the systems into one thermostat?

4) …for that matter, would it be cheaper and otherwise more efficient to use the heat pumps when it’s above freezing outside? Or would using the boiler for just a month or two out of the year make it even more wasteful to have it sitting in standby much of the time?

5) What do I do with it when I go on vacation? I can’t turn the thermostat down much further without it basically being off. Of course I can’t have the house freeze. Any specifics I should consider?

6) Care to venture a guess on what exact type of piping I have? It is 2-pipe, where it goes in the top of one side and comes out the bottom of the other (to the return “bus”/pipe), but from the videos I watched, it seemed like that system should have steam traps in it, and I don’t see any.

7) I have one radiator that doesn’t work. The pipe going to it through the kitchen does get hot, but the radiator never gets warm. It has an on/off lever like the rest, but that doesn’t seem to do anything. Does this not get hot because of a clog in the piping? Any ideas?

8) Can anyone tell me what this big “U” is in my piping. I believe that is actually in the steam line, not the return, and it is toward the end of the run. And I think this is the pipe that goes to the radiator that doesn’t work. I saw water level piping fixes and return traps on the videos, but I can’t figure it out considering where it is at in the system. I assume I can take that bottom cap off and clean it out in the summer? But what else do I need to know about this?

9) According to the spec plate, the output BTU is 212,000. Having done the Manual J for my previous house – and knowing what the size is for the current house’s air conditioners and heat pump (and being in the same town as the previous house) – I would guess a properly sized furnace would be about 100-120k BTU. Is this insanely oversized or do boilers need to be sized much higher? My heating bills are not shocking, but I certainly don’t want to spend more than necessary.

10) The radiators all have these nice-looking covers on them with holes just in the front. Dan said this lowered the efficiency (or emissivity or something) greatly, but the heat has to go somewhere, right? So is my gas consumption actually higher because I am still using these things? Also, Dan said that radiators are a certain color for a reason, but mine have been painted random colors that the walls were once painted. Anything I can/should do about that?

I know the near-boiler piping is not perfect from Dan’s videos, but the system works very well and heats much smoother and more comfortably than my previous old house’s retrofitted furnace. It does make plenty of noise that I’d like to mitigate, so any constructive ideas are welcome. I think I’ll be quite happy with the system once I’m certain I am maintaining it as well as possible and that I can troubleshoot is as necessary.

Thank you for any advice you can provide.


    EBEBRATT-Ed Member Posts: 15,513
    Apparently Dunkirk made that boiler for HB Smith. You can find Smith boilers by googling Mestek (mestek owns Smith) they are in Westfield, MA and maybe they can get you a manual. Or you can google Dunkirk and get in touch with them

    Your system doesn't look like it has any electrical power going to it so I am guessing it is a 'millivolt system" the pilot gas flame generates asmall electrical current to power the main gas valve. This circuit runs through the pressure control and low water cutoff control.

    The only way to shut it off compleatly is to shut the gas off. But then to start it you have to relight the pilot. You can wire a switch into the limit circuit to use as an on-off switch and just let the pilot burn year round. Milli volt controls require special controls with low resistance contacts so be careful changing controls

    Your boiler looks like the piping (near boiler piping) looks undersized, check the manual when you get it.

    Steam systems are sized by calculating the EDR of all the installed radiation and totaling that up. EDR=square feet of steam so you just pick a boiler that will heat the sq ft of radiation installed.

    You have a 2 pipe vapor system that should run at low pressure. I will let the vapor experts on this forum comment on that

    Since the system heats well I would budget for a new boiler of the right size at some point in the future. I would guess that boiler is a 1970s-80s. The year might be buried in the serial #.....can't read the whole thing
  • Jamie Hall
    Jamie Hall Member Posts: 23,273
    Let's see here... 2, turning it off. Opinions differ. I never do on the ones which I maintain. Others do... and on chemicals, again, opinions differ. I use no chemicals. Others do, but only in moderation (the instructions usually tell you to use more than needed.

    3. That thermostat did, originally, have a way to set it to a night/day type schedule. It's highly unlikely that that still works. The simplest replacement -- if you actually do need to replace it -- will be one of the battery powered programmable Honeywell Home thermostats. They work fine -- do what they're meant to do -- provided they are set up for steam. They won't work any better than what you have, but you can program them. I'd advise against trying to integrate the various themostats. That gets complicated.

    4. Yes it would be more energy efficient to use the heat pumps when it is above freezing, and just keep the boiler on standby for the colder days. No harm to the boiler.

    5. I'd just turn the thermostat down as far as you can, within reason, and not worry about it.

    6. Now it gets interesting. I suspect that your system was originally a vapour -- very low pressure -- system. Are there any markings on a typical radiator valve? That said, it was intended that the valves on the radiators would let steam in at a rate which they could condense, but not more, and thus there would be no need for radiator traps -- which you may not have (a closeup of the return elbow would help). However, this type of system is very pressure sensitive -- and the control you have on the boiler for pressure (that grey box) is not suitable. You need what is called a vapourstat with a 0 to 16 ounce pressure range. They aren't cheap -- but the system will work better.

    7. and 8. go together, if that loop arrangement is part of the piping for the radiator which heats poorly. That loop arrangement is a water seal. If all is well, condensate comes in one side and flows out the other -- but neither steam nor air can pass. However, if the boiler pressure is too high, the pressure will force the seal water out of the loop and steam can then get through to the side which isn't supposed to have it. That will happen to that seal -- if those concrete blocks are standard -- at around 1.5 psi. You don't want that. This may be part of the problem with that radiator, though there may be other problems. For that problem radiator, study how the return side piping goes. It needs to go into a dry -- high level -- return and on to the main vents somewhere.

    9. Steam boilers are NOT sized by Manual J or the heat loss of the structure. Rather, they are sized by "EDR" -- equivalent direct radiation. To properly size them, you need to determine the EDR of all the connected radiation and compare that to the nameplate rating. If the boiler doesn't cycle on and off repeatedly, it's probably pretty close.

    10. Those covers do reduce the heat output some -- but the effect of that is to cause the boiler to shut down on pressure sooner. It won't waste fuel -- it will just burn less of it. Colour is not relevant, except for the metallic silver or bronze paints.

    The near boiler piping isn't perfect, but -- if it ain't broke, don't fix it.

    Now one other comment -- which actually is sort of relevant to some of the above. Try to trace out all your piping and determine what lines are steam mains or runouts, what lines are dry returns, and what lines are wet returns (if any). Then find your main venting, which should be where the dry returns come together before dropping down to the boiler. This venting is very important, as it is where all the air in all the radiators can get out so the steam can get in. Also look at the ends of the steam mains. There may be crossover traps between the steam mains and the dry returns, or there may be vents.

    Hope this helps some.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,060
    It looks like a 24 volt transformer mounted on the ceiling, upper right in your first picture. Your tstat wires may go to that location also.

    Your pressure gauge may never move, it looks original and may go from 0-30 PSI.
    That range is required by code and usually fails within a few years.
    Best to leave it in place and add a 0-3 PSI or less somewhere else.

    What is the pressuretrol set to now?
    An important maint item is to clean the pigtail loop under it, that is often plugged and not allowing the control to sense correctly.

    Very neat collectable old tstat. I would leave it in place. But install a modern one near by. Is there a port to wind the clock?

    The Honeywell TH 5000 series has been a good workhorse for me.
    IIRC, the TH 6000 is programable.

    That end of main drip pipe? in the electrical panel picture would usually have that reducing 90 rotated 90 degrees CW so that pipe would drain completely.
    If no hammer there, then not to worry about it for now.

    Looking at the 4" sq box at electrical panel, those blocks look to be maybe 12 inches (wall tile?).
    EBEBRATT-Ed Member Posts: 15,513

    I think your right. I blew up the picture and there's 2 24 volt cables taped to the gas pipe so 1 is 24 volt power and the other one is the stat. I was thinking it was millivolt
  • Steamhead
    Steamhead Member Posts: 16,826
    edited February 2022
    @MussSyke , from the looks of the radiator shutoff valve and the return elbow, I'm going to go out on a limb and say that might be a Kriebel system. Does the valve say "Vapor Vacuum Heating Co." on the top?

    And, what @EBEBRATT-Ed , @Jamie Hall and @JUGHNE said about the piping.

    Where in Maryland are you?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,281
    @Dave in QCA, don't you have one of those Minneapolis-Honeywell Chronotherm Thermostats too?
  • Chris_L
    Chris_L Member Posts: 336
    I was also going to say that is a millivolt gas valve because it just like one of mine, aside from the plastic color at the terminals. (Mine is red.) But after reading other comments, I am not sure.

    I don't know if Honeywell used any type of color coding for the plastic around the connectors, but one sure way of telling whether it is a millivolt valve is to look for labels PP and PP/Th for the connections. It will likely be molded into the plastic in very small letters.

    PP indicates powerpile for a millivolt system. If it is is a 24v gas valve, I believe the label will be Tr for transformer instead.
  • Dave in QCA
    Dave in QCA Member Posts: 1,785
    edited February 2022
    Hello Erin! Why, yes I do have one of those thermostats. It may be new old stock, or it may be a used one that was put back into the original box in the course of troubleshooting or something. Anyway, the box is labeled with both the vendor, Republic Electric Co of Davenport, Iowa, and the customer, Montgomery Elevator Co., Moline, IL. The label on the box says, Chronotherm type T105A30009X1. The installation instructions are still in the box, but there was no wiring schematic. I was able to find that online. It is a bit unusual, and different than anything else I have ever seen, in so far as the wiring and the operation.

    Two of the wires are for a 20v power supply to the clock. The other three wires are for the thermostat, but it is not a typical 3-wire setup as is used with 3-wire zone valves, etc. Rather, of the three wires, 1 is common, and the other two are for the contacts. There is a small and adjustable differential between the closing temperature of the two contacts. These three wires must be wired to an Honeywell R19A relay or equivalent. In operation, as the room temperature cools, the first contact will close. It has a circuit running through a heat anticipator heater and then to the relay and the corresponding relay contact will be open, so there is no effect from this contact closing. Upon further cooling, the second contact in the thermostat will close, activating the relay coil. The relay coil will cause contacts that control the heat to close. A second set of contacts in series with the first mentioned contacts in the thermostat and the heat anticipator to be activated. Also, through this contact, a second route supplying voltage to the relay coil is established. However, since the two thermostat contacts are in parallel, there will be no current through the resistive anticipator heater. As the heat operates, the room temperature rises. When the temperature is sufficient, the second set of thermostat contacts will open, and the first contact remain closed. In this condition, current continues to flow through the contact because of the holding circuit in the relay. The current flowing through this contact is also flowing the through the series wired anticipator heater. The anticipator will generate heat in the thermostat and cause the contacts to open.

    Note, the contacts point positions and differential are adjustable. The primary pivot point is adjustable. Clock setback is on a 24-hour basis. The setback temperatures and the recovery temperatures are adjustable. This is entirely an electromechanical device. The publication date is January 21, 1941, and at supersedes a version published April 24, 1940.

    I picked this thing up in a Restore Shop. I have wondered if some of the older pros have experience with how it works in controlling a steam system. I am used to my Tekmar system, which produces VERY even temperatures, but there is a tendency for actual room temperatures to drift a bit. One degree is common and 2 degrees is frequent.

    If anyone needs the installation instructions and the wiring schematic, I would be happy to scan those and post them on here. I might consider selling the beautiful thermostat too. I may even have a compatible relay on the shelf downstairs. I tend to accumulate things I don't need. Ha!
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,281
    edited February 2022
    Thanks @Dave in QCA. Great info!
  • MussSyke
    MussSyke Member Posts: 4
    Hi everyone. Thank you. I am thrilled that so many of you have replied. My mind is shot today after doing my taxes, but I hope to have coherent and intelligent replies to all of you once I survey again and try to make sense of all that you said...
  • MussSyke
    MussSyke Member Posts: 4
    Thanks again for all the info and helping me dig deeper into this. I’ll try to answer everybody without double posting.


    Great advice about contacting Smith. They sent me a scanned copy already. I can hardly believe when an actual person still answers an Email, and is helpful yet. I didn’t read it yet, as I just got it this moment. He did say that they don’t have parts or offer service, but they refer people to Dunkirk when it comes up. He gave me a phone number.

    Yes, there is a transformer on this thing, which I think on a later post you conceded. It’s a 20amp circuit coming off the panel, going through 2 emergency cut-off switches before hitting the little transformer. The wires go down through the switch and the pressure troll before heading back up to the thermostat.
    I probably need to read the manual before I push you for more conjecture, but does that change your view of how to idle this thing? I keep ruminating on this because – if I wasn’t very clear before – the heat came on for the first time when I was at work when the thermostat was down as far as it goes. So the thermostat doesn’t actually have an “off” position, and I don’t get why the boiler boils water when it’s not making steam. I guess the pilot light stays on even if the power is out (switch is off)? In that case, I suppose it just won’t spark or heat to light the pilot light again if it were to go out?

    OK, I have heard about EDR before, but I need to read up on that. Even so, the input BTUs had me concerned about my gas bills, but I guess it doesn’t run nearly as often as a furnace would. My gas bills aren’t crazy (I was sweating over that after first seeing those input numbers).

    You said, “…I would budget for a new boiler of the right size…” That sounds like you think this isn’t sized correctly, or am I just reading into it?

    @Jamie Hall

    So if you don’t turn your boilers off in the cooling season, do they still randomly boil water and does that increase the load on your air conditioners? Does leaving a boiler on help keep corrosion from setting in?

    Noted about the thermostat. My concern is that mine is “sliding”. The heat is great, but the other thermostats show slow swings (which I really don’t feel too much – definitely not like in my previous house with forced air) from around 65-70, and sometimes up to 72 during a “super cycle”, as my wife refers to them. Are “super cycles” normal?

    I’ll have to start experimenting with the heat pumps, especially when the humidity is not already too low. I’d sort of love to have a super sophisticated thermostat that can handle all the systems, but you are probably right that it gets too complicated, particularly since most manufacturers don’t seem to pay much mind to boilers.

    I will attach pics of the radiator valves. Most of them look like the first picture, but at least one is like the second picture. Is the third picture of the elbow you were talking about?

    The next picture is of some crazy green thing where the two returns come together. This may be some sort of release, except it’s in the return line. (edit: Sounds like this is the main vent, but I wasn't expecting it in the return):

    This is the piping underneath:

    I do hear what sounds like the two upstairs bathroom radiators (middle of house, front and back) venting – not so much the other radiators, but the valve pic is from the one bathroom and it looks just like the others.

    Do you still think this is a vapour system? I have not read up on them specifically yet.

    I apologize because I gave the wrong description of that “U” picture. It seems that there are two main trunks off the boiler feeding the radiators via branches. The one actually goes from a large pipe suddenly into this “U” before going all the way around the house and does another crazy loop that I can barely describe before going into the other main trunk that goes back to the boiler. I drew a little picture (but it’s really hard to tell if this is perfectly accurate because half these pipes are hidden):

    That said, I’m glad I don’t have to ask you to explain about the water seal, but maybe this is something like that anyway. Is this piped like that so I can remove the cap and clean it out? I guess this is still a water trap of sorts, but why… well, I don’t know what this is for…

    I assumed all returns were wet, as in they bring condensate back to the boiler. Am I missing something?

    Thank you for the rest of your comments. Last paragraph:

    OK, now I guess I am certain that green thing is the main venting. Is it possible there are other vents, because I still don’t see any.

    My little picture above: it may be possible that the mains go into the loops and then hit the returns instead of how I have it drawn. I don’t really think so, but there are parts I can’t see really well. These pictures (below) are of what I assume is the other-side (other main) equivalent of that “U” (note that three pipes go through a brick wall and the pics are from either side):


    Correct about the transformer. Thanks for catching that. I explain it above, but wires go from there to pressure troll to starter then up to thermostat.

    Yeah, I don’t think I’ve ever seen that pressure gauge move from 0. Why would code have it go to 30 psi if 2 psi is all you ever need (something Dan’s videos have hammered into my head)?

    Is there a way to clean the pig tail loop other than to run the quick drainage line every week or so to get rid of the metal flakes? I have been doing that, at least. Would love to have two of those in parallel as I saw on a video.

    I agree – if/when I change the T-stat, I’ll leave the old one in place.

    I think you’re right about the drip pipe, but still looking for more info. What does it do? Do I need to clean it, etc.?

    Those blocks are just my foundation walls. (someone painted everything white, which is fine, but it makes the utilities harder to identify). The entire house seems to be made from those big red hallow blocks, with an outer layer of really nice, scraped brick.


    I posted pics of the valves and elbows above. The majority say, “American Radiator Co”. I definitely haven’t heard of a Kriebel system, but will be interested to look it up. Do you still think this is a possibility?

    I’m in Frederick. Oh, I see you’re just over in Towson…

    @Erin Holohan Haskell

    Thanks for noticing…


    Thanks. I am really curious about this millivolt system now, but since I think this is with transformer, I guess I have to save that for when my mind isn’t clogged with new house stuff.

    @Dave in QCA

    Dude, you are like the Super-nerd of Thermostats. Please understand I say that with lots of respect and admiration.

    I’ll have to read through your description a few more times on a few more different days until that all sinks in, but it sounds really cool. And definitely good to know if/when I change it out.

    I mentioned earlier that mine doesn’t really have an “off” setting and that it has a slow swing of about 5 degrees F, but keeps everything comfortable. Any cause for alarm or any ideas for shutting it off/vacation/etc. Once we got it comfortable, I’m afraid to adjust it because it’s sort of a crap shoot for getting it back where you want it.

    Yes, I would love to have any documentation if you are willing to provide it. Here is a pic of what the previous owner left me. I am actually only the third owner of the house, which is now 98 years old…

    …Someone asked earlier what the pressure troll was set at. Finally had the courage to look, and I guess Dan from the videos would approve: looks like 0.5-1.6. Please sanity check me and let me know if I’m crazy.

    Another question: I assume this is the pressure relief valve. Something in one of those videos made it sound like that going off at the wrong time could kill you. Does that mean I should NOT test it?

  • MussSyke
    MussSyke Member Posts: 4
    @Jamie Hall
    @Erin Holohan Haskell
    @Dave in QCA

    I tried to call you guys out in the above post, but didn't get it right. Hopefully this works.

    Also wanted to say thanks again, but I hit the character limit. Man, am I long-winded...
    Erin Holohan Haskell