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My guys just finished a new install of a Weil EG30 in a small home, everything done correctly of course, with dropped header etc. The system has two 2” supply mains. One is parallel flow and only about 5’ long with 3 take-offs/radiators. The other is counterflow, about 12’ long, also with 3 takeoffs/radiators.
They fired it up and no steam would enter the counterflow main, even after a considerable time. I told them to change the radiator vents on the parallel flow side to #4s. No effect.
They said there was a plugged tee at the very end of the counterflow main (which presumably had a vent at one time) so I told them to remove the plug. They did this, and still no steam would enter the Counterflow main.
I then told them to close the king valve on the parallel flow main. This had the effect of sucking all the water out of the boiler, causing it to go off on low water, and then the water belched out the end of the counterflow main (where the plug was removed).
Try as they might, they could not get steam to enter that counterflow main, and being late, they gave up.
Unfortunately, they failed to take pics, though I trust that they installed everything correctly.
So I am headed up there next, but I thought I’d run it by the wall for any ideas, as at this point it is a head scratcher...
Thanks.

New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
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Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
Did you put a drip on the counterflow?
You can choose to do what you want, but you cannot choose the consequences.
I am at the edge of my seat for this one.
> Which one is the counterflow in the pic? Left or right side?
> Did you put a drip on the counterflow?
The pic is from current install, just for header reference. Yes, the counterflow is dripped, tied together below the water line with the other return.
Also, the counterflow main is well above the boiler for its entire length.
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
NJ Master HVAC Lic.
Mahwah, NJ
Specializing in steam and hydronic heating
> Did they feed directly into the counter flow ? I ve found on counter flow mains to drop down from the top into the bull of the tee let the run pitch downward into a drip .This method over all other has always been the clear no issue winner in my book and I ve piped them ever which way there is over the years . Also I usually always use a vaporstat on counter flow systems ,just wondering has any body checked the radiator hand valves and made sure that there open and that the radiator vents are totally wasted doin nothing you hi to low ,just thought I de ask Peace and good luck clammy
They didn’t check the counterflow radiator vents because the end of the main was open and still no steam.
It’s piped like this:
Except one side is parallel flow
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
Maybe burner gas valve shipped for propane and your burning natural gas. As a result boiler is only firing at say 40,000 instead of 75,000 BTU?
"Reducing our country's energy consumption, one system at a time"
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Baltimore, MD (USA) and consulting anywhere.
https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
High velocity over the return created a venturi and sucked water into the main?
Did they close the king valve while it was steaming?
What happens if you let it cool down, close the king valve on the side you don't want heating and start heating with a cool boiler?
The piping is not insulated. If the piping gets steam hot and the boiler shuts down the steam shrinks in volume 1700 time. That will cause a vacuum and pull water out of the boiler.
Sounds like a stoppage. Maybe the wedge on the king valve broke off or there maybe a rag in the pipe.
Jake
NJ Master HVAC Lic.
Mahwah, NJ
Specializing in steam and hydronic heating
> King valve stuck shut?
I thought about that, except the boiler water made it to the end of the main, unless it went up the drip...
Hard to fathom how a new king valve could fail closed...
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
> Maybe customer added a "little" stop leak to the system and clogged a two inch main???
>
>
> Maybe burner gas valve shipped for propane and your burning natural gas. As a result boiler is only firing at say 40,000 instead of 75,000 BTU?
Except the boiler water made it out to the end of the main no problem.
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
> Just shooting out random ideas.
>
> High velocity over the return created a venturi and sucked water into the main?
>
> Did they close the king valve while it was steaming?
> What happens if you let it cool down, close the king valve on the side you don't want heating and start heating with a cool boiler?
Yes, they closed in when steaming. But since then the customer reports no heat from the counterflow radiators.
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
> Why would a shut valve or clogged main suck water out of the boiler? Shouldn't the equalizer stop this even if the return is left open?
Vacuum?
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
> Ryan that’s a real head scratcher ,couple of things I would feel around for is cold spot on near boiler s equalizer drop sometimes 10 to 15 inches above the Hartford loop ,also would check the counter flow drips and see if they ever get hot .is all your near boiler piping getting hot ? To me it seems as if it air bound maybe possibly in the near boiler piping . From the photo with that hi of a riser and a dropheader that steam is bound to very dry so I know that’s not the issue . I ve seen guys add air vents to headers to get the air out quickly ? I think I would also follow out the piping and make sure nothing out of the normal has been done in the past . Maybe check the size vents that are on your parallel main possible way over vented in comparison to a slow vent counter flow ,it’s a hard one but possible something over looked . As other stated check that king valve peace and good luck clammy
No vent on the parallel main as it is only 4 or 5 feet long.
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
If no steam comes out of the disconnected pipe, you've likely got a bad valve or a clog in the counterflow riser from the header.
I had something similar happen to my system when I first moved in. The main vent on one of my mains would never get steam. I put a bigger vent on it. No steam. Put multiple vents on an antler. No steam. I took the vent completely off and had an open 3/4" pipe. No steam. I pulled off the insulation on the main and found that the pipe had bent to the point that pooled water completely blocked the line. This was after the last riser so all the rads got hot, just took forever.
18 Ounce per Square Inch Gauge
Time Delay Relay in Series with Thermostat
Operating Pressure 0.3-0.5 Ounce per Square Inch
"Reducing our country's energy consumption, one system at a time"
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Baltimore, MD (USA) and consulting anywhere.
https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
Yours, Larry
Probably...
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
> Hi, How about looking at everything with IR and see if it gives you some clues? ... this from a hot water guy
>
> Yours, Larry
That’s a good idea, but I would have to borrow Gordo’s...
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
> Does the counterflow main pipe have a sag somewhere in it that has pooled water blocking the flow of steam?
>
> I had something similar happen to my system when I first moved in. The main vent on one of my mains would never get steam. I put a bigger vent on it. No steam. Put multiple vents on an antler. No steam. I took the vent completely off and had an open 3/4" pipe. No steam. I pulled off the insulation on the main and found that the pipe had bent to the point that pooled water completely blocked the line. This was after the last riser so all the rads got hot, just took forever.
No. It’s uninsulated, and no sags...
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
https://www.flir.com/applications/home-outdoor/
Yours, Larry
> Did both sides heat before the boiler replacement?
Don’t know. Boiler was junk when they bought the home.
New England SteamWorks
Service, Installation, & Restoration of Steam Heating Systems
newenglandsteamworks.com
Is it a bad idea to plug that tee and with the parallel closed and see how high the pressure goes? If it just builds there has to be something blocking the main
I'm definitely not a pro, so if that idea is not safe don't do it!
NJ Master HVAC Lic.
Mahwah, NJ
Specializing in steam and hydronic heating
"Reducing our country's energy consumption, one system at a time"
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Baltimore, MD (USA) and consulting anywhere.
https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
If air cant get out, steam cant get in.
Definitely sounds air bound.
I would separate the unions on those radiators to make sure theres no obstructions there