One screwed up steam system (ME)

Mark Eatherton1

Sometimes people that work on steam systems, shouldn't.

Case in point, HO calls us ou to take a look see at their system. Said they've been "maintaining" it themselves. Come to find out the maintenance procedure was to blow down the low water fuel cut off at the beggining of the heating season...

When I go to blow it down, a pudding like substance oozes out of the pipe and it stops. Time for a new LWCO for sure.

The original system was a solid fuel (coal) boiler that was later replaced with a gas cast iron boiler some time in the 40's or 50's. The boiler sits in the basement of the carriage house, some 20 feet away from the main house. System is a 2 pipe parallel flow design. At some point in time, someone replaced the gravity returns with two condensate receiver/pumps. The problem is that there is no logic in its operation. When the receiver gets full, it dumps its condensate into the boiler whether the boiler needs it or not. The boiler has an automatic make up system, so I have a suspicion that the boiler probably gets flooded out at times.

In addition to that problem, the near boiler condensate lines are showing severe signs of condensate corrosion. The pH of the condensate was at around 6.7. I don't have Dans steam book here at home, but I remember Steamhead saying something about a lack of air vents or vacuum breakers causing the CO2 to come out of suspension and cause acidic corrosion.

The boiler probably needs replaced, and I have a pretty good handle on that. THe problem lies in the gravity to forced conversion. I forgot to mention, the end of the main also has a condensate receiver/pump and it pumps back to the near boiler receiver/pump, hence two pumps.

If it were your customer, what would you do.

What logic would you use to control/manage the condensate and make up. I see where McDonnel Miller has a new probe type LWCO/make up water controller. Is this the best way to go?

Replacing the condenate return mains under the sidewalk is not an option, unfortunately.

Beat me up steamers!!.

Thankfully,

ME

J.C.A._3

Mark...

At the VERY least, I would pressure test the underground line to make sure they are not the culprit! (salt sand or groundwater getting there, feeding the return could well be the reason for the rotting pipes) . It may seem impossible to replace, but if it is the problem, what choice do you have?
Keep us posted. I'll be watching for the responses. Chris

Unknown

Controlling the pumps

Think about using a M&M 150 to replace the LWCO. Run the condensate pump motor from that, rather than the float in the tank.

The tank might be big enough, if it is keeping up now.

The next issue is make-up water. The Float in the tank is what should control it, but it makes on rise, instead of breaks on rise. I wonder if the switch will work if you turn it upside down (wink, wink)? Then you can feed the make-up water from the tank float switch.

Just some thoughts....

Noel

Dave Yates (PAH)

finite water level control

install a feed water tank & the two other condensate tanks can then pump anytime they want & the boiler can signal the feed water tank when & only when it needs water. No flooding.

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Art Pittaway

Daves got it right, but

you need to connect the makup water to the boiler feed tank float valve, not the boiler piping. When you buy a boiler feed, the tank and pump assembly will come with a mechanical float valve and maintain a minimum level in the tank. Then as the water cycles through the heating system the tank level will rise and fall above the float valve shut-off level so no make-up water is introduced until it is needed. Also, cold make-up piped into the tank gets "preheated" a little by the returning condensate. I saw a similar install years ago. Local contractor replaced limed up sections every other year. His "Boiler feed" was a plastic pedistal sump pump (literally) in a rusty steel drum buried in the floor. When the boiler flooded they would dump it down the drain and thought that was normal.

Dave Yates (PAH)

absoroutley

Memory test - we did a Contractors' Corner for HVACtv.com where we detailed the replacement of an old steam monster with two steam boilers (the old one had two zones using motorized valves). The landlord wanted to divide for separate gas metering. I sang the opener with that old ditty about "double your pleasure, double your fun". No doubt that's why everyone scattered for the hills!

so..... Two boilers and one common return? Absoroutley tootley - we installed a feed water tank with two pumps and didn't order the duplex control. Instead, we wired each pump to a single boiler's LWC. They share the tank and return condensate while steaming out to their respective zone. Separate gas meters.

That one had had an old style condensate receiver, which also pumped at will.

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[Deleted User]

we had a similar situation

where a two pipe gravity return was converted to pump return...why...who knows..we had to replace the boiler, so we also threw away the condensate tank and repaired all the steam traps....what do you know,,when we put the system back the way it was originally designed it actually worked...by gravity,,just like the dead men who biult the place designed it to...funny how that works..customers happy,,we look good..and all we did was put it back to design specs...

Steamhead

I agree with Gerry

If that system was originally gravity-return, why use pumps?

My guess is it may be a Vapor system which had a Return Trap to force the water back to the boiler if the pressure got too high. If the Return Trap went bad, someone probably thought a feed pump was the only answer.

But since we now have Vaporstats, we can control the boiler pressure down to the ounce, so there should not be any need for feed pumps.

How about some pics, ME?

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