beginner mech needs help t-shooting


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Old 11-18-06, 08:23 PM
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beginner mech needs help t-shooting

Hey guys!

I've got a New Yorker gas-fired steam boiler. It has an automatic water feeder(24V), and an McDonnell LWCO(also 24V). The sight glass shows the boiler is full(plain sight glass, no float). When I try to drain it down to proper level after it drops only 10% the LWCO signals low water and the feeder kicks on and it fills back to the top. Bad LWCO?
And please answer this question, If the LWCO has only one sensing element and that is what triggers the feeder, what tells it when to stop? I see no other device attached except the pressure sensor(Honeywell) which is "cut-in" only and set at 8 psi(seems high to me).

I am eager to learn, any help is greatly appreciated.
Thanks.
 
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Old 11-19-06, 08:20 AM
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Lwco

Is it a float-type LWCO? They tend to stick if you don't blow them down to test 'em regularly. If it's the kind that senses by conductivity (electrical) it could be dirty I guess.
8 lbs is way too high, yeah. The Empire State Bldg only uses 5 lbs steam pressure. Most residential systems cycle @ less than a pound.
 
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Old 11-19-06, 08:24 AM
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There should be more than one sensor if it is the conductivity type. That's what tells it to stop, when the second element completes a circuit to ground through the water. How long has this set-up been in?
 
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Old 11-19-06, 07:29 PM
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Question LWCO is the probe type

Thanks for responding bodhisatva!

This boiler was installed about 5 years ago, and it works fine except for the high water level.
This is what confounds me, the feeder is wired to the LWCO and nothing else. The LWCO(probe type) is wired to a J-box with the transformer. There are only 2 other devices tapped into the boiler, a siphon pressure dial(no wires) and a pressure limit switch("cut in" only). I see no other sensor to indicate when to stop feeding.
Also, the few boilers I have worked on had 2 pressure switches high limit(cut-out) and a low limit(cut-in). How does this one work with a "cut-in" setting only? Does it have built-in differential? If the current "cut-in" setting is at 8 psi, than the boiler should never turn on, right? Did the installer use a low limit switch as the high-limit?
There is no external aquastat.
There is only one thermostat wired to the same j-box where the wires from the LWCO, limit(cut-in) switch, and the gas valve also meet.

Any suggestions here would be greatly appreciated.
 
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Old 11-19-06, 08:24 PM
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Usually how it works is the thermostat runs the burner and the burner runs until the steam pressure set on the pressuretrol is reached. I sure hope it isn't set at 8psi. It should be set at 1 psi with a differential of .5 psi. That is the most common setting, or a starting point at least. If the blowdown valve drops the level in the external water column, the feeder thinks the whol eboiler is at that level and adds water. If you want to avoid that minor problem, turn off the water valve by the feeder whenever you blowdown the LWCO. The open it again after you are finished blowing down.

Ken
 
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Old 12-07-06, 07:31 PM
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Cut-In

I just discovered the bottom feeder for the sight glass was clogged. I unclogged it. My concern: prior to finding the clog, I had most of the system filled with water (into the pipes).

During this time, the pressure soared to 5 - 8 psi. I'm concerned that the cut in did not prevent the boiler from coming on.

Any ideas?

Thanks


Originally Posted by KField
Usually how it works is the thermostat runs the burner and the burner runs until the steam pressure set on the pressuretrol is reached. I sure hope it isn't set at 8psi. It should be set at 1 psi with a differential of .5 psi. That is the most common setting, or a starting point at least. If the blowdown valve drops the level in the external water column, the feeder thinks the whol eboiler is at that level and adds water. If you want to avoid that minor problem, turn off the water valve by the feeder whenever you blowdown the LWCO. The open it again after you are finished blowing down.

Ken
 
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Old 12-08-06, 06:51 AM
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You should find out why the boiler ran with pressure above the cut-out of the pressure control. I would make that a high priority. Or have someone who is knowledgable with steam systems come and check over everything. Now that you know there is something wrong with limit control, you need to repair it ASAP.

Ken
 
 

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