Is my system short cycling and why?

vermuele

I have Smith GB300 that has two main vents and two steam traps plus all of the vents on the radiators...approx., 4 radiators per apartment (12 apartments). After cleaning the system out this fall it seems to be short cyling wherein the system fires and will run for 5 minutes and then cut out and then fire again 5 minutes later. I did clean the traps and they were filled with a lot of crud. I also replaced one of the Hoffman 75 main vents and still the same outcome on 5 minutes and off 5 minutes. I have not seen any appreciable rise in pressure at the guage ( the pigtails for the gauge and pressuretrols (L4079B-1033 steam pressuretrol (manual reset) and Steam Pressuretrol PA404A-1009 (pressure is at 1.5 with differential of 1) were cleaned) I have two Ignition Control UTC 1003-616A and one CSD-1 Reset Module UTC1145-1. If someone has an idea of my issue I would greatly appreciate some guidance. If I have missed some info that is pertinent I will provide it if asked...thx.

Jamie Hall

What you need to do is find out which control is shutting it off. It doesn't sound like the pressuretrols, but how about a low water cutoff?

vermuele

I clear those low water cutoffs daily and run until clear(which is just a few seconds)...is it your thought that one of the low water cutoffs could be causing the system to turn off and then one it senses water fires again?

vermuele

The pressuretrol that control the on and off is Steam Pressuretrol PA404A-1009...which is the one set to 1.5 and a differential of 1. The other control monitors the low water and requests additional water when needed.

Jamie Hall

vermuele said:

I clear those low water cutoffs daily and run until clear(which is just a few seconds)...is it your thought that one of the low water cutoffs could be causing the system to turn off and then one it senses water fires again?

I wouldn't dignify it with a thought -- more like a guess.

vermuele

I did notice every now and then the boiler while it doesn't go into lockout, it does require one of the low water cutoff valves to be manually reset....so is it possible that lower water cuttoff is causing the system to shutdown and it is simply trying to restart after 5 minutes?

Fred

Where is your thermostat? Does the boiler bring that room/area up to temp? Are you sure it is set properly for Steam? It sounds like it may be programed for "Forced Air.

vermuele

I have the thermostat located on the 2nd hall floor South side of building. With it cycling up and down it takes quite a while before heat reaches that radiator....thus, it is calling for heat quite a bit with temps in twenties this morning. I was just there and out of the clear blue the system stopped as though heating requirements were fulfilled; However, when I checked the thermostat it was still calling for heat by two degrees...I lowered it under the desired temp and waited 5 min and then raised over current room temp by a couple degrees and it called for heat and was running when I got to the boiler room. It makes me think this could possibly be a thermostat issue. The reason I didn't initally think it was because I have a blower that runs when it calls for heat and since I hear the blower running I can see it is calling for heat so one would expect it to be running until it satisfies the demand. I have not tried to call for heat beyond 5 or 6 degrees as I have seen it sometimes run longer.

vermuele

It is properly set for steam...it is very strange because last year I would get lockouts periodically but tt never short cycled and always ran out until the demand was satidfied...now this season not one lockout but short cycling.

neilc

vermuele said:

I did notice every now and then the boiler while it doesn't go into lockout, it does require one of the low water cutoff valves to be manually reset....so is it possible that lower water cuttoff is causing the system to shutdown and it is simply trying to restart after 5 minutes?

i'ld say you need to run with this thought,
down to the boiler room,
and watch what's happening while a call for heat comes thru,

having to reset the manual LWCO is very telling,(and your issue),
and your current short cycling is likely the water level bouncing off the higher, automatic LWCO,

what pressure do you see thru a boil cycle?
what does the water look like in the sightglass? dirty?
does that water level bounce while boiling? more than an inch?

and,
does the water level drop more than an inch or 2 overall, during a cycle?
I'm guessing yes it does, and you're triggering the LWCOs,

we need to see a picture of the boiler, floor to ceiling, showing the piping above,
and pictures close up of the sightglass, Ptrol and pigtail, and LWCOs,
has the pigtail been serviced? is it free breathing back into the boiler?

mattmia2

First step is to figure out which control is shutting it down. An ac voltmeter will do that quickly, look for which switch is 24vac instead of 0 when it should be closed.

If it is the lwco, the water isnt leaving the boiler as steam in 5 minutes, it is either being thrown up in the mains because of oil in the water or too high a ph or incorrect near boiler piping (most likely) or it is being bushed out the return(less likely)

Fred

Do you put any additives or cleaners in the boiler water? They can sometimes be brutal as far as foaming and surging goes, especially if you add a "Little extra for good measure".

EBEBRATT-Ed

Guessing does no good, wastes time and potentially costs money for parts that don't need replacement.

Get a test meter and learn how to use it. Find the control or Control(s) that are keeping the boiler from running as @Jamie Hall & @mattmia2 mentioned.

Or call a professional. Anything else is a waste of time

vermuele

I appreciate all of your input...it is greatly appreciated. The manual low water cut off is the one I have to periodically reset and then I hear the boiler run through its startup procedures and fire. I did clean out both lwco's and they were scaled up and I kind of figured with all that scale the manul lcwo could have been causing the control to cause the boiler to short cycle. What I have serviced and replaced:
pigtails services, traps serviced, lwco serviced, one Hoffman 75 main valve replaced. I have not had an opportunity to check the ph level and there should n't be anu oil in it but have am not sure how to confirm. Am just a little curios as to why it appears to run for 5 min...then fires again 5 min later. As I had stated earlier last year we had instance where the system would go into lockout and would have to manully reset the board next to ognition controller and all would be fine again. Now this year I have not had one lock out but have been dealing with these short cycles. I did find the thermostat was not registering the temp correct so I did replace but it made no difference. I juast find the cut in and cut out time interesting as it is almost to the t 5 minutes down and 5 minutes up...am wondering whther the UTC1145-1 motherboard would be causing any issues or even perhaps the ignition control modules. This boiler is in the oldest working apartment in Omaha (1897) and was specifcally built for the trans mississippi exposition in 1897...so it has quite a bit of history...it can be seen by googling "The Sherman" in Omaha Again, that you for all your input.

neilc

you really don't mention what pressure you see,
and I can't make out that water level,
and you don't say if the drops out while boiling,

you could take a sample of water from the boiler,
bring it up to the stove, and boil it there,
if it foams like bad pasta, or any kind of violent jumpy boil,
then you have water issues, oils, or ph / chems,
you want to see a calm steady boil.

vermuele

what pressure do you see thru a boil cycle?
what does the water look like in the sightglass? dirty?
does that water level bounce while boiling? more than an inch?


The questions above are from neilc. I'll try to answer each one.

I don't see any pressure reading from the gauge (I ensured the pigtail was clear of any obstructions, but still no reading...I tested the gauge and it does work);...took plug out and in horizontal line and steam was being emitted. The water in the site glass is fairly clean. The water level in sightglass does bounce a little when boiler is heating( I will pay closer attention to get a better idea of how high and how low).

neilc

twice now you mention one hoffman main vent,
and list 12x4 = 48 radiators, which is getting a bit large,
one hoffman probably isn't doing enough main venting, and system may be building and holding pressure,
and we're back to what is actually shutting the fire off for those 5 minutes.
are rads 1 pipe or 2 ?

vermuele

There is actually two hoffman 75 main vents but I only found one malfunctioning so I replaced it. It is a 1 pipe system. I am heading back to the building here shortly and will use a meter to see if I can determine which lwco is causing the system to shutdown.

vermuele

The output of the GB300 is 1,2 million BTU.

mattmia2

How is the condensate or feed pump set up? This being a large commercial boiler it really should be worked on by a licensed and competent professional.

Your near boiler piping isn't right, If the water quality is causing water to get in to the risers the header is going to tend to push it in to the system instead of in to the equalizer and back to the boiler.

Is the water i the gauge glass low when the burner stops? It could be the burner isn't firing right and is shutting down as well if the 5 minutes off is how the control works if it detects a problem. the scorch mark on the jacket isn't a good sign.

vermuele

The feed pump is run from the lwco on the right side of the boiler. The condensate comes into the large stainless tank and is pulled from when demanded by the lwco. The scorch mark occurred years before I took over the building. Prior to this year's heating season the only issues I experienced was an occasional lockout on the reset module next to the ignition module. The site glass water level stays pretting consistence and only rises when there is a call for water. When the burners shutdown the water level is normal...which adds to the mystery of why the lwco's would be the curprit. It would make complete sense if the water was at a low level at cutout...when I cleaned the manual lwco I thought if the water was bouncing it could have caused that lwco float to trigger an error...but since I have cleaned I am not having to reset the lwco but system is still shutting down at five minutes and then restarting after 5 min....perplexing...thanks for all the input.