Replacing Low Water Cut-off (float type)

EdwinD

I have a Weil-MClain EG-55 gas-fired steam boiler. I had to replace the 2 water gauge cocks, so I figured I might as well replace the low water cut-off, limit control, and the pressure gauge - given the system was installed in 1985. ITT recommends replacing the low water cut-off after 10 years - though mine is still working I thought it might be prudent to replace it....while it's warm outside. I have 2 questions:

1) The low water cutoff I'm purchasing is Model 149400
https://www.supplyhouse.com/Mcdonnell-Miller-149400-67-Float-Type-Low-Water-Cut-off-Steam
I'm pretty sure this is what I need but want to make sure. Attached is my existing low-water cutoff and label.

2) Also, I need to replace the pressure limit control and pressure gauge. Based on your experience, I need recommendations on replacements for these two items
Attachments for the existing pressure limit control and pressure is gauge attached.

Thanks!

Steamhead

First thing I'd do is see if that boiler has a tapping in it for a probe-type LWCO. If so, go with the probe, since it's more reliable and doesn't need weekly blow-downs.

KC_Jones

My original boiler from 1982 was an EG-45 and it had the probe type LWCO, so yours should have the tapping. I agree with @Steamhead on this one.

The only issue would be if it's plugged, and getting the plug out after 33 years.

Would need a wider picture to be able to tell.

EdwinD

Correction: actually I replaced the entire cast iron section after one section went bad - Dec 2017. The cost was almost the same to replace all sections with labor costs. So as far as a tap, it shouldn't be a problem removing, but I don't know of a plug you're referring to. There is a nipple with a cap on the left.

EdwinD

Ok, I'm guessing the nipple w/cap on on the left should be removed and that's where the low water probe is inserted and attached to the control housing?

Steamhead

EdwinD said:

Ok, I'm guessing the nipple w/cap on on the left should be removed and that's where the low water probe is inserted and attached to the control housing?

That is correct. The one to use is a Hydrolevel Safeguard 400, assuming the control circuits are 24-volt.

I noticed there are instructions for feeding water to the boiler every week. You should not have to add much water to the boiler on a regular basis- a gallon every couple months is about where you need to be. Any more than that and you need to check for leaks- bad vents, loose packing nuts etc. Having to add water like that will shorten the life of the boiler.

EdwinD

Thanks Steamhead! When I bought the house, the directions were on the boiler, but I usually add about every 1 1/2 to 2 months...depending on usage.

Also, I need to replace the pressure limit control and pressure gauge, any recommendations on what I should buy.

Thanks!

Steamhead

Is this a one-pipe or two-pipe system?

EdwinD

2 pipe system

EdwinD

Clarification: 2 pipe system as in the 2 large pipes from cast iron sections feeding steam to all household radiators?

nicholas bonham-carter

Two pipe systems have two pipes connected to the radiators, an inlet with a valve, and an outlet, usually, but not always, with a steam trap.
Generally speaking, you can operate these systems with very low pressure, (1-8 ounces), so I would get a 0-16 ounce vaporstat. Get a 0-3 psi gauge from Valworx, to verify the settings you make on the vaporstat.
It will be important to establish how the air can escape as the system begins to make steam, and make it as efficient as possible, so as to reduce short-cycling. There may be secondary steam traps (crossovers) to vent the air out into a final vent.
Pictures of the various valves, traps, and mystery pieces will enable the identification of your system, and it’s improvement.—NBC

EdwinD

Thanks Nicholas!

EdwinD

Thanks to everyone for the helpful advice

Fred

Also, know that the pigtail (looped pipe) to the control is mounted wrong. That loop is to hold water to protect the control. The way it is mounted, it won't hold any water and the direct steam can/will damage the control.

Steamhead

Yes, that was typical for older W-M EGs with 67 LWCOS. Can't remember how many I changed.

Easiest way to mount the Pressuretrol would be to come out from the skim tapping with a 1-1/4"x6" nipple to a 1-1/4"x1/2" tee whose bull is pointing up, with another 1-1/4" nipple coming out the other end of the tee with a cap on it for skimming purposes. Screw a 1/2x1/4" bushing into the bull of the tee, install a straight pigtail in that and mount the Pressuretrol on top.

EdwinD

Thankjs Fred. So, are you saying the loop needs another half turn?

EdwinD

Steamhead, i get the mental picture. I'm pretty handie but as a laymen, in my setup where is the skim tapping?

Also, I've decided to stay with the manual LWCO, whoever wired this boiler, did it the hard way and I'd prefer to stay with what I know and buy a new manual LWCO instead of a probe type. Question: does that change your earlier advice about "Pressuretrol would be to come out from the skim tapping ?"

EdwinD

Steamhead, Attached is a picture associated with my previous question.

Steamhead

The skim tapping is in the larger circle.

I'd re-think your LWCO choice. After replacing that section you want it to last as long as possible. I've never seen a dry-fired boiler with a probe LWCO but have seen plenty with the #67. And 24-volt wiring is pretty easy to do.

Fred

EdwinD said:

Thankjs Fred. So, are you saying the loop needs another half turn?

No, You need to replace that pigtail with one that is a straight configuration. That 90 degree configuration is going to be upside down no matter how you turn it, unless you put an elbow on the LWCO first but they always get clogged.

EdwinD

Steamhead...thanks! That makes a lot of sense. You convinced me to give the probe LWCO a go. Based on your experience what do you recommend for EG-55:

1) Pressuretrol
2) Probe LWCO

Thanks

Fred

Where is the Pressuretrol on that boiler? The gray box in the pictures is an aquastat. I assume you have a hot water loop on that boiler too.

EdwinD

Thanks Fred - no I don't have a Pressuretrol. The Aquastat was on the boiler originally when I bought the house. There was never a hot water loop to my knowledge. I have had numerous inspections over the years and never a word was said about that.

Steamhead

That actually IS a pressure control, but the White-Rodgers version is build differently from the Honeywell.

@EdwinD , how many pipes are connected to each radiator- two, or just one? Take a picture of a radiator and post it here if there's any question.

EdwinD

Steamhead,

Two pipes to each radiator throughout the house - see attached.

EdwinD

@Steelhead see attached. 2 pipes

EdwinD

@Steamhead 2 pipes. see attached

EdwinD

Sorry for the multiple photos of the same.

Gordo

@EdwinD: No problem with the multiple pics! Glad to have them!

It looks like you have a two-pipe vapor system (i.e. very low pressure steam heating).

Could you please provide a close-up of the fitting on the radiator at the lower left-hand side? That may provide a clue as to which vapor system you have. It looks like a Broomell or similar.

EdwinD

@Gordo Thanks! See attached.

Gordo

Ah, thank you. That looks like an "O-E" system as depicted in The LAOSH.
The words on that fitting should be "OE Specialty Mfg. Co. Pat Pndg" and on the other side the logo "OE"

Jamie Hall

Actually... if it were mine... I'd replace the McDonnell Miller in kind-- they work just fine if you pay attention, and add a probe type, manual reset low water cutoff at a lower setting. Belt and braces...

Since this is a vapour system, it will work best if you limit the pressure, so I would use a vapourstat (try 12 ounces cutout to start with)(yes, I know they are expensive) as the primary pressure control, and --- belt and braces again -- add a manual reset pressuretrol as a backup. I would put them on separate pigtails if you can figure out where to tap them in -- one of them can go on the McDonnell-Miller, though, but with the pigtail redone to actually hold water.

EdwinD

@Jamie Hall Thank you for the advice! After a little research, I'm considering the Safegard 400 series probe LWCO for steam boilers. Is that a pretty decent unit? Thoughts?

Steamhead

That's what I'd use. Also, a Vaporstat for your pressure control, that cannot be set higher than 16 ounces. I hope Honeywell has worked the kinks out of their Vaporstats though...........

EdwinD

@Steamhead Thanks! One last question. Re the Vaporstat, would this be the correct one to install?
https://www.supplyhouse.com/Honeywell-L408J1009-Vaporstat-Controller-Steam-0-to-16-oz-in2

EdwinD

@Steamhead I appreciate the help. Another question. Rather than mount the Vaporstat (Pressuretrol) out of the skim tapping, would it be acceptable to mount the Vaporstat up top in the rear (blue circle) . see 1st attachment. The probe LWCO will be located on the side beneath it. (red circle)

I based my thinking off a configuration similar to attachment #2.

Thoughts?

Jamie Hall

That will work nicely. You will still need a pigtail, of course. The low pressure gauge on the same pigtail is a nice addition, and not expensive. Put the manual reset pressuretrol on the tapping from the McDonnell-Miller, if you use it.

Steamhead

@EdwinD , that will work fine. I must not have seen that tapping before............

EdwinD

@Jamie Hall I won't be using the McDonnell-Miller, switching over to Safegard 400 series probe LWCO . I'm new to all of this. Is there a certain Pressuretrol I should choose? I noticed there are several. Max pressure? Min pressure?

EdwinD

@Steamhead Thanks - my fault, I never sent a pic showing that addt'l tapping. One other question: Is there a particular Pressuretrol I should select? Max pressure? Min pressure?

Fred

The L408J1009 Vaporstat that you referred to above is the correct one to use. As Jamie said, set the "main to 12 ounces and the "Differential to 8. That will give you a Cut-in at 4 Ounces of pressure and a Cut-out (max Pressure) of 12 ounces.

You can use that top tapping for the Vaporstat but that usually has a Pressure Relief Value on it. Does you boiler have a Pressure Relief valve installed? If not, you must install one there so that if the controls fail and the boiler were to continue to run and build pressure, the valve will blow at 15 PSI and prevent an explosion.