Changing to a probe style LWCO

jaytav · February 6

I have a Utica SFH3100S Starfire steam boiler. It currently has a McDonnell & Miller 67 float style LWCO.

As far as I can tell, the boiler doesn't have any tappings for a probe style LWCO. Can I retrofit a probe style cut off by assembling some nipples like this and putting in the place of the mechanical LWCO?

Jamie Hall · February 6

Yes, you. But why? If I were doing it, though, I'd provide valves so that I could flush that gauge pipe regularly, and I would make it a point to test that probe type LWCO regularly as well -- perhaps not as often as flushing it -- by actually lowering the water level from time to time to make sure it was clear and working (not just press the test button and hope).

clammy · February 6

That is 1 inch piping your looking at in the picture , your sight glass piping is 1/2 . I don’t think it would be a wise choice given that on most steam boilers the lwco probe is screwed directly into the boiler block so it is wet . In remote piping without flushing the chances of it becoming clogged and the probe still being wet is greatly increased and the chance of dry firing .Usually on a boiler equipped so a gauge column can be piped the choice of a low water cut off or a boiler feed pump control would be a float type using a probe type in a gauge column piping ill advised w possibly bad result . Unless the boiler has a tapping of a probe type low water cut off your sol .
Peace and good luck clammy

SteamingatMohawk · February 7

Can anyone identify if the pressuretrol is of mercury vintage? If it is, it is not properly oriented relative to the pigtail.

The low pressure gauge should not be left in service when not attended. A few years ago, I questioned several manufacturers and they said the maximum pressure is around 130% of full range. For this gauge that is 3.9 PSIG. The relief valve is set at 15 psig.

The Steam Whisperer · February 7

The piping in the picture probably does not meet the manufacturer's requirements. Hydrolevel makes a special fitting for using a probe in 1 inch piping. Hydrolevel also makes a direct replacement for the #67 that is a probe design,.

Steamhead · February 7

The Steam Whisperer said:
The piping in the picture probably does not meet the manufacturer's requirements. Hydrolevel makes a special fitting for using a probe in 1 inch piping. Hydrolevel also makes a direct replacement for the #67 that is a probe design,.

The manifold to use is the 711C, part# 45-310, which comes with a set of quick hookup fittings:

https://hydrolevel.com/manifold-fittings/

You install the manifold on the sight glass and add the proper Safgard or CycleGard probe LWCO, and a 3/4" full-port ball valve in the bottom for the blowdown. Yes, you still have to blow this down, but it has no moving parts like the 67 does. We've used this setup quite a few times and it works well.

Hydrolevel also makes a two-probe version for jobs where you need more differential:

https://hydrolevel.com/safeguard-711-724-series-steam/

109A_5 · February 7

Hello @jaytav,
Why don't you like the M&M 67 ? Is it broken ? Mine is about 50 years old, changed the blow down valve a few times, did a thorough cleaning (without having to remove it from the boiler) about 1.5 years ago, still going strong. It has no issues of the electronic stuff.

Sylvain · February 7

SteamingatMohawk said:

The low pressure gauge should not be left in service when not attended. A few years ago, I questioned several manufacturers and they said the maximum pressure is around 130% of full range. For this gauge that is 3.9 PSIG. The relief valve is set at 15 psig.

recommendation about the choice of a gauge valve and why one need one:
https://www.deppmann.com/blog/monday-morning-minutes/pressure-gauge-accessories/

jaytav · February 8

Thanks for the info, all. I’m going to grab a needle valve and a 0-30psi gauge to place before that low pressure gauge. I want to replace the current LWCO because I would like to install an autofeeder and read that you really want to make sure your LWCOs are working well if you are going to use one. I thought a probe style would be more dependable. I was hoping to do away with the weekly blow down, but it sounds like that isn’t possible with 1/2” pipe.

109A_5 · February 9

Hello @jaytav,
OK, interesting. The M&M 67 has a second switch section that could trigger an auto feeder. For me the less amount of electronics to fail and/or act weird between me having heat or not the better.

I think a float is almost as simple as it gets and I am willing to clean it.

I don't do the blow down weekly, however I do look at the boiler almost daily.