McDonnell Miller

McDonnell Miller is a Xylem brand that makes low-water cutoffs, combination cutoff and feeder controls, and pump controllers for steam and hot water boilers. A low-water cutoff shuts the burner down when the water level in the boiler falls below the lowest safe water level. The combination units also admit feedwater or start the feed pump.

BoilerSupplies.com carries McDonnell Miller controls on one page, among them the Model 150S-HD, 150S-M-HD and 93-7B-HD and the Series 94 and 157S. The 150S and 157S families and the 93 and 94 series are low-water cutoffs and combination low-water cutoff and feeder controls for steam boilers. The Series 94 also serves as a pump controller. The models are told apart by pressure rating, by mounting (water column or direct to the boiler), and by function (cutoff only, or cutoff and feed). Sight glass sets for McDonnell Miller water columns are on the site as well.

Key facts

• McDonnell Miller is a Xylem brand.

• The 150S and 157S families and the 93 and 94 series are McDonnell Miller low-water cutoffs and combination low-water cutoff and feeder controls for steam boilers.

• The Series 94 also serves as a pump controller.

• BoilerSupplies.com lists the Model 150S-HD, Model 150S-M-HD, Model 93-7B-HD, Series 94 and Series 157S.

• Sight glass sets for McDonnell Miller water columns are on BoilerSupplies.com.

How is a McDonnell Miller combination feeder cutoff different from a low-water cutoff?

A low-water cutoff only shuts the burner off when the water drops below the lowest safe water level. A combination low-water cutoff and feeder does that and also opens a feed valve or starts the feed pump to bring the water back up. The 150S and 157S families and the 93 and 94 series cover both types.

What else is a McDonnell Miller low-water cutoff called?

Low-water cutoff, LWCO, low water cut-off, feeder cutoff, combination feeder cut-off, boiler water feeder, pump control and float control all describe the same McDonnell Miller family. Technicians also say the 150 or the 94 and mean the whole control. Search by the model number stamped on the nameplate, since that is the term the listing carries.

What off the nameplate do you need to match my McDonnell Miller control?

The model number (for example 150S-HD or 93-7B-HD) comes first, then the boiler's maximum working pressure, the voltage, and the mounting: water column or direct to the boiler. A photo of the nameplate and one of the control in place is usually all it takes. Add whether it is the complete control you need or a replacement part for it.

How do I tell that a McDonnell Miller low-water cutoff has to come out?

A McDonnell Miller low-water cutoff comes out when the float sticks, the switch no longer cuts the burner on a blowdown test, or the float chamber leaks. Sludge the blowdown will not clear is the other reason. Read the model off the nameplate, match it on BoilerSupplies.com, and order the same model or request a quote.

Where do I find the sight glass for a McDonnell Miller water column?

BoilerSupplies.com lists sight glass sets for McDonnell Miller water columns. Measure the glass length between the gauge valves, note the valve size, and send those with the water column model so the set matches the column you have.

Put the nameplate model number, the boiler pressure and the mounting in a quote request on BoilerSupplies.com, or call Boiler USA at 1-770-957-9599 or toll free 1-800-780-3776.