News from McDonnell & Miller

Steve_35

has been false negatives. IOW, the resistance from the probe to ground was excessive causing the system to lock out. According to the MM techs the problem was mostly with new systems when flux coated the probe.

They sent us another prototype that in addition to the wobbler also has a bit higher voltage through the probe. I like that approach better as I can see the wobbler getting gunked up too.

DanHolohan

MCDONNELL & MILLER INTRODUCES INDUSTRY’S FIRST SELF-CLEANING PROBE FOR LOW WATER CUT-OFFS

Chicago, Ill., November 7, 2005 — An innovative “self-cleaning” probe that prevents the build up of lime on the probe tip during boiler operation and provides five years of maintenance-free service has been introduced on all McDonnell & Miller electronic low water cutoffs.
Designed to prevent nuisance boiler shutdowns and potential flooding, the new self-cleaning probe reduces costly callbacks. It also reduces the time required to service a boiler.

This technologically advanced “industry-first” makes use of the water turbulence around the sensing probe to initiate the cleaning element to oscillate at the end of the probe, preventing accumulation of lime.

Ideal for both the residential steam and hot water boiler markets, the self-cleaning probe is standard on all McDonnell & Miller electronic low water cut-offs including all Series PS-800s, the RB-122, the 750-P-MT-120 and the RS1-LP.

See it here: McDonnell & Miller

McDonnell & Miller
McDonnell & Miller, a unit of ITT Industries, is a leading manufacturer of boiler controls, flow switches, liquid level controls and steam specialty products for residential, commercial and industrial applications. For more information visit www.mcdonnellmiller.com, or call 773/267-1600, fax 773/267-0991.

Constantin

Neat device...

Our neighbor in the rental building we're in had a dry-fire incident last year. Pretty freaky. I wonder how well these LWCO's will function though under the same abusive conditions (i.e. she did not drain/refill the steamer 1/4 via the valve underneath the LWCO once a month as some Wallies have advocated).

...so, I hope it can do what it promises as it could dramatically increase the safety and longevity of boiler systems.

[Deleted User]

But, I thought...

that ALL probes were self cleaning...

How many people actually go back and replace the control probe every so often, and the control every so often per the manufacturers insturctions. I only do it on failure.

I think its probably the manufacturers way of disconnecting themselves from the non maintenance factor. "It was out of warranty"...

JMHO

ME

Steve_35

We use the RB-122 since you can use them with oil or gas

and the probe is just that. A probe only. The new ones have a little offset plastic thingy the person in tech support I speak with calls a wobbler. It's supposed to spin around and keep some of the probe clean so there's minimal resistance due to flux, oil, general system crud.

These things are darned close to spec when stuff is clean. We've had on and off problems with them and figured the probes needed to be cleaned and that seemed to take care of the problem but I wanted to find out what the specs were so I called MM tech support.

The unit is supposed to lock out at 15k ohms. We measure 14.5k ohms with a clean probe. They've been around 19k when we get the no heat call.

I have my doubts just how well the wobbler is going to work as the flux settles in the system. I like the idea of bumping the voltage up a bit to compensate for the flux on the probe.

I don't think this is a CYA thing. More an attempt to reduce the number of returns.