A gentle suggestion for ITT/MDM

Unknown

The RB-120 and 122 are some of the newest models in the MM lineup. It just may be that someone has already brought this up so they incorporated the warning into the newer manual. The PS-851 model has been around for quite a while and shows very little in the way of installation drawings in the manual. I might add that the RB-122 is the only manual that has the warning abount water and air pockets. My assumption would be that all of the subsequent manuals will incorporate this. I've even had LWCO's that didn't perform as desired due to them being installed in longer horizontal nipples off of a tee where they may have also been grounding out because of the close proximity of the side wall of the nipple.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Constantin

A LWCO, is a LWCO, is a LWCO...

As you may all recall, I made my heating contractor install a LWCO. When we burped and flushed the heating circuits today, the system locked out due to the LWCO. At least we knew it was the LWCO since its error signal shut the whole boiler down. We were scratching our heads for a while (as the heating system had functioned OK before) before we started to investigate what was making the LWCO so unhappy.

The LWCO was installed on a T with an extension between the triple-header and the Vitola boiler chamber (i.e. per Viessmanns specifications re: location). There even was a hint that LWCO had been installed following the lower LWCO piping diagram in the Vitola installation manual (page 28). Trouble is, that diagram shows the T for the LWCO pointing up, presumably to simplify the drawing. Yet, IMO, a "exploded view" drawing would have been better to drive the point home that the "T" will, most likely, have to face sideways to be effective.

To cover all eventualities, the Viessman manual also explicitly states to install a LWCO according to it's manufacturers specifications, so no help there. On the other hand, the diagram at the top of page 28 shows a LWCO installed with the probe oriented horizontally. Yet, due to preceived space constraints, the professional installer then installed the "T" vertically because there were no clear instructions in the McDonnell-Miller instructions re: allowable orientations of the LWCO.

Initially, I pulled the sensor to see what the resistance was when the sensor was immersed in water vs. air, which was fine. Then, the answer hit me as I examined the shape of the sensor and thought about how it works. The bell-shaped outer sensor housing of the MDM is a perfect air pocket, one that is only made worse by the nipple in the T leading to the header assembly. Thus, we had a perfect insulator surrounding the probe, one which would nuisance-trip the LWCO from time to time.

The fix was easy enough - change the orientation of the "T" to face horizontally, then the air in the pipe could escape. Re-orient the LWCO and we were back in business. Now, it may seem obvious to nearly all the professionals who are reading this that a LWCO would only work as described - with the probe arranged horizontally - but the manual for the LWCO does not make that point explicitly.

And it's a point that the pro who installed the system didn't catch either, along with the Teflon tape he used to seal the threads of the probe against the housing (a major electrical no-no, according the manual).

In its current incarnation, the ITT/MDM manual simply shows the LWCO being mounted with the probe in a horizontal position. A single sentence or a simple series of pictorials in the ITT/MDM manual re: allowable orientations of the LWCO would be a great addition as it would have made trouble-shooting the installation a lot quicker and perhaps a bit fool-proofer.

Yes, I know that they keep improving the fools... :-P

thp_8

Every picture

in the instruction booklet has the control mounted with the probe in a horizontal plane.

jim lockard

connie

I install my LWCO flat (hortzonal) behind a valve with a bleeder so that it can be serviced, and bleed. Best Wishes J.Lockard

thp_8

That might

not be code in some areas. With a valve the safety control could be isolated from the system full of water and the boiler dry firing.

[Deleted User]

In some areas...

LWCO isolation is REQUIRED. Caused the hair on my neck to stand up. I told Hartford I refused to install isolation around the device for the convenience of their inspectors. Who is responsible if the former landscape man, now chief mechancial engineer for the apartment complex inadvertently shuts one or both valves in a broken pipe furvor, and the boiler melts down....

Ya hear crickets out there....

Connie, that's a correct assesment on your part.

Most manufacturers have to assume that the installer can't read, so they depend heavily upon pictograms to portray their wishes. I like the german ones with the gruff looking guy in a laboratory coat like all the Heizentechnics in germany wear. Cracks me up. Talk about super stereo typing.

As far as nuisance lock outs, my guys, who do know how to read and can look at the pictures, have on occasion installed them vertically, causing nuisance lock outs. We now have a company wide poilcy, telling them exactly how and where the LWCO shall be placed.

So much for pictures and instructions..

ME

Constantin

Spot on

Every picture in their manual makes the right point, and 5 minutes of reflection of how the probe ought to work does the same thing. Yet, it wasn't obvious to the guy who installed the T, nor to the technician who was there with me. He's been in the business for 20+ years, yet he had never installed a LWCO sensor into any hole other than a pre-made one, it seems.

Hence my suggestion to MDM: Please put in a little pictorial and/or a sentence to the effect of: The LWCO MUST be installed with the probe in a horizontal position to be effective. Installing it in any other position may result in nusiance lockouts or may prevent the probe from protecting the boiler. That language and the extant pics will drive the point home.

As an example to follow, Grundfos has a couple of neat little graphics in their install manual that illustrate which ways the pumps can get installed. Thus, if the installer doesn't use the manual as a kneepad...

Alan R. Mercurio_3

Constantin, Please consider contacting the following individual below. I assure you he cares and I know he would want to be made aware of this. Just for the record I can honestly tell you the items you covered that were not in the instructions are in their presentaion they provided me with for training. I'm sure they would want to see to it, that gets in the next printing of instruction.

Greg Roder
M&M ITT Industries
(773) 250-1314
greg_roder@fluids.ittind.


Your friend in the industry,
Alan R. Mercurio

www.oiltechtalk.com

Al Corelli

Although not truly necessary, I, whenever possible, mount the "run" of the LWCO tee vertically to make sure air does not get in there.

Constantin

Thanks for the replies, gentlemen

I will contact ITT to see if the pictorial/sentence can make it into their next manual for the PS851/801.

It would also be very, very nice if Viessmann could make the whole process more foolproof by providing a plugged LWCO hole on their safety-header. Seem reasonable?

Glen

The engineer -

that you should chat with then is Ayman Youssef in Waterloo. 1 800 288 0667. Now if I could think out loud for a moment - the cast header is included in the certification of the boiler as a boiler - and also included in the CRN. Would modifying it then subject the boiler to re-certification? The vent header is an intergral part of many of Viessmann's product's. Good idea though ...

Unknown

Instructions

The Instruction Manual clearly shows as illustrated that the probe can't be located where water or air may be trapped. This was scanned from their on-line manual for an RB-122. Also none of the illustrations show a vertical nipple being used. The instructions state that the probe needs to be in the flow of water.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Constantin

So I guess we could have a conflict...

...between the manuals published by MDM since they show the RB122 installed in a vertical position (third drawing from the left) while the drawings included with the PS851 found on my boiler (see link above) do not. Perhaps the RB122 works on a different principle than the resistance method used by the PS851?

The MM-202 manual that is included with the PS851 LWCO makes no mention of allowable installation orientations... even though it only shows horizontal ones... nor does it mention the possibility of air getting trapped anywhere. Perhaps this explains the confusion on the part of the installer.

I'm just glad that the heating system is not only working, but doing so silently as well.