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Wet rotor circs have a magnetic rotor (yep, attracts iron particles). When we design these things we have to take into consideration the amount of fluid exchange in the rotor can (they are water lubricated by the system fluid).

Some ECM magnetic rotor folks actually filter the system fluid before it goes into the rotor can (works as long as the filter doesn't plug up).

So, us manufacturers of magnetic rotor circs test the heck out of em against iron oxide attacks and other stuff. However, in extreme cases and the right conditions they might fail (and most importantly, IF they fail due to system fluid and nothing is done to fix the water issue, they will continue to fail).

Not just iron oxide particles either - I've seen copper particle failures (copper pipe rotting due to real bad pH).

Don't panic - I've been involved in ECM product design & development for over 8 years. The percentage of failures is actually very low. I like to point out "the better the system fluid is the longer these things last" - and if one fails, inspect the rotor - it can tell the root cause...

Yes, the key is don't avoid ECM technology, and most important pay attention to fluid quality.

I've recently heard that iron ferrite is something like 10X of limescale as far as putting the damper on heat exchange.

You REALLY don't want it (iron ferrite) in any part of your system., even if the circs can handle small levels.

It's a very tough product to get out, almost like a thick ink or paint, not really a particle you can get a hold of and separate easily. And in large quantities you would need to service the separator on a regular basis.

That's why everyone is looking at the mag sep add on. Grab as much as possible first trip. We put X amount of ferrite in a circuit and measure what collects.

Still the best plan would be to treat the problem, not the symptom. Why are we seeing the iron ferrite. Has it always been flowing around the systems? I've really never looked for it until it started showing up in permanent magnet circs.

One thing to remember about vortex separation, it takes some fairly high velocities to make them work. We built a clear plastic version, connected to a Grundfos Magna so we could dial in exact flow rate Connected the ultrasonic flow meters to confirm.

As we see more and more variable speed circ on both side, boiler and distribution, the ability to use vortex separation efficiently may be in question. Or perhaps program the pumps to assure high velocities for certain periods of time, then modulate.

Having built clear samples of both, no question the media type seperators are amazingly effective from very low, to well over the normal velocities you would expect to see in typical hydronics. We run 'em out to 10- 12 fps on the test bench

I can vouch for the SEP4. It is continuously pulling out particles from our system.

Good questions, I'd look to then folks in the UK the issue started showing up there first due to all their open systems. A lot of the magnetic separation products were developed there, Fernox, etc.

We have a growing collections of pics sent to us of failed, or rotation error ECMs. Here is one of two from our own shop that started seizing and showing rotation errors on the display. Took it apart myself..

We also get pics from installers of the magnetic particles that the mag separators "suck" out of the systems, it is a real concern.

The symptom is easily addressed with magnetic separators, probably see a bunch more at AHR.

My bigger concern is WHY so much ferrite in supposedly tight systems. It took ECM to bring the issue "out of the closet" But it doesn't take a lot, really to jam a circ, maybe a 1/2 teaspoon on this one pictured.


Our shop is all alu pex, copper steel and stainless boilers??

I'm going to check my radiator alpha during some future work - will post some pics if there is anything interesting. The Alpha would have been exposed to a good dose of iron oxide.

Wow - good posts guys. Couple of observations...

100% correct excessive iron oxide is probably a bad sign - systems rotting out from the inside out - probably caused by excessive air (but could be a PH issue or excessive water velocity). Challenge is what is excessive oxide

The only magnet in a non-ECM circ is the magnetic field the stator generates that grabs the "nails" in the rotor, causing the rotor to spin. BTW, iron oxide will cause premature sleeve bearing failure in std wet rotor circs (it's abrasive). Same goes for mechanical sealed circs (premature seal failure) so this awareness is not only for ECM. I just don't like the idea the ECM circ becomes a sacrificial anode, collecting the iron kind of like a magnetic dirt separator.

I'm not an installer but it kind of makes sense to me the better the system fluid the better the system (longer component life and better heat transfer medium).

I've reached out to some of my contacts overseas and will let you all know what they say. ECM's have been around there since 2001 so they have 5 or 6 years of experience ahead of us.

Our system serving 12 condos units was a poster child for iron oxide contamination. There had been a leak at some point between 1999 and 2010. As a result a large amount of iron oxide from a cast iron component settled to the lower radiator lines, mostly plugging them. No heating contractors figured that out for years, but that is another story. The old boiler was a copper fin type, so the source must have been our previous reverse indirect Ergomax. I will try and dig up the bucket of iron oxide I purged from the lines, at that was after I had dumped a lot more beforehand. It was amazing. Besides the Ergomax, there was very little iron in the system, if any. Only PEX and brass. I plan on some PEX work to clean up a crappy section soon. Hopefully the brass components will be in good shape. I installed a SEP4 and the magnet is continually picking up particles. They must be dispersed over the 3 levels of the system. The water quality seems fine besides the particles. Once they react with O2, perhaps they are not reactive in that environment anymore - not sure. When I initially found the problem and purged the system water it was pretty foul. My plan now is to fix up a couple things and add a bunch of purge valves so I can backflow all the radiant and radiator zones, then add two rounds of chemical cleaner, then a passivisation additive. I will also descale the boiler heat exchanger. I confirmed there are no current leaks. The fill valve is shut and system pressure is solid at 12Psig. Progress is slow though..

GMP= BTUH / DELTA "T" (20 Degrees) X 500. That's the Hydronic formula for determining the GPM's when using 100% water. That changes every day based on the heat loss or the load of the structure. If we move too many GPM's, we bring heat back to the boiler and short cycling occurs. If we move too little GPM's, not enough heat will be delivered and we'll get calls. If the water moves too slow through a zone we can allow air to develop in the system. If we move it too fast we risk noise and if it really moves fast, we may risk wearing away some of the metal in the delivery system. Just the flow that's needed allows for comfort and efficiency.

If one elects to use a delta P, delta t, or variable speed ECM circ. then those flow rates are ever changing with system demands

With delta p in a TRVed system TRVs, are modulating flows rates change.

With delta t if your trying to hold 10, 20 what ever that flow rates Is not always the same based on the load.

If your modulating the circ with the boiler output flow rates change.

In all cases water temps are a floating target when using outdoor reset.

There is a multitude of ways to incorporate these ECM circs in a hydronic design.

There are designs where flow rates are constant, but water temps are still not.

You guys are taking this to a level not seen in hydronic heating.

1. Water does not reach a boiling point in hydronic heating. In certain circumstances there is occasions where water flashes to steam in the eye of the circulator volute . Other wise we are 180 ish down to ambient. Always a moving target.

2. Most particulates are already in the fill water, or pre existing in the system infrastructure. These are solids down to a micron level.

3. The goal here is to capture those particles, and keep the system Fill water clean as possible. In particular ferrous particulates that can foul ECM circulators, and SS, AL HX's of certain designs. Fire tube types are less prone to fouling by design.

4. As far as ECM circs go there may be certain systems that prove to be beyond there use. Such as an all iron pipe gravity system.

5. We can fill flush, purge flush, chemical treat flush, chemical treat. all day long. In something like an all iron system I believe it would be a never ending cycle of treatments, and maintenance. One has to ask is the money saved by an ECM circ taken away from the extra maintenance, and treatment a system needs to gain anything the low watt circ can offer.

6. System variables in particular flow rates. In my mind an initial multi system purge cleaning, and treatment is going to be the highest flow rates the system will ever see once operational. Any contaminates there after still in the system will most likely settle out in the widest parts of the road to stay for ever. I think type of system pumping has an effect. Be it constant circulation verses on off circs, and zoning with valves, or circs. Out of the options I think a,system with varying delta p will kick up a lot more settled out particulates from the initial system cleaning at various times, and certain conditions.

As for Hot Rods system with iron ferrite particulates when none exists in system components. I think you will find that all components can be contaminated during the system build. Whether it be sanding clothes to clean pipe, or wire brushes. To just plain contamination at mills for copper. Via transportation, and handling at distribution sites down to the supplier. The bigger the system build the larger the probable volume could be. Then there is the fluid fill choice be it well,city, distiller, RO water the particulates are there just in different ppm.