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Mark Eatherton

Mark Eatherton

Joined on November 10, 2007

Last Post on August 26, 2014

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Not just a steam term, but….

@ August 26, 2014 9:28 AM in Swing joints. How do they work?

Swing joints are critical for the longevity of a piping system with extremely long runs. If left to its own action/reaction, a piping system can tear itself apart at the joints due to uncontrolled expansion AND contraction. I have seen long runs of PEX used for snowmelt system that literally tore itself out of the plastic supports due to contraction, a condition that no one anticipates on the start up of an extremely cold slab.

A properly installed expansion compensation system will have the ability for the pipes to move without causing undue wear on the pipes (slides and or guides) and is anchored such that the growth/contraction is directed towards the expansion compensator, and is virtually silent in operation.

Expansion joints (other than near boiler piping on steam boilers) can be comprised of 4 elbows arranged in a large U shape (there are actually required leg lengths based on anticipated growth) or in the case of copper or plastic, a large (again, calculated) circular loop, or a telescopic device sealed with O rings.

Again, even though it may be installed, if improperly blocked and supported, they may be useless if the expansion and contraction are not being directed towards the compensation device. In the case of contraction, the initial setting would be half way between compressed and relaxed to compensate for contraction. If used for heating only, they would be set in a contracted mode to allow for expansion.

This required anchoring is a detail that is typically overlooked by the design engineer, the inspector and the contractor and the expansion joints can be a waste of time if improperly applied and controlled.

Residentially, long runs of PEX, if improperly applied and controlled, can equate to a very noisy piping distribution system. In my opinion, "Comfort", does NOT include any noises associated with the operation of the system. Control is as simple as blocking and locking the tubing on the far ends, having an expansion joint in the middle of the run, and supporting the tubing with glides that will allow for a smooth movement of tubing without creating ticking and clicking.

This is one major reason I am not a fan of suspended tube, a.k.a. staple up tubing for RFH applications. When the tubing cools to room temperature,and then is heated up due to call for heat, it sounds like a herd of crickets running through the floor joist…

Got questions ?


@ August 25, 2014 8:59 PM in Fire Side chats with the RPA...

Still some seats available. Send email to

This is going to be fun and educational.


Back in the day...

@ August 20, 2014 4:26 PM in Altitude and Deration

Carl, I have always derated atmospherics at 4% per 1,000 feet. I then take into consideration the density and caloric content of the fuel and adjust the orifi' accordingly, and have never had any problem whatsoever. Most appliance manufacturers are unaware that Denver has diluted (they pump air into it at a compressor plant east of Denver) gas and are usually surprised when told about it.

As for blower equipped premix systems, I have found that the 2% per gets you real close, but have also been told by product engineers familiar with Denver's gas that the neg reg venturi orificed fuels systems already compensates for the lack of fuel and lack of atmospheric density. Now that statement didn't make any sense to me either, but the combustion numbers always worked out using the 2% formula without having to change orifices or offset pressure settings. I've clocked NG systems using this method, and like you, it comes in real close to expectations, but it is a completely different beast. The problem is with LP systems. I have yet to see a meter on the fuel supply side of an LP system, so there is really no way of confirming "exact" caloric input and net output of the appliance.


Never done that, but...

@ August 20, 2014 10:15 AM in Caleffi Boiler Mix Valve.

I once installed a circulator backwards, pumping against a check valve, with the brain surgeon homeowner (seriously) and my ex partner looking over my shoulder….

And come to think of it, I MIGHT have mis-wired a pump or two :-)

It happens to everyone Harv.


Emerson Swan joins RPA's Hydronics Industry Alliance-Commercial efforts

@ August 19, 2014 12:02 PM in Emerson Swan joins RPA's Hydronics Industry Alliance-Commercial efforts

Emerson Swan has joined the efforts of the RPA's Hydronics Industry Alliance-Commercial efforts.

Thank you to them for their foresight to join this historic industry effort to bring the advantages of hydronics to the attention of the people who are making decisions about what types of system go into commercial buildings.
If you are a manufacturer of hydronic related equipment and you are interested in joining this effort, contact

If you are not yet a member of this organization, you should be. We have your best interests in mind and are here to help you achieve your goals.

Please visit the RPA website at and click on JOIN.

Thank you for your interest.


It's just a matter of time….

@ August 18, 2014 9:19 PM in Snow Melt

THe further away from the reacting surface the tubing is, the longer time it takes to get that surface to the melting point, and the more energy you will use getting it there. Any reason you can't do the structural slab first, then tie tubing to mesh on the top of that slab, then finish with grout and stone? I've done it this way numerous times and it worked like a champ. Don't forget to put insulation at the very bottom of the slab profile to avoid send heat to Mother Earth.

We shot 6 x 6 x 10 Ga. wire to the poured and cured cement, and tied tubing to that. Stone masons set wet pack and stone on top of that. Make certain your snow detector is flush with the intended final surface and doesn't trap moisture, or you will be back there soldering an extension onto the snow cup… Don't ask me how I know this :-(


Fire Side chats with the RPA...

@ August 5, 2014 1:27 PM in Fire Side chats with the RPA...

The RPA’s Weekly Live Chat… and how to get in on it!
On Saturday September 6th, the RPA’s first live chat session will go, well… live!
The bi-weekly, invitation-only chat sessions will feature guest speakers such as prominent industry authorities, manufacturers, contractors and other trade organization directors. 
One hour, open-forum discussions will cover a variety of topics, from ground-source heat pumps, hydrogen fuel cells and other emerging technologies, to controls, ANSI code and certifications that concern today’s installer or engineer.  During the first discussion, industry trainers Robert Bean and John Siegenthaler will team up to dispel the myths about radiant heating and cooling. 
Co-hosted by the RPA’s executive director, Mark Eatherton, and F.W. Behler’s Dave Yates, the sessions – currently called, The Boiler Room - will include 45 minutes of structured discussion before opening up for Q+A. 
Since attendance is limited, contact Eatherton ( to request an invitation.  Anyone can request a seat, but only RPA members will have access to recorded sessions in the RPA archives. Paid members will get priority over unpaid members if maximum available slots are filled for attending the show.
Soon after its first session, we’ll be looking to rename The Boiler Room, so join the name contest.  If you have a good idea for a name, email it to Eatherton.  If yours is picked, you’ll receive a lifetime chat session invitation and a $50.00 Visa Gift card.  Submissions should be sent no later than November 7th, and should be sent to
Don’t miss this opportunity to stay on the cutting edge of your industry, share your ideas with peers, or even become an interviewee yourself.   The one thing that hasn’t changed from the “old” RPA, is the sense of camaraderie and interest in a common cause, and the need to share vital information.

If you would like to be an interviewee, drop Eatherton a line and let him know what you'd bring to the discussion. New products? New applications? Interesting concepts? No holds barred. Just need to be interesting and knowledgeable.
Got a problem that can't be solved? Bring it to the discussion and let some of the worlds most knowledgeable hydronics brain trust give it their best shot.

Thanks to Dan and TLM for giving us the opportunity to present you with this information.

I think AO Smith owns the world, don't they?

@ August 4, 2014 6:02 PM in Emerson swan


Or at least it seems like they do.



@ July 30, 2014 8:10 PM in Pool heating

If the pool chlorination systems uses salt, your regular flat plate heat exchanger WILL turn into Swiss cheese in a year or less. Chloride stress cracking. Use a material that is compatible with sodium if it is present.


Paint that puppie HR...

@ July 22, 2014 9:48 AM in Electric Baseboard Vs Hydronic Electric Baseboards

I had a copper sheet radiant heater on the ceiling of my office many years ago. As I sat below it, with my system running full out, I really didn't "feel" that much heat pouring off of the panels.

I attached a delta T temperature recorder and confirmed my beliefs. Not more than a 2 degree delta T across the 4' X 4' panel,

I then painted the outward facing surface of the radiator with a flat white latex paint, and my DT jumped to 5 degrees F., and when I sat below the radiator, it felt like sunshine falling on my face.

Copper, especially shiny copper, makes a terrible heat emitter, and any radiator that is painted a metallic color significantly reduces the radiant output of the heat emitting surfaces.

I always wondered why the old upright radiators were painted silver, copper or gold…

Dan has an article in the archives written by one of the hydronic ancients that spells it all out. Check it out. As Dan say's, it pays to wander off the Wall. Lots and lots of resources in the Library.

Just joshing you about painting yours HR. I suspect you really don't need the extra BTUH output of it anyway :-) That is a beautiful work of pipe art from Pipe Dream Acres.

Thanks for all you and your family have done and continue to do for our industry.


A watt is a watt, just like...

@ July 21, 2014 8:35 AM in Electric Baseboard Vs Hydronic Electric Baseboards

A BTU is a BTU. There are only 3.413 btu's per watt, oil or not. The addition of oil to the convective process doesn't enhance the delivery of thermal energy. It only spreads it out over a wider time frame.

If you really want to deliver excellent RADIANT comfort, look into Cove Heaters They mount at the junction of the wall and ceiling and they WILL influence the Mean Radiant Temperature, and that drives the bus of human comfort.


Reverse calculation for head...

@ July 15, 2014 10:57 AM in How Long

1. Pressure test to confirm vessel integrity.

2. Connect a steep curved pump to the pipe with pressure gauges before and after the pump.

3. Read pressure differential across pump with pump running wide open and free.

4. Take manufacturers performance curve and figure out how many guppies per minute (GPM) you are currently moving.

5. Take pressure drop chart for the pipe you are connected to, and knowing (from initial differential test) how many GPM you are moving, and knowing the pressure drop of the pipe per foot per GPM, divide known overall circuit pressure drop by the pressure drop per foot (or one hundred feet what ever your chart reads) and calculate length.

The problem with air purging is that unless you have a substantial CFM availability (thinking tow behind compressor here), chances of getting a good and complete purge into buckets or drums is slim. And once you start flowing water out, you can not stop until it stops itself. Could get a little (lot) messy if you are not prepared.

Don't forget to compensate for fluid temperature in your calculations.

My assumption is that there are no obstructions or kinks in the pipe. Otherwise, all bets are off.


I definitely wouldn't have missed that...

@ July 12, 2014 8:17 AM in Radiant Ray is mia

Thanks for the picture HR.

I can now ask people if they've seen him.

If you know his whereabouts, call me at 720-375-3107


I hear you Gordy...

@ July 10, 2014 12:18 AM in Jury Rules That CSST is a Defective Product

And I hate to use the old saw of you can't fix stupid. We can only do so much in our efforts to protect people from potential life threatening systems. Can't tell you how many combustion air vents I've come across that were completely blocked off…

I believe that this lightning technology could be incorporated with a pressure sensor, and if the gas pressure drops after the strike has been indicated, then the system locks out. If pressure is stable, then it could automatically reset itself.

And you are right. Given enough nuisance calls, people will defeat ANY system of protection…


Solution to the problem...

@ July 9, 2014 8:09 PM in Jury Rules That CSST is a Defective Product

I have a solution to this problem. As stated WAY up in this thread, there is a LOT of this stuff in homes throughout the world, and it is just not real to think we can deconstruct peoples homes to repipe in rigid pipe. I know for a fact that the people who make this stuff also frequent this site and read these threads, so I HOPE that they view my recommendation as an inexpensive solution to a potentially ex$pen$ive problem.

There exists on the market, a device known as a "Near strike lightning detector". It is adjustable and can be set to detect strikes within 1 mile of its location. They are used on golf courses to warn golfers of pending lightning dangers.

There also exists normally closed solenoids rated for use with gaseous fuels. They are used in conjunction with LP detectors here in certain parts of Colorado, and shut down the fuel distribution systems outside of the building served if LP is detected.

If these two units are combined (lightning detector and solenoid) and a near strike is detected, the fuel valve is closed when a near strike is detected, annunciating a BEEP BEEP audible signal inside the affected dwelling, requiring the consumer to call their plumber to retest the vessel integrity of the CSST system, and if clear, reset the system to allow fuel to flow again.

Seems a lot cheaper to me than possibly having your product banned by the NFPA and being forced to recall ALL of your material from the field.

i have documented the date of the idea of conception of this product, but I never pursued it any further.

Remember me and my family in your will…


Best resource on the interweb...

@ July 9, 2014 9:16 AM in Radiant cooling

Is Robert Beans web site,

Typically, radiant cooling is set to handle the sensible loads only, and depending upon the actual loads, possibly not ALL of the sensible loads, but in most normal cases, can handle all of it. A typical installation requires tubing at 6" O.C.,and an approach fluid temperature of 55 to 70 degrees F.

If the tubing is at a wider center (typical) then it will carry half as much as it would at 6" centers, but in your case it would still help offset the loads.

The possibility of creating condensation using fluid temperatures greater than 55 degrees F are slim to none.

Chris, the airport in Bangkok uses a DOAS (Direct Outside Air System) to control the HUGE transient latent loads and environmental humidity that they see in that environment. They use large surface area finned heat exchangers, along with super cold water to wring the humidity out of the air coming into the building.

Radiant cooling is just like radiant cooling in that it affects the Mean Radiant Temperature. On the heating side, we use the "standing outside on a cool day in the sunshine" to give people an idea of how it affects us. On the cooling side, it is like "standing in a basement on a hot summer day". It "feels" cooler.

Having ceiling fans with a floor is a good idea to break up the stratified air to avoid a muggy feeling.

Radiant cooling is no longer a "theory", but instead is a p proven method of delivering excellent human comfort. Shedding as much load as possible in the first place using off shelf technology (reflective window coverings, operable screens to keep fenestration gains out, over hangs, etc) makes excellent sense, but radiant cooling is a possible option.

Robert helped Uponor in the development of the programs they use for calculating its ability to cool.

If you've never been to, plan on spending some time there to educate yourself. Robert does a fantastic job.

If you join the RPA, we can teach you all of these things :-)


Interesting stuff Chris...

@ July 8, 2014 10:45 AM in Peer review please...

We could learn a LOT from the ancients, if we'd just listen :-)

Oh wait, you and I are considered ancients, are we not :-)

Borderline Dead Men, standing in line waiting for the next threshold…


All great points HR...

@ July 8, 2014 10:37 AM in Peer review please...

And just so it is clear, I am not advocating flat concrete panels in lieu of properly placed solar collectors. I guess what I am saying, is if you are going to install a snowmelt system, why not take advantage of whats there energy wise for not a lot of extra cost and effort. It just seems to make sense to me. And yes, availability and load have to be matched, or storage taken into consideration, which will add costs. I see your points and they are well taken. It won't be for everyone, but commercially speaking, I do believe there may be some opportunities there that can and should be utilized.

In order to test all of this, its going to require some dependable instrumentation. Do you know of any flow sensors that are reasonable in cost and can be compensated for use with fluids other than straight water? I believe you were working with some Grundfos flow meters at one point in time.

I have the necessary computer power for data logging to show us the potential, and it is flexible enough to handle pretty much anyones sensors. I can get 32 points of monitoring, and 8 points of output control for fairly cheap. Just need the ultrasonic flow sensors to make it work.

Thanks for your perspective.

By the way, I seem to remember a European plan (Swedes or Danes) who were planning on doing this very thing (road based snowmelt/energy harvesting system). Wonder what ever happened with that?



@ July 7, 2014 9:59 PM in Peer review please...

What about degrading PV efficiencies over time?

I hear what you are saying regarding a 300% efficient device versus a 95% device, but still, using a solar PV array at a 20% peak efficiency versus a flat plate at around 60%?

My gut tells me we end up at the same place efficiency wise (except for your graphic delta T in storage example), but the ST systems efficiency will not degrade significantly over the life of the collectors, Having to completely replace the PV array before it has paid for itself just doesn't sit right with me for some reason. Plus, we can completely recycle a ST collector, but can't do the same with a PV array can we?

Lots of numbers to chew on. :-)

Buyer beware…

Thanks again for chiming in.


Thanks HR...

@ July 7, 2014 1:34 PM in Peer review please...

Much appreciated as always.

Obviously, this is still in its conceptual stages, and I don't want to limit the application to residential settings. Anywhere that there is a good and continuous hot water load is a good candidate. Restaurants are a great example. They can use the snowmelt system in the winter to avoid slip fall hazards, as well as decrease the maintenance costs (salt and chemicals are BAD for carpet and tile), and they can use the hot water it provides when available. Remember also that the operation of this system is not limited to the availability of solar energy falling upon the surface, although the advantages of that are quite obvious. There are times, at night, when the slab is still being exposed to significant energy potentials from the higher ambient air temperatures,

In addition to DHW, there are a LOT of other thermal loads that can be satisfied with low temp (120 F) energy. Hot tubs, swimming pools, spas, even some space heating needs. As for storage, there are a whole bunch of new phase change materials coming across the pond that will revolutionize thermal energy storage. That, and good old Mother Earth ( Plus, as we have proven over the years, a slab, at night makes an excellent heat emitter, providing a passive cooling source for radiant cooling loads.

I think it is a huge opportunity staring hydronic contractors in the face. Once we prove it is technically and economically viable, we (The RPA through IAPMO) can start pushing for tax credits for the equipment necessary (except for the slab and boilers) to make it work. How many square feet of snowmelt systems is currently sitting there doing nothing for most of the time, right next the the physical plant for heating hot water and buildings?

I think just about every system I installed would make a great candidate. Plus, by cooling the slab, and keeping it relatively stable temperature wise, we lessen the opportunity for thermal expansion and stress related cracking of the slab. Imagine the looks on peoples faces when they step onto a pool deck that is cooled? Probably as nice as the look they have on their face when they step on a warm floor for the first time...

Need to round up some volunteers (equipment manufacturers and end users as well) to document the potential to move the initiative forward. I have one candidate (consumer) already, and am looking for more.

Did I mention that we can "make" water by keeping the slab below dew point, and can use that water to maintain our Xeriscape Landscaping? Green, green, green, green, green. Plus, by condensing moisture out of the atmosphere, we can slow down global warming, because in reality, its not the Co2 that's causing issues, it is WATER vapor :-)

The Bean is giving me many articles from IGSHPA folks to read. They've been looking at this for some time now. I know of a building in Aspen Colorado that has received numerous awards for its design that uses its snowmelt system as a cooling tower.

Thanks for chiming in Bob. I look forward to your contributions.



@ July 3, 2014 2:53 PM in Peer review please...

Here are some conceptual drawings I generated. My apologies for the roughness of some of them. I've been away from Visio for way too long.
I am posting four concepts.:
1. basic high efficiency SIM,
2. High Efficiency SIM that also does DHW (for the family with lots of teens),
3. SIM with single stage DHW preheat, and
4., SIM with 2 stage DHW preheat.
Comments and questions are welcome.


Our deepest condolences...

@ June 29, 2014 11:06 PM in One of the greatest heating tech' has passed away

To the Milne and Aiello family. JCA was one bright candle out in the deep dark woods of life. He will be greatly missed, and passed way too young.

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