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Steve Thompson (Taco)

Steve Thompson (Taco)

Joined on January 27, 2012

Last Post on May 23, 2014

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Recent Posts

Series Pumping

@ May 23, 2014 6:56 PM in Series pumps and my hydronic comedy of errors

Mark, I would be careful about series pumping with circs of drastically different performances (I would always recommend the circs be the same size in this application).  Reason being, if the big circ is downstream of the smaller one it can potentially suck the system fluid out of the smaller circ.  If the big circ is upstream it will make the downstream small circ ineffective, with it's energy overpowering the small circ.

Regarding NPSHr, all wet rotor circs require a "minimum inlet pressure", not NPSHr as with a dry rotor circ.  This is to stop the water from boiling (flashing into steam) in the rotor/can area, killing the sleeve bearings.

Typically small circs are approx 2 PSIG min met pressure with the pump running.  Larger ones can go as high as 14 PSIG.

I kind of think reverse flow might the best solution.  Or how about some electric glass as a supplemental heat source???


@ January 28, 2014 6:42 PM in Happy Birthday Dan Holohan

If I was a jerk I would convert to dog years, but I'm not (it's 448 by the way).  Don't feel too bad Dan - I'm not far behind you!

Sincerely though, thank you for being a HUGE part of making this the greatest industry imaginable.

Hope your special day was the best and wish you many, many more!

One request - what do you see as the three most important innovations in your career (other than electricity :-))???

Taco Party @ AHR Show - Tuesday Jan 21st

@ January 3, 2014 9:43 AM in AHR Expo - who's going?

Hey fellow Wallies, here's an open invitation to our AHR event!  Invite attached - hope to see you all there!

An of course all the best for 2014!

Noisy Bumble Bee

@ November 1, 2013 1:19 PM in Taco Bumblebee Buzzes-

Please contact me at or 401-441-2934.

I'll hook you up with our B Bee Product Manager and engineering team to look into the noise issue.

Say It Isn't So

@ October 21, 2013 9:48 AM in I'm finishing up the seminar part of our business.

Well, I get the part that you will have more time to "hug your kids".

Your last session (damn, this still hasn't set in) will be a very special event to be sure (kind of like your very first Power Point presentation :-)).  Thank you Dan for all you have done for our industry - you are a true hydronic icon and always will be.  Unfortunate the new guys coming into the business (hopefully) will not have the opportunity to here "Dan the Man" live.

Thanks for the advanced warning - and good food for thought for all of us "aging" hydronic guys - this wonderful thing we are all part of won't last for ever - have fun while you can...

Opinion on a Delta T Solution

@ September 29, 2013 12:31 PM in First high efficiency boiler on my own...short cycling! Help!

Zman, Chris, Rich and Eric, what's your opinion of using a Delta T circ as a solution for this short cycling issue?

I would think if we slow the BTU train down (thanks Dan - use this a lot) increasing the delta T would help the boiler to stay on longer.

One man's opinion

@ April 25, 2013 1:50 AM in Very Nice

Sorry, I can't resist weighing in on this...

I was the product development guy that developed the Stratos and ECO back about 6 years ago (not a huge deal, mainly North Americanised what was already available in Europe).  However, what was a big deal was preparing you guys and develop the first North American ECM training program (installation, operation, application, Brain Box etc).  And yes, these were the first ECM circs brought into North America - so you can blame me :-).  Based on my experiences AND working for companies that believe in delta P and/or delta T, I have a couple of observations/comments/questions for you folks:

1)  Siggy has been after someone to develop a circ that can do both delta P and delta T.  Assuming both will "more or less" provide flow regulation (let's leave it at that), my question is how would you guys decide which control to use (other than boiler protection, injection and snow melt that are all delta T only) - not an easy question to answer is it...

2)  I apologise if this sounds biased but without knowing the system curve and where it intersects with the pump curve, how do you know what speed to set a 3 speed circ at?  Or what is the best delta PV setting?  It's the "right" setting once a sensible delta T is reached - so we are back to delta T.

3)  Two European manufacturers at ISH will be bringing over new ECM technologies - one includes delta T and the other includes set-point temperature control (yep, they are starting to do this overseas).  In conversation with all 3, they all admit there is a place for delta T and are excited about this new (for them) control for on-off zone control (I never thought I would here that from those folks).  So, you better get used to seeing more delta T circs in North America - like it or not.

4) What the statement about delta PC or delta PV is saying, basically PC is for low friction loss systems.  PV is for higher friction loss systems (steeper system curves), or systems that the piping component of the friction loss is higher than the heat emitters.  One part of the O/M I had a hard time translating - sorry.

5)  Please, repeat PLEASE don't bash a guy that has a HUGE amount of passion for this industry and remember we are all entitled to our opinions.  John Barba has devoted his career to helping us all and really knows his stuff.  Do I agree with John all the time?  Nope (we do have interesting differences of opinion and yep, sometimes he doesn't agree with me - go figure).  Did I proof his post prior to publishing - yep.  And agree with what he says.  BTW, the bit about the circ not changing it's speed is referring to what happens if the delta P dial is not set high enough (needs to be re-set for systems of high flow and low heads), and the pump runs at max speed (I even asked about that).

6)  Finally (whew), let us all remember our biggest competitors are the scorched air guys.  Let us all promote the hell out of hydronics, provide superior comfort and make dough!


@ April 10, 2013 6:34 PM in Circulators that you can set GPM

Guys, this is a lot tougher than it appears...

First, an ECM circs "calculates" or estimates flow - and none of us are that accurate (hate to say it but that's the way it is).  Second, it's a function of the where the system curve meets the circ curve.  If the system curves does not move then you could set constant flow with a 3 speed circ.  But if the system curve moves(flow and/or friction loss changes) delta T, delta P or three speed can not guarantee constant flow.

A true constant flow circ would have to have code written it the software that would have it react to flow changes like it does with temperature or pressure control (like a constant pressure setting).

Again, stupid question - other than chillers, when would you want constant flow?

Reverse Delta T

@ April 10, 2013 6:16 PM in BumbleBee question

Guys, I get the reverse setpoint.

Stupid questions (yes, I am known for these):  When would you need a reverse delta T (pump speeds up as system delta T goes down).  Also, can you let me know when you would NOT use a fixed delta T?

Happy Birthday

@ March 5, 2013 12:04 PM in Alex Marx!

Hey Alex - have a great day and thanks for trying to teach me how to speak New Yorkese - I'll hold off on some of the new words you taught me as this is a public forum :-)

I think I have an answer - but...

@ February 16, 2013 11:52 PM in How would you control a Bumblebee circulator in a pure TRV situation?

Good question.  I think I have the answer but want to check with Mr. Barba and a few others first.

Stay tuned folks - we're on it.  Get back to you shortly.

March 2nd is out for ST

@ February 11, 2013 11:52 AM in 2013 Long Island BIG UGLY....who's in?????

Sorry guys, I'm now going to be on a plane to the ISH show, can't make it.

Next time!


@ January 26, 2013 9:25 PM in AHR/ASHRAE Taco Party

To all "Wallies" planning on making the show in Dallas - this is a reminder and open invitation to our "little" party Monday night.  Hope to see you there!

Shark Bite or no Shark Bite

@ January 17, 2013 12:45 PM in Shark Bite or no Shark Bite

Fellow Wallies, I request your opinion...

I am one of the unfortunate folks with Poly B in my house and yes, some of the fittings are starting to leak (my plan is to replace with PEX).

What's your opinion of Shark Bite fittings - yea or nay?

Count me in

@ January 14, 2013 1:23 AM in 2013 Long Island BIG UGLY....who's in?????

Yep, I'm in!  Wouldn't miss it.

Pumps vs Circulators and Pressure vs Thermal Tanks

@ January 3, 2013 11:02 AM in Point of no pressure change - help me understand

Sorry guys, couldn't resist...

Pumps boost pressure (aka submersible well pumps, pressure booster pumps, irrigation pumps, boiler feed pumps etc).

Circs (regardless of HP) provide flow to move the BTU train hopefully at the right speed to provide heat (delta T) in a comfortable and efficient manner by overcoming system friction loss in a closed loop system (whew, that was a mouthful).

Some/all (depending on the tank and circ size, air and system pressures etc) of the differential pressure a circ provides will be absorbed by the expansion tank instead of overcoming friction loss if the tank is installed after the pump.  This potentially can cause premature tank bladder failure, lack of flow (comfort) in some zones, boiler and circ cycling, difficulty removing air, excessive make-up water and premature relief valve failures, internal corrosion, just to name a few.

If in doubt think about the differences between a closed loop heating thermal expansion tank (absorbs thermal pressure change as the system heats and cools) and an open system potable water pressure tank (a pressure storage battery to reduce pump cycling).  Pump into the pressure tank with a pump and away from the thermal with a circ.

Yes, water is NOT compressible and yes, pumping away from the thermal expansion tank is, in my opinion, one of the few "has to be with no it depends" in hydronics.  And yes, some low mass boilers actually require the circs to be installed on the inlet (but PUMP AWAY FROM THE THERMAL TANK).

All the best for 2013 to all of you - hope to see in Dallas at the AHR/ASHRAE show and our Taco party!

sizing circulator

@ September 16, 2012 3:08 PM in sizing circulator

Agree a "reverse engineer" is required.  My question is are you planning on one circ for the whole job or does the boiler have a dedicated circ?  Reason for the question is if you use a delta P circ you may run into issues with low boiler flows under low load conditions.

If you are using one circ it is sized to overcome the friction loss of the primary loop (plus boiler and fittings) @ 40 US (assuming a delta T of 20 deg for a 399,000 BTU output boiler) and the highest loop friction loss.  This is where the heat loss of this loop needs to be calculated to determine the flow of the loop.  Once the flow is known then the friction loss can be calculated based on the length of the loop.

Our Viridian VR20 (2") would deliver almost 40' @ 40 US - enough to cover your butt.  Even better it can be powered from 110/1/60 to 240/1/60.  Plus you can adjust the delta P curve slope from 60% to zero (constant pressure) if there are low load boiler flow issues.  Too bad the Bumble Bee doesn't go larger - would be a perfect fit for this application.

Information on the Viridian is attached.  If you have any questions feel free to contact me at or 401-441-2934.

Only 4 Months with Taco - and WOW

@ May 21, 2012 1:56 PM in Happy Birthday Johnny White

Johnny - happy belated birthday from your new guy - hopefully missing your day is not a "CLM" :-)

Every day new excitement, meeting more fantastic people - thank you for having me on board!

All the best Johnny - see you tonight...

History - from an old "X" GF guy

@ April 21, 2012 1:14 PM in Grundfos pump

This is an old 6000 Series dual volute- two pumps in one volute (I sold these back in the 80's).  Doubtful they will ever run together at the same time - probably set up for main/standby/alternating.  You might be able to replace the powerheads with the current VersaFlo but one issue is not having the ability to individually isolate each head.  Probably has metric flanges too.

This would be an excellent application for our Viridian commercial ECM (a VR 30 - 3" ANSI single phase will handle this no problem).  Sorry for the sales pitch but it is an excellent product and would be a great solution - can stop myself from bragging a bit!

Danger Here

@ February 8, 2012 12:55 PM in Hydronic Coil Air Haindler

I see some potential issues with this type of system (using the heat from a DHW for a heating zone).

1  Possible issues with thermal expansion.

2. Most importantly, what happens in the summer when the heating zone is not seeing any flow for months?  The water will "die" and become toxic (that is why wet pipe fire sprinkler systems use backflow preventers).  This is nasty stuff and I would for sure stay away from it (I agree with the other posts on this).

One last point, the older Armstrong circ was manufactured by Wilo, not Grundfos (note the steel terminal box).  Newer models of the Armstrong circs are no longer manufactured by Wilo...

The Birthday Boy

@ January 27, 2012 10:03 AM in Happy Birthday Dan Holohan

62???  Let's see, that makes you 434 in dog years...  Nope, hang on - 8.9 dog years.  Or about 50 in metric years.

Question for you Dan, how many BTU's does a flaming inferno of 62 candles produce?

Great seeing you at ASHRAE, keep doing what you do Dan!  Have a great birthday and all the best!

PS:  I'll hugged my kids today :-)