# Anyone using the Taco variable speed Delta T circulators?



## patch53 (Jan 5, 2010)

These pumps would seem to be ideal for use with gasifiers w/ hot water storage.


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## deerhntr (Jan 5, 2010)

patch53 said:
			
		

> These pumps would seem to be ideal for use with gasifiers w/ hot water storage.



Patch,

Read my blog, and the response to Rowcroprenegade in his thread. I installed one in the injection loop on the load side of my HX. It was recommended by the GARN manufacture, Dectra. I DO NOT think they are an Ideal fit for a system with a wide operating temperature range that is found in wood boiler storage systems. Taco needs to add a ABSOLUTE temperature set point to the equation so the pumps will not get stuck at a false operating point. I would stay away until they acknowledge these pumps are designed for tight operating temp ranges, and they have a fix for the wood boiler application.


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## patch53 (Jan 5, 2010)

Thanks Russ, I called Taco support and left a message for them to call me back to see if they had fixed the glitch.

I plan on running my system next year, with storage,  with a boiler cut-out at about 185F and fire up at about 155F, with a delta T in the 15-20 degree range. Do you think these variable speed pumps would work properly under those conditions?

Thx, Pat


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## deerhntr (Jan 5, 2010)

I do not think they will work correctly, until they change the firmware in the microcontroller that does the delta-t calculation. As long as the difference temp satisfies the equation, the pump will throttle down. That is what I found. So, if the supply, and the return lose temp at the same rate, the pump will think all is well. The pump does have a "hidden" set point mode, that varies speed to maintain a constant absolute temp on the return side. That temp ranges from 120F - 165F. I have verified correct operation of that mode But, I don't think it's worth the extra 3x in cost of a normal circulator.

BTW, I'm pretty sure they will not acknowledge there is a bug. But, they will tell you there is a bug in the equivalent grunfos circulator.

Good Luck, I will post when I get things going on my end.


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## patch53 (Jan 5, 2010)

Russ, a guy from Taco tech support just called back and said the only pump that had issues was the 008, and that it was fixed. I would probably be going with an 0012 for my situation. I ran several scenarios by him and he assured me that the pump should function as needed in all scenarios I described.

So, not sure what to think now. Talk is cheap and they are in the business of selling pumps, so not real surprised by what he said. I wouldn't be needing the pump till next summer, so I guess I'll just wait and see if anything develops. If they're not working like they are supposed to I'm sure more reports of problems will surface.

I really hope any issues they may have are corrected, these pumps sound like they could save money in the long run.

thx, Pat


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## deerhntr (Jan 5, 2010)

patch53 said:
			
		

> Russ, a guy from Taco tech support just called back and said the only pump that had issues was the 008, and that it was fixed. I would probably be going with an 0012 for my situation. I ran several scenarios by him and he assured me that the pump should function as needed in all scenarios I described.
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> So, not sure what to think now. Talk is cheap and they are in the business of selling pumps, so not real surprised by what he said. I wouldn't be needing the pump till next summer, so I guess I'll just wait and see if anything develops. If they're not working like they are supposed to I'm sure more reports of problems will surface.
> 
> ...



Pat,

I will be working on having them upgrade my board, and I will post when it is all in place. I agree, at first glance they appear to be perfect for this type of application so I would think they will work the bugs out.


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## patch53 (Jan 5, 2010)

OK sounds good Russ. BTW, what size circulator did you have?

Pat


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## ewdudley (Jan 6, 2010)

deerhntr said:
			
		

> patch53 said:
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Looking at the position of the VDT supply sensor in your photo I'm thinking you might should experiment by moving it to sense some point on or very near the HX.  With it sitting right there next to the pump, the pump doesn't know what the supply temperature is unless the pump is running fast enough to find out, kind of a chicken and egg problem, single equation, two unknowns.

Then again, the idea of maintaining a constant return temperature might have merit as well.  Is controlling the absolute temperature setpoint of the return side working for you?


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## deerhntr (Jan 6, 2010)

patch53 said:
			
		

> OK sounds good Russ. BTW, what size circulator did you have?
> 
> Pat



Yes, I have the 008 VDT.


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## deerhntr (Jan 6, 2010)

ewdudley said:
			
		

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Yea Eliot,

I'm with you. Tried all of that and then some. I believe, kind of what you elude to, but single equation, multiple solutions, and there in lies the problem. A Local Minimum! The circulator has a startup sequence that is supposed to bring the supply sensor up to temp. It runs full out for 30 seconds then switches over to VDT mode. So now that, if the Supply sensor was closest to the source, and the return was at the farthest point from the load, then you would think the Delta T would be the highest. The problem with my Outdoor GARN, and most OWB applications, the real "supply" is 110 ft from the HX, so when I'm moving H2O at 2.2 fps, I'm 50 seconds from the HX. By that time the pump has settled into VDT mode, the "Hot" supply is only 2/3 of the way to the HX. I guess I could come up with a delay to hold things off, but my belief is the pump logic is flawed for this application, and the OWB with a wide temperature range is an application where VDT should shine!


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## ewdudley (Jan 6, 2010)

deerhntr said:
			
		

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I see, you're way ahead of me in this exercise!  Thanks for taking the time to share your analysis with us, it has made me aware of another pitfall to take into account.

Maybe in the future Taco and others will move more stuff into EEPROM or flash where we can get at it should the need arise in a case like yours.

Cheers   --ewd


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## deerhntr (Jan 6, 2010)

> Maybe in the future Taco and others will move more stuff into EEPROM or flash where we can get at it should the need arise in a case like yours.
> 
> Cheers   --ewd



Unfortunately......I'm afraid the pump manufactures are in the DARK ages...We don't need any stinkin EEPROM!  They still have to spin a board to make a fix. Hence the denial of a problem. Kinda sounds like politics ;-)


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## DaveBP (Jan 6, 2010)

Hot Rod said once on this forum that the Taco VSDT circulators are controlled by internal Tekmar circuitry. For probably a little more money (don't know how much more) one could get the separate Tekmar controller to use on the pump of choice and then you would have digital displays and LOTS more programmability.
Here's the literature:

http://www.tekmarcontrols.com/literature/acrobat/a157.pdf

http://www.tekmarcontrols.com/literature/acrobat/d157.pdf

Page 4 of the data sheet gives a list of approved circulators for the variable speed feature.

Not much help if you already have the Taco VSDT. 

My quibble with the deltaT controllers that I have read about is that they are all oriented toward solar applications and slow the circulator on close approach. I would like to be able to INCREASE the circulator speed as the deltaT gets closer.


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