Taco VDT DIP setting question

[MarkW]

So, I've got this VDT on my loop from storage to loads. Reading the instruction sheet, it seems to me that DIP switch #3 set to off stops the circ from running 100% speed for the 30 sec default when the loads call and should ramp up to meet delta setting. Obviously, the 30 sec full speed isn't optimal for my stratification. So I switched to off on that setting last night. Works initially meeting the delta t I've got set but just seems to taper down from there. Eventually, it was down to not pumping at all though the loads were calling.
Am I misunderstanding the instructions? Perhaps this is not how the VDT is supposed to function with the #3 set to off?

 

[Vizsla]

Where are your sensors, and when it stopped flowing what was the DT compared to the setpoint DT? When you say stopped flowing, I haven't had a VDT stop ever. Just down to its min flow rate, like 6 GPM or 10 watts for example. What size are your ports on the storage? And how far out does that size come out before a 90 turn or change in size or device. I try to keep 12" of uninterrupted pipe to not unstack the tank. Which size VDT

 

[MarkW]

I don't have temp sensors so I can't give you exact readings of what the real delta was. Put it this way, delta was set at 25 last night. I had storage at 180 and return was cool to the touch.
Circ sensors are on the lines.
Where I have it now, there isn't enough room for 12" before a 90. More like 6". 1 1/4" fittings on tank.
When I say it wasn't pumping, I mean the % flow led was off as if the load wasn't calling.
I can't recall which pump it is and Its out in the shed.

 

[Vizsla]

Did you notice a strat problem during the start up blending. Unless you have something bigger than the 009VDT 1 1/4" should be enough to prevent turb in the tank. high speed on the 007 & 009 is like 12-13 GPM I think. This why they put 2" taps on factory tanks. Sometimes you have to play with the DT to get what you want. Actual can be different than what it sees. Such as reading off circ and copper pipe versus big black fitting or ball valve. Heat soaked materials, were copper changes quickly and accurate. Had a few issues with bumblebees and sensors to close to the cast iron boiler exchanger. The supply would read much higher than just a few inches away on the copper, where the return dropped fast, so the bee would ramp up and stay there. Sometimes justly taking the insulation off one. And you know how hot the circ cases can get. Trial and error

 

[MarkW]

I will have time tomorrow to mess with it more. I'm thinking of playing with the delta setting to see if there is a happy range where it will keep running. Both of the circ sensors are on copper and insulated well. I'll take a look at those too.
I was just looking at some of the Taco spec sheetsand it does note that flow rates are from 0-pump spec. It sure seemed to be not flowing at all.
I guess I'll find out tomorrow.

 

[Vizsla]

That's interesting, I take lots of notes, I'm a stickler for fine tuning. I'm sure you will getter handled. I have customers that want to see a DT of 20 on all there thermometers to match the circ setting. But sometimes all those, probes and what not don't match. I'm just stumped at the no flow. I'm gonna try to induce that when I goto the farm tommarrow and check the greenhouses.

 

[ewdudley]

So, I've got this VDT on my loop from storage to loads. Reading the instruction sheet, it seems to me that DIP switch #3 set to off stops the circ from running 100% speed for the 30 sec default when the loads call and should ramp up to meet delta setting. Obviously, the 30 sec full speed isn't optimal for my stratification. So I switched to off on that setting last night. Works initially meeting the delta t I've got set but just seems to taper down from there. Eventually, it was down to not pumping at all though the loads were calling.
Am I misunderstanding the instructions? Perhaps this is not how the VDT is supposed to function with the #3 set to off?

DIP 3 selects reverse acting or direct acting. In reverse mode acting you're telling the pump that increasing the pump speed will decrease the deltaT, and the 'goal' is lower deltaT down to the setpoint. In direct mode you're telling the pump that increasing pump speed will increase the deltT, and the 'goal' is higher deltaT up to the setpoint.

The setpoint of the pump is the deltaT to be maintained, so in direct acting mode the pump will slow down as long as deltaT is above setpoint setpoint because its goal of higher deltaT has been achieved, and it will stop entirely if deltaT stays above setpoint because the pump has already slowed down all it can it an attempt to lower the deltaT.

You can't decide to prefer reverse or direct acting mode. If it is a reverse acting circuit then DIP 3 needs to be set for reverse acting.

 

[MarkW]

Now that makes perfect sense explaining what I'm seeing. Thanks for that! Guess I'll just have to live with it until I change my system this summer.
Perhaps you could help Taco with their directions? You were much more concise!

 

[ewdudley]

Guess I'll just have to live with it until I change my system this summer

Don't know how your system is set up, but if your goal is to minimize flow and to minimize return temperature to storage, a simple and effective change might be to substitute in a deltaP pump like Wilos Stratos or Grundfos Alpha, and use an aquastat and a cycle timer to cycle the pump on and off when return temperature gets too warm and the pump is running at minimum speed.

The problem is that when the pump is turned off, the sensor can't see the need for more heat because it loses feedback from the system. This is why (in reverse acting mode) Taco has to run for a while on startup and has to maintain a minimum flow, else their whole deltaT bright idea falls apart. DeltaT is just that, a bright idea but pretty much useless.

 

[MarkW]

I got this pump for another purpose and it was 1/2 the price of regular retail. Admittedly, when I started looking into all this before buying my boiler I hadn't heard of deltaP. I've just been reading up on it in the last month or so. Definitely looks far better for my needs vs ^T.

Unfortunately, in a moment of confusion I forgot to place a valve on the storage side of the pump so there's not going to be any switching out until heating season ends.

I was ok with the minimum flow part but I can't fathom why it is that the pump can't ramp up until it meets setpoint. Perhaps an overly simplistic PID handles the flow% and can't control both over and under setpoint? Whatever the case, I'll be going deltaP next season.

 

[Vizsla]

Don't know how your system is set up, but if your goal is to minimize flow and to minimize return temperature to storage, a simple and effective change might be to substitute in a deltaP pump like Wilos Stratos or Grundfos Alpha, and use an aquastat and a cycle timer to cycle the pump on and off when return temperature gets too warm and the pump is running at minimum speed.

The problem is that when the pump is turned off, the sensor can't see the need for more heat because it loses feedback from the system. This is why (in reverse acting mode) Taco has to run for a while on startup and has to maintain a minimum flow, else their whole deltaT bright idea falls apart. DeltaT is just that, a bright idea but pretty much useless.

A grundfos sales rep.....wow, sounds very familiar to some posts on several other sites.

This originally started out with an issue about the initial full speed start up possibly disturbing stratification in the tank. By the way Mark , were you able to confirm that this was even happening. Like I said if you have the 007 or 009 with 1 1/2" taps, it should not be an issue, unless the piping or fittings are creating excessive turbulence.
So everything was fine except the initial high speed, right? If I am understanding right, this circulator is for the zone valves, not a primary loop application.
What I see here on this 009 VDT is to turn dip switch 2 off. With it on it has a minimum flow. I don't know what 4&5 do. I don't think there is a need for reverse acting mode in this application.
Before you run out an jump on the DP band wagon, maybe you should test more. DP is a great circ, but NOT the answer to every application. Most of these DP promoters see it work on one job or one zone and that's all they need. As soon as we have temp probes on each S&R pipe for each loop/zone, you can see where both pumps fail poorly in some retrofit applications. And retro is a big reason why these circs are popular.
Anyone have info on full details of dip switch operation and application. I'd like to know more about the reverse acting.

 

[ewdudley]

A grundfos sales rep.....wow, sounds very familiar to some posts on several other sites.

Wilo, Grundfos, B&G, Taco, take your pick, but if variable speed deltaP ECM fits the bill you need to drop Taco from the list. If Taco had an ECM deltaP offering you can bet they'd be singing its praises, but it's too late now, they've painted themselves into their own little detaT corner so now they have to pretend that's where they want to be.

Anyone have info on full details of dip switch operation and application.

http://www.taco-hvac.com/uploads/FileLibrary/102-143.pdf

I'd like to know more about the reverse acting.

See above post #7.

 

[MarkW]

A grundfos sales rep

I was actually thinking Bumblebee.

I've no hard data to suggest that the pump is actually disturbing my stratification other than it runs full speed for the 30 sec rather than ramping up to delta as the instructions suggest it will.
This circ is running 3 zones atm. Currently, it's going into water to a HE's and that can be an issue. If one HE out performs the other, the circ will lower flow reducing the effective he output of the system. I'm well aware that this system is not optimal, hell, it's not even good. I hadn't even intended to use the boiler this year in this house. I was just hoping to use it more effectively. Apparently, it is my misinterpretation of the instructions that is the issue.
I have a support request in to Taco last night to see if they can answer this question.

Thanks again to both of you for your assist!

 

[MarkW]

Thanks for the post. Just went to tacos site to discover its delta t only. I was reading elsewhere that it did both. That would have been buyers remorse.

 

[Vizsla]

Taco was the first with the Delta T and its patent. The rest followed up with the DP because they couldn't do DT.

Thanks very much dudely, it's the applications I'd like to see. That wasn't in our binders at the last seminars. Just the basic one they list one the 00vdt page. Since the Bumblebee, not much material on the VDT.
Using either circ always works better when you have balancing devices to work with. The good ole boys always put them in, now I come across those who ask what they are. For me it's holding a proper DT, and both have worked in different apps. I most use Taco, unless it was spec otherwise.

Well in the 30 seconds I'm guessing the few gallons aren't doing much harm , if its even doing anything. I appreciate the link cause I already have plans with that info. More than just a VDT now

 

[MarkW]

While that link is interesting, it's not for my VDT. That's for the VS. Those DIP settings do not correspond to what is in my insturction sheet.

http://www.taco-hvac.com/uploads/FileLibrary/102-359.pdf

If you check page 2 regarding switch #3 you will see that it does not describe direct acting and reverse acting as functioning like the VS instructions, hence my confusion.

 

[ewdudley]

While that link is interesting, it's not for my VDT. That's for the VS. Those DIP settings do not correspond to what is in my insturction sheet.

I believe they are all the same except switch 2, which I thought would be clear enough to the attentive student, if I may be allowed to take a pedagogical role. The 00-VS document goes into detail about switches 4 and 5, which the 00-VDT sheet does not, so I thought it would be a better resource for satisfying viz's curiosity.

 

[Vizsla]

This circ is running 3 zones atm. Currently, it's going into water to a HE's and that can be an issue. If one HE out performs the other, the circ will lower flow reducing the effective he output of the system.

Thanks again to both of you for your assist!

That's not exactly accurate. Now it. Might be what your seeing, but when a zone is open and at the DT20. And another zone opens that temp drop is caught by the sensors. Both my bumblebees and the VDT maintain a tight tolerance. I have seen trouble hold on some jobs, like when an IDW is also in the same header. Very different HE types mixed together. Fin tube, flat plate, panels....etc.

Only way to really know is having a strap on dial on each S&R line.

Back to your circ,,,,,???? What model is it exactly? Did I read that right that you got a great deal on it? I wonder if it was one of the early VDT , some say they had issues in the pic programming board.

 

[MarkW]

I believe they are all the same except switch 2, which I thought would be clear enough to the attentive student, if I may be allowed to take a pedagogical role.

Be an educator, if you like. I'm good with that. However, one cannot escape the ambiguity in Taco VDT instructions for switch #3. You may be spot on, I have no way do disputing/confirming that. But that's on Taco, I guess. I will agree that the VS instruction sheet is far more illuminating vs VDT. Wonder why that is?

Got a response from Taco. Basically, leave #3 on. That's the way it has to work to meet deltaT.

I don't want to delve into this current mismatched system and waste your time solving problems unnecessarily. As noted, I had not intended to use the boiler this season in this house. My existing wood furnace is nearing the end of it's life and needed some work. So rather than put money into it, I chose to get the boiler going and learn more about hydronic heating before it gets installed in our new home. My reasoning for this post is to learn the equipment and it's functions. I guess we've gotten to that point with DIP switch #3.

Thanks again for the help. Support here was better and faster than Taco!