Turn your Taco VDT into a VS pump ...

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Pat53

Minister of Fire
Aug 21, 2010
613
UP Mich
I was talking to one of the field app reps at Taco yesterday about my 0014 VDT. Told him it did not work as a primary pump for my boiler. I had previously talked to one of the tech guys BEFORE I bought the pump, and they assured me the Delta T pump would work in sort of a reverse mode to keep the Delta T on the boiler output at whatever I wanted. Well, it didn't work that way. So I asked the rep yesterday if there was a way to configure the VDT pump to work just as a Setpoint pump. He called back a little while later and said yes, the new, and quite expensive, setpoint pumps use the same board as the VDT's. By changing the dip switch settings and just using one sensor instead of two, the VDT pump can be run just as a Setpoint circulator. In other words, you can set it for any boiler output (supply) temp you want and it will speed up or slow down to maintain the setpoint temp. Anytime the outlet water temp exceeds the setpoint temp the pump would run full speed.

Now, I haven't tried my 0014 yet in this mode of operation, but I probably will within the next 2 weeks or so, and we'll see if its true or not.

It seems to me that this would be the absolute ideal pump for guys who have storage. To be able to just send 180F-195F water ONLY to your tank during the entire burn cycle would be fantastic and improve efficiency.

The VDT pumps run about $200-$300 less than the VS pumps, so quite a difference in price to do basically the same thing.... if its actually doable ?

Pat
 
I've been manually throttling my taco pump with a motor speed controller. I'd really like to automate the the pump speed.
 
Pat53 said:
I was talking to one of the field app reps at Taco yesterday about my 0014 VDT. Told him it did not work as a primary pump for my boiler. I had previously talked to one of the tech guys BEFORE I bought the pump, and they assured me the Delta T pump would work in sort of a reverse mode to keep the Delta T on the boiler output at whatever I wanted. Well, it didn't work that way. So I asked the rep yesterday if there was a way to configure the VDT pump to work just as a Setpoint pump. He called back a little while later and said yes, the new, and quite expensive, setpoint pumps use the same board as the VDT's. By changing the dip switch settings and just using one sensor instead of two, the VDT pump can be run just as a Setpoint circ. In other words, you can set it for any boiler output (supply) temp you want and it will speed up or slow down to maintain the setpoint temp. Anytime the outlet water temp exceeds the setpoint temp the pump would run full speed.

Now, I haven't tried my 0014 yet in this mode of operation, but I probably will within the next 2 weeks or so, and we'll see if its true or not.

It seems to me that this would be the absolute ideal pump for guys who have storage. To be able to just send 180F-195F water ONLY to your tank during the entire burn cycle would be fantastic and improve efficiency.

The VDT pumps run about $200-$300 less than the VS pumps, so quite a difference in price to do basically the same thing.... if its actually doable ?

Pat

That 0014 s a fairly high head circ. Does the Seaton have a HX that requires that much head? Typically on a primary loop pump you want lots of gpm, but not a lot of head. A flat curve cirs, so to speak. Taco 007, 0010, and 0012 are typically a better choice if you have a low pressure drop boiler and piping.

15 GPM = 150,000 BTU/hr, 20 GPM would move 200,000 BTU/hr at a 20 degree delta T. Usually wood boilers only presents few feet of head through them.

With any of those 3 circ you could use a variable speed solar controller to run it. It could be used as a setpoint or delta T function. Mine keeps the circ off until the boiler reaches the temperature I program in, I think 155F. Then it constantly ramps up the circ speed as the boiler warms or cools. It might be a less expensive and more versatile control. But you need a pump with a current draw of 1 amp, the relay in those solar controllers could not run that 0014.

Becareful using a speed control to vary the speed of a circ. If it controls by lowering the voltage it will damage the motor. Those motors need to run 10% plus or minus the voltage listed on them. As you lower the voltage, they draw more current, overheat and self destroy.

hr
 

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hr, the 0014 may be a bit more than I need, but does it really matter if the pump is only running at 1/2 speed to achieve the same results as a smaller pump? The VDT will vary its speed to match your settings, and from what I understand, the slower it runs the less energy it uses, similar to a manually adjusted variable speed pump. As you know I'm currently having some issues with my Seton, and until I get that figured out I'm not sure what size pump I might need, but the 0014 should be plenty big enough.

Pat
 
That 0014 s a fairly high head circ. Does the Seaton have a HX that requires that much head? Typically on a primary loop pump you want lots of gpm, but not a lot of head. A flat curve cirs, so to speak. Taco 007, 0010, and 0012 are typically a better choice if you have a low pressure drop boiler and piping.

I am no expert on boilers, but I am confused about this as I install bigger pumps for a living. The "head" is the resistance the pump is pumping against ie.. vertical lift, length and size of pipe(friction loss), and the type and number of fittings ( again friction loss) all added together to give you the total head in the the loop. Typically with any pump the lower the head, the higher the GPM is.
So if you really want more GPM only the 12 would give you more GPM than (at an assumed low head) a 14. I think the assumption is that a typical primary loop from boiler to storage is going to be fairly short with just a few fittings thereby having a low total head.
Any pump manufacturer will tell you, the requirements should fall in the middle of the pump curve for the best performance. So a 14 ideally should be pumping 15 to 20 GPM against 12 to 14 total ft of head.
It is possible on a very short primary loop to only have a few feet of head, which would put you completly outside of a 14's and a 12's pump curve.

Pat
If you want to know if the pump is the right size you need to size it properly to the loop you are installing it in. With help from guys on this site I found Tacos program here http://www.taco-hvac.com/en/products/Taco Hydronic System Solution (HSS)/products.html?current_category=84. It is a great program that with a little fiddling around with you can figure pipe size requirements and pump requirements.


In hot water is right about cutting the voltage to to slow the pump down as it will result in premature pump failure and may not be helping if you have a pump that is to big.
Again I am no expert on boiler systems but I do understand pumps, and even in my foggy brain I can see if X size pipe carring x GPM = x BTU's its pretty important to not only size your pump properly but your pipe as well. This is why there are no less than 11 different pumps on the pump curve table in hot water posted.
I guess my long winded point is a pump that is "more than you need" might be causing more problems than varying the speed can overcome.
 
Digger873 said:
That 0014 s a fairly high head circ. Does the Seaton have a HX that requires that much head? Typically on a primary loop pump you want lots of gpm, but not a lot of head. A flat curve cirs, so to speak. Taco 007, 0010, and 0012 are typically a better choice if you have a low pressure drop boiler and piping.

I am no expert on boilers, but I am confused about this as I install bigger pumps for a living. The "head" is the resistance the pump is pumping against ie.. vertical lift, length and size of pipe(friction loss), and the type and number of fittings ( again friction loss) all added together to give you the total head in the the loop. Typically with any pump the lower the head, the higher the GPM is.
So if you really want more GPM only the 12 would give you more GPM than (at an assumed low head) a 14. I think the assumption is that a typical primary loop from boiler to storage is going to be fairly short with just a few fittings thereby having a low total head.
Any pump manufacturer will tell you, the requirements should fall in the middle of the pump curve for the best performance. So a 14 ideally should be pumping 15 to 20 GPM against 12 to 14 total ft of head.
It is possible on a very short primary loop to only have a few feet of head, which would put you completly outside of a 14's and a 12's pump curve.

Pat
If you want to know if the pump is the right size you need to size it properly to the loop you are installing it in. With help from guys on this site I found Tacos program here http://www.taco-hvac.com/en/products/Taco Hydronic System Solution (HSS)/products.html?current_category=84. It is a great program that with a little fiddling around with you can figure pipe size requirements and pump requirements.


In hot water is right about cutting the voltage to to slow the pump down as it will result in premature pump failure and may not be helping if you have a pump that is to big.
Again I am no expert on boiler systems but I do understand pumps, and even in my foggy brain I can see if X size pipe carring x GPM = x BTU's its pretty important to not only size your pump properly but your pipe as well. This is why there are no less than 11 different pumps on the pump curve table in hot water posted.
I guess my long winded point is a pump that is "more than you need" might be causing more problems than varying the speed can overcome.

Digger, thanks, I'll take a look at the Taco link. What exactly do you mean when you say that more pump than you need may be causing more problems ...?

thx, Pat
 
most boilers have big pipes and can use a small pump - low head & lots of GPM. What I have found if you size any where near the cure line you will be disappointed, the pump can't get there, maybe in a lab but not in the real world. My 012 is coupled to a huge boiler and is piped with 1.5 inch copper about 10 fittings. I assumed not drop threw the boiler or the 200 gallon hydraulic separator and with a the few fitting used that it would be 30-35 gallons and it's only 20 GMP. I have some long pex lines and did all the math and those fell short on the 011 GPM also. Every thing works fine "just saying"
 
Pat53 said:
hr, the 0014 may be a bit more than I need, but does it really matter if the pump is only running at 1/2 speed to achieve the same results as a smaller pump? The VDT will vary its speed to match your settings, and from what I understand, the slower it runs the less energy it uses, similar to a manually adjusted variable speed pump. As you know I'm currently having some issues with my Seton, and until I get that figured out I'm not sure what size pump I might need, but the 0014 should be plenty big enough.

Ideally the boiler manufactures run flow tests on the boiler and can provide you with some important info. Mainly what the pressure drop is through the boiler at various flow rates. I'll assume that Seaton is in the 150- 200,000 BTU/ hr range? So it's looking for 15- 20 GPM of flow. If the boiler is more like an EKO or Tarm 40KW for example 40kw X 3.41= 136, 000 BTU/ hr, call it 80% efficient so you need to move 108,000 BTU/hr, around 10 GPM.

Without this data we are just guessing. Then you need to calculate the resistance thru all the piping in the boiler circuit, pipe, fittings. valves, etc. This is for a boiler that is piped as a primary secondary, or with a separator. Not a system where all the distribution piiping is in the boiler circuit, or that needs to be calculated in.

I'm guessing that would be in the 5-8 ft of head range for your boiler, Fred might have that data. IF that boiler can transfer 150, 000 BTU/hr then you need a circ to move 15 GPM at 8' of head.

The issue with high head circs is cavitation. Water boils at a wide range of temperatures based on the pressure. The one place in a system where the pressure can see a drop is the eye of the pump impeller. Water will boil at 170F at -8.6 psi, and that is a very real possibility with a high head circ that is misapplied. Water boiles, bubbles form, pumps cavitate.

Run the system, if you hear a crackling sound, or have chronic air removal issues you may have a cavitation issue induced by a mis applied circ.

It's a very common problem with those un-pressurized OWB as they sell them with high head circs intending to move a lot of GPM or heat. They cavitate to death in a short period of time. No pressure on the pump, high temperatures, some times in excess of 212 ;) Now you have a major cavitation party in progress.

Just saying.... Know why you are installing a high head circ, and if it is being sized based on real data not the intent of moving more heat through a compromised, or fouled HX.

There was a time when our buildings were heated hydronic without circulators. Gravity systems were designed and built to move energy based on pipe size and hot water buoyancy. The introduction of the hydronic circulator brought as many problems as it solved when they were, and still are mis-applied.

True the variable speed function can correct for some mis calculations, but start with the correct pump first, then look at modulation. A wet rotor circ is only about 20- 25% efficient wire to water when running on its sweet spot. When you start running them off the curve...

The problems with noise and heat transfer in your boiler got me to thinking about the circulator and it's relationship to the expansion tank, piping. etc.

Pat
 
What exactly do you mean when you say that more pump than you need may be causing more problems ...?

Well Again I am no expert but if your pump is too big, it might be moving the water through the boiler to fast to get good heat transfer making it very inefficient.
I would assume that is why you are trying to slow down the pump via pump speed.

Example
I have a 300' plus primary loop in my design on the software I told you about.
My BTU requirements are 200,000 btu's. Taco recommends a pump that will pump that will pump 13.3 GPM with a total head of 32.7 ft in an 1 1/4" line.
I dont know what your btu requirements are or the total head of your primary loop, but if you have a very short loop from the boiler to your storage with just a few fittings, I doubt you need 20 to 30 GPM being pumped through your boiler. Even if you had avariable speed pump and went 50% each way of what Taco recommends for my primary loop you would have something like a low of 6.65 GPM up to 19.95 GPM on the high side.
I dont know if your pump is the right size or not I am just saying if you are having issues and you are thinking about or trying to slow the pump down, the first thing I would do is figure out what size pump, and pipe I needed.

most boilers have big pipes and can use a small pump - low head & lots of GPM. What I have found if you size any where near the cure line you will be disappointed, the pump can’t get there, maybe in a lab but not in the real world. My 012 is coupled to a huge boiler and is piped with 1.5 inch copper about 10 fittings. I assumed not drop threw the boiler or the 200 gallon hydraulic separator and with a the few fitting used that it would be 30-35 gallons and it’s only 20 GMP. I have some long pex lines and did all the math and those fell short on the 011 GPM also. Every thing works fine “just sayingâ€

I cant say about your experience and I understand there are many many variables that change from project to project but you have to start somewhere.
I have checked my math many many times against the manufacturers math and have measured real world results many times as I must pass inspections with pump tests. While you will get variations of up to 2 or 3 GPM. Its pretty close if the math is done right.
As a contractor on the hook for warranty if the math isnt done right and the pump fails, trust me I'm pretty careful, as some of the pumps I install cost in the thousands.
If I buy a pump that does not meet the stated pump curve I will not buy any more from that manufacturer.
I am not an expert by any means, but I have learned the hard way how important it is in my line of work, and when you add btu requirements I can only assume it is that much more important if you want the best performance for your money.

Pat was saying he was having issues with his boiler, was thinking about a variable speed pump or slowing the one he has down with a manual controller, and his pump was probably more than he needed. I guess I just connected the dots and was trying to point out how too big a pump could be contributing to his problems.
Just sayin:)

Sry Pat Didnt mean to hijack your thread
 
Hr, the Seton is rated as 130K btu. I have figured my head at about 6-7 feet for my loop from the boiler to storage, plus whatever the HX is, which shouldn't be much, so probably about 10 feet of head at the most. So if we use 10 feet of head and need to move 13 GPM that would put us somewhere about on the Taco 0010 pump curve? Now I'm currently running a Grundfos 26-99 3-speed pump. 13 GPM on the 26-99 curve would put it in the lower 1/2 of the pump curve, or somwehere in between speed 1 and 2. The problem I'm getting is that at low speed I get a very high Delta T (30+) across the HX with even a modest fire burning (400F or so stack temp) and I still get kettling noise. On speed #2 I get a little less Delta T, but still close to 30 degrees and plenty of kettling. On speed 3 I get solid 25-30 degree Delta T and plenty of kettling, at even lower stack temps (360F and over). So if I am even close on my head calculations, with the 26-99 running on high speed I should be moving well over 20 GPM thru the HX, yet I still get a very high Delta T and lots of kettling/boiling sounds. If the HX is NOT plugged or restricted, I would think the Delta T would be much lower, and why would I still have kettling, that is what i don't understand? I talked to Fred about this and according to him, there should be no kettling from running TOO MUCH water thru the HX, only if there is too little moving thru the HX, and that would make sense to me also.

Another weird thing is that if I throw a few pieces of scrap cardboard into the firebox just to get rid of it, as soon as it flares up I hear the boiling start inside the HX, even if the stack temp is only about 325F or so. Any time there are lots of flames hitting the HX it makes a lot of noise, no matter what pump speed its on.

The pump runs smooth and quiet at all speeds, and I can definitely hear it ramp up, or down, when I change the speed setting. There is no cavitation whatsoever. So to me the problem still seems to be too little flow thru the HX?

Pat
 
Digger, my problem isn't lack of heat transfer, I'm getting plenty of that. My problem is the kettling noise and what appears to me to me to be too slow of flow, even with a pump that is plenty big for the system. Other than that, everything is working well. I'm using very little wood and I can heat up my 500 gallon storage tank in only a few hours time. I just don't know why I'm getting the kettling/boiling noise and why my Delta T is so high.

And you're not hijacking, I need all the help I can get .. LOL

thx, Pat
 
one of the things that changes in regards to heat transfer when the velocity is increased [more GPM with same head] is the flow is laminar not turbulent . This changes the ability to transfer heat. It's called a boundary layer that can/will cause the transfer to be less. It's like a pipe inside a pipe. In Pats case I think it's a different problem, I think slag has build up on the inside of the tubes and it has a very high turbulence and when the velocity is increased so does the turbulence increase, and is allowing for a low pressure area that is flashing in to steam. My guess if he ran it with a very small fire and lower temps this would stop regardless of the flow rate. May be over thinking this!!
 
bigburner said:
one of the things that changes in regards to heat transfer when the velocity is increased [more GPM with same head] is the flow is laminar not turbulent . This changes the ability to transfer heat. It's called a boundary layer that can/will cause the transfer to be less. It's like a pipe inside a pipe. In Pats case I think it's a different problem, I think slag has build up on the inside of the tubes and it has a very high turbulence and when the velocity is increased so does the turbulence increase, and is allowing for a low pressure area that is flashing in to steam. My guess if he ran it with a very small fire and lower temps this would stop regardless of the flow rate. May be over thinking this!!

EXACTLY, when I keep the fire relatively small (under 400 stack temp) it runs nice and quiet. Of course the only problem with that is I have to go out every 2 hours or so and throw on another piece of wood (when I'm charging storage). I try to time my burns so that by the time I go to bed the tank is charged and all I have left in the firebox is some chunks of charred wood. By morning I usually just have to stir the ashes a bit and bring up a few hot coals to get it going again. Rarely do I have to actually make a new fire.
 
That being the case I would think big burner is probably on to something.
Maybe blockage and or turbulance?
I am curious though, on the Seton if it is the same as the greenwood design with a plate heat exchanger right on the back of the boiler?
Does your loop run from the boiler to your storage than to the HX and than back to your boiler or does it run from your boiler to the HX than to storage and back?
I am curious because I am fixing to hook up a greenwood 200 and the dealer I bought from told me he didnt use the HX the way it was designed because of those kind of problems.
 
Digger873 said:
That being the case I would think big burner is probably on to something.
Maybe blockage and or turbulance?
I am curious though, on the Seton if it is the same as the greenwood design with a plate heat exchanger right on the back of the boiler?
Does your loop run from the boiler to your storage than to the HX and than back to your boiler or does it run from your boiler to the HX than to storage and back?
I am curious because I am fixing to hook up a greenwood 200 and the dealer I bought from told me he didnt use the HX the way it was designed because of those kind of problems.

Digger, the Seton has a water tube HX. My loop just runs about 45 feet from the boiler to the storage and back to the boiler. Also, I just posted another topic on the HX .

Pat
 
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