Wrong pump?

[ulooknatme]

I'm having second thoughts about the pump I just purchased. (taco 0012 vdt) the new variable output pump. Before I install this thing I'd like to know if I should just go with a 3 speed. To give you a little background, this pump has to pump 160' from woodshop to house thru 1-1/2 '' copper pipe, then thru 3 tanks totaling 1700 gal.
My problem is, won't this pump run on high when the temp's are greatest and slow when temp's are close? Isn't this the reverse of what I'm looking for? I'll be running a tarm 60 I bought 2 years ago. Took lots of pic's and spending lots and lots of money. Will post them soon when all is complete with a cost breakdown. thanks

 

[jebatty]

The answer may depend on how your system is plumbed. If the 0012vdt is serving only to charge storage with the boiler, and you have one or more other circs to supply the zones, then I don't see how the vdt provides you any benefit. In this situation, my take is that there is a benefit to having flow increase based on boiler output temp, so long as boiler output temp is higher than storage return temp. OTOH, a constant flow in this situation is OK also.

 

[Chris S]

You can pump a lot of btus through 1 1/2" pipe, how many gpm are you trying to accomplish? The tanks will not really have any effect on this unless the piping is small.
My only other thought is that as the temp is rising , on a new fire fore instance, and your circ is racing, and your storage is cold, ..thermal shock.
I would say overpumping your system is a bigger concern- the opposite problem of what most people here a lot of posters with pipes too small

 

[in hot water]

the pump size depends on how many GPM you need to move through the system, and the heard, or resistance, it has to overcome.

With a delta T (temperature difference) circ one intent is to give the boiler return temperature protection. As the return temperature to the boiler drops below 140F, for example, the pump slows it's flow to let the boiler heat up.

hr

 

[ulooknatme]

I think I might have figured this thing out. The delta t for this pump can be set from 5-50 degrees. Let's just say I set it to 30. Temp leaving boiler at 160 and return coming back at 110. Pump says speed up to get the DT closer to 30. Not what I want it to do. What I need ( I think? ) is to keep the water temp going into the tank as hot as possible so I get good stratification. What I did find is a fixed set-point pump from taco, but I can only find it in 007. It keeps the water temp leaving the pump set anywhere from 30-210 degrees, and if the temp goes above this temp the flow increases. I think this would almost allow me to drop putting in the thermovor valve. (which has me upset because i've run 1-1/2'' pipe and the couplers that attach to the thermovor valve only have an inside diameter of a dime)
To answer the question above, yes, this pump would only supply water to the tanks, and I was told I needed at-least 1-1/2'' pipe to circulate 200,000 btu's thru 320' feet of pipe. Was also told to use a 0012 or 0013 pump.

 

[jebatty]

Be sure you provide return water protection for the boiler, which IMO should be 150-160F.

Although the Tarm 60 is maximum rated at 198,000 btu, output over a typical burn cycle likely will be in the 120,000-180,000 range. You may get the 200,000 btu output only at delta-T>20 and/or during a maximum burn period, which is only part of the burn cycle.

You may be tempted to rely on what "you are told" by someone, but the better way is to do your own system pump head calculations and size your circ accordingly. Take into consideration what others say, and if different, ask why. Also, if you estimate average 150,000 btu output, you only need to move 15 gpm with a delta-T=20, and I think a 0012 or 0013 will meet or exceed this based on your info. But if you plan on moving 200,000 but, delta-T=20, you need to move 20 gpm, pump head increases a lot, and the 0012 probably cannot handle that, while the 0013 still should be able to.

And if you hope to move 200,000 btu at delta-T a lot less than 20, I wish you good luck. For example, at delta-T=10, you need to move 40 gpm, and 0013 will not do that. It won't do it at 150,000 btu either.