Variable speed temperature setpoint circulator

Joe_28

I'm trying to complete a major modification on my baseboard fin tube dual fuel heating system and need a variable speed temperature setpoint circulator to maintain an output temperature in the neighborhood of 180 degree F. on my wood boiler. I will be storing BTUs in a Triangle Tube TR120 indirect and have a Solo 110 for shoulder seasons. Wondering if a Grundfos Alpha would work if it was receiving a signal from a temp sensor rather than a pressure sensor. I'm looking for a reasonably priced circulator. Any suggestions?

EricAune

Taco 00-VS

Why not a Taco variable speed set-point circ?



http://www.taco-hvac.com/uploads/FileLibrary/CAT100-024varspeedoocirc.pdf



http://www.taco-hvac.com/uploads/FileLibrary/00-VS%28PA05%29.pdf

Ironman

Exactly Eric

The Taco is a delta T pump. The grundfos Alpha is a delta P and cannot be modified into a delta T.

CMadatMe

Not True

You can set gpm requirement on an Alpha. The difference between the VDT and an Alpha besides the motor is that the VDT is looking at a delta-t while the Alpha is not. Now if only the Bumble Bee's would start their migration.

Ironman

Sorry Chris...

But it is true. Setting the gpm at a fixed rate does not make the Alpha a delta T pump. If the btu input into the circut is varied (as in this poster's case), then you in no way have any control over the delta T with a fixed gpm.

EricAune

Set point is the key

If I am understanding the question correctly.....



Fixed temperature is the goal.  I don't think you can do that with an Alpha but with the proper piping and sensor placement of a Taco variable speed set point circulator this is not a problem. 



How is the draft controlled on the outside furnace? Motorized dampers? Are they tied into an aqua-stat?

croydoncorgi

'Controlling' a woodburner

As has been pointed out, the Grundfos Alpha range of pumps modulate based on pressure and/or volume - NOT temperature.  (In fact, very cunningly they do NOT actually sense flow or pressure directly.  It's all done via counting turns of the impeller and the operating current.  Amazing!  In UK / Europe practice, the 'injection loop' is not usually present, so a variable rate pump based on temperature is not needed.  For 'Variable Temperature' (VT) heating circuits, we usually use a 3-way blending valve, so there will be two pumps (one for the VTcircuit, one for the primary circuit feeding the blender(s)) instead of three.  I wonder which is most effective / least cost / causes fewest problems??



Other interesting sidelights on your original posting is: What are you trying to achieve? Will it work? And (most important) will it be safe?



One of the big no-nos here in UK is attaching an 'uncontrolled' heat-source to an indirect water heater.  You can turn off an electric heater and a gas or oil-fired boiler only contains a limited amount of heat once the burner is turned off.  BUT anything involving solid fuel (including a wood-burner) is not controllable to the same extent and (in UK regulations) there MUST be a way of isolating anything that could boil and / or pressurise destructively from the heat source.  Assuming that the woodburner is producing TOO MUCH heat, what do you do with the excess?  And how do you make sure the woodburner itself is not in danger / dangerous after it's got too hot and the fire is still burning?  A BIG heatsink is needed somewhere and the indirect heater is not it!



(I assume everyone has seen the Mythbusters Exploding Water Heater.)

Joe_28

Thanks for your replies.

Taco's 00-VS circulator would do the job but the quote I got was 10 times the price of a plain vanilla wet rotor circulator and 5-6 weeks out.



Our wood boiler combustion air is manually controlled. We've been using this unit for 30+ years.



Excess heat will be dissipated through a high limit dump zone. Hot Rod had suggested several years ago using a Grundfos MixiMizer but I've been told that unit is no longer available. A delta-T type circulator is readily available but will not fill the bill since I am looking for a setpoint circulator.



I am temporarily circulating through the wood boiler with a NRF-22 that I had available and am controlling it manually. When I get the system completed, I hope to be able to post some pictures on the Wall.

Ironman

Automatic Damper Control

How about motorizing the damper and let an aquastat control it?

hot_rod

Grundfos Miximizers

I got a 26-64 MixiMizer this summer to test with our solar controllers. With the MixiMizer you can give it a 0-10VDC signal from some of the solar controller interfaces.



I believe a 15-42, 26-64 and 26-99 Miximizer are all still available.



Looks a lot like a tekmar board under the hood, in the wiring enclosure.



It works fine with the controller, by the way.



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