Which is better? 2 pumps or 1 pump w/ mixing valve?

[SIERRADMAX]

Getting ready to place an order for plumbing materials to plumb up an econoburn 100. Last on the list is either a pump or a mixing valve. Econoburn's instructions show two pumps. One in the bypass and one for the primary loop. I have one variable speed pump allready and the cost of a mixing valve is probably going to be the same as buying another pump w/ pump flanges. Any recommendations?

 

[Bob Rohr]

Getting ready to place an order for plumbing materials to plumb up an econoburn 100. Last on the list is either a pump or a mixing valve. Econoburn's instructions show two pumps. One in the bypass and one for the primary loop. I have one variable speed pump allready and the cost of a mixing valve is probably going to be the same as buying another pump w/ pump flanges. Any recommendations?

Is this for return temperature protection? The thermostatic valve is a simple and reliable method, it has a small pressure drop depending on flow rate. If you use a pump it consumes electricity and will need some sort of control to modulate it based on temperature. Some pumps like the Grundfos MixiMiser or Taco have this control (delta t) built into the pump, but of course cost more $$.

 

[SIERRADMAX]

Yes, for return water protection. The econoburns controls have built in dual pump control. The bypass pump turns on when the boiler is turned on and shuts off at 150. The Primary pump then kicks on. Regardless, I'll always have 1 pump running, even with a mixing valve.

 

[goosegunner]

If you are going to use storage the 2 pump method in the book it will not protect the boiler properly. When you have just a small amount of water, boiler and load capacity, the boiler will hit 150 relatively quickly and the boiler will maintain the temp with good fuel load.

With storage, the boiler water hits 150, turns on the pump, in my case I have 1000 gallons cool storage water that would return to the boiler, drop its temp and stop the pump until it hits 150 again. With a Danfoss or similar it will blend supply and return and the boiler will just cruise along brining up the storage temp.

The new danfoss valves also close down the hot port once the return water hits its set point.

I would use a mixing valve, it will give you more options in the future.

I also changed my start temp to 160.

I would be glad to talk to you by phone about other observations if you pm me a number.

gg

 

[goosegunner]

Here are a few pictures of my piping,

Initial piping used for 2 seasons,





Upgrade this summer, parallel pump added for additional flow near end of tank charge, battery back-up, and or redundency if problems with top pump.



gg

 

[Clarkbug]

GG, that has got to be one of the cleanest looking boiler rooms around.

 

[goosegunner]

GG, that has got to be one of the cleanest looking boiler rooms around.

Thanks

gg