4 Way Mixing Valve Piping

Badger Mike

Hello to the Wall - I am a new member planning improvements to an inherited in-floor radiant system.  My present system features a single zone supplied by a Thermo Control 2500 wood boiler (125K BTU, 130 gallon water capacity, 180 degree Aquastat with 20 degree differential on the outlet).  A Taco 007 circulator supplies the system through a Taco 3-way thermostatic valve.  There is only one piping loop for the system supply and return, with no provision for boiler return temperature protection.  It seems that a smart 4-way valve with outdoor reset will improve efficiency while providing boiler protection.  My question is this:  Must I create a primary/secondary piping arrangement for the 4-way valve?  The Caleffi Idronics manual #7 figure 6-11 suggests that P/S is not required, while the Taco installation instructions show that it is.  I prefer the simpler installation, but don't wish to ignore the benefit of a P/S arrangement.  Any assistance and opinions will be greatly appreciated!  Thanks.

Zman

Minimum Flow?

The only reason for primary/secondary in your case would be if your boiler has a minimum flow requirement. Is it staple up or in slab?

Carl

Badger Mike

No minimum flow requirement

Hello Carl - thanks for the response.  The coils are stapled up to the sub floor between the joists.  The tech info for the boiler does not stipulate a minimum flow requirement.  I hope to use the existing circulator for the system - I believe this will work as the flow around the existing loop seems to be fine.  The system heats the area OK, it's the boiler protection and the advantages of ODR that I'm interested in.  Mike.

Zman

Condensation

Mike,

 I would be surprised if boiler condensation is much of an issue with a staple up system. They just don't unload the BTU's like a slab.You also have a good amount of buffer water to absorb the cold water that will come in when a zone calls.

Carl

Badger Mike

If condensation isn't an issue...

Wouldn't it still make sense to utilize ODR?  Presently, when the call for heat is satisfied (indoor wall thermostat), the single circulator shuts off.  When the system restarts, the cool return water causes the pex to creak and groan as it heats up.  I do not set the thermostat back at night.  It seems that using ODR would allow the circulator to run continuously thereby avoiding the swings and providing a more stable delivery to the system.  Without ODR, I feel there are a couple other less attractive options for continuous circulation:  (1) Lower the boiler aquastat to reduce output temperature, which will increase boiler air damper cycling, or (2) Control the temperature in the house by opening windows, etc.  Is my thinking logical?

Zman

ODR

Mike,

You should do ODR. It will reduce the noise and provide better comfort. What temp are you mixing to now? Most tubing noises stem from rapidly heating the water or improper tubing installation. Continuous circulation will help as will reducing the water temps.

If you lower your boiler temp too much you will have condensation issues. Try to keep your boiler return temps above 140. Depending on your heat loss you could probably run around 130-140 to the floors on the coldest day with your staple up.

Carl

Badger Mike

Not sure what I'm mixing to

The 3 way thermostatic valve in the system is an old-style Taco with a number range rather than a temperature setting.  In any case, this valve will be replaced.  I figure by going to a smart 4 way, I can regulate the delivery temp to the system, incorporate ODR and provide boiler protection.  I think that's going to be my direction - I truly appreciate your assistance with this!!  Mike.