Low-Loss Header

Jason Horner

Viessmann makes a low-loss header which they recommend for use with the Vidodens boiler.

My understanding of their suggested use is that it is most appropiate when hooking the Vitodens up to exisiting cast iron rads.

a) Have I got this right?

b) Would using this low-loss header be useful with a Weil-McLain Ultra boiler or is the Ultra less susceptible to the pressure differentials? I don't believe Weil-McLain offers a similar header.

Thanks.

joel_19

low loss

We use this header on every Vitodens we install no exceptions. You could probably use it if you want. You could also get a Caliefe header instead. I got one for a 600k BTU job and it's a really HQ piece of Italian craftsmanship. it's going on conventional boilers for lots of good reasons, not presure drop. I really like decoupling the flow and on this project where staging in boilers. The real question is why are you using an Ultra and not a Vitodens??? Putting A Viessmann header on an Ultra is like putting Mercedes AMG wheels on your Chevy.

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Mike T., Swampeast MO

The type of radiation has NO bearing on whether or not the low-loss header is required.

The header is ALL ABOUT FLOW. If the system REQUIRES flow at a higher or lower rate than recommended through the boiler then you install and use the header.

The low-loss header is Viessmann's device that still allows the burner to modulate and the unit to keep low flow and high delta-t across the heat exchanger regardless of the flow rate in the system itself.

If you don't use TRVs or FHVs it can be difficult to ensure that your flow rate is low enough for the boiler--particularly if you're zoning with multiple pumps.

If you use TRVs and/or FHVs (or if this simple well-balanced system) it will be a rare system that cannot be properly supplied at the recommended flow rates. In these instances, the low-loss header is not required and you can often do everything with a single variable speed pump (built-in the two smaller models).

Many tend to believe that standing iron systems REQUIRE high flow--nothing can be further from the truth. Iron radiators perform wonderfully with low flow and high delta-t. You just have to design for low flow or add TRVs for EVERY radiator.

Unknown

LLH

don't use it. Don't use it with a WM boiler or any other. You think the Ultra less susceptible to the pressure differentials?

I don't think WM would understand (approve) of you using Viessmann's LLH for one of their applications. Build your own. Not hard to do.

Read Dan'd book about primary/secondary.

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