Whole home viessmann boiler

Mn1985

GGross said:

I'm sorry that rep is mistaken. The low temp zone in this case needs to have a mixing valve, it doesn't have to be a motorized mixing valve, but it must have a mixing valve (motorized is best). So it sounds like they are turning off the pump to the low temp zone while the high temp zone is calling? This is not the correct way to set up this system. This is either a case of the rep actually not understanding how this system should function, or they are afraid to tell the contractor to fix it. How do they know the typical AHU call is 6-8 minutes when the system hasn't been started up yet?

This is exactly what they did 

GGross

Mn1985 said:

Additional info from rep 

The AHU would have never shutoff would only be the way your RFH would get starved, typical AHU/Furnace run around 6-8 min then it will switch to your RFH should be a great system, this is how I program all our IBC Boilers too and have never had an issue.

They are so very wrong about this, I am speechless.. They even took OUT the mixing valve that they already installed.....

Mn1985

So at this point is it bad advice from the rep that the installer is following. Not sure what else I can really do. 

dko

Link this thread to the rep

Mn1985

Directly from viessmann tech academy which shows mixing valve. But factory trained rep doesn’t know this. 

mattmia2

Does the rep actually work for Viessman or ar they just an independent rep contracted by Viessman? Might see if you can get someone that works in a Viessman office involved. The way it is might work if things align just right but isn't the recommended installation and there will be some at least brief periods where the radiant gets much hotter water than it should. That may or may not be a problem. My biggest concern is that it may end up essentially heating the space off of the hydroair and never get the benefits of radiant.

hot_rod

If the AHU is a zone of its own, and properly sized, would it not run non stop on a design or colder day?
So does the boiler time it out and rotate loads somehow?

GGross

mattmia2 said:

Does the rep actually work for Viessman or ar they just an independent rep contracted by Viessman?

I am 99% sure who the rep firm is, it is an independent manufacturers rep firm from Minnesota. They seem like a big outfit which makes this design all the more bizarre. They should really know better than this, there is no excuse.

auneplumbing

Thanks to Paul P for the heads up about this conversation. I’m in MN, if you want to contact me offline I may be able to help. I’ve been installing and servicing Viessmann for almost five years. I’m on the north metro. Aune Plumbing & Heating. 

Mn1985

mattmia2 said:

Does the rep actually work for Viessman or ar they just an independent rep contracted by Viessman? Might see if you can get someone that works in a Viessman office involved. The way it is might work if things align just right but isn't the recommended installation and there will be some at least brief periods where the radiant gets much hotter water than it should. That may or may not be a problem. My biggest concern is that it may end up essentially heating the space off of the hydroair and never get the benefits of radiant.

Yeah that is my concern. But won’t know until winter arrives again 

auneplumbing

Thanks to Paul P for the heads up about this conversation. I’m in MN, if you want to contact me offline I may be able to help. I’ve been installing and servicing Viessmann for almost five years. I’m on the north metro. Aune Plumbing & Heating.