Would this be a viable solution to lower the return temp?

hot_rod

the fin tube output you want to look at is with the average water temperature not supply water temperature

You can get a bit more output by upping the flow to 4 gpm. Some fin tube charts show both 2 and 4 gpm outputs.

pdanaher8

The Viessmann will be a system boiler. I'll run a 52 gallon DHW tank on that side of things.

https://forum.heatinghelp.com/discussion/comment/1822002#Comment_1822002

I'm not sure the boiler goes to 190 degrees. I'll have to look at that, but in the end, I'm stuck with this BB design and I know what boiler I need, so it is what it is. Hope it works.

pdanaher8

https://forum.heatinghelp.com/discussion/comment/1822007#Comment_1822007

Hi hot_rod. Everything I'm seeing says…..

The average fin tube water temperature in a typical hydronic heating system is around 

180°F (82°C). What average should I be using?

hot_rod

https://forum.heatinghelp.com/discussion/comment/1822106#Comment_1822106

what temperature does the boiler run up to? That is the supply temperature aka SWT. Call it 180. It should be adjustable inside the control.

The temperature typically is designed to drop 20 degrees though the loop, aka delta t

So return temperature, aka RWT, would be 160

The average of 180 plus 160 is 170

170 is accurate number to use to determine actual btu output through the loop

Also note that the fin tube at the beginning of the loop will have higher output, as it sees the hottest SWT

In some cases the rooms at the end of the loop may have more fin tube footage as their output is lower , seeing the lowered water temperature

pdanaher8

AAHHHH. Got it. Thank you for the explanation!

pdanaher8

One more question. The Viessmann model I am looking at is the 8.5K- 85K 200w. For an extra couple of $$ I could get the 8.5K- 120K. With the same output on the low end of modulation, would it harm anything to get the more powerful model? This would be to better keep up with things on the DHW side of everything.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1822217#Comment_1822217

The only benefit you would get is faster recovery on the water heater, if it was set up for 100% firing rate.

pdanaher8

Thanks HVACNUT.

GGross

If you aren't installing viessmann accessories (mixing valve etc, the tank still works with 100-w) and not terribly concerned with the fancier control I would recommend looking at the 100-w equivalent B1HE-85, should be less money, still has the lambda pro+, built in diverting valve and pump for nice piping to indirect heater. That's the one I put in my house

pdanaher8

Hi GGross. Do you run more than 1 heating zone with your 100W?