Solar and Tankless

Mark Custis

You could lower the holding tank temperature on the differential controller below the low mod of the tankless.

Or call the tankless teck guys and ask them what to do with their equipment.

I hac a nice day with Norits tech help this week.

Josh M.

I have been running into several severely short cycling and water temp fluctuating tankless water heaters lately. They all have one thing in common... A solar preheat tank has been connected directly upstream!

The problem? when the tank temp rises but it is still below the required temp, let's say 100 degrees, then the water going into the tankless might not require the minimum BTU's that the tankless can put out.

Let's say for example you are running your shower and it is flowing at 2GPM and your preheat tank is 100 degrees, and you are trying to heat it to 120 degrees. How many BTU's is that? 10,000 rounded off. The tankless we serviced today has a minimum modulation rate of 15,000 BTU's. What do you think it will do? Fluctuate and short cycle.

My question is this.. Has anyone had this problem too? And better yet, how about some solutions? I'm working on a few myself.

hot_rod

some do

I've herd Rinnai does modulate well enough. Multiple burners with multiple turndown functions?

Caleffi makes a unique thermostatic valve for tankless to solar tank intergration. It's available in Europe, not listed to be used here, yet.

hr