tankless heaters w/ mix valves

Rich Kontny_4

Great success with my Takagi supplemented with "The Heating Box" which comes with two tempering valves,a pump for the domestic water, a pump and two heat exchangers for my infloor heat and a control that gives priority to the domestic water needs.

I run the Tagaki at 180', tempering my domestic water to 125'and tempering my infloor to 130'. The Heating Box has LED readouts of supply temp from Takagi, mixed domestic temp, infloor supply temp and infloor return temp.

The Heating Box has two models one is for a closed system and one for an open system. The open system is about half the cost of the closed system. This product was designed by a former Takagi engineer to allow one heat source (a tankless heater)to provide both domestic water and space heating water.

I set up two test sites for this system and would only consider the closed system model. For domestic use only I would think that this would be overkill, however "Navien America" has a system where tempering valves and on demand water heaters do indeed work properly.


Rich K.

kevin coppinger_12

I remember a while back....

seeing a post where someone had used a sparco type mixing valve w/ a tankless(rinai/noritz type) water heater...they had issues w/ it...should you not use the two together or are there special piping scemes that only work......ty, kpc

Jack

Basically

to get the mix valve to work you set the water heater at 120 and the mix valve at 120 and you get hot water. The problem with mv's and tankless is that there is a minimum flow and fire requirement to initiate operation. Set the heater at 140 and the mv at 120 and frequently the mix ratio will not allow the heater to reach its minimums to fire. Low flow shower heads and lavs can be a big problem. A tempering valve on a Rinnai is a solution in search of a problem.