Another tankless water heater replacing boiler thread

[OurTown]

I'm considering using an additional temperature controller instead of the Weep Mizer's output 2 because it looks like it has only a 1 degree differential. Correct me if I'm wrong.

 

[OurTown]

This is the temp sensor I was considering buying two of for both primary and secondary pump circuits.

https://www.supplyhouse.com/Johnson...perature-Control-w-19-1-2-Leads-120-240V-SPDT

 

[Randy]

There's one on Amazon that looks pretty interesting
bayite AC 110V Fahrenheit Digital Temperature Controller 10A 1 Relay with NTC 10K Sensor Probe

 

[OurTown]

There's one on Amazon that looks pretty interesting
bayite AC 110V Fahrenheit Digital Temperature Controller 10A 1 Relay with NTC 10K Sensor Probe

I have used that one before for a non-car wash project but they are made to mount in a panel.

 

[2Biz]

I'm back on this project. Are you saying that if using two heaters the two pumps should be in series and then split off to each heater inlet? Or do you think there needs to be two pumps per heater? I'm still trying to figure out pump sizing on the primary loop.

I don't know that you would need 4 pumps (2each in series). 90% of the time, only one heater will run. Even if both heaters run, you'd only be looking at about 12-13 gpm...(2) 013 Tacos in series will deliver 30gpm at 40psi....I get about 6.0gpm with one heater at 40 psi...It flucuates a few tenths of a gpm based on how cold or warm the inlet temp glycol is....

 

[2Biz]

If I use the old buffer tank and run it vented on top will I need a larger pump to circulate the secondary loop? Will this introduce oxygen into the system? It was vented before and used a cast iron pump, but that does not necessarily mean it is okay. I should not need an air eliminator or an expansion tank, correct?

If you run the buffer tank and its vented AND if you run a trough loop. The tank will over flow....And yes, it will allow oxygen into the system. I run mine closed loop...Never had a problem, knock on wood! I don't think the size main loops circulator would make a differnece either way. If you run it open, you don't need an air eliminator or Expansion tank...The buffer tank is the air eliminator and Exp Tank! LOL

 

[2Biz]

I'm considering using an additional temperature controller instead of the Weep Mizer's output 2 because it looks like it has only a 1 degree differential. Correct me if I'm wrong.

Why....When it gets cold out, temp is coming down and usually goes past setpoint....Slabs already warmer from the higher temps of the day. I control my floor heat pumps from output 2...Never have seen it short cycle...I have output 2 set at 32°....Using a different controller and The larger diffferential you set will keep it on longer than necessary that wastes energy. If the temp is rising, why would you want it staying on at 33° or more after the slabs are already warm? I'm sure you are already aware, but you need to make sure you have a relay big enough to handle the load of all your pumps. Use output 2 to control that relay...I'm sure the bayite controller will work though. I have several of them controlling various things...Coin Box heaters, Pop machine heaters, Attic fan ventilators at home, etc....They are a great little temp controllers that doesn't break the bank @ $20 each!...