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[mlappin]

From another member stuck in posting purgatory:


  I need to add an aqua stat to my system. My current set up has a Central Boiler  1450 that goes to a heat exchanger in the house. My indoor boiler is on the other side of the heat exchanger. I have three zones in the house one  is priority hot water and two heat zones. The problem is my indoor boiler has an aqua stat on the return line that fires the boiler if retuning water is below 140*  So when the call for heat comes in the water goes below 140* and the boiler fires . The heat coming in from the furnace is 190* so the heat is there but the indoor boiler does not know this. I want to place an aqua stat on the furnace water line coming in and wire it to the other aqua stat. Will any strap on aqua stat do or is there a specific one I need. I also want a strap on one to go on the Pex.

[slimjim]

Now that's an odd one, i'm not sure I have ever seen a boiler that monitors return temps and keeps the unit temp up, especially that high so before we change anything, lets be sure we get it right OK.
What brand and model is the boiler?
How is it fueled, gas, oil or electric?
Was it properly installed according to the manual?

[tinfoilhat2020]

that is odd...I have almost and identical set-up. My utica boiler has an aquastat on the boiler. I have the temp set to 160° so if my returning temps drop below 160° the boiler will fire off LP. My incoming water is also 180-190°. the Indoor Water Boiler rarely fires off LP in the deep winter when the system is calling for heat on a regular basis. In the early fall and Spring I will turn the aquastat on the water boiler down to the minimum of 135° because it will go hours without firing and when it does the water on the house loop has been sitting and is cold so the LP will kick on for a bit longer.
It seems that there should be a simple fix to your system....like slim said i would get the manual out and make sure that it is set up correctly to start

[patvetzal]

I used to run into this system in the Toronto area on apartments. Seems that fossil fuel boilers did not like cold water being pumped into them so the plumbers would hook them up so they fired asap. Didn't seem to care about discharge temp. I was servicing electric boilers and didn't care about the return temperature, just needed the discharge to be between 120 and 140F, no more no less. We could control both the flow with a mixing valve AND the KW that were energized...