Hey all,

Homeowner with a 95% tankless boiler (Lochinvar WHN085) & radiant system controlled through a Taco SR-504 switch relay. Trying to replace a traditional DHW with an indirect. Plumbing is accurate but I’m pretty sure I have the wiring screwed up. When the aquastat calls for heat, the DHW pump will turn on (like its supposed to) but the boiler and boiler pump won’t kick in. So basically I just circulate cold water through the tank. The aquastat is connected to zone 4 of the SR-504 with priority. Also, FWIW the tank did heat successfully when I cycled power on the boiler (the boiler & boiler pump turned on during that cycle). So I know the system is at least capable of heating the tank. But I obviously cannot keep cycling power when I want to take a shower. What I don’t understand is why zones 1, 2 & 3 work fine for space heating yet the boiler & boiler pump sit idle when zone 4 (DHW) is on.

My questions are: First, anything obvious that I’ve done wrong? If not, is there someone skilled enough on this board to offer advise if I post a couple photos of the wiring? Or should I just suck it up and hire a pro? Slight hesitation on the latter for two reasons. 1) I think I’m close and 2) I realize pros are usually not eager to fix DIY botch jobs.

I installed the radiant & boiler myself 3 years ago with help from DIY radiant supplier. It was probably the most ambitious DIY job I’ve tackled but it works great. I had assumed adding an indirect would be a lot easier but right now I’m stumped.

Thanks,

Brian