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Need help ! Takagi slow flow issue
I'll be honest, I've made some mistakes, but this seems the worst by far, and I think I've gotten way over my head on this one. Any wisdom would be greatly appreciated.
The system is was an attempt at a 1200 sq ft radiant under floor system, using a Takagi T-H3-DV-P ODWH with 1/2" O2 barrier PEX 8 Loops all at 250', with a grundfos alpha I ECM circulator.
So far the highest observed flow that I can achieve is 1.8gpm. I assumed I had made an error on the pressure losses based on the flow rate for the water heater and upgraded the circulator to a grundfos 26-99F (max 32ft of head) thinking that the higher head would help the underestimated situation.(at this time the system pressure was around 35psi and this didnt help either) still only able to get 1.8gpm.
Reading some of the wise threads on this site, It sounded similar to the snow melt system with the T-D2 takagi heater, and anticipated the required low pressure valve situation and increased the pressure to 50psi, assuming the pressure relief valve limiting the full flow of the water heater. Sadly no luck either, but does the heater board need to be reset or is it reset every time it is unplugged?
Some of the remaining things that I have yet to confirm, is the low gas line pressure(the propane company ran the new 3/4" line but first 2' of it is still 1/2" which I found odd but I'm not a gas expert, or some possible venting issue, but I guess I'm clueless since I followed all, well most of the guide lines(the current vent is 30 ft with a concentric discharge).
Also not sure if I put the expansion tank in the right place, but I can easily relocate that to output of the ODWH as both sides have an air separator as shown
I've attached some pictures of the system. I'm still leaning towards a silly miscalculation on my part and it's got something to do with the water heater, but clearly it wont be the first time I've been wrong.
With the System operating, the pressure readings(psi) are 41-Circulator-52, return at 48 and the expansion tank is at 48. Delta T is at 22 Degrees.