We had a Trio P3 cast iron oil boiler with a Riello single stage burner and Bradford White 40 gallon indirect water heater installed last week. We chose this particular oil boiler after much research. The old oil boiler (EFM PK750) would run constantly even in the summer months just to heat up water. The Trio is a low mass, cold start oil boiler that only holds 3.6 gallons of water. Paired with an indirect water heater meant to us that the oil boiler would only fire when it called for hot water, saving us oil. So to our surprise after install, we kept hearing the oil boiler firing up at 130 degrees. We contacted the installer to ask if the aquastat was set up as a cold-start. He told us he had the low limit set at 140. This morning he came and changed the aquastat to the off position which we thought meant cold start. When we went to shower later in the day, the hot water turned to warm and never got hot again. The temperature reading on the oil boiler showed around 83 degrees and the Taco 4 zone switching relay was lit up for zone 4 but the oil boiler wasn’t turning on. We even turned on the heat for zone 1 and the boiler still didn’t turn on. We contacted the installer again to find out what was going wrong and he instructed us to turn the low limit back on which we did for now. This isn’t making sense to us as it seems to defeat our goal of having a cold start boiler because now the oil boiler keeps turning on at 130 degrees but we have no choice in the moment because we need hot water and this was the only way to resolve it. We reviewed the installation manual for the aquastat and the Trio boiler and something seems off. There is no thermostatic bypass on our boiler which is “highly” recommended by Trio to limit condensation. It also appears that the wiring may be incorrect. We just want the oil boiler to run as we anticipated as a cold start but per our last conversation with the installer he never installed an oil boiler as a cold start with an indirect water heater.