Rob R. wrote:
That radiant slab will really suck some heat. There are a few things you can do to reduce the "shock" on the EFM.
1. Turn down the temperature of the water going through the floor via the mixing valve. 100F is probably plenty.
2. Adjust the bypass valve(s) on the EFM to reduce the amount of cold water being returned to the boiler.
3. Increase the feed rate on the stoker. 3 teeth is too low to do much of anything. 4 is the minimum for most applications, and 5 will noticeably reduce the recovery time.
I would start by adjusting the mixing valve, and increasing the feed rate. You already have it piped primary secondary, so returning really cold water to the boiler should not be a problem. I suspect the floor just sucked all the heat out of the boiler and the feed rate was too low for it to recover in a reasonable amount of time.
I think you are right that the floor sucked all the heat out of the boiler. I hadn't even thought about adjusting the mixing valve down, good call. I was trying to adjust the Tstat for the floor but it is such a pain to program. I think I'll get the wife to do that, she does good with those. I checked the floor temp and it's runing mid to upper 70s. I'll bump the feed up some and adjust the bypass and see where that gets me.