EFM 520 new home aquecoil/aquastat settings

I've done a ton of reading about aquastat settings using the search function, but unfortunately, I'm not able to find anything that directly relates to my application.

I recently built a new home and insulated with spray foam. I have a heat pump and an EFM 520 that I ran all last season. The 520 feeds an Aquecoil hydronic coil in my air handler and I'm concerned that my aquastat settings, and probably wiring, may not be ideal for my setup.

I have an L8124A set to 160/200/10 and have been using the domestic coil, which is run to my electric hot water heater. Both the Aquecoil and water heater are about 50 copper pipe feet away from the boiler.

My boiler never gets over 180 degrees and my buddy who installed it works for a large HVAC company that isn't really well versed in coal boilers, for obvious reasons. I don't believe the aquastat is wired up properly. As it stands, the boiler runs to 160 and comes back on at 150, I believe. I also believe my single zone circulator to the air handler heat exchanger runs pretty much constantly. The only other zone I have is to a Modine style water to air heat exchanger in my garage. I don't have that dialed in properly so I'm not using it right now (simple enough fix).

I also shut off the feed to the domestic coil recently because I've been reading that the coal demand can be as high or higher than those for heating calls. I just wanted to see what the difference would be, but I left the aquastat diff at 10 degrees (I'm now reading it should be 25 without the domestic coil).

It's just my wife and I and we don't use that much hot water, but I do have a pretty overkill shower in the master bath with 3 large showerheads and I've reamed the regulators out, so they're pushing even more than the rated 2.5gpm EACH. Generally only 2 are in use at once, but still, I'm reading that's probably more than the 520's domestic tank can put out continuously.

Sorry for the Tolstoy novel post but it gets exhausting researching all this stuff and there are some really knowledgeable people here.

My boiler came from Scrapper as a unit he reconditioned, so it's in top shape. He's from my home town and I could talk to him or an old school guru plumber I know from Pine Grove, but you guys seem to enjoy helping dummies like me, haha.

Thanks in advance for any insight you guys can give me. This community is awesome.

Welcome. Based on what you described, it sounds like the boiler is operating off the low limit in the L8124A. Can you take the cover off the aquastat and see if there are any wires connected to the terminals labeled "T T" ? Typically this is where the thermostat wire is connected, so the boiler knows when there is a heat call and will run until the high limit is reached.

As for the tankless coil output, 3 big shower heads would certainly put a big load on the boiler - but if the boiler temperature is not getting dragged down and you are not getting cold showers, I would not worry about it. Your current aquastat settings of 160/200/10 should be fine.

Thanks, I'm going to look at the aquastat wiring tonight and will report back. I'm a nuts and bolts kinda guy and wiring isn't my thing, but it doesn't seem too complicated.