design of & controlling my new hydronic system

Boon

Hi All. Home owner here, converting my forced air into hydronic w/panel radiators [runtal]. I posted more than a few months ago and I've been changing & reviewing things many times since posting and after receiving a copy of Seigenthaler's book. I'm beyond ready to trust my numbers, order radiators, and get busy hanging them. I thought it might be prudent to have a second set of eyes, if anyone has time & interest....

Summary
Manual J: 37,000 Btuh at 17° design day
Design: Home run system; manifolds; pex; a couple emitters will be in series
Boiler: Modcon, Lochinvar, 1st choice is KH085 (turn down is 10:1), 2nd is WH055 (5:1 turndown)
Storage tank: Boiler buddy 18.
Supply °F @ Design: 173°F
Emitters: Runtal UF series
Indirect DHW: not chosen yet; least of my worries.

Originally I tried to keep the return water under 130°F but I had to give up on that; the rads got too big, too many, too expensive. Besides, when I design for 170 supply, the Manual J and climate data suggests that the modcon will be in condensing mode for 65%+ of the heating season, which still seems pretty good to me.

If I could only ask one more question about this ever [I won't, but...]: How do I control this system? I want room-by-room control. I thought "TRVs at each emitter," solves my problem, though pricey, but more importantly I don't quite understand how the system is turned ON/OFF without a main thermostat; From what I read [here and elsewhere], I can choose a variable speed ∆P pump that will circulate 24/7 until the ODR turns off the system at, say, 60° or so. Something about that is still confusing... it isn't clear how the pump deals when no zones are calling.



I wish I knew how to thank all of you for your contributions to this forum. Until I do, a 'thank you' will have to do ... Thank you!

SWEI

Boon said:

I want room-by-room control. I thought "TRVs at each emitter," solves my problem, though pricey, but more importantly I don't quite understand how the system is turned ON/OFF without a main thermostat; From what I read [here and elsewhere], I can choose a variable speed ∆P pump that will circulate 24/7 until the ODR turns off the system at, say, 60° or so. Something about that is still confusing... it isn't clear how the pump deals when no zones are calling.

The ∆P pump will slow down as the valves close, and if all of the valves are closed (highly unlikely if you set up the reset curve correctly) it will go into an idle mode. I would suggest installing a conventional thermostat and setting it 2-4°F above your desired space temperature, which can help prevent overheating (from solar gain, a woodstove, etc.)