Buderus Boiler Cycles Every 20 Minutes

abro42

Hi and Hello:
New to boilers and Aquastat for control of water temp at boiler. House came with radiant heating and all the trimmings with alum diffuser plates, 2-3 in radiant barrier, and R19 insulation below radiant barrier. Its a staple up design with 3/8 in PEK, 1-ZONE operating at the moment. TACO cir powered by Taco SR. Cold start configuration per TACO illustration .

Aquastat (L7224U-1002) set for HL=160, HLd=20, LL=OFF, no DHW. TSTAT= Tekmar (WIFI 561), floor temp= 75 w/ sensor. Room temp=68. Supply temp gauge shows 140 to ZONE loops. Boiler supply at Buderus = 170 when fired and just before OFF

Boiler keeps firing every 20 mins based on above. Oil consumption my biggest concern. TSTAT shows HEAT ON mode constantly.

What is going on?? Boiler tech says everything is OK. Set for cold start and operating per design. No ODR module but will install this week. (boiler tech says waste of money...dah!!!!!!).

Any comments? Recommendations?? Wiring diag can be supplied. When does boiler fire in relation to call for heat and in relation to HL, HLd, and LL???

thx..you guys are the best. Learned a lot at this forum. Radiant heating is nice but boiler ON/off is stumping me.

abro42
Vernon, VT 05354

Jamie Hall

Unless your boiler can modulate to match its firing rate to the heating load, it has to turn on and off from time to time to match the heating load (which is really just another way of modulating, actually). Which is probably what you are seeing.

abro42

so are you saying the cycling is OK? Several of my friends have rad ant heating and they have said their boiler fires 2-3 times per day.
Thx for the imput

Jamie Hall

Most likely. The firing interval depends on so many factors. Certainly yours is not unusual.