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JonathanS 01-21-2011 10:49 AM

No power to circulator: new aquastat didn
I had this situation on a Honeywell aquastat:
-25V coming in at thermostat: a call for heat
-120V power at the line in
-Oil furnace operates correctly: on at 140degrees, off at 180degrees
-No power at the circulator contacts on the aquastat

I disconnected the circulator from the aquastat, and put 120V directly to the circulator, and it ran fine and heated the house. I bought a new Honeywell aquastat and installed it.

I have exactly the same situation back again.

My next guess is a short in the wires from the aquastat to the circulatror. My question is what else should I be looking for?

beenthere 01-21-2011 05:18 PM

Check if the circulator terminals on the aquastat have 120 volts when the thermostat calls for heat.

t_maher 10-13-2012 12:11 PM

have same problem. no voltage at contacts to circulator in aquastat. should there be any low voltage to the zone valves from the aquastat? or do the zone valves supply voltage to the aquastat? i measured 0 volts at the two T-T contacts with wires going to the zone valve.

Honeywell 8124C aquastat.
taco 571 zone valves - 2 zones.

biggles 10-13-2012 01:10 PM

24V to the circ relay:wink: when the stat calls the valve moves and the N.O. contacts close to start the circ or the stat closes the contact on the module direct....the only reason the boiler runs is the water loop is changed as the circ runs pulling cold water back to make the limit as you circ the short cycle on the boiler to maintain the there a zone valve with more the a pair of wires connectd to it?

t_maher 10-13-2012 01:31 PM

yes. each zone valve has 2 tstat wires connected to terminals #2 and #3. Terminals #1, and #2 are jumped between both zone valves. On one valve, terminals #1 and #2 go to the aquastat T-T contacts. I measure no voltage out of the zone valves to the aquastat T-T contacts. can i by pass the zone valves and connect the tstat right to the T-T contacts in the aquastat to confirm the zone valves as being the issue?

biggles 10-13-2012 01:56 PM

if the zone valve don't move nothing is going to run...see that push bar that some zone valves have if it moves over with no resitance pushing it...the 24Vs is swung the valve...if it is slow to the finger push there is no 24Vs present and it is closed and you are manually forcing it open....24vs with a boiler module can handle itself using it to power 24V zone valves is a NO-NO VA in the Honeywell module is dedicated to that module...that is why you see an add on 40 VA TR for the repest for thse reading kurking the boiler gas or oil doesn't cycle unless the circ reloops the cold water thru the boiler and the limit picks up the drop so it runs to limit....160-180 adjustable to make 68F-70F on a typical stat with rads or baseboard

t_maher 10-13-2012 02:02 PM

ok. i switched zone valve bodies and still no voltage out of the zone valves and to the aquastat. are the zone valves supposed to provide 24 volts to the aquastat? if so, they are not working. can i connect the tstat wires directly to the aquastat and by pass the zone valve? this should tell me if the aquastat is working or not, no?

biggles 10-13-2012 02:16 PM

if you don't have 4 wires(2-24v/2- N.O contacts) coming out of the zone valve each then the stat calls the circ in directly from the module...remove the stat off the subbase and jup R to W ...that is a direct constant heat call... something has to be opened or running...forget the boiler itself nothing is going to happen till the water is looped thru it(circ...:huh:) and the limits make to heat the water to setpoints

t_maher 10-13-2012 03:15 PM

jumped the tstat. same result. burner kicks on, blower kicks on but no power to circ. when call for heat stops, i detect 24 volts at aquastat. when heat calls, no voltage at aquastat. this must be normal operation. i was thinking opposite. still no power to circ in any mode.

biggles 10-13-2012 04:08 PM

blower on a boiler....induced draft motor:huh: is this boiler for domestic HW also

beenthere 10-13-2012 04:26 PM

Posting brand and model number of your equipment and devices always helps.

t_maher 10-14-2012 06:57 AM

model #s are in first post. anyway, i determined that aquastat to be at fault. zone valves are working properly, tstats are sending 24 volts to zone valves. it appears to be a relay problem in the aquastat. changing out aquastat monday.

t_maher 10-16-2012 08:56 PM

replaced Aquastat. relay was bad. all is good, heat and hot water galore.

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