L7224 aquastat / burner problem


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Old 01-13-09, 05:30 AM
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L7224 aquastat / burner problem

Hello I am new to the site, looks like a great resourse hopefully someone can be of some help. I just wired a second zone to my boiler. I installed a Taco SR503 switching relay to both pumps and according to the diagram given I wired it for a Tankless boiler with zone 1 priority. When I turn everything on the L7224 aquastat calls for heat, the zone 1 pump turns on and It calls for the burner to fire, however the burner will not start. Nothing on the burner motor turns on its like I have no voltage, the diagonstic signal light is not on and pressing it will not to anything. I have 120 power at B1 on my aquastat, and nothing at B2. I left the jumper between TT on the burner motor, not sure if i still need it there but removing it did nothing either. Its a weil Mcclain tankless boiler with a Beckett burner, I dont have the model of the burner infront of me but I bought the whole package unit less then two years ago. Any help would be greatly appreached

Thanks
-Mike
 
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Old 01-13-09, 03:28 PM
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Mike, when you return with the burner info (most likely it's an AFG), let us know what PRIMARY CONTROL is on the burner. It's the GRAY or (most likely since it's newer) BLACK box on top of the burner.

You DO need to leave the TT jumper on the burner primary control. The burner will NOT start in any case if you remove that jumper.

You don't need the priority ON... because you have a tankless coil... the priority would only be if you were using an indirect water heater. So install the jumper from P to ZC.
 

Last edited by NJT; 01-13-09 at 04:07 PM.
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Old 01-13-09, 03:51 PM
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You removed the circ wiring for the existing circ from the 7224, is that correct? and wired it to one of the zones on the 503, also correct?

And you moved the thermostat for the existing zone to the 503 panel?

And the 7224 T T contacts are now OPEN (no wires)?

Is the jumper from ZC to X1 on the 503 installed?

Here's a simple test you can do...

Jumper the T T terminals on the 7224 . The burner should fire (if the boiler is below the HI LIMIT setting). If it does NOT then the problem is between the aquastat and the burner.
 

Last edited by NJT; 01-13-09 at 04:25 PM.
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Old 01-13-09, 06:10 PM
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Thanks for the tips however Im still at a loss. I have taken the circ wires off the aquastat and placed them on the switching relay, as well as the thermostat wires. Now when I jump the TT switches on the aquastat Im not getting anything. So I agree the problem lies between my aquastat and burner.

the primary control is a honeywell r7184u when I test the leads going in I cant seam to get L1 power however I am getting 120 v at the Limit wire, and theres a note on top of the control that says that the Limit is tied in series with a line voltage thermostat ???
 
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Old 01-13-09, 08:44 PM
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OK, the 7184 needs a constant source of 120VAC on the L1 and L2 to power that control. The LIMIT comes from the aquastat B1 and serves to 'trigger' the 7184 to fire the burner.

I have no idea how a line voltage thermostat might be wired into your system...

Start by tracing the L1 wire back from the 7184 to see where you are losing the voltage... that may be your problem... in fact, probably is... but look for that 'line voltage thermostat' too... ??

Pictures might help us... free account at Image hosting, free photo sharing & video sharing at Photobucket , upload pics there, and drop a link here for us to view them.
 
 

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