Honeywell 845A Hookup

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  #1  
Old 01-08-04, 01:23 AM
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fstedy
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Unhappy Honeywell 845A Hookup

I have just finished installing a Weil Mc Lain Ultra 105 boiler. My problrm is I don't have any voltage on the 845A relay at terminals 3&4 with the relay closed. I have 120v at termminals 1&2 and when I connect the Circulator leads to 1&2 the system works fine.
Are their jumpers somewher on the circuit board I need to connect?
 

Last edited by fstedy; 01-08-04 at 01:35 AM.
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  #2  
Old 01-08-04, 05:15 AM
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In order for the additional circulator to operate correctly with the reverse aquastat, the wiring is a little more complicated. Does your boiler also make domestic hot water? If not you can use the simpler way to wire the relay. Either way, the wiring schematic is on the paper that came with the 845 relay. If you don't have it, I can find one here and copy it for you.

If my memory serves me correctly, the 3 & 4 terminals are just a contact closure. So if you want terminal 4 to get power when the relay pulls in, you will have to supply power to terminal 3. If you jumper terminal 1 to 3 you will get that but thet may not be what you really want to do. Let me know about the domestic water and I'll dig up a paper from the 845.

Ken
 
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Old 01-08-04, 10:39 AM
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fstedy
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I have the schamitic that came with the unit. I also have an indirect hot water heater installed but that is wired directly to the high voltage side for the DHW circulator and a self contained aquastat on the low voltage side of the boiler terminal strip. This boiler sets up a little differently. It also has a boiler circulator that wires direct to the boiler terminal strip.

I assumed from the diagram on the 845A cover that it was wired internaly. Do I just jump 1 & 3 on trhe front surface of the control with a wire ?

Seems redundant for a control like this to make you do dditional work like this. Most electronic boards that I repair have a simple jumper that goes over several header pins to select various board options.

Thanks for the help.

PS From our previous discussion about installing a bypass on the Ultra boiler. Weil Mc Lain recommends only using the pri/sec connection. This boiler has all kinds of built in programmable options and I guess the by pass function is taken care of ( I installed the bypass but have it closed).
 
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Old 01-08-04, 10:48 AM
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You can just jump the terminals with a piece of wire. If you look at the more complicated schematic you will see that the two sets of terminals need to be isolated to work properly. In your case, the #3 can be hot with the #1 terminal so go ahead and jump it.
 
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Old 01-09-04, 08:21 AM
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fstedy
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I still am having a problem with this hookup. The jumper was installed and the circulator closes in when it is the system calls for heat but now the relay will not open after the thermostat does not call for heat any more. I have a white wire coming from the thermostat and ( both on the same connection on the 845A ) white wire going to the heater low voltage terminal strip on the heater. On the other terminal on the 845A I have a red wire from the thermostat and a red going to the heater low voltage terminal strip ( they are specific terminals on the heater for these connections as well as the 845A ). Since this is a DC voltage does it make any difference which side the red and white wires are located?
 
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Old 01-09-04, 08:46 AM
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It's not a DC voltage but that's not your problem. You will need to use another set of terminals to trigger the boiler. They may be marked X and X on the 845 relay. Those terminals close when the relay is energized. You will need to have the thermostat control the relay and the relay control the boiler and circulator. Hope you understand that.
 
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Old 01-09-04, 01:05 PM
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fstedy
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That makes a lot of sense. Thanks a lot for all your expertise.
 
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