New boiler trying to figure L7248 and 845a

mlathrop

Installed a new slant fin ld30 grabbed my second zone 845a wired it as previously expect for the L7248 has only a ZR terminal n no ZC how do I wire it up. I've attached pics for reference of how the factory wired the 7248 and how my 845 is wired from oil boiler thanks in advance. 

EdTheHeaterMan

Your new boiler control is not equipped with a ZC. Does the new boiler have a tankless coil to make your hot water?

I hope not, for 2 reasons. But for now, since your control is not equipped with ZC you must power terminal 1 on the R845 with hot from the burner switch (this is the term we old folks use for the power switch to the heater). To get the burner to operate when the thermostat for the zone operated by the RA845 you must power ZR on the L7248.

When ZR has power the burner will operate safely with the aquastat limit in the circuit. The circulator connected to the L7248 will lot operate when ZR is energized. This way the burner and second zone will operate independently of the zone 1 circulator.

EdTheHeaterMan

It is difficult to see where the yellow wire is connected on the R845 control is and some of the other wires too. I doctored up the diagram from the R845 control directions to match what you should do... Blue dots are connected wires. If no blue dot, then the wires that cross do not connect.


Still want to know where you get your hot water from?

mlathrop

There is no domestic hot water coil i have a separate electric hot water tank not connected.  The yellow wire is connected to term 4 on the 845...the incoming power comes from main junction box on boiler cut off by emergency switch. 

mlathrop

123456 

1 is what was connected to ZC

2 is connected with power supply netural and zone 2 cir natural. 

4 is yellow wire that was connected to ZR

3 is connect to power supply hot and jumpered to 5

6 is connected to zone 2 circulator hot

mlathrop

Should I turn ELL on or Off?

EdTheHeaterMan

OK, the wiring configuration you described is for the older system you replaced. Once upon a time, maybe long ago, in a place called your basement, there was a boiler that made hot water with a domestic tankless coil.

#1 came from ZC to power the R845A so the circulator would not operate if the boiler water temperature was not hot enough to take a shower. This was the correct way to do this job.

Now that you don't use the boiler to make your domestic hot water, you don't need to deal with ZC anymore. Your new boiler will never be too cold to provide you with hot water because your electric water heater has nothing to do with the boiler.

The manufacturer of your new boiler knew that you did not need to use ZC on their magnificent creation so they banished it to the Island of Unused Control Terminals never to be seen in your basement again.

So the #1 terminal on the R845A needs to get the power from the electric switch that powers your new boiler. This way your circulator pump, operated by the R845A, can operate whenever the thermostat for that zone calls, and they will live happily ever after. in the world of Your Home

I hope you liked my story and that it was helpful in resolving your query.

Ed

PS.
Put a jumper to 1, 3 & 5 with power on 3 (or 1 or 5)

Do not connect the wire that was previously on ZC

mlathrop

Thank you it seems to be working as usual wired this way. So im assuming leave ELL off on the 7248. 

EdTheHeaterMan

Yes ELL off