I just installed a wood boiler into an existing hot water oil boiler system. I want to use the single aquastat (Honeywell L6006A) in the wood boiler to turn off/on the oil boiler burner using a relay. This way when the wood boiler is in use, the oil boiler is disabled.

The single aquastat would connect to the relay as well as the power to the oil burner. When the single aquastat is up to temp, it would trigger the relay disconnecting power to the oil burner.

The wood boiler manufacturer recommended the Honeywell RA89A relay but from what I can tell, this relay is controlled by a 24V source such as a thermostat. Can it also be controlled by a 120V line voltage source such as the single aquastat (L6006A)? The wiring diagram for the wood boiler is attached as well as the wiring diagram for the relay.

 

You can do this a couple different ways. The R89A relay would work, but you should also be able to run the power going to the oil burner directly through the L6006A. Basically the L6006A will act as a high limit...when the wood boiler reaches a temperature of say 160F, the R & B contacts on the L6006A will "break" and prevent the oil burner from running. If the wood fire goes out and the boiler cools to the aquastat setting minus the differential (e.g. 160 - 10 degrees differential) the power will be restored to the oil burner.

I did something similar with my wood boiler, but I used the TT contacts on the honeywell oil burner control to prevent the burner from firing while the wood fire was going.

 

They want you to use the relay so that the 120V loads are isolated from each other. I wouldn't recommend deviating from the diagram in that regard.

Yes, it can.

What you would do is to put a jumper across the thermostat connections in the RA89 relay, and run the 120 VAC wiring to the L1 and L2 terminals in the RA89. When the wood boiler energizes the 120 VAC line there, since the thermostat is jumpered in the RA89, the relay will pull in.

Be mindful of how you wire the oil burner in, neither of those diagrams you posted are what you want.

You will REMOVE the jumper from 1 to 3. [corrected, NJT]
Terminals 3 and 4 will be used to switch the oil burner.

You could also use a single relay as shown in the diagram.

 

Thanks Rob... That is something I was thinking about too..but that single aquastat also runs the wood boiler circulator when the temp gets to 160 so I don't think t would work the opposite way for the oil boiler?? maybe it would.

Also, My oil boiler uses a Riello burner and a honeywell L8124L triple aquastat but I couldn't find where to jumper the TT connections on it.

 

NJ Trooper, that is the exact answer I was looking for, I will give it a try. n referring to removing the jumper, you mean the jumper currently on 1 and 3 in the diagram correct?

Thank you

 

I hain't seen many Riello, but IIRC they don't have the TT connections that the Beckett and some others have on their primary controls.

Yes, remove the jumper from 1 to 3. My bad... I'll go back and edit the correction into the previous post.

 

Thanks Trooper.. I just made the changes you suggested- adding a jumper on TT, removing the existing jumper on 1 and 3 and connected the line to 2 and 1 and the load to 3 and 4.

The relay is now working in that I can hear the relay turn on and off when I adjust the single aquastat. However, I am not getting any power to the oil boiler burner (load- 3 and 4).

This is how I wired 3 and 4 (load). I cut the red wire, running from B1 on the oil boiler aquastat to the oil boiler burner, and ran one cut end to connection 3 and the other cut end to connection 4. Is this correct or totally wrong?


I disconnected everything and connected the red burner wire back together the burner ran fine. What could it be?

 

Your description sounds correct... according to what I paid attention to so far... but I just noticed something... and I think this is the problem.

The wood boiler wiring diagram shows that the oil burner is wired to the NORMALLY CLOSED contacts of the relay.

The RA89 does not even have NORMALLY CLOSED contacts.

Shame on the tech for telling you that you could use that relay.

What is happening here is that the 'action' is going to be reversed. The oil burner will be enabled / disabled OPPOSITE of what you want it to be.

One might think that one way to correct this problem would be to move the hot wire between the relay and the 6006 from the NO on the 6006 to the NC on the 6006... (leaving the wire from the NO / 6006 to the circulator where it is)... but what that will do is hold that RA89 energized when ever there is no fire in the woody...

You don't want that relay energized all the time... it's just plain bad practice... so you will need a relay with a SPDT action ... I think the Taco SR501 is suitable, the 845 from Honeywell... and also the newer 8845 will work... just check to make sure there is a NC terminal before you purchase... hopefully you can take the 89 back...

But, to test my theory, you could see if the burner fires when the woody is firing... or you could move that wire from NO to NC on the 6006 TEMPORARILY...

 

Thank you Trooper.... Correct me if I am wrong, if the RA89A has no NC contacts and the opposite of what I want is happening, than the oil burner should have fired when the wood boiler was hot (instead of what I want, when it is cold). The oil burner wouldn't fire at all, whether the wood boiler was hot of cold (i kept adjusting the 6006 up and own to switch the relay). If the RA89A is a NO contact, than when it has power, it should have been closed causing the burner to fire but it didn't. This stuff baffles me.

 

I believe the Honeywell RA889A relay will work as seen below.

Also, I contacted another boiler manufacturer and the recommended the Functional Devices RIB2401C. I believe the Honeywell RA889A is basically the same thing?

 

But how to I connect the oil boiler to the relay? Everywhere I read , it says to connect the line voltage to 1 and 2 as I have done, and the load to 2 and 4. (as opposed to 3 and 4.)

 

Shawn, remember that you are using this relay outside of the 'typical' configurations that will be illustrated in the install manual.

I know that the RA89 shows the load coming from 2 and 4, but that is because they are assuming that you are NOT desiring ISOLATION of the two AC sources. You DO want the isolation, so the 1-3 jumper is removed, and you are using 3 and 4 as the 'switch'.

Remember that a relay is nothing more than a remote 'switch'. What the wood boiler diagram is instructing you to do is to break the 120VAC connection to the oil burner, and insert the NORMALLY CLOSED contacts as a 'switch' between the break.

If you use the 889, you will wire the oil burner to COM and NC. There will be NO CONNECTION to the NO, or the X1 or X2.

You would still use a jumper across the thermostat connections R(T) and W(T) as before.

L1 and L2 will be wired to the woody 6006 etc... as before.

The LED RELAY may, or may not light... (it probably will though), when the relay is energized.

Honestly though, the 889 is more than you need, and probably more money than you need to spend.

If using the 2401, the WHT/YEL and WHT/BLK would go to the woody 6006. The WHT/BLU would get a wire nut and tape and is not used.

You would wire the boiler to YEL/COM and BLU/NC and the ORN/NO would get a wire nut and tape and is not used.

Really, what you want is a simple $15 relay...

Patriot Supply - R4222B1082

You would want to mount this in an enclosure, or on a 4" j-box with the following plate/socket/cover, etc (another $13)

Patriot Supply - Q633A1007

 

Thanks again Trooper. I purchased the RA889 (much cheaper) and now everthing is working perfectly.

 

Great! I like a happy ending... thanks for lettin' us know. Good Luck!