Hello,
First, a description of my system - it is a weil mclain oil / hot water furnace with 2 taco 007-BF4 circulator pumps, controlled by LUX programmable thermostats ( 2 wires connected ). The furnace is set with a 160-180 cut-in / cut-out range. The following scenario occurs when the furnace is at 180 and not running. I flip on heat on the upstairs thermostat and I hear the circulator pump for this zone activate. All OK at this point. So now I deactivate the heat upstairs and I flip on the heat on the thermostat downstairs. The circulator pump for the downstairs zone comes on... but the furnace also immediately fires up. (... Remember, the furnace temp is still at 180, so the furnace should not come on )... The furnace will run until the water temp is 220 and the limit switch shuts it down. I have switched the thermostats to rule them out as an issue. The wiring in the 2 aquastat relays looks correct, as well as the relays activating and deactivating. The zone which fires up the furnace is connected to a honeywell L8124A triple aquastat relay. As long as I leave the downstairs heat set to off, the system runs fine. Please correct me if I'm wrong but the room thermostats should only activate and control the circulator pumps, while the furnace thermostats control the cycling of the furnace. Thanks for your time.

Something is wired wrong or some component is defective. The thrmostats only control the circulators and the temperature control of the water is usually done by the aquastat not the safety limit.I would be checking the first floor circuit and find out what is triggering the boiler to come on with the circulator and why the control is not controlling the boiler at that point..

Sounds like you have a faulty aquastat. Thermostats do not control water temp. What is your aquastat temp set at?

The cut-in is set at 160 and the cut-out is set at 180. The furnace cuts in and out at these temps... as long as the downstairs zone isn't activated... thanks

Well then, hvac is exactly right. Something is miswired on your downstairs zone. Not familiar with the triple aquastat. Usually there is only one aquastat that controls boiler water temp.

How long has this been a problem?

I kind of just noticed it recently... I checked the wiring to the aquastat - 2 wires go to the thermostat, 2 go to the 120v feed, 2 go to the boiler and 2 go to the circulator - not much to mess up - not sure why it's called a triple aquastat - maybe because there are auxiliary terminals for zone control. The upstairs thermostat wiring goes to a honeywell RA89A relay. Thanks for your time.

Found this on honeywell's website - the configuration I have is shown at the bottom of page 4...
http://customer.honeywell.com/techli...it/95-6571.pdf

I believe both up and downstairs thermostats should be wired through a relay. Can you take a picture of your wiring setup and post it here? The more pics the better.

Well, here's a start ( sorry about the lack of camera picture quality )... picture attached is the aquastat that has the downstairs thermostat connected...

You now have the wiring diagram so follow it. Both thermostats should be connected to the aqua/stat unless you have two zone valves and then the end switches should be connected to activate the aquastat.

Post brand and model of zone valves.

There are no zone valves - the downstairs thermostat is connected to the Honeywell L8124aquastat and the upstairs thermostat is connected to a Honeywell RA89A relay. I did rewire the downstairs thermostat to the RA89A relay and the upstairs to the aquastat. The problem stays with the thermostat which is wired to the aquastat. Is the aquastat perhaps faulty? All the wiring looks correct, to me. I have a local heating technician coming to look at it next week. I will post what the problem was. Thanks for everyone's time.

The RA89A in your case is working as a isloation relay for the upstairs. It allows the upstairs thermostat to be connected to the L8124 aquastat on the boiler or activates the pump by going through the RA89A so the circuits are separate/isloated from each other so as to not cause or allow interference between the two circuits. Now with all the part numbers the game of figuring out the problem is much simpler.

Since the upstairs section is running all the time the RA89A more than likely has its contacts stuck or is energised all the time by the thermostat. See diagram below.

http://customer.honeywell.com/techli...s/69-0791b.pdf

See figure 2 on the wiring diagram to test.

Remove one of the thermostat wires off one of the (T) terminals. This is where the thermostat hooks to the control, Both T T terminals are for the thermostat but by removing one wire it will drop the RA89A controler out of the circuit and stop the call for heat from being sent to the L8124 main boiler aquastat. You should here a audible clicking sound as you remove the wire with the power on. This is caused by the relay inside the RA89A kicking on and off quickly since during the T wire removal there will be times during removal that the circuit will be made or broken. If you do not hear the clicking then once the wire is removed touch it back on the T terminal you removed it from and then you will definitely hear the clicking.

If you do not hear the clicking as described above then the relay is stuck or electrically burnt closed. The next test will prove that point.


Go back to the figure number 2 in the honeywell instructions and find terminal number 4. This terminal is one of two that controls the load. The load signal is what actually activates the boiler or pump as a signal that the upstairs wants heat. This time turn the power OFF then disconnect the wire from number 4 terminal and put a piece of tape on the wire so as to prevent it from shorting out on a back feed condition. With the number 4 wire disconnected there should be no way the upstairs thermostat can call for heat or cause the boiler to activate.

This simple test will prove weather or not the thermostat or thermostat wire is causing the problem upstairs or if the controler RA89A for the upstairs heat is causing the problem.


NOTE: When there is a call for upstairs heat and as the circulator comes on to satisfy that call for heat the boiler may activate at sometime durning that call for heat. The reason is that the boilers temperature will drop as heat is sent upstairs and naturally the boiler will want to heat the water back up to maintain the preset boiler temperature.
Post back with results.

Hello and thanks for the information!
To clarify my issue, the upstairs zone ( connected to the RA89A ) is working fine, i.e. thermostat calls for heat, the circulator kicks in and the boiler turns on only when temp drops below 160 as set by lo setting in aquastat - it is the downstairs zone ( connected to the aquastat ) that causes the boiler to activate, i.e. themostat calls for heat, circulator and boiler start, regardless if boiler is within 160-180 temp range... if I leave the downstairs thermostat activated, the boiler will go to 220 and shut off... does this info change your troubleshooting procedure?. or, did I misinterpret your answer?

Sure it changes the procedure because I misunderstood. I was under the false impression that it was the upstairs causing the problem. Since the boiler aquastat assembly is the only controller for the first floor it has to be the problem since the thermostat will turn it off and on but the aquastat lets the boiler overheat.

At this point I feel the aquastat on the boiler is the problem. Now it could be wired incorrectly and I have provided a diagram below or the contacts could be welded together from years of use.. Sorry about the confusion on my part I guess I am getting old.

http://customer.honeywell.com/techli...it/95-6571.pdf

No problem... at this point, I also feel it's a faulty aquastat... I will recheck the wiring and update the post once the technician checks it out... thanks for all your time