Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Electronics => Topic started by: hondaracer2oo4 on July 11, 2014, 10:02:31 PM
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I need to cut my pump on my owb from circulating when the oil burner thermostat in the house calls for heat. The most simple way for this to be accomplished that I can think of is to have the oil burner thermostat trigger a 24 volt relay out at the owb which would break the power from the pump. My question is will I need to buy a 24 volt transformer to trigger the 24 volt relay with the thermostat or can I somehow use the 24 volt transformer built into the oil burner controller? Thanks.
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Honda Yes you can use just the TT wires and transformer to make and break a relay but there is not enough power to run zone valves and such off the transformer on the oil burner, there is a better way, help me understand your system a bit, you want the circ to shut down when the oil is used right? Why wouldn't you simply unplug it or shut it off in the summer months and use an aqua-stat on your incoming wood boiler lines to kill the oil burner when the wood boiler goes out to protect your lines. Any simple break on rise/ make on drop,strap on aqua stat can be used to do this.
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Slim, thanks for the reply. I actually stopped by your place a couple Fridays ago (7/30) in the afternoon as I was passing through, you weren't in the shop though so I continued on. Not before looking through the boilers though on my way out. Anyway my system currently is very simplistic. Circ runs 24/7, OWB thermostat calls for heat which turns my FHA blower on and off through a Honeywell YHR845A1030. What I need to happen is that if the OWB has some sort of problem when I am not home my wife can simply turn the OWB thermostat down to a low temp and turn the FHA oil burner thermostat up to the desired temp and the oil burner will take over. When this happens I need the circ on the OWB to shut off everytime the oil burner fires(or ideally when the FHA blower is running). I have found that if I run the oil burner with the OWB circ moving water through the water to air hx that the cool water extracts the heat from the FHA oil burner providing only luke warm air from the vents. My thought was to simply run the circ on the owb off of a relay that is normally closed, but is opened when the FHA oil thermostat calls for heat.
The second project that I am trying to tackle is putting a Honeywell L6006C1018 strap on low limit aquastat on the feed line from the owb to shut down the blower on the owb when my water temp drops below a certain amount to save the coals. I am away from the boiler for long periods of time sometimes(14-15 hours) and come home to an empty boiler and cool water. I then have to restart the boiler and get the temp back up. I would like to save the coals so that it can easily be restarted. My thought is the Honeywell L6006C1018 run in parallel with a simple 60 minute bathroom timer. When the temp drops below a temp the aquastat kills the fan, I then feed the boiler and turn the timer to 60 minutes and walk away. Sound like I am on the right track?
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I sure wish I had been home, I could have explained it far better in person over a cold adult beverage but the same aqua stat that you are using to kill your blower can be used to kill the oil burner motor simply by using the break on rise terminals instead, it breaks on rise with the R+B terminals, place it on the incoming wood boiler line and wire it to interrupt the burner circuit on the oil unit, Glad you are doing that on your wood boiler, I have been promoting it for years, it works great with gassers to keep the ceramics hot!
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Slim, I am not really following you on using another strap on aquastat and killing the oil burner motor? My goal is to kill the circ pump for the owb when the oil burner thermostat calls for heat(or when the Fan limit switch flips the FHA blower on for the oil burner).
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What I am now thinking is that if I can use the fan limit switch to switch a relay, which goes through a 24 volt transformer, sends 24 volt power to owb, second relay at owb which cuts pump on and off that would be best?
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I don't understand why you would want the circ connected to the tt on the hot air unit, doing that will give you no protection from freezing your lines to the wood boiler in the winter months when backup heat is required, it is possible to do, I just don't understand why you would wish to do it
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I need the owb circ to stop circ water when the oil burner is running. If I don't stop it from circ water when the oil burner is actively firing trying to meet the thermostats call for heat the water circ through the water to air hx will cool the air down and not allow me to heat the house. When the oil burner thermostat is satisfied then the owb circ will be re energized and circ water to protect lines from freezing.
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Ok I can understand that theory, can you run a TT wire out to the boiler? if so this will work
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I edited my previous stupid response after I looked more closely at the wiring diagram for the 501, duh! So this is my thought. It would be most simple to just hook the 501 up to the oil burner thermostat with thermostat wire and cut the circ when the burner fires. My thought though is that even though this is a back up situation that I may want to do this a little bit better. I think that the best option would be to cut the circ when the FHA burner fan is running which would be switched by the Fan Limit control. This is line voltage though. So I would need to send the line voltage from the Fan Limit to a 24 volt transformer, then to a Relay out at the owb to control the circ pump. Would it be worth the hassle to buy these two parts separately and wire it this way? I believe that any 24 volt transformer should work and any relay with a N/C position and a break on signal relay should work?
This is what I have which I think will work for this application. White Rogers 90380 SPDT with N/O and N/C contacts. http://www.supplyhouse.com/White-Rodgers-90-380-Fan-Relay-Type-184-24-VAC-Coil-50-60-Hz-SPNO-SPNC-Coil-Data-77-Ohms-DC-Resistance-125-mA?gclid=CIGr2u3EwL8CFUIQ7AodQ2YA-Q (http://www.supplyhouse.com/White-Rodgers-90-380-Fan-Relay-Type-184-24-VAC-Coil-50-60-Hz-SPNO-SPNC-Coil-Data-77-Ohms-DC-Resistance-125-mA?gclid=CIGr2u3EwL8CFUIQ7AodQ2YA-Q)
And Transformer http://www.supplyhouse.com/White-Rodgers-90-T40F1-Transformer-40VA-60-Hz-120V-Primary-24V-Secondary-Foot-Mount-14927000-p (http://www.supplyhouse.com/White-Rodgers-90-T40F1-Transformer-40VA-60-Hz-120V-Primary-24V-Secondary-Foot-Mount-14927000-p)
I am confused with the transformers, there are a lot of different model transformers but I can't figure out the difference?
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Other than the VA rating, there probably isn't really that much difference between them.
What turns the blower on for the OWB heat? You will want to make sure the that it doesn't interfere with the OWB operation.
It would probably be easiest to just run off the wall thermostat instead. Just run wires from the W and C in the furnace out to the OWB and connect them to the coil on the relay. Then if you connect the pump the the normally closed contacts it should shut off the pump every time the oil burner fires.
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I assume you mean the FHA blower in the house when you ask about the blower for the owb? If so that is triggered to turn on by a second thermostat inside that powers the blower through a Honeywell transformer/relay.
So as far as cutting the pump for the owb you think that it is not worth the extra effort to kill the pump when fan limit switch calls for heat on the oil burner? You think I should just cut it out when the burner is actually firing?
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Yes that's it!
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Alright, thats what I will do then. Ill only get the relay and run the thermostat wires off the oil burner out to the owb and make the connections out there. Thanks.
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I would try it that way and if you don't like the way it works you can add a transformer later and just move the wires.
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Sounds good, thanks for the help!
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Ok, unfortunately I am in need of little more help. So I have a Honeywell R8184G boiler control. It has two inputs, T T for thermostat and the F F for the eye. What wires on the output of the controller do I run out to the relay?
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Oh, :bash: I forgot you don't get access to the C connection on an oil burner control. You would need to get inside the control to get the other point needed to run the relay.
You could connect a transformer to the output of the control but you might as well just use the fan power like you originally wanted to do.
Since you are just running a relay, the smallest 24v transformer should work fine.
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Honda, I thought you said you have a forced hot air unit? Either way the drawing that I posted will work with another relay.
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Slim, Yes my oil burner is FHA. The 501 control would work to cut the pump when the oil burner runs, although it is a little pricey($50) for just being a relay and a transformer. I can get the two of those for about $20 total instead.
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OK you threw me off a bit with the control when you said boiler control, Did you understand the drawing, look at the TT wiring as one continuous loop, when the thermostat makes connection (calls for heat) it simply completes the circuit.
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Slim, yes the 501 will very much work for the situation, just run the thermostat wire out to the 501 on the owb then back to the boiler to complete the circuit. Couldnt I just split the thermostat wire in the house though and run one set to the 501 outside and the other set to the burner control?
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Ok I can understand that theory, can you run a TT wire out to the boiler? if so this will work
I am not sure if I am looking at your diagram right. What connections on the Taco 501 do you have the TT wires connected to? If the TT wires, you are running the transformers and relays in series which doesn't seem like a good idea. It will be 48V between them and if it gets wired wrong could burn out the control on the oil burner or the taco relay or both.
Another thing with running the circuit like that is if something happens to the wiring or Taco relay you will lose the oil heat.
If you want to use that relay, I would use a relay with a 120v ac coil and connect it to either the blower power or the output of the Honeywell control.
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I'm having trouble seeing that inside my head RSI, could you draw it for me?
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It looks like you might be able to connect a relay from the 2nd T to the bottom F connections and make it work. I am not sure if anything would get backfed though. It is probably best to just use a separate transformer.
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I'm having trouble seeing that inside my head RSI, could you draw it for me?
I can try.
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I guess this was more complicated then everyone thought? I figured however it is done is common practice with anyone with a FHA oil burner since they need to have some way of cutting the pump when the oil burner is firing or you will get little to no heat out of the vents.
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I'm having trouble seeing that inside my head RSI, could you draw it for me?
Not sure if this will help.
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I guess this was more complicated then everyone thought? I figured however it is done is common practice with anyone with a FHA oil burner since they need to have some way of cutting the pump when the oil burner is firing or you will get little to no heat out of the vents.
Just putting a transformer on the fan power like you suggested earlier will be simple. It will supply 24v whenever the blower comes on. Then you just run the 24v straight to the coil on the relay. You will need to make sure the power isn't backfed to that point when the OWB thermostat calls for heat. If it does, it will turn your pump off when the OWB thermostat calls for heat.
If that happens, you will need to connect to the output of the oil burner control instead.
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If you want to use the Taco 501 relay, this is how you would hook it up except the pump would connect to the NC instead of the NO as shown. (TT on boiler would be TT on your oil burner)
I think separate relay and transformer would be easier and you would only need to run 2 wires instead of 4 like this.
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RSI, yes I have come to the same conclusion that running a 24 volt transformer from the fan limit switch and running the 24 volt out to a relay on the owb would be easiest and best to do. Not sure where you are concerned about backfeeding power though? The OWB thermostat only powers the FHA blower by way of a Honeywell RA89A switching relay. The line voltage from the RA89A is pigtailed together with the line voltage from the fan limit switch, then the line voltage heads to the FHA blower.
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Then power will get to the transformer you are adding when the OWB thermostat calls for heat.
You can test it easy enough, just wire everything up and turn up the OWB thermostat. If the pump shuts off you will either need to move the transformer to the oil burner control output or add a 120v relay.
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Just another thought, you might be better off replacing the Honeywell RA89A with a DPDT fan center relay. Then you could use it's internal transformer and not need to add another and not have the issues of the OWB thermostat also killing the pump's power. (would require a slight rewire on the blower)
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Maybe i'm not understanding? I'm thinking the goal is to kill the circ @ the wood boiler whenever the oil burner does fire, would you not be better served to run the circ off an aqua stat at the boiler only allowing the circ to run when the wood boiler temp is up to set point and another aqua-stat at the rad to kill the oil burner when water temp is up @ the rad, this could all be done locally @ wood boiler and Oil burner with line voltage
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Slim, the goal is to allow the owb circ to circulate when I am using the oil burner to prevent freezing of the unit but cut the power to the circ when the oil burner or fha fan is running in the house. If I wired a low limit aquastat to the line at the owb to kill the power when it dropped below a certain temp it wouldn't be able to circ water to prevent freezing.
RSI, I do see what you are saying now. When the RA89A powers the blower it backfeeds line voltage to one side of the fan limit. The side that it backfeeds to is the side that the 24 volt transformer is on which in turns powers it and cuts the circ pump.