Gas and Oil Home Heating Furnaces - replacing oil burner Primary Control

I'd like to replace my old-style primary control with a new electronic version - it's a regular old Beckett burner, with the control mounted on top of a junction box and a steel lid (White-Rodgers). There are a total of 7 terminals, it operates my A/C. We will be installing a heat pump soon, and the oil will become the emergency heat. Does anyone have a suggestion for a specific electronic control which might work well for me? One reason is the transformer of this old style hums constantly and is warm, so I assume it uses more electricity than necessary. I haven't checked the current.

I also thought it might be possible to have the primary control (or thermostat) turn on the fan as soon as the furnace ignites somehow, to start getting some heat out of it even before the fan limit switch would turn it on.

Neither Beckett nor Honeywell make an electronic primary with the large transformer. Carlin might but I'm not familiar with thier controls.

The transformer on an oil burner is a step up because a higher voltage needs to be generated get a spark hot enough to ignite oil that doesn't have anything to do with your control system and the reason for the fan/limit control that turns your fan on after the burner ignites is so you don't blow cold air in the house you can adjust that to turn on at a lower temperature there should be an adjustment pointer under a silver cover if it is a honeywell or on the outside of a black rectangular box if it is a camstat

There are TWO transformers on an oil burner. One is a step up from 120v to 10,000+ volts. This is for ignition.
The other is a step down from 120v to 24v. This is the control transformer. The primary control contains the step down transformer.

Yes, I was referring to the 24V transformer / relay that the thermostat hooks up to. This switches the furnace motor and blower motor voltage on right? I was interested in a newer type (not necessarily electronic) that might be more reliable and use less power when on "standby". If the electronic ones don't have a transformer, where does the thermostat etc. get the low control voltage? Even if identical, I would like to have another for spare. It has gone out once before and they put a rebuilt one on.

Mine says it is constant ignition, and I've seen there are intermittent ignition. I can get some exact model #'s off it tonight. If there's any other options I have besides a direct replacement primary control, I'd be interested in exploring them.

The transformer on an oil burner is a step up because a higher voltage needs to be generated get a spark hot enough to ignite oil that doesn't have anything to do with your control system and the reason for the fan/limit control that turns your fan on after the burner ignites is so you don't blow cold air in the house you can adjust that to turn on at a lower temperature there should be an adjustment pointer under a silver cover if it is a honeywell or on the outside of a black rectangular box if it is a camstat

I'm familiar with the fan limit switches because of having problems with the blower cycling on after the furnace shuts off (residual heat). I have it working right now, but there can be up to a minute of furnace run time before the fan turns on (130 On, 80 Off).

One thing I might try is putting a diode between the thermostat's fan and heat terminals (at the furnace). This should turn the fan on immediately with the furnace, but the furnace wouldn't turn on if the thermostat was set to Fan. The fan would stay on when the furnace shuts off, because of the fan limit switch. Anyone foresee any problems with doing this, other than cold air blowing at first? That cold air wouldn't bother me, infact I often turn the fan on just to circulate air in the house.

The electronic primarys do have a transformer but not one heavy enough to operate a second relay. A replacement for yours would be a Honeywell R8184M-1051. This is the only primary control with the heavy (40 va) transformer Honeywell still makes. It has intermittent (formerly called "constant") ignition. The White-Roddgers # is 668-451.

Not sure about your diode idea.

The electronic primarys do have a transformer but not one heavy enough to operate a second relay. A replacement for yours would be a Honeywell R8184M-1051. This is the only primary control with the heavy (40 va) transformer Honeywell still makes. It has intermittent (formerly called "constant") ignition. The White-Roddgers # is 668-451.
Not sure about your diode idea.

It says White-Rodgers 668-454 on it. Same thing as Honeywell R8184M-1051?

I was just looking at the terminals. Looks like C turns the fan on (I'm seeing 27V A/C there only when the thermostat Fan mode is On). W turns the burner on (27V A/C from the thermostat). Downloading the Honeywell install instructions etc. now.

Thanks Grady!

The White-Rodgers you have & the Honeywell R8184M-1051 are interchangeable.

Closure of the circuit R-W brings on the burner. Closure of the circuit R-G brings on the fan. R-Y energizes the contactor in the A/C condensing unit. C is common & needed only for a secondary relay such as the fan or condensing unit.

The White-Rodgers you have & the Honeywell R8184M-1051 are interchangeable.

Closure of the circuit R-W brings on the burner. Closure of the circuit R-G brings on the fan. R-Y energizes the contactor in the A/C condensing unit. C is common & needed only for a secondary relay such as the fan or condensing unit.

Ok, things are making sense now, the voltages I was reading were really confusing me until you said it is Closure with R. This is great communicating with someone who knows their stuff :D

I think my diode connection of W to G would work, I'm going to read about the R8181M a little to be sure I don't burn something out :eek: There would be the possibility of burning the thermostat out I think, if the additional current (G+W) from the thermostat is too much for the thermostat W. It may take a relay.

If you have a digital thermostat, most can be selected for "electric heat". In this configuration, anytime there is a call for heat (R/W closure) there is also a closure between R & G (fan comes on). One thing to be aware of is with the closure between R & G, the fan is going to come on at the cooling fan speed.
Honeywell makes a Fan/Limit (L4064W-++++) which has a 24 volt "pre-heater" in it. This particular fan/limit is commonly used in downflow or horizontal applications where natural warming can be a problem. When there is a call for heat this heater is energized causing the helix to warm & bring on the fan sooner than it would by sensing the air temperature alone. Since you are going to be installing a heat pump & using the oil fired furnace for back-up, I personally wouldn't spend the time or money trying to bring on the fan sooner.

If you have a digital thermostat, most can be selected for "electric heat". In this configuration, anytime there is a call for heat (R/W closure) there is also a closure between R & G (fan comes on). One thing to be aware of is with the closure between R & G, the fan is going to come on at the cooling fan speed.
Honeywell makes a Fan/Limit (L4064W-++++) which has a 24 volt "pre-heater" in it. This particular fan/limit is commonly used in downflow or horizontal applications where natural warming can be a problem. When there is a call for heat this heater is energized causing the helix to warm & bring on the fan sooner than it would by sensing the air temperature alone. Since you are going to be installing a heat pump & using the oil fired furnace for back-up, I personally wouldn't spend the time or money trying to bring on the fan sooner.

I hadn't noticed the difference in fan speed using Thermostat ON versus Heat, but I do now. Glad you pointed that out. It was just something I thought would be nice to do if I figured out an easy way without buying a different limit. Does that mean the heat pump would use cooling-speed fan even for heat then, since the fan Limit Switch wouldn't be controlling the fan?

The heat pump's fossil fuel kit could probably be configured to bring on the fan on a lower speed for heating than cooling. I don't work on many heat pumps so I'm not sure if they normally use different fan speeds for heating & cooling or not. You could possibly end up using 3 different fan speeds depending upon in which mode the system was running. An example would be: Low for heat pump heating, medium for oil heating, & high for cooling.

An update and another question;

I got the Honeywell R8184M and installed it. It is much quieter than the old White-Rodgers which was on it and also isn't warm to the touch like the WR was constantly. I was afraid of it burning out, staying hot like that.

If I had a relay calling for High fan speed, while the fan limit switch was calling for Medium speed, would that harm the motor? I can switch the fan on high from the thermostat while the furnace is on and it over-rides the medium speed but I didn't know if that is bad for the motor?

Thanks!

I have it working right now, but there can be up to a minute of furnace run time before the fan turns on (130 On, 80 Off).

Why dont you just turn the on down to 120o and 80o off???? most of the tiem most people turn the fan off about 90o.;)

The fan relay will close and turn the blower on when the tstat calls for heat with the heatpump.

Does anyone have a suggestion for a specific electronic control which might work well for me? One reason is the transformer of this old style hums constantly and is warm, so I assume it uses more electricity than necessary. I haven't checked the current.

Like said 24V transformer is on all the time for power to the tstat. Yes it will be warm. Now the Noise it makes . Play with the screws that hold it to the box. lots of time tighten them or losen then . will stop the noise.

I don't think the relay will allow the fan to be fed from two sources at once but I'd have to see a wiring diagram to be sure. I think once the "fan on" mode is selected, it breaks the feed from the fan side of the fan/limit control. If the fan switch we turned from ON to AUTO & the furnace were hot enough, the fan would then be powered thru the fan side of the fan/limit to whatever speed it was wired.

I don't think the relay will allow the fan to be fed from two sources at once but I'd have to see a wiring diagram to be sure. I think once the "fan on" mode is selected, it breaks the feed from the fan side of the fan/limit control.

Yep, that's exactly right. I looked at the Fan Relay (it was inside a steel box) and the Limit Control (Low speed) goes through the Normally Closed terminals whereas the Fan On (Med speed) goes through the Normally Open terminals.

Ed, I have my Limits at 70 and 130, any lower than that at the high side and the fan cycles on a few times after the furnace shuts off.

If you are happy or at least satisfied with the way the fan operates, leave the settings where they are. On most oil fired furnaces we set the 'fan on' at 130-140º & the 'fan off' at 100-110º. Any lower & we get complaints about "cold blow".

The transformer on an oil burner is a step up because a higher voltage needs to be generated get a spark hot enough to ignite oil that doesn't have anything to do with your control system and the reason for the fan/limit control that turns your fan on after the burner ignites is so you don't blow cold air in the house you can adjust that to turn on at a lower temperature there should be an adjustment pointer under a silver cover if it is a honeywell or on the outside of a black rectangular box if it is a camstat

hi i have a question i have a old herculese cast iron furnance does the transformer stay on all the time and arc a spark or should it shut down the problem i have is there is only 3 wires coming from the stack control and two are twisted together are hot and one is ground some one took them apart and i didnt see how or if this is right the furnance is runing but i dont want to burn it up its a superigition transtormer 10'000 volts thanks in advance

It is common to leave the ignition transformer on the entire time the burner is running. Your stack relay seems to be made for interrupted ignition but I don't encourage it's use. With a cad cell relay & shorter safety time interrupted is ok but using a stack relay I'd stick with the intermittent.