Old Furnace Down - New Burner?

leezilla

I have an ancient oil fired furnace that was converted to natural gas in 1980. I assume, based on the inspection tag that is on the unit. Looooong before I lived here regardless.

The furnace died during the cold snap we are having, since that's the time a furnace usually dies. I have experience with electrical, so I did a basic check to make sure we had current. Coming back from the switch, the limits appear to be working, and coming down to the burner itself, the sylinoids are both working if I jump them manually. I don't know how to test the ignition unit, but considering nothing else works it's likely not relevant yet.

The unit is over 40 years old, I found that a couple of gas conversion burners exist, the Wayne Combustion P250AF looks very similar in layout to the existing burner. However the inspection tag on the burner implies to me that the existing unit is 364k BTU, while the P250AF is a 250k BTU max. However reading the manual indicates that this would be almost a drop-in installation for the system I have.

Is there a major deficit to running this much lower of an output burner? Any experience replacing an older upgrade? Other options? I'm interested in trying to DIY this, but I'm not sure if thats a terrible idea or not.

EBEBRATT-Ed

If you put a smaller burner in you may get flue gas condensation.

Suggest you get a professional. If you replace the burner you will need combustion test equipment. If you can get that one going it going to take some troubleshooting skills.

Start wit seeing if the burner blower will run and getting the pilot to work.

I suspect you have a pilot that has to be manually lit unless that is spark ignighted

WMno57

Another Birchfield boiler in this discussion:
https://forum.heatinghelp.com/discussion/98435/1920s-Birchfield-Steam-Boiler

mattmia2

It could be replaced with a newer power burner but that is a job for a tech that understands power burners well, it isn't a DIY project. Even that power burner needs to be looked over by a competent tech every few years to make sure it is burning properly and the safeties are working.

What is that bolted in to the door above the burner, is that what proves flame? Does it have a reset button? is the pilot always on or is there some sort of electrical ignition?

That power burner is probably from somewhere in the 50's through the 70's.

mattmia2

Where does that ignition cable that goes in to the ignition tube go, i can't see what it is connected to behind and to the right of the main gas valve.

WMno57

Found this on duck duck go image search. Image only on the search engine. Linked site has changed.

EBEBRATT-Ed

@mattmia

I think on the boiler door is an old oil burner stack switch that just got left there. Hopefully that is out of the picture LOL you never know.

leezilla

@mattmia2, @EBEBRATT-Ed is right about the box being an old leftover box from it's oil-burning days. It's gutted, has no wiring going to it.

mattmia2

I'd start by looking at where the thermostat wire goes and jumper that and see if the relay closes that runs the power burner. Be careful if there are extra wires because many of those parts are likely not available.

The relay probably energizes the power burner motor then there is a centrifugal switch on the motor that energizes the pilot and spark, probably another control that proves the pilot flame for the main valve.

leezilla

@mattmia2 I was able to confirm that the call to heat is getting triggered. The call to heat fires a relay that routes 110v through a safety interlock (high limit) before powering the burner in the photos. I do get power down to the burner, and when I use the test-switch on the interlock, it interrupts power. I'm confident about everything down to the burner box.

Inside the burner "box" (I don't know it's name, but this is where the 110v line comes in), I confirm I am getting power down into the blower motor. I am guessing from the wiring that I am supposed to get a 110v signal out that activates the gas solenoids and spark unit. Nothing ever happens though. Normally the first thing I get when the call to heat hits is the blower turns on for 30 seconds before it tries to fire the burner.

The wiring internally seems to be in good shape. There was some sketchy wire nuts poorly installed, so i replaced those with modern lever nuts as seen in the photo. But the rest of the wiring was left as-is, and I marked my wires before touching anything.

mattmia2

The blower motor isn't running? Is there power to the motor itself?

I think there is a centrifugal switch on the blower motor that triggers the rest of it. Those certainly can go bad. Might be an electromechanical sequencer that triggers the pilot valve and the transformer then triggers the gas valve sometime after. Might be lighting the pilot then waiting 30s or it takes 30s of the pilot lit to heat whatever is proving pilot to allow the main valve to open.

leezilla

@mattmia2

The blower motor isn't running? Is there power to the motor itself?

Correct, the blower never spins up, it DOES get 110v.

mattmia2

Motor's bad. Might be able to find another one if it is a standard form or fix that one, especially if it has a run cap. Does it even hum or anything?

leezilla

@mattmia2 not even a little bit of noise. I need to remove the motor to see the whole label for a model number, but the blower motor is from Universal Electric Co. They seem to be around still.

Looks like I might be able to remove the motor. I think I can access the mounting bolts holding it to the housing. Your theory about the centrifigal switch makes sense given the wiring. I have 4 wires that go in, one neutral, two hot and an unknown "green" wire. I'm betting the 2nd hot line hits the switch and the green wire is the completed circuit when the fan picks up speed.

leezilla

Blower motor:

I just realized it says "cent switch" right on the bottom of the label!

mattmia2

You might try giving it a nudge and see if it starts. I think that is an induction motor but it might be a universal motor and have a bad spot or the bearings may be stuck. All those adjustable depths and shutters need to be set by a burner tech so try not to move that stuff or at least mark it.

leezilla

Good call out on the marking.... I'm going to scribe reference lines on anything adjustable before touching it.

Not luck simply spinning the motor by hand. I was able to get a dowel into the squirrel cage and spin the fan over. It's not exactly as easy spinning as I think it should be, but it's not sticky either. Doing some additional reading, I'm going to try to pull the motor off the housing tonight after work and see if I can learn anything from there. Once it's on my bench I can try powering it directly outside the system and whatnot.

I'll let you know what that turns up. Thank you so much for your help so far. Fortunately we have enough secondary heat sources that I can spend a minute and try to find a cheap solution for today. We've been saving up for a full heating system upgrade and I'm hoping not to burn a bunch of that money on a fix for a unit I want to replace in a 18 months.

mattmia2

Even if you get it working, you really should have someone that understands power burners look it over and make sure it is burning correctly and the safeties are working. Probably someone that works on oil burners and/or commercial equipment will be more likely to know than someone that mostly does gas. You will have to vet them first or you will just get a bill and no assurance it is working correctly.

The thermal overload may be a manual reset button. It may just be that the oil has dried up, which will damage the bearings but it might still work for a while if you re-oil them. It should spin pretty freely.

leezilla

@mattmia2 That is the culprit. I pulled the burner out and got the blower motor out of the housing. I've worked with enough motors to know when one is shot, but I put it in a vice and tried to power it in isolation. I could feel and hear the hum of a stuck motor with it up there.

I wired the next step in the circuit around the centrifugal switch and used a small high volume blower I have to force air down the throat of the burner and got flame. Just a seconds worth, proved out that the rest of the system is working and it's down to this one part.

I spun the motor using a drill and got the centrifugal switch to put in, dropped resistance on that wire pair to zero. Even that part seems to be working.

It's unfortunate. I've been fastidious at the rest of the maintenance. The folks we got the home from left me detailed maintenance schedules, and the old guy insisted that if I do that maintenance it would be reliable. This motor and the cleaning I SHOULD have been doing on the burner were not part of it (he may not have known). To his credit, what I've learned about these things the last couple days, he had the OTHER stuff well documented for me. I bet if I knew about the need to oil this little motor it would still be going.

I'm definitely going to find someone to come out and evaluate the system before I leave it running though. You are right about the risk of life and property that I am running.

I haven't sorted out a new motor or replacement solution yet, but I'll figure that out pretty quick now. I owe you a huge debt of gratitude for sharing your experience with me. Thank you immensely.

mattmia2

You might take the blower wheel off and see if there is just crap wound around there. try putting several drops of oil in each bearing and let it sit and see it it loosens up. look in a century and fasco and marathon and us motor catalog and see if you can match the motor up.

I would have turned off the gas to the main valve or disable it and tested to see if the pilot lit and the safety energized the main valve.

It would be nice to know what rate that was actually firing at. that would be set by the orifice and the regulator adjustment. there are definitely commercial power burners that big but replacing the burner will be somewhat pricey and not necessarily what ou want to do if you want to replace the boiler.

Is the boiler set up as hot water or steam?

EBEBRATT-Ed

@leezilla

You could take it to a motor shop but it will probably cost more to fix than it's worth unless they no longer make that motor.

EBEBRATT-Ed

I went to Universal Electric Motor website and typed in the model of your motor and the exact model# comes up. But when you click on it you get no results.

You might call them or they have a chat

Might be worth a shot at a motor shop

mattmia2

Looks like wayne makes gas power burners in that range but you will need a good tech to pick the right mounting parts and set it up.