Boiler fires intermittently. New Aquastat didn't help.

Rob123

Title says it: Boiler will hardly ever fire on its own. Need to hit the red button on the R8182D Aquastat (once) and it fires right up. https://inspectapedia.com/heat/Honeywell_R8182DH_Aquastat_Manual.pdf

Circa 1960's boiler with tankless DHW. With the boiler off, it makes no difference if there is a call for heat or DHW, I have to tap the reset once. The boiler will then bring temps up and when it shuts down, it won't relight. Water temps can go to ambient and still no dice.

High limit 200, Low limit 160 and about 15 deg differential.

I thought it was the Aquastat so I bought a new one. Two actually...... broke the immersion bulb on the first one I bought :-(



If you need more info please let me know. Getting a bit chilly up here in Maine.

GBart

https://heatinghelp.com/find-a-contractor/

GBart

It looks as though the find a contractor page has no one in Maine or NH, although you need 1 year of school and more in the field training to fix this, you are going to get 400 posts below this that are going to suggest all kinds of things............you need to call a pro, you already bought two aquastats and you would have saved money in the first place, you may end up creating an unsafe condition.

STEVEusaPA

That's a mess, flame rollout from bad/missing gaskets (scorch marks)-and a very old 1725 burner. The boiler is probably in the need of a good REAL cleaning (better than a real good cleaning).
The front of that boiler (with the burner) has to come off and the chamber and heat exchanger need a proper cleaning. Might even need some chamber rebuild.

Circa 60's? Maybe 1960 or earlier...
I'm not the first person who told you you should consider replacing it.
-Poor efficiency, parts becoming scarce (and more expensive like that J pump), and it's 60 years of service, anymore longevity is pure luck.
-Probably rusted out at the bottom (at least, or more like unfortunately, it's dry base).
-Making domestic hot water the most inefficient way, with a coil that's probably crudded up.

It's going off on reset because it's not detecting a proper flame. That could be in the control, could be the cad cell wire itself, and/or the cad cell eye. Being that cad cell was an add-on, it could also be mis-aligned and not seeing the flame. But you have to get a pro in there to clean it, tune it up, check all your safeties and do a combustion test for draft, smoke and (forget efficiency) safe operation

Rob123

If the CAD cell didn't detect a flame, how is it that the boiler operates right up to the time it reaches high limit or the thermostat set temps? Doesn't the CAD cell monitor the flame the entire time the boiler is running? Does pushing the red reset somehow disengage the CAD cell?

The Aquastat was replaced because the "Pros" that investigated this issue told me that was the problem. For only $ they would put in a new one. I declined their generous offer and picked up new one for $.

The boiler has been cleaned and serviced several time since I've owned this place. 5 years now.

One thermostat (connected to Aquastat) shows 20.6 v and the other shows 23 v when not calling for heat. They will drop to 0 v when I twist the thermostat and I can hear a "Click".

When calling for heat B1 and B2 show 0 volts. Obviously when running (using the reset to start) B1 and B2 show 120v. I'll pull the flame detector and replace it and see what happens. Thank you for all the replies.

Jamie Hall

Somewhere in there there is a safety or control which is locking out. Why? Dunno -- I'm not there. Nor which one. However... the voltage you are quoting (20.6 volts) is low; even 23 volts is low. When the thermostat is not calling for heat, one terminal should be at 24 volts or more and the other at ground. When calling, both should be at 24 volts or more. If they are connected to the aquastat, then the aquastat should be 24 volts or more on both terminals when cold, and 24 volts on one and 0 on the other when hot.

You could also have a problem in the burner control circuits themselves.

Or... only way to find out is to get in there with a multimeter and a good understanding of the circuits and start measuring.

As @STEVEusaPA said, though, that whole unit is in pretty tough shape and doesn't owe you anything.

Rob123

I found a schematic online for the R8182D and will grab a Fluke from work and give it a go.

Pulled the CAD cell and cleaned it up. So far so good but it has only been a few cycles and the boiler has done that before. Sometimes it will run for a day or so without any intervention, and then the next few days I will have to tap the red reset...

This nonsense started about 3 weeks ago.

HVACNUT

Anyone can plainly see the problem is some fool installed the burner upside down.

Whole heartedly agree with ^^^.
My thinking is if a modern burner was there, you'd see the same symptoms but those modern controls would probably send the burner into recycle 3X rather than directly into safety.
And some primary controls will actually display the fault with an LCD readout or connecting to the primary with a contractor tool.
In a language your burner will understand, the the 21st century, well, it's The Bees Knees.
It really could be any number of things.
Intermittent ignition, in those dinosaurs, sometimes if you lose the spark, you lose the flame.
Restricted oil line, filter, strainer. Will start off fine then too much vacuum and there will be flame loss.
Dead spot in the motor windings.

At the very least, a shiny new retention head burner is in order.
Put the 8182's back on Let Go and get a Hydrostat 3250 Plus.
1 L8182 is expensive. You bought two?

As you can tell by my posted pic, I'm very fond of the ancestors to modern fuel oil burners but it's time to go on the wall.

STEVEusaPA

For this type of troubleshooting the first thing you need to figure out is when its locking out?
-Is the boiler running to high limit and locking out when the aquastat stops the burner at high limit (would be a first for me)? -Or is it running, happens to lock out near high limit, IOW, either its losing flame, or the relay 'thinks' it's losing flame and locking out?
-Or, Runs to high limit, still calling for heat, burner shuts off. Then when the temp drops enough to fire the burner, the burner doesn't fire and locks out?

Any scenario could point to bad motor, bad start windings/switch-checked with meter, ohms and amp clamp.
-Could be a weak transformer-also checked via ohms.
-Bad cad cell or wires, check ohms
-Could be a bad pump-checked with pressure/vacuum gauges. Pump could be binding, overloading motor, etc.
-Could be a slipping coupling.
-Could be related to the scorch marks. Not enough over fire draft (dirty/plugged boiler) has allowed excess heat to damage the transformer, motor, and/or cad cell eye/wires.
And on and on.
All checkable by a competent professional, in about 20-30 minutes. The problem is most techs either don't know, and/or won't spend the time.
In the rare exception when I just could not find a nuisance lockout (happened 3 times in 27+ years) I hooked up my OnWatch which is basically a data logger to figure it out. I wouldn't classify yours as that as yours locks out frequently. I had one that locked out from a bad primary after 385 calls, I think about a month or so later.
Like @HVACNUT said, modern controls are starting to have some diagnostics on them.
But the conclusion to my long winded post is that you need a competent pro. Also that boiler should be properly cleaned every year.

Rob123

The boiler has been working fine for the last two days. Nothing to get excited about since it has done that before and then simply quit, forcing me to use the red reset button for the next few days....

But, I have noticed a few things.

One, the run time is much longer than before, and the period between those runs has increased dramatically. Before, it would run for about 3, maybe 5 minutes and then shut off, stay off for twenty minutes or so and (if lucky) restart. Run for another 3 or 4 minutes and then shut down.

Most of the time it wouldn't restart, and I would have to hit the red reset.

Now.....

It now runs about 10 or 12 minutes and is restarting on it's own after an hour or so...Right now ambient temps are low 40's F.

Boiler shows temps steady between about 160 and 200 F

Second thing is that while checking the wiring w/a Fluke meter I noticed that the second Taco pump (furthest from the boiler in the picture) is wired to another Honeywell box (RA89A) in the ceiling, not the Aquastat attached to the well on the boiler.

That box contains an always live 120v line, a transformer with connections to the second thermostat (in the back of the house, a 1,000 sq ft ranch ) and run down to the second Taco pump in the picture.

No matter what the temps in the boiler are, if I call for heat in the back bedrooms that second pump will run. Even if the water in the boiler is at ambient. Does that sound right? The other Taco pump connected to the C1-C2 on the Aquastat will NOT run if the boiler temps are low. I confirmed all this with the meter: Low boiler temps kill the 120v to the C1-C2 terminals on the Aquastat but not on the RA89A box. That second pump runs with a call for heat no matter what.....

Seems to me that second pump should NOT circulate low temp water, especially if taking a shower. I'm starting to figure out why I could never take a 10 min shower in the Winter...

BTW, the three Pros that I've called (and actually showed up) were here about 15 mins each. The script goes like this:

It is old, you need a new one, we will contact you in a few days with an estimate. Most of the Pros weren't willing to troubleshoot or suggest repairs. One did, he suggested that the Aquastat was bad and charged me $150 to let me know. That is why I bought one.

Estimates ranged from $ for a PTWGO3 tankless system (115,000BTU) to $ for a larger PWGO4LB (145,000BTU) with a 36gal indirect DHW tank.

I don't think any heat loss calculations were done. Nobody asked me anything about insulation or did any interior measurements.

Not saying they didn't know what they were doing. Maybe if you do this enough times you get a feel for it??

The pros spent all their time in the basement studying the existing boiler. The Pros weren't really interested in repairing or replacing any parts. If I had the $$ I would go new for sure....but that isn't happening this Winter.

Maybe the CAD Cell cleaning did the trick but I'm not all that confident it did. I don't like the fact that the second pump can run anytime it wants to.

Wish there was a real tradesman or old timer around here that knew these old relics of heating equipment. I did start a new boiler fund this week, and if things go well by next Fall the cash will be there.

I did order a few extra cords of wood just in case :-)

Thank you again for all the suggestions and comments. I am getting a real education on how complex a hydronic residential heating system is. I actually find it really interesting. Can anyone recommend a textbook on the subject?

Rob123

Well, the boiler fired as it should for almost a week.

Then it didn't.

New CAD cell, Aquastat controller, and oil filter on the tank hasn't helped.

I don't think it is a fuel problem but instead is ignition related. The Aquastat is wired correctly, as is the new CAD cell.

Going to check the ignition transformer and electrodes to see what is going on. Current transformer has a date stamp of 2009 if that means anything.

The weird thing is, any time the boiler won't fire I only have to tap the red Aquastat button only once and it immediately fires. Every single time.

It will then run (usually) until it hits the high limit (200deg). Once in a great while it will only hit 185+ or so....

STEVEusaPA

I just hate that you keep throwing parts at it without a proper diagnosis.

Your circulator problem with the other zone is probably a mis-wiring issue. How is the second relay wired, and how do those wires transfer to the aquastat?

I wouldn't recommend a text book but rather see you find a competent technician.

-Might not be any parts, might just be set up incorrectly.
-Might be as simple as the set screw on the plate holding the electrodes is cranked down so hard it's blocking the cad cell from reading the flame properly. Or the holes are filled with crud, blocking the proper flame reading.
-Might be poor draft and heat build up is affecting the transformer or motor.
-How's the end cone?
-How's the insertion depth?
-How's the Z dimension.
-Might be, might be, might be-that's why a pro tests before replacing parts.
-What are the combustion numbers, including draft and smoke?
-Was the fuel pump properly checked-pressure/vacuum/cut-off?
-Is this a gravity or lift job? Was it properly bled?

I'm not saying their aren't nuisance lock outs, but every component is testable, as are the adjustments for proper operation.

HVACNUT

I thought we decided you were going to have a Riello installed. Put the Arco to pasture.

Rob123

Thank you all for the comments. Much appreciated.

The second thermostat isn't wired to the Aquastat as far as I can tell. That is probably why the second circulator pump runs whether the boiler temps are up or not.

BTW, if that circulator pump is indeed only controlled by the thermostat not a single "Pro" that had looked at this system over the last 5 years ever mentioned it to me.

I rather trust a textbook than some newly minted kid out of trade school. True journeymen that aren't just parts replacers are getting scarce around here. I can toss parts at this monster as well as any kid but finding a real tradesman with actual troubleshooting knowledge is almost impossible. Not knocking the kids, we all start somewhere. The last one tried to unscrew the inspection plate, not realizing that you never unscrew anything connected to a 60 year old rust bucket boiler. He didn't know you "lift" the entire plate up with an index finger.

He never mentioned it. I found out when the red glue he used to put it back failed a month later and the boiler started roaring when if fell off. I JB welded it back on ;-)

I'm moving into Ignition Land for now. I think the issue is somewhere in that maze. Every.Single.Time the red reset is tapped the boiler instantly fires. Never need to tap it twice. And it runs to the High Limit (or very close) and shuts off as it should.

Why is that?

BTW, after tossing a new Aquastat at the problem I now tossed a new CAD cell and I cleaned/replaced the filter housing and fuel filter at the tank.

Still intermittent.

Rob123

Thoughts on this textbook?

National Oilheat Research Alliance “Oilheat Technicians Manual”

Here is the table of contents:

Note that it is a downloadable .PDF

https://noraweb.org/wp-content/uploads/2017/03/NORA-Silver-Contents.pdf

Leonard

Rough looking furnace.
REAL OLD oil burner,likely not even flame retention head ( for oil $$ savings)

Wonder if your wiring to cadmium light cell is intermittent. As a test, shut off power, disconnect cell's wire from aquastat, put ohm meter across wires to cell, and wiggle cad wires, look for intermittent reading. Apparently wire open > 45 sec will shut it down. Intermittent shading of cell by a broken piece of insulation might do it too.

Did you clean out the temp well and put new heat transfer compound on new aquastat's temp sensing bulb?? Page 3 of aquastat manual

2nd zone Circulator running even when boiler is "cold" does sound like it's not wired right. Liekly 2nd zone thermostat relay not wired right, see aquastat manual page 7, Unlikely to trip the safety.

Scorch marks Does look like it's got gasket problems.

Get a pro in there, with old furnaces the fire insulation in the chamber can break and fall off. That could be a hidden danger that's causing over heating of surface , and the scorch marks. ( but likely unrelated to your red button issue)

Unrelated but Your running your hi limit on the high side (200 degs). Guessing you cranked it up because your DHW is cold, from calcium hard water fouled DHW coil.

SuperTech

You need to have the windings of the burner motor checked with a megohmeter.
It's quite possible that you have bad windings on the motor. We've all seen intermittent lockouts caused by a bad motor or capacitor.

You need a pro, that old beast looks scary. I hope you have a good low level CO detector or two in your house.

CTOilHeat

Get a pro and have them bring a burner with them and replace that. It'll save you so much to pay so little.

HVACNUT

For all your money and time wasted you could've had that kid install a modern retention head burner. Because that's what he knows, modern. Not what great grand pappy had.
It seems at this point your on a quest, so yes, you've nailed it. Your problem is ignition. Transformer (good luck finding one for your burner), electrodes, cracked porcelain.
Tick tock, its getting cold. I hope you dont have others freezing while you tinker.

Leonard

System looks pretty basic. Seems to me like all need to do is read aquastat manual and determine what conditions it will trip out on (red button).

Breifly skimming manual/schematic in 1-st link ,looks like that's:
-- no light on cad cell, or intermittent cell wire
-- or maybe too much current drawn by blower/ignitor ( if it has a motor starter safety build into aquastsat. Not obvious that it has one from schematic)

Guessing there's no red button trip on over temp, (I didn't read it thoroughly.)

Should have a pro look at it though. If not cleaned for long time or If drafts aren't set right you could be blowing CO exhaust out those apparently missing gaskets by burner scorching...... should have a CO detector to save your life while you sleep. It has the appearance that routine maintenance has not been done for quite a while.

Leonard

If Aquastat wiring, and cad cell/wiring are good, you might actually have an intermittent no-fire condition. And the saftey is doing it's job, protecting you from letting pump eventually empty your whole oil tank on floor, or house/chimney fire. There's a reason these things are called SAFETYS.

After boiler runs up to temp and is satisfied, listen to burner as boiler cools down and eventually aquastat calls for re-fire (might take hour or so). If burner motor runs but doesn't make fire, Fix the burner and/or fuel supply.