I should add - the boiler was serviced recently since our ownership - and we know it was serviced annually - it's 13 years old.

I'm hoping that the fact that it doesn't smell all the time - seemingly only when colder out - will help to narrow down what might be causing it...

This post was edited by grasswhisperer on Fri, Dec 19, 14 at 22:32

The best person to answer your questions is the technician, who needs to come back to your house because he seems to have done a poor job with the prior service call.

Thank you, Snidely!

Yes - I'm a homeowner so not planning to fix this myself and of course will be calling this in. I'm posting this request for help here because I'm fairly confident they might not know the answer - they will be coming during the day when it most likely will not smell.

I'm looking for any knowledgable folk - either techs or other owners who might know what to look for or where to begin. I'm also anticipating that some responses will say "it could be many different causes..." Well I'm looking for what those causes might be - there must be some likely culprits...

Many thanks -
Brad

It is either a Field or Tjernlund power venter. The oil tech will likely come out and increase the post purge time of operation. On a PV, once the t'stat is satisfied the burner will shut off, but the venter will continue for several minutes to eliminate the oil by products in the boiler. If the time is to short, the residual heat in the boiler can back up throught he burner. That will heat the oil in the tray assembly (burner tube) and therefore cause it to expand and kinda pee out of the nozzle onto the hot block and smoke back out of the burner or the barometric.

Now, perhaps, increasing the post purge time will not solve the rael problem. Given that this happens only when it is cold outside you may have inadequate combustion air. A long run time or more frequent running of the boiler would use more air from inside the building. If the building is pretty tight you can dig a hole in the air supply creating a negative pressure in the building and you end up with exactly the condition you have.

If you are getting the oil drip or the combustion air issue it can dirty up your cad cell eye. Also, both Tjernlund and Field make combustion air fans, Fields' is called the Fan in a Can. Tjernlund's is the Enforcer. I much prefer Tjernlund equipment.

Awesome insight, Jackfre - thank you!

Yep - we have a Field power vent.

For what it's worth (maybe not much) - when the tech was last out - I had mentioned we smelled oil (didn't smell at the time - here during a relatively warm daytime). He did test the combustion (stuck a probe in the exhaust). The boiler is in an unfinished but fully insulated room about 13'x8'. We keep the door open - if not fully at least a good crack - 6 inches or so. There are also 2 vents cut into the wall into the finished part of the basement. The entire basement is about 1000 to 1200 sq ft. He said all systems normal (aka enough combustion air) tested with door open and door closed.

But are you saying that when it's colder (aka more call for boiler firing for longer periods of time) - there might eventually be insufficient air flow? Not sure I follow as if there is enough air flow to run for 1 minute wouldn't there be enough to run for 20 minutes or more when calling for heat?

Would you suggest we set the PV to run longer as a first step to see if this solves the condition?

Which begs the question - is this an adjustment I can make on my own just to test?

Thanks!
Brad

Yes, the combustion air problem can become worse with long run times. It is a difficult thing to diagnose. On a cold night, the doors are all closed and have been all night. The system is running longer using more air and it can create a deficit in the available air to supply the system. Look at the number of appliances you have pumping air out of the house. Fart fans, range hoods, power venter, etc. What provisions are made to replace the air. Generally, the answer is none. Once the system hiccups and you have a service call, the tech opens the door and the problem is solved. He can't see it because once the door is opened the negative pressure in the house is solved. I do not know what you firing rate is on your boiler. There should be a tune-up tag on the system that lists the burner firing rate is. A 1gal firing rate = 140,000. A .85 = (140,000x.85) and so on. You need 50 cu ft of air/1000 btu of firing rate. You cannot take the gross dimension of the basement. I have seen people say the basement is big enough but they fail to consider that 4' of the basement is taken up by stuff and junk. There is a simple adjustable timer on the control...somewhere. It may be worth a try, but be aware that it could exacerbate the issue as well.

yeah - I wasn't trying to suggest we've got enough air down there - just passing along any pertinent info. But that makes sense it's more about cubic volume vs. square footage, etc.

btw - smell is indeed worse when we've got a fire going in the fireplace - obviously the draft is causing tendency for negative pressure. BUT - the smell is still evident even when no fire going - but when boiler is running long/often (aka when cold out). Trying to think of any other negative pressure causes - during these smelly times we aren't running bathroom vents, clothes dryer, or anything like that...

I don't want to change too many variables at once - one at a time. I haven't figure out yet how to run the PV longer, but will take a look. In the meantime, maybe easiest first test would be to somehow provide more air down there? Crack a window in the basement? Leave the garage door open a bit? (garage is under and on same level as basement - in fact the garage door is just outside the door of the "boiler room"...

Do you think that could help make a difference to test or would I just be wasting my time (along with making it cold in the basement!)?

Of course it's possible that both conditions are causing the issue (not enough air AND PV not running long enough to cool off the system?) I see what you're saying that by running the PV longer it actually exacerbating the negative air issue. so maybe I'll try one thing at a time, but ultimately may need to try both at the same time (run PV longer AND crack the garage door for more airflow?) Despite the techs telling me no, maybe we do actually need an air tube to the outside so the burner can get all the air it needs?

Thanks again - this is really helpful as hopefully I'll be able to do a bunch of diagnosing to help our techs. Good guys but this is the type of thing that you need to live it to figure out what's going on. Hard for them to swoop in and solve in a 30-60 min visit...

Okay - finding the time to get back to this issue now.

I've done some primitive testing on airflow - leaving various combinations of doors/windows cracked didn't seem to eliminate or reduce the smell. I realize this doesn't prove that I don't have an airflow/pressure issue, but for now I think I'll test the other possible culprit: running the power vent longer.

I've got a Field Controls model CK 610139 power vent. The vent runs for 1 minute after the boiler shuts down. manual says 3-5 minutes is typical (I've read some people talk about running it even longer, which I realize puts me at risk of negative pressure...)

Anyway the manual for "CK-61" (which I assume is for this model?) says there is an adjustment for the Post Purge Timing Adjustment (see page 6 of the manual - link here: http://www.manualslib.com/manual/399837/Field-Controls-46144900-Ck-61.html?page=6#manual)

Well I can't find this adjustment on my unit. I popped the junction box cover - and I think I've identified the pressure switch adjustment (I think it's the round piece attached to the junction box itself, with a screw adjustment - I'm not planning to change this setting.) Is the timing adjustment in the junction box, or somewhere else? Perhaps it's in the junction box and I'm looking right at it - but I can't seem to locate this adjustment.

I'll try posting a pic in this thread - apologies if it doesn't work.

Thanks!
Brad

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The pressure switch is not or at least should not be adjusted. A pressure switch is a primary safety and I just don't know how Field gets away with having an adjustable pressure switch. I believe that the dial you are referring to is the post purge adjustment. 1min is way to short.i'd probably go with 6 min and see how it does.

I'm with you 100% - I have no intention of touching the pressure adjustment - only the post purge adjustment. The problem is - I can't find the post purge adjustment. Any thoughts? I posted a pic - is it in the junction box shown?

Thanks!
Brad

I believe it to be the knob that is facing down on that white sided relay. Check the wiring diagram on the inside cover for clarification...and do get clarification. Note the position of the nob prior to turning so you can test and return if necessary. If the drawing is not on the cover check Fields website.

One thing we have not discussed is, "how clean is your Field power venter"? Power venters are great but they must be cleaned when the boiler is cleaned. Keep in mind that everything that goes through the boiler is going through the venter and it is a very harsh environment. It is quite common for the service company to clean the boiler and never touch the PV. As a result, cumulative deposits build up and the venter performance deteriorates and ultimately the wheel will get out of round and require replacement. ALWAYS ask if the company serviced the PV and insist that it be done. They may tell you that they do not service PV's. Buy your oil from someone who does. It is a system after all.

With your help, I figured it out.

The white-sided relay was in sideways - I had to remove the screw that holds it in place and rotate the relay 90 degrees to expose the post purge set screw. For those curious here's a pic of the rotated relay - now I can see (and access) the post purge adjustment. Able to boost the run time now. I think it's minimizing the smell but not entirely eliminating it. PV fan running for about 5-6 minutes now (vs 1 minute originally).

THANK YOU. Pic below.
Brad

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I found this post in a search for 'oil smell when the outside temperatures drop', and it's helpful but I have a gravity-fed oil stove, so no major components really. I'm just trying to figure why I get the oil smell.

I've been dealing with it for two winters now and have found some relief by changing oil companies for some reason, but the oil smell still happens when the temperatures drop below (about) -1C and below. It was -6C overnight.

I've talked to numerous oil technicians, and have not found any answers. The smell seems to emanate from the regulator though. Trying to get parts for this stove is impossible. One technician did take the cover off of the regulator and said everything looks good. So I don't know. I think it might have something to do with the oil getting slightly thicker with cold temps, but the oil smell has never happened in the 25 years we've owned the stove. Just the last two years - right after the oil tank got a little too empty because the delivery was later than usual. So I'm thinking there's a connection there... maybe sludge.

I don't know, but it's ruled my life for two years now! Can't beat the heat from this gravity-fed oil stove though. I'm in Canada and oil stoves are not easily found here anymore.