HVAC problem

[JLEONARD]

I have an "issue" with my boiler for my baseboard HW heating system.

This oil boiler also supplies hot water via a domestic coil.

The boiler is a 4 year old Burnham, with a Becket burner. Has been serviced annually, but the techs have not been able to fix this issue.

When the system is cold and calls for heat, like in the morning going from it's setback temp of 62 to 65 degrees, the unit starts the blower for 15 seconds and fires like it should.

But here's the strange thing... it runs for 3 minutes, the flame stops suddenly, then in 3 to 5 seconds it fires again, then will run continuously until the boiler temp is satisfied (8 to 10 minutes), then will fire and run normally until the thermostat is satisfied.

It will do this every time the system is "cold". (We call it a double start). Runs exactly 3 minutes shuts off like the fuel solenoid is disconnected from power, then fires again. (When I say 3 minutes that is time by my alarm clock. It might be 2 min 50 seconds, or 3 min 20 seconds, but 3 minutes rounded off).

Very repeatable, been like this for at least 2 years, maybe since new I am not sure.

Seems to be getting worse meaning a double start more often and a second or so longer before restarting.

Does not "sputter" or sound like fuel is restricted then dying, it is sudden off, then on. I have 2 filters, one below the tank (original to the old boiler) and one just ahead of the new Burnham.

Thoughts?

 

[rscurtis]

Assuming you have a two-line system with the tank below the burner, you have an air leak. When the slug of air reaches the burner, it momentarily stops firing. Once the burner is running regularly, the off time is not long enough for the slug of air to develop.



When I had my rental business, I had this problem with the showroom burner, a Wayne Blue Angel- a real POS by the way. It was never a problem, so I never bothered with it. When I updated to a Riello burner, I had to fix it, as the Riello would not tolerate the off time without tripping out on safety. I relocated the fuel filter to the floor near the burner, and that solved the problem. The elevated fuel filter was the original source of the air leak.

 

[JLEONARD]

I have a one line system. Tank is approx 40 feet away on the same level as the burner.

You think it's the same problem?

 

[rscurtis]

Could be. What you may try is get some fittings and temporarily install a section of clear plastic tubing in the line and see what happens. Typically, a one line system assumes the burner is below the fuel level in the tank, as a one line system is not self bleeding. A very small amount of air can upset a one line system, where it may not even be noticed with a two line system because of its much higher oil flow.

 

[JLEONARD]

rscurtis thank you for your insights. I have a furnace guy comming today for an annual service and I plan on trying to get him to troubleshoot.

If he can't help I'll definately try the clear hose. I also have a section of that copper feed line that goes under the cement floor (in front of a door) so maybe it's time to install a new line that is properly insulated. Currently the copper looks bare as it goes under the surface.

 

[JLEONARD]

Update after the service guy was here. He thought it was the thermostat (electronic). I did not believe that but I did an experiment this morning to rule it out. I just removed the T stat and jumped the wores. 3 minutes, then the stop-start still happened.

The tech heard the relay drop out and re energize on the Honeywell control box when the stop - start happened. So I believe it is a controls issue not fuel.

I am going to pull out the schematic tonight but I think the only thing that would control the relay in that box is the temperature probe that sticks into the boiler.

 

[mwilson]

On a one-line system you would have a leak rather than air if there was a fitting, filter or line problem as that is gravity feed when your tank is anything above an 1/8 of a tank. That is assuming your tank is an upright and placed in the cellar along with your boiler.



The two inputs from the boiler itself should be low limit (lowest water temp allowed) and the high limit (maximum water temp allowed).

That is the bare bones basics of the system.



For example my small boiler here at work kicks in at a low limit of 150 degrees and kicks out at a high limit of 180 degrees.



When a thermostat calls for heat then the circulator for that zone kicks in and sends boiler temperature water through that loop. The return water is colder and robs the heat from the boiler. When the boiler cools down to 150 degrees the signal is sent to the gun control via the low limit switch that says "Hey, we are loosing ground here, make some heat". The gun controls then take over.



It sounds to me that your double start issue is with the controls for the gun, I would think a bad low limit switch would result in a no start, rather than a double start.



Just my opinion... ...



Mike.

 

[rscurtis]

When this happens, does the burner continue to run and not fire, or stop running altogether? That click you hear could be the start of the countdown cycle when the photocell loses the flame. If you want to really be sure, set up a one line system from a separate fuel supply and use the bleeder on the pump to get it to prime. A malfunctioning control should stop the burner, not just the flame.

 

[JLEONARD]

When this happens, does the burner continue to run and not fire, or stop running altogether? That click you hear could be the start of the countdown cycle when the photocell loses the flame. If you want to really be sure, set up a one line system from a separate fuel supply and use the bleeder on the pump to get it to prime. A malfunctioning control should stop the burner, not just the flame.

The flame stops and the burner motor continues, then the flame re ignites in a few seconds.

However the flame stays strong, no fluttering or anything else to indicate it is running out of fuel or not burning correctly.

The guy yesterday heard/felt the replay in the Honeywell box click like it was giving the burner the "I'm satisfied" signal to shut off the fuel. Then the relay energized again and the flame re ignited.

That's what it sounded like.

I have no problem at all setting up a seprate fuel system. I have a 3 gallon plastic outboard engine tank and a line with a squeezball to prime with. I can easily set that up with some diesel fuel.

I still think it's a control thing not a lack of fuel issue.

 

[JLEONARD]

Mike,

Thanks. I understand how the systems work. The "standard" limits around here are 160 F to 180 F. The stop-starts happen with the circulator running which means the boiler temp is over 160, yet the boiler water temp is still under 180... . unless the Honeywell unit "thinks" (or gets a signal) the temp is 180 and says ok boiler is happy... . oh crap wait a second I screwed up I still need fire.

Normally after the double start at the 3 minute mark (you can set your stopwatch by that) the burner will run another 8 to 10 minutes (with the circulator running) before the high temp is satisfied.



Is it possible that the temp probe on the Honeywell unit is in "just the wrong place" that it gets the "I'm hot enough" signal then 3 seconds later gets the "I'm too cold" signal (from cold water returning to the boiler)?

I can't see it reacting that quickly. I have adjusted valves to change the flow rate thru the house and nothing has changed in how the system operates.

 

[mwilson]

No, I can't see that the placement of the probes in the boiler would make a difference at all. It might make a degree or two difference in the cut-out or cut-in but nothing like the symtoms that you are seeing.



The three minute thing should be a tip-off to the technician, where it is a constant event there should be a trouble-shooting tree that would mention that.

That control system is not seeing something that it needs.



Did or have you tried your own google search of the symptoms??? You might get a hit or two.



Dive right into Honeywell controls, worth a shot.



Mike.

 

[JLEONARD]

Did or have you tried your own google search of the symptoms??? You might get a hit or two. 



Dive right into Honeywell controls, worth a shot.

I did at one point but it's worth another try.

So far none of technicians have had a clue.....

 

[mwilson]

I fooled with it at lunch, but just a generic search. I found the two new style Honeywell controllers like the work furnaces have in about 30 seconds, also found some diagnostics. My new ones are Natural Gas fired but found references to purge cycle timing, pilot time, etc.



Found one that Honeywell provided with the household Beckett burner, assumed that one was similar to yours. There were some references through Well-McClain for trouble-shooting.



I bet with a model number and a little perserverance you will find something.



You've got nothing to lose at this point.



In my experience burner techs get tunnel vision after a while, sometimes you have to increase their field of vision... .



Mike.

 

[rscurtis]

The point I was making in post #8 is that the controls won't shut off just the fuel solenoid (assuming it has one), it will shut off the burner. A burner that momentarily runs out of fuel will easily restart, assuming it has continuous ignition, which it most likely does. A clogged filter causing the pump to pull a vacuum will give you an unsteady flame. IMO, the click you hear is the result, not the cause.

 

[mwilson]

The point I was making in post #8 is that the controls won't shut off just the fuel solenoid (assuming it has one), it will shut off the burner. A burner that momentarily runs out of fuel will easily restart, assuming it has continuous ignition, which it most likely does. A clogged filter causing the pump to pull a vacuum will give you an unsteady flame. IMO, the click you hear is the result, not the cause.

You make an excellent point...



With the above being said, I had made the assumption that your burner tech had changed the two filters on your system recently.

Has he???



The Home Heating Oil that we are getting up here has, for lack of a better word, sucked for the last couple of years.

It is dirty, nasty, black stuff. not uncommon to need several filter changes to get through a season.

Could it be that simple... ... ... ... ?? If your luck is like mine probably not, but worth the question.



Mike.

 

[rscurtis]

That's interesting. When I lived on LI, I heated with oil until I switched to NG before I sold the house. I figured getting rid of the two tanks and having a brand new system would be a sales incentive- perhaps it was. What I found out that in the last several years, the quality of the fuel improved. I bought all fuel from a local oil company located next door to my rental business. I used their fuel to heat the showroom building and to fuel all our diesel equipment. Clogged filters were a non-issue. I used the same fuel in my house and used a Dahl 100 fuel filter for the Riello burner with a single line system. It could go years without cleaning. Now, I understand that heating oil is actually 15 PPM diesel fuel.



I know of several people who dealt with discount COD/cash only suppliers who were constantly changing filters and nozzles. Perhaps it was cut with used motor oil, ATF, or parts washer solvent.

 

[JLEONARD]

Not a dirty filter problem. No way. I have a filter (original) directly under the tank, and a second at the burner. I changed the one under the tank a couple of weeks ago. Yes it was dirty. The tech changed the ine at the burner. It was clean. The screen at the burner had some black in it, the nozzle was clean. Nothing has ever changed with the 3 minute double start euither just before or just after a filter. nozzle, etc change.

I just sat in front of the Honeywell and watched the readout. It was reading 175 boiler temp. The second zone called for heat , the circulator started and so did the burner. According to the Honeywell L7224U manual I downloaded yesterday that is correct operation.

I watched the temp readout the entire cycle. The temp gradually went down to 166, then slowly climbed and the burner shut off at exactly 180.

Circulator still running until the thermostat shut it off. No double start but I didn't time the cycle, I don't think it was 3 minutes.

It looks like temps are set correctly. low limit is 160, high is 180, differential is 10.

Going out to fill my 3 gallon can with diesel and will see if I have enough plumbing to connect it.

Stay tuned.

 

[JLEONARD]

Ok, independant fuel supply connected.

NO CHANGE in operation. No change in sound of the flame before or after the re-start. Flame looks good... it should it just got a new nozzle.

I heard one small click as the flame stopped, then another 1/2 second before it re-started.

Boiler temp was down in the 155 F range when I energized the system. The frst re-start was when the temp reached 162. Then the circulator brought back some cold water and the temps went down to about 144 and that's when the second re-start occurred.



At least now I have all the plumbing I need to connect to a second fuel source for when I change the feed line from the tank.

 

[JLEONARD]

Yesterday I changed the HL from 180 to 175, changed the LL from 160 to 155, and changed the Low Diff from 10 to 15. Could not find a way to change the HL.

Went thru 2 heat cycles without the double start and I was getting excited thinking the problem was solved, but later in the day it did a double start. I didn't time it.

It did another double start this morning, but it was 4 minutes this time, so something has changed.



Edit: Came home today and the house and system were at the setback temp, 62 F. Turned the T stat up and the system ran for almost 8 minutes, then the burner shut off as the boiler temp was at the HL, circulator kept running for maybe another 5 minutes, then the boiler fired again, etc, etc.

Maybe things are fixed. Stay tuned.

 

[JLEONARD]

Back again to the double start at 3 minutes.