Hydrotherm issues

hankwylerjr

hate these boilers… no heat call. Customer says something about bad roll out. Checked all power and fuses breakers. Water level ok taco 007 working cleaned burners. Thermo couple good gas valve seems ok. Jumped the thermostat flame comes on for 1 minute shuts down to pilot. Weird smell almost like a burnt odor. I’m thinking soot on the exchange didn’t have time to disassemble it can’t see with mirror. Any other suggestions? Plumber not hvac pro don’t even like working on these any help appreciated

Jamie Hall

Has it ever been cleaned and serviced? Start there.

hankwylerjr

@Jamie Hall yes it was done this morning

JUGHNE

That rollout safety switch looks to have a burned wire on the bottom terminal.

Is that a manual reset switch?

Is there a blocked vent stack switch up on the draft diffuser?

You probably have to pop the top off of the boiler and brush down the sections…..remove the burners first.

hankwylerjr

@JUGHNE bottom wire was taped together I’m going to cut and new connections on it, blocked vent switch??

Yes it’s got to be disassembled to get at the top thought these models had a different exchanger setup but yes will have to remove the soot

JUGHNE

Blocked vent safety switch may have come later in requirements.

It is a thermo switch up on the vent draft diverter and would open if the exhaust gases "rolled out" up top because of blocked chimney or such. It is usually a manual reset switch.

Today the front burner rollout safety is a one time fuse link that must be replaced if opened.

clammy

I ve never seen a reset type rollout switch in the burner compartment on the flue collector yes . That rollout should be a fuseable type that is not resettable . I would think that the oem went and some one replaced it w what was on hand which is not correct for that application .

Peace and good luck clammy

HVACNUT

How much water do those boilers hold? If it fires without resetting anything, maybe it's not moving water and making limit quickly.

Alan (California Radiant) Forbes

It could be a bad ignition control module where it can’t keep the MV relay closed.

Also may be air in the system preventing circulation. Is the boiler making a loud clunking sound?

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1814004#Comment_1814004

When asked about cleaning/maintenance, Im trying to understand the time line here.

1. Customer calls you (a plumber) with a no heat call problem, that may or may not have to do with a roll out switch maybe.
2. Then someone performed all the manufacturer recommended maintenance items this morning.
3. Now you still have a problem?

That seems like a very short time line from No heat, to maintenance, to the problem you have now with a burning smell that might be soot on the combustion side of the HX.

Someone needs to get back there and actually look at the HX to verify the soot. Then Quote a price for cleaning the HX with a brush and vacuum. Then once the HX is spotless, look for a reason for that condition to happen. Just cleaning the soot may not solve the reason the soot got there in the first place. Was the boiler room recently sealed up as part of a renovation? That can reduct the amount of combustion air available for complete combustion. Is the chimney blocked at the base, or by wildlife moving in recently? Check the chimney or call a chimney professional.

flame comes on for 1 minute shuts down to pilot

So why does the flame shut down to pilot? Is the gas pressure insufficient? Is the thermostat satisfied (or jumper fall off) does another limit or safety break the 24 VAC to the gas valve? If you can determine how the gas valve is not feeding gas to the flame, then you will be closer to your answer.

If you have a multimeter, you can see when the gas valve gets 24 VAC and that is when the flame should start. Then when the flame drops out a minute later, to pilot only, does the gas valve still have 24 VAC? If not then there is something opening the 24 VAC circuit to the gas valve. Locate that open circuit and you will have your reason.

hankwylerjr

@EdTheHeaterMan thx for the detailed explanation, yes I am a plumber, a licensed and insured plumbing contractor, semi retired Any who, I don’t routinely work on these boilers. This morning I returned to the call. I took apart the vent and all the connections and top of the jacket.,I used my soot saw and brushes and throughly cleaned the exchanger. I had 2 inches of soot at the bottom, no pictures today the cellar was a complete disaster and carbon was everywhere. Used the respirator and was done in an hour. Job ran under 3 hours total I reassembled the unit and after changing out the old lux pro thermostat that was also bad I fired the boiler up. Although the flame was yellow due to the particles in the room it stayed on and she started getting heat within 40 minutes. I also cleaned out the vent and ran my Milwaukee drain camera to the roof it was clear but I recommend to install a ss liner asap due to the breakdown of the mortar. Had my brother in law the master HVAC technician bring his combustion analyzer over he ran the tests and he advised me that all have passed. Checked for co and natural gas leaks as I do every job all passed. Stayed another 30 minutes to ensure proper operation and passed handed the customer a modest invoice for our time she was happy now to install a new chimney liner in our parts in several grand but that’s not our job

HVACNUT

Glad it all worked out, but was cause of shutdown ever found? In you're first post it says, "Customer said something about bad roll out." As @clammy mentioned, down in the burner compartment is a manual reset disc limit, NOT a fusible link Rollout. Did that need to be reset? Did ANYTHING need to be reset?

Other than cleaning the HX (and burners?), no changes were made and combustion numbers are good? In times like these, "he ran the tests and he advised me that all have passed." vague comments don't really fly anymore. Hard numbers and draft readings at steady state would've been nice to see. (Trust but verify)

Its as if you got the money back but the burglar got away.

EdTheHeaterMan

@hankwylerjr, thanks for the update. Looks like you did everything you could to get the heater going. I just wonder how that soot started to accumulate… (Oops, this is a gas heater, they burn clean and don't make soot, according to the natural gas folks) carbon started to accumulate? Did you look at the boiler room for signs that you are getting enough combustion air? An open basement with sufficient cubic footage and reasonable amount of infiltration is all most gas boilers in basements need. But there are specific minimums that often get overlooked when someone refinishes a basement with insulation, paneling, and a drop ceiling. (or just seals up the home to make it more efficient) That open floor plan basement now becomes a comfortable living space with a heating appliance tucked into a confined space that can not provide enough combustion air resulting in SOOT on the HX.

Other reasons that carbon can start to form on a HX are:

1. The dryer vent from a natural gas clothes dryer is too close to the air intake of the burners.
2. The dryer vent from any type of clothes dryer is allowing dust and lint to block combustion air openings on the burners.
3. Wildlife in combustion venting system, air intake or exhaust
4. Combustion fan (if equipped) is not performing to specifications. Motor running slow or debris on the fan blades.
5. someone placed a box or other items too close to the combustion air intake of the burner.

There are too many things to list here. The bottom line is that carbon starts to accumulate when there is insufficient air for combustion, as the carbon builds up over time (days, weeks or months) and another carbon atom attaches to it, eventually the build up becomes part of the restriction. Even if the original cause of the insufficient combustion air is removed, once the blockage is there in the HX, it becomes self sustaining and self perpetuating, until it eventually goes from plenty of room for combustion to completely blocked in a matter of minutes.

Whenever I see soot, I look for the reason. The reason is there somewhere.  It’s our job to find it.

jumper

»something opening the 24 VAC circuit to the gas valve. Locate that open circuit and you will have your reason«

Yes. For example somebody may have installed a flowswitch somewhere and wired it in. Flowswitches fail.