Heater High CO levels

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Cam_Arntsen

Member
Sep 18, 2023
7
Barrie, ON
Hello All,
A service call on my 8 yr old Hayward Heater resulted in it getting red tagged and shut down. The tech said the CO levels hit 650ppm, and says the heat exchanger is likely 'clogged'. Says he can attempt to remove and service the heat exchanger, but recommends to just replace the whole heater.

I am by no means an expert, but to my understanding, the heat exchanger is a closed system full of water that sits above the burner. I am unclear how any failure of the heat exchanger could cause CO levels. Would it not more likely be related to a problem with the burners? The explanation given sounds more related to a home furnace where a cracked heat exchanger allows the air to mix

Not opposed to replacing the full unit, just want to ensure I am acting on good advice.

Heater is Natural Has, Pool is Salt.
 
Cam_Arntsen said:
Hello All,
A service call on my 8 yr old Hayward Heater resulted in it getting red tagged and shut down. The tech said the CO levels hit 650ppm, and says the heat exchanger is likely 'clogged'. Says he can attempt to remove and service the heat exchanger, but recommends to just replace the whole heater.

I am by no means an expert, but to my understanding, the heat exchanger is a closed system full of water that sits above the burner. I am unclear how any failure of the heat exchanger could cause CO levels. Would it not more likely be related to a problem with the burners? The explanation given sounds more related to a home furnace where a cracked heat exchanger allows the air to mix

Not opposed to replacing the full unit, just want to ensure I am acting on good advice.

Heater is Natural Has, Pool is Salt.
Click to expand...
Which heater is this? Brand and model?

Heat exchangers can be clogged by soot from incomplete combustion. That is usually caused by improper gas pressure at the main valve, or debris that has fallen onto the burners and blocking them, or clogged burner orifices (usually spider nests). The flame is then a "fluttery" yellow instead of a nice blue flame.

It takes a bit of dismantling the heater to find out. Removing the top of the heater can give access to the exchanger. A straw broom (not a wire brush) can be used to clear the areas between the fins on the exchanger, then the burner tray needs to be vacuumed clean. It is a bit of work, but might solve your issue.
 
The heater is a Hayward H250HD 250,000 BTU on Natural Gas, Approx 8 years old.
So by 'Clogged' you are talking about externally. The little fins clogged up with soot or debris, not allowing airflow. I was envisioning Internally clogged and disrupting the flow of water. Makes more sense now.

The reason I placed the service call is that the flame sounded like it was struggling and there was a strong exhaust smell. I assumed it just needed a maintenance cleaning. The tech didn't really dismantle or inspect anything. He checked the gas pressure and made a minor adjustment, then put his CO meter on the exhaust and concluded the heat exchanger was clogged.

Sounds like replacement might be pre-mature and a 2nd opinion is warranted. I will attempt to dismantle tonight an have a look at the exchanger.
 
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Is the heater outdoors or indoors in a shed?

You are in Canada and have different regulations then I am familiar with. But in the US I don't think an outdoor heater can be red tagged for excessive CO.
 
Natural gas is mostly methane CH4.

Complete combustion requires the correct stochiometric ratio of oxygen to methane.

CH4 + 2O2 --> CO2 + 2H2O

One molecule of methane reacts with two molecules of oxygen gas to yield one molecule of carbon dioxide and two molecules of water.

When you have complete combustion, the flame is very hot and the color is blue.

When you have incomplete combustion due to insufficient oxygen, the flame is orange (Meaning less heat) and the exhaust will contain carbon (soot), carbon monoxide, carbon dioxide and water.

9CH4 + 15O2 --> C + 4CO + 4CO2 + 18H2O

600px-Combustion_reaction_of_methane.jpg



Verify that the gas pressure static and dynamic are within the required range.
 
Cam_Arntsen said:
The tech said the CO levels hit 650ppm, and says the heat exchanger is likely 'clogged'.
Click to expand...
Was it a pool tech or an HVAC tech?

Pool techs usually do not have a CO meter.

Did you see the CO meter and the reading?

Can you show the system?

If you are getting CO, then you are probably also getting soot (carbon), which will clog the heat exchanger.

The soot reduces airflow and this reduces the amount of oxygen available for combustion, so the problem gets worse and produces more soot.

Cam_Arntsen said:
He checked the gas pressure and made a minor adjustment, then put his CO meter on the exhaust and concluded the heat exchanger was clogged.
Click to expand...
What was the gas pressure static and dynamic at the inlet?

Did they check the manifold pressure?

If yes, what were the readings?
 
Update...
I pulled out all 5 gas orifices. number 4 was partially blocked, number 5 was completely blocked. Cleaned them all and re-istalled.
Took the top off to see the exchanger. No evidence of any soot or blockage, but above burner 5 (blocked) the fins have a green patina look to them. Note that photo is before I vacuumed it.
I reassembled and started it up. It sounds good. Was hoping to see the flame color, but cant find where it is visible.
Will let it run a while and see if we continue to smell the exhaust. If no, I assume it is resolved.
Should I have any further concern?

AJW22, it is outdoors freestanding away from the house.

1695065732011.png
 

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Cam_Arntsen said:
The reason I placed the service call is that the flame sounded like it was struggling and there was a strong exhaust smell.
Click to expand...
You need to figure out why the heater is having these problems before you replace it or the new one will likely do the same thing.

Can you show a video of the heater operating including looking at the flames?

Show a picture of the heat exchanger when you get to it.

Is the voltage correct for the heater?

Note: Do not change the voltage unless you are 100% sure that you know what to do.
 

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The tech was an HVAC guy that does residential furnaces as well as Pool heaters. I have no previous experience with him.
I saw the CO meter myself. it was at 650 and still climbing when he turned it off. The tip was stuck down into the exhaust grill
He check the gas pressure and said it was fine, just off slightly. I didnt see the values.
There is a view port, but I am unable too see the flame. I will take another look shortly.

At the moment it appears to be running nicely, and sounds good. No noticeable smell, but I do not have CO meter to take a reading.
I am hoping it was nothing more than the blocked orifices
 
I would want to know the actual CO reading now.

Hayward High CO emissions

Hello, I have a Hayward H200 natural gas heater we have had for 8 years and my family and I almost lost our life last month as the heater started to emit high levels CO into our home out of the blue. Luckily our CO detector functioned as it should and alerted us. The levels reached 150 ppm...
www.troublefreepool.com www.troublefreepool.com
 
Safety of the appliance should be the primary goal of all technicians.

The production of carbon monoxide (CO) in the flue gases should be kept below 100-ppm air-free, even though the allowable limit in the stack is 400-ppm air-free.

Performing a Combustion Analysis

Safety of the appliance should be the primary goal of all technicians. The production of carbon monoxide (CO) in the flue gases should be kept below 100-ppm air-free, even though the allowable limit in the stack is 400-ppm air-free.
www.achrnews.com www.achrnews.com

 
Thanks everyone for your input.
Since cleaning the spiders out of Orifice 4 and 5 the Heater is running, sounding and smelling good. With my indoor CO detector I could not get any reading at all (cant be correct). In the viewport the flame is 99% blue with the occasional yellow flicker.

I suspect the technician was either trying to make a quick buck on an unnecessary replacement, or is not fluent in how pool heaters work. Remember, he never even looked at the burners or heat exchanger.

The season is done here. Heater remains off and I am likely to close down the pool in the next couple days. When I reopen in the spring I will call in a different company to do a maintenance/tune up and see what they find. If nothing else, it gives piece of mind that everything is good.
 
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