750mv empire heater dv215 voltage drop once main burner is on

CASCADE1404

I have this heater of mine that comes in my ice castle. First found a problem with the gas valve. At that point also ordered a new pilot assembly and Thermopile. Checked for inlet WC and it was running exactly at 11. 

All parts are directly from Empire. First checked the Thermopile with a small torch to make sure it worked. Read as high as about 800mv. Lit pilot. MV check on the Thermopile alone and was getting around 650+. Then hooked up the Thermopile to the pilot valve. Reading 450mv. 

Turn on the main valve with a jumper and the burners turn on as normal. As I'm watching the meter I notice that the MV start to slowly drop... keeps dropping until the main valve closes with the pilot valve... 

My initial thought was to change out the main burner because when I pulled it out while installing the new gas valve I noticed that there were a bunch of holes filled with surface rust. I cleaned all the holes and blew it down with air compressor. 

The reason I'm thinking maybe change the main burner assembly is when I listen to the heater after I light the burner I can hear noises. Not popping... but as if the burner is not inconsistently running... like "swoosh" sounds.. MV keeps dropping and then no more pilot. Keep in mind burner and pilot are encapsulated and only accessible through a site window. 

What are your thoughts? 

EdTheHeaterMan

OK this sounds like the pressure of the LP gas may be low after the main burner lights. The larger opening at the gas valve or burner orifice (not the burner openings) will allow more flow of gas. This will lower the manifold pressure at the gas valve inlet. The lower inlet pressure will be reflected in the size of the pilot flame. The smaller pilot flame will be reflected by a lower voltage at the pilot generator. Eventually the pilot flame is too small to generate enough electricity to sustain both the pilot burner and the main burner solenoid valves to stay open. The valve closes on safety lockout until you light the pilot again. Try increasing the inlet pressure to 13”WC at the closed valve to see it that helps.


Or perhaps see if the pilot generator can be positioned in the pilot flame or the pilot burner may be partially blocked. Sometimes the air flow thru the pilot burner is restricted by dust or the pilot orifice is partially blocked.

EBEBRATT-Ed

You could also have a sticking gas regulator. Propane has been known to make a regulator stick if there is any moisture in the propane or in the tank.

You need to check the gas pressure when the main flame is on. The only gas pressure that really matters is when their is a load on the system.

CASCADE1404

I was watching the manifold pressure and it maintained 11 inches of WC even with the main burner going. With the main burner going I also had another heater going as well maintaining 11 inches the whole time. The main regulator has a high btu rate. I can't remember the rating at the moment. 

I understand the logic though. But this one doesn't seem to be the case of low manifold pressure. 

EdTheHeaterMan

OK then look at the pilot burner during the condition where the voltage drops. See if the pilot flame gets smaller. or if the increase in the draft thru the heater makes the pilot flame move off the pilot burner and causes the pilot generator to get less heat. Less heat = less voltage

Sometimes a small adjustment in the position of the pilot flame is all you need. You may have inadvertently made that "out of adjustment" when you replaced those parts

CASCADE1404

I can check the pressure again tomorrow. But under a load I did not see a drop in pressure. 

You fellas don't think I should replace the main burner manifold? Somehow I feel like I didn't get all the rust partials out and they are making the inconsistent flame going on the main burner... which is what I'm hearing with the flame when lit

EdTheHeaterMan

CASCADE1404 said:

I can check the pressure again tomorrow. But under a load I did not see a drop in pressure. 

You fellas don't think I should replace the main burner manifold? Somehow I feel like I didn't get all the rust partials out and they are making the inconsistent flame going on the main burner... which is what I'm hearing with the flame when lit

The main burner is not causing the low voltage condition. The pilot flame is the only thing that can generate the electricity in the pilot generator.

I will repost my previous post again

OK then look at the pilot burner during the condition where the voltage drops. See if the pilot flame gets smaller. or if the increase in the draft thru the heater makes the pilot flame move off the pilot burner and causes the pilot generator to get less heat. Less heat = less voltage

Sometimes a small adjustment in the position of the pilot flame is all you need. You may have inadvertently made that "out of adjustment" when you replaced those parts

CASCADE1404

Copy that. I can't see the flame of the pilot unless I open the sight window... when I open it it seems like the MV reading goes up.... so this first picture is the High reading at the pilot valve with heater calling for heat (burner on). 

Then it starts to drop fast...

All the way down to the 90s and then shut off... 

In this test I did increase the manifold pressure to 12.5 wc. No pressure drop at all... but visually when I started to notice the drop in voltage... I opened the sight window and noticed half the burner was lit. It made the pilot burn very weird. But with the sight window open long enough the oxygen evened out the burner. 

This is what the right side looked like which was not lit. The flame in the picture is the pilot:

This is the left side which was lit:

CASCADE1404

Once I opened the sight window after about 20 seconds the right side that was not lit... came back to life looking like this. 

CASCADE1404

This is a Phone drawing of the results from catching half the burner nor working... eventually leading the pilot to fail heating the thermopile... 

pedmec

sounds like you don't have enough combustion air. is this a sealed combustion unit?

mattmia2

Does this have a blower? Does it happen after the blower kicks on?

Do you know the hx is intact?

Is however the air gets in to the enclosure clean?

Why did you think the valve was bad?

CASCADE1404

I was thinking maybe the combustion route too... this is a stand alone 750mv heater. No blower. This is the dv 210 empire model: 


Very similar to my DV-215. 

retiredguy

After you have checked everything else, I would check the upper chamber and the combustion air inlet and burned gas outlet to make sure that there is no restriction like soot, spider webs, dead rodents or mice. Make sure that there are no restrictions of any kind.

pedmec

this is a direct vented unit meaning its taking air for combustion directly from outdoors. you need to make sure the the air intake is not plugged. it is part of the venting system. combustion is being drawn in around the exhaust and entering from the rear of the burner if i'm reading the parts list correct

HomerJSmith

Wall thermostat? Check voltages with the thermostat disconnected and the gas valve jumped,

tim smith

Check across the wires going to your thermostat at gas valve. Much of the time it is millivolt loss to the thermostat. Should be somewhere less than 50 mv drop across thermostat circuit when calling for heat. Most critical on mv circuits are to clean all the terminals and connectors. Use a small piece of 180 grit sandpaper or a toothbrush wire brush. I clean the mating surfaces, the underside face of screws that are making contact with wire. Amazing how much loss you get just from tarnish. Also some of the newer mv thermostats are causing too much loss and keeping valve from firing. After all above check and see what you are getting back to main coil on valve when a call for heat. Per Robertshaw should have minimum of 110 mv to valve main coil to operate.
Good luck
Tim