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HTP Phoenix light duty combustion ?'s

Driven11
Driven11 Member Posts: 7
in Domestic Hot Water
So I had one of these put in about a month ago and it's always had a woosh sound when it fired up. Not loud or anything but noticeable. After a week or so I switched it to eco mode because I couldn't make the thing run out of hot water if I tried. It recovers insanely fast. It started making that foghorn noise when in eco mode. Only for the first 15 seconds or so after firing and then it quit. So I talked to the guy who installed it and he said put it back to regular mode and he'd call me when he could stop by. I'm still waiting for that call...

So being the handy guy I am I started reading. And reading and reading and reading... These gas valves are quite sensitive from many posts I've read. I got frustrated with all the posts about flex pipe and regulators causing these issues. Decided to get rid of the flex and hard pipe it myself since this was one of those "favor" installs. I also found a shut off valve with a really small opening that seemed restrictive so I replaced that with a full port ball valve as well. It definitely changed the sound of startup and operation but something still isn't right.

I used an analyzer and a manometer to check the flue mix and gas pressures. I see 9.7% CO2 at high fire and 9% at low fire, both below 20ppm CO. Those numbers seem great to me (based on my hours and hours of research). The thing I'm confused on is the low fire mode. High fire has a nice, sweet looking blue flame. Low fire get much more yellowish. I know color doesn't mean everything but I'm looking for an answer on why that would happen. Also am I the only one with a sight glass right behind the gas valve? It's almost impossible to see anything where it's placed.

Comments

  • Driven11
    Driven11 Member Posts: 7
    Also, I watched this video and had other questions. This guy says the outlet pressure tap should read .02" WC at low fire. I'm reading more like .24 at low fire. I noticed his setup in the video has the little port by the offset open to atmosphere. My unit has a hose that ties into the PVC intake. Since I'm installed in the basement and had this installed direct vent I figured maybe that reading needed to be referenced to that hose so I tee'd into it and it still reads high. Is that .02" number a hard reference value that is screwing with my low fire?

    I'm an OCD perfectionist (electrician by trade) and I can't control my curiosity. :| I have to know everything about the operation of this gas valve and I'm just not finding much info out there.

    Which brings me to another question... :D If this valve mixes prior to the inducer why doesn't the flame just burn inside the blower since the mix is stoichiometric? Seems like it would travel all the way back to the valve where it would finally be too rich to burn. Yea - I'm mental but I can't help it. I analyze new stuff until I understand every aspect of it or it drives me nuts.

    https://youtu.be/eX0FfYyQ5Lg
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    What's your inlet gas pressure? Are you sure about your pressures... .02 and .24 (not .024)?

    There was an error rendering this rich post.

    Driven11
  • Zman
    Zman Member Posts: 7,611
    I am not very familiar with the HTP models. I do work on that honeywell gas valve frequently.
    I would suggest try running it richer on low fire to eliminate the noise. This involves adjusting the offset screw and raising the CO2. You can go as high as 10 as long as the CO does not spike.
    Do be careful and keep track of your turns, you can make a mess of things quickly with the offset screw.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Driven11
  • Driven11
    Driven11 Member Posts: 7
    STEVEusaPA said:

    What's your inlet gas pressure? Are you sure about your pressures... .02 and .24 (not .024)?

    Inlet is about 6.75"WC. I'm using an actual water column not a digital meter so that's as precise as I can get. I'm 100% sure about the .24". I have a Dwyer that gets precise down low but won't go above 3"
  • Driven11
    Driven11 Member Posts: 7
    Zman said:

    I am not very familiar with the HTP models. I do work on that honeywell gas valve frequently.
    I would suggest try running it richer on low fire to eliminate the noise. This involves adjusting the offset screw and raising the CO2. You can go as high as 10 as long as the CO does not spike.
    Do be careful and keep track of your turns, you can make a mess of things quickly with the offset screw.

    Why do you say that? The guy in the HTP video just adjusts that offset willy nilly to get his CO2 right. The offset and throttle are independent I thought.

    I also googled that Honeywell (VK8205) and there is very little info out there and what is available says this is an international valve.

    If I knew the .02"WC was a set standard for low fire with that valve - and the throttle is *not* independent from the offset - I'd adjust to the .02 and go from there to get the high fire right with the throttle.

    I'm also genuinely interested in this valve tech just for my own curiosity. The Trane rooftop HVAC units seem to be the only other negative valve setup I can find online. If you have knowledge that I'm not searching for properly I'd love a bump in the right direction.
  • Driven11
    Driven11 Member Posts: 7
    Found this just now while poking around. Sounds like the yellow color at low fire is normal. Some other interesting stuff in here but it's not exactly a Honeywell valve.

    https://www.hotwaterproducts.com/service/resources/munchgasvalve.pdf
  • Zman
    Zman Member Posts: 7,611
    Based on my experience with Triangle Tube and Lochinvar boilers using that valve, the noise goes away if you run it a little richer. You can try to do it with the throttle screw alone, my guess is that your CO will spike on high fire.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Driven11
  • Driven11
    Driven11 Member Posts: 7
    Well sheeeeet. I got a calibrated analyzer and set my fires with just little turns just like in the HTP video I posted above. I'm at 9.5 CO2 and 48 CO on high fire, 8.5 CO2 and 19 CO on low fire and 9.5/50 running normally in ECO mode. If I lean out the throttle to drop the CO2/CO it starts the damn warbling noise. It was installed direct vent with a 10' run straight up then a 10'-12' run horizontal out the side of the house. Exhaust shoots straight out and the intake takes a 90 up about 12" the has a tee on top. Someone asked about pressures and I made spot on measurements right at the valve (they match exactly what I read if I tap in at the trap too). 6.5" idle, drops to 5" when the flame makes the woosh sound, settles in at 5.5" during normal op.

    Someone mentioned the offset screw can really jack these things up. Is there a procedure to get it back to factory? It hasn't been adjusted much but IDK if it came to me set up right. Just like setting the H and L screws on a 2 cycle carb after a rebuild. They will say bottom both screws then open the H 2 turns and the L 3 turns then adjust from there while running.
  • Zman
    Zman Member Posts: 7,611
    Most manufactures set the CO threshold at <100 ppm. Others are higher.
    I am not telling you to disregard the manufactures recommendations but....
    If I had the choice of listening to the noise or letting CO be 50ppm, I know the choice I would make.
    If you adjust the offset screw, just be sure to count your turns so you can get it back where you started.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    STEVEusaPA

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