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propane lockup regulator, 11" WC input

GaryAitken
GaryAitken Member Posts: 3
in Domestic Hot Water
Our house has a 2nd stage propane regular delivering 11" WC. I am replacing an old on-demand water heater which had a pilot light with a rinnai heater with igniter. The old appliance regulator was a Maxitrol RV48L which is a non lockup regulator and has a max single appliance capacity of 160,000 Btu/h. The rinnai is 200,000 Btu/h.

The new heater will work from 8" - 14" WC, but because it is pilotless I need either a lockup regulator which will work with an inlet pressure of 11" W.C. I'm having trouble finding anything. The Maxitrol RV52 requires a vent, and I would really like not to have to deal with that.

The Maxitrol 210D line includes models which will handle low input pressure but those seem to be limited to too low an outlet pressure. For example 8" WC in goes to 6" WC out (from natural gas table in Maxitrol spec sheet; not sure how to translate that to propane. How much does the change in gas specific gravity effect the inlet / outlet pressure range? I know it affects flow but that's not an issue with the 210 series)

thoughts / suggestions?

Comments

  • ratio
    ratio Member Posts: 3,774
    The so-called ventless regulators are about 10x the cost of the vented models around here, and they aren't such a good idea on propane. Ventless doesn't mean ventless, just that they are unable to vent enough to cause a dangerous gas mixture to occur, usually by a vent limiter (that further restricts the mounting orientation too). With nat gas, it just trickles out of the limiter (slowing response too, btw) and disperses, but propane, being heavier than air, will tend to collect in the low spots and may still build up to an explosive concentration.

    At least, that's how it was explained to me the last time I tried to get a 2nd stage propane regulator. The durn fool plummer took the line from the 1st stage regulator straight to the nat gas piping when they moved the bldg to propane while waiting for the gas company to feel like installing a new meter.

  • Zman
    Zman Member Posts: 7,611
    Am I picturing this correctly. You have a second stage regulator on the outside of the house that has an outlet pressure of 11"WC and a btu rating higher than the appliances in the house?

    If so why do you need another regulator other than the one installed inside the appliance?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • GaryAitken
    GaryAitken Member Posts: 3
    Ouch on connecting the propane 1st stage to the house.
    Thanks for the explanation; should have connected the dots myself. Guess I will put in a vented one and run it out.
  • Zman
    Zman Member Posts: 7,611
    The piping in the house needs to be sized for the low pressure. Usually the house is sized and run at low pressure.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • GaryAitken
    GaryAitken Member Posts: 3
    Thanks, zman
    Yes, the 2nd stage regulator is output 11" (Rego LV4403 B66R). The only appliances in the house are a 6 burner stove-top (no oven), and a 200,000 Btu/h demand heater. Internal piping is 3/4" iron to the heater and 3/4" (i.d.) CSST to the stove. Run to heater is about 10 ft. Stove about 40. Why the 2nd stage to the house is not 2 psi is beyond me. Installed about 18 years ago.
  • Zman
    Zman Member Posts: 7,611
    The propane company usually runs about 10 psi from the tank to the house.
    The second stage you have is usually mounted just outside the house.
    The entire house would then run at the lower 11" WC pressure.
    In this setup, there would be no need for an additional regulator on the appliance.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein

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