Hayward H100ID propane not igniting

[joshuam]

I've got a propane heater not igniting and I would sorely appreciate any advice. My troubleshooting, with only one concern, suggests that it should ignite!

I have a Hayward H100ID Spa/Pool Heater, Propane. It’s hooked up to a propane canister (not tank) via a 100,000 btu regulator. I’ve taken it apart and verified that the orifices are clean - the whole machine looks very clean (I bought it used, but minimally).

When the thermostat calls for heat, the blower starts up. Gas output pressure at the valve is ~2” WC. Input pressure, however, is higher than called for - maybe 15-20”? This is issue #1; I'm not clear about pressure off this canister.

The heater does not ignite. I’ve pulled the ignitor, and verified that it’s sparking like mad and has no carbon buildup. It’s clean and white, with about a ⅜” gap. The gas valve audibly clicks, and I can smell gas. (Issue #2)

My questions:
1: Why does my 100kbtu regulator (brand new) provide so much pressure? Is this the right amount, and if not, how does that work? The heater wants 100kbtu in, so a 100kbtu regulator seems correct. I'm comfortable with most of the rest, but I know little about propane cans (I'll be replacing that small can with something larger later on.)

2: In any case, given the output pressure is correct, am I justified in thinking that there is some other problem preventing ignition?

3: What could that other problem be? What else could I check?

Thanks a million y'all;

Joshua

 

[joshuam]

I should mention that I checked the blower's grey hose and it's fine - in any case, gas is being dumped into the heater so it's not any of the safety devices - as I understand it, if any of them were not working, the whole shebang would fail to turn on.

 

[bk406]

How big is the propane canister? You dont have an adequate supply of gas.
Propane exists in the tank as a gas and a liquid. The suface area of the tank dictates how much gas is available at any one time. As the gas is pulled out, the liquid vaporizes to replace the gas that was used. Depending on the air temp, there may only be 60% worth of usable propane in even a full tank. The hotter the air temp, the more gas in the tank. If you have a large appliance like a pool heater pulling a large amount of gas, it will use the gas rapidly. You also need ~11 inches WC at the heater.
You need a 100 gallon tank to run that heater.

 

[joshuam]

Thanks a million for the response. I think you're right.

I'm trying to understand, though, how that is the case, given what I'm seeing. Pre-manifold, I have 13.4" WC. That seems like enough pressure. Is it that, due to the lower level of gas in the can, I'm getting less overall flow through there once the can is half empty? (I've gotten the heater to run perfectly, twice, both times on full cans. It runs until it reaches temperature, but then shuts off and doesn't restart. (Hence I suspect you're right.)

Is it that there is enough pressure in the can to give me the 13.4", but insufficient to maintain it? Or is the 'flow' related to the BTU capacity of the regulator? The relationship between regulator BTU rating and pressure rating puzzles me; this says it's a 75kbtu regulator, 0.5psi.

Thanks again for the input!

 

[bk406]

Is it that there is enough pressure in the can to give me the 13.4", but insufficient to maintain it?

Basically, yes. You dont have enough volume of gas to maintain the heater's use of gas. You need a 100 gallon tank, at the least.

 

[joshuam]

Thanks. Understood; 100 gal tank.

I'm still not clear how a larger tank produces the needed pressure. I think that perhaps not enough propane can vaporize quickly enough within the tank to maintain the pressure?

Anyway, thanks again. I really only intended to test the heater with this small can, and then get a larger one. If I could understand the physics behind sufficient vaporization, I could better predict how often I'd need to get a refill, etc. . . . but I can always find out by just buying one and checking.

Thanks again.

 

[bk406]

Again, it's not really a pressure issue per se. It's the fact that the tank isnt big enough to hold enough propane to sufficiently supply enough vapor to the heater. The larger the tank, the more surface area that is available to help vaporize the liquid. The 100k heater pulls the vapor out faster than the remaining liquid can be vaporized; it cant keep up.

 

[joshuam]

Great! Surface area is what I was looking for; it's not strictly the volume of the tank, but its greater diameter that makes the difference, then. So even a 20gal tank is not going to work; the larger volume is insignificant. It's that the 100 gal tank is horizontal and has more exposed liquid for vaporization that's going to make the difference.

What's odd is that the heater runs fine until it turns off. I suppose more flow is needed for initial ignition than to maintain the heat.

I wonder whether I could hook up a couple cans in parallel to provide additional vaporization surface. I will find it hard to put a 650 pound tank in there (100 gal), because it's a hard-to-reach location - but I could truck in 20lb cans without much trouble. What do you think?

 

[joshuam]

Thanks for the very informative reply. Most of the people I've talked w/ about this don't really seem to understand what gas systems *do*.

 

[Bama Rambler]

You can hook two cylinders in parallel, in fact our RV has two 30lb cylinders hooked in parallel. However, I'm not sure that would completely solve your problem. That's still a pretty small surface area for a 100k btu output. Our RV furnace is a 30k btu unit and on a cold day we can freeze a cylinder down.

How is your regulator hooked to the cylinder?

 

[joshuam]

Thanks for that idea! As it turns out, in 60 degree temperatures, a cylinder is plenty of surface area for 100kbtu (though the parallel hookup was my next step - where did you find the hardware to do that? What's it called?). At 50 deg, it does freeze up eventually, but it will at least start (and run for an hour or two).

As it turns out, all that it took was a larger feed hose - even though it was very short, the 5/8 hose was not wide enough. Replaced it, and all is good. Thanks for the help.

 

[Bama Rambler]

The parallel hookup is a standard RV hookup. If you get ready to do it just search for RV propane regulator. Or you can just buy high flow (green ACME nut) pigtails and tee them together and hook that to your regulator.

 

[joshuam]

FWIW, this heater runs fine on 5# cans. I get about 5 hours out of each one. One is more than enough to heat all 500 gallons up to 104 or so, and then each can lasts a week or two. Initial heating will freeze out a can, so I swap part way through to allow it to warm back up. In case this is useful to others.