Flutter sound - Martin Propane Direct Vent Heater MDV20VP

loltun9

Just installed this heater and had propane company come hook up the propane line to it. He did a pressure test and adjusted the pressure at the main pressure valve per heater recommendations. It has another pressure valve closer to the unit (maybe 7-8ft) and he didn't do anything with that one.

I Ran the heater for a few hours and didn't notice anything out of the ordinary. It had some initial burnoff smell and some crackling/popping sounds as the metal heated up. Temps were mild today only in the 50's.

After about 4 to 5 hours running it, when I was outside by the vent, I noticed a sound coming fromm it that was hard to describe. I thought it was muffled rattle type sound but soon realized it sounds more like a flutter.

When inside and listening to the unit it seems to be coming from the area where the exhaust tubes are located (Outer tube has air intake that surrounds an inner tube which is the exhaust). The pilot flame looks consistent and good from low to high settings.

It seems to have more flutter at lower temps and even with the burner isn't going, only the pilot vs when it's turned up higher...but that could also be because the gas and unit is louder when it's running high and I just can't hear it as well. As soon as I turn off the pilot, it goes quiet.

I've kept it off because I don't know what damage I could do not knowing what the issue is. Any ideas before I pay the propane service tech another $100 to come look at it? Thanks

retiredguy

You did not say the size of the heater or the propane tank supplying that heater. If the propane tank is too small, the tank pressure could fall below the required minimum inlet pressure for the device. As you use the propane gas for the heater more gas is evaporated from the liquid which causes it to cool and lower the tank delivery pressure.

loltun9

Sorry about that. It's a 20,000 btu heater and it's hooked up to a 320gal propane tank that has 2 regulators running. Propane tech checked pressure at first gauge at the tank, but that's it. When I told him it needed to be adjusted to 11 to 13 WCs based on the manual specs, he said we don't do that, we do pounds. It's getting 20lbs of pressure.

EdTheHeaterMan

There are different parts of a profane gas company. The drivers of the deliver trucks. The technicians that do the tanks and first stage pressure regulators. The guy you need is the one that connects the appliances. they have the gauges the do the inches WC. they also have more experience and may even do furnace and boiler repair that include controls, heater piping and circulators and even some ductwork to swap out a propane furnace from time to time. The smaller LP gas companies may not have the appliance tech. All they do is to shut off the gas if there is a problem with an appliance that they feel is not safe to operate.

Depending on your LP supplier, you may or may not need to get an HVAC service tech. Call the Gas supplier and ask for appliance service on a space heater. If they don't ask them if they can suggest someone they know is good at fixing Space heating appliances

loltun9

Thanks @EdTheHeaterMan. The propane company I used, is the place I rent the tank from. I told them specifically what I had installed and needed it hooked up to the propane line already coming through my wall and adjusted to the right pressure for this heater. I'm waiting for the manager who is in charge of installation/repair crew to call me back. I'm not sure they have all those different kinds of technicians, but will ask. When I spoke with him the first time, before he sent the guy out, he just said ok, Ill send out "Bob." I appreciate this insight. I assumed since they hook wall heaters up all the time around here they would be well versed in 'adjusting' new ones they hook up at the time of service. One shouldn't assume.

kevster

@loltun9 Did you ever figure out the problem? My gas fitter doesn't have a clue and the manufacturer isn't being much help!

mattmia2

You need to find a gas tech that understands combustion. Look for someone that is nci certified.

rick in Alaska

What you need is someone who knows that heater! It sounds like the heater needs the air/fuel mix adjusted inside of it. You will need someone who has a manometer, combustion analyzer, and the manual, and knows how to use all of it. My guess is not enough combustion air.

Rick

Bob Harper

You should have a 2 stage regulator system. The red or high pressure regulator takes the 100-150 psi typically found in the gas cylinder/ container and drops it to 10 psi. That gets delivered to the side of the house where the brown second stage regulator drops it to 14 inches of water column, which is the maximum the gas control valve in the appliance can handle. If that appliance has seen psi, you need to shut it down, replace the combination control valve, then correct the inlet gas pressure. The combination valve typically comes with test ports on the valve for the inlet and manifold pressures, which must be within spec.

If the second stage regulator is chattering or unable to provide consistent downstream pressure, replace it. It must have an upstream shutoff, sediment trap, union or means of disconnecting, the regulator and a means of attaching a manometer for the delivery pressure within 18" of the regulator. Do NOT operate the appliance if the pressures, valves or regulators are defective.

It is uncommon for a direct vent straight through the wall to resonate without cause. It is a very simple system: air in, stuff out vent. If the gas control valve, pressures, orifice and air shutter are properly set, problems are rare.

As noted above, make sure all this is set correctly then run combustion analysis to ensure proper setup and performance.

kevster

I had another guy come in (owner of different company of 10 guys) today $$$$ later and he didn't have any luck either. Even replaced the reg with a more expensive one so we could get the higher WC the mfg told me to do. (I've got 3 regs, one at the tank, one at the house, and then another dedicated one to knock it down to inches of WC). Confirmed inlet, manifold WC, all is as specified. It has never seen PSI.

It is very bizarre makes no noise for the 1st minute or so of pilot light burning and then it slowly starts up like popping corn until it sounds like a boat idling. If I turn down the pilot light to minimum, then it stops, but is too dangerous as it might not be enough to light the burner while the thermocouple is still satisfied….

Flames are all nice and blue with the little bit of LPG yellow on the tips every now and then..

The unit is ever so slightly unlevel side to side but perfect with slope down the vent, could this be causing issues?

Kaos

Sounds like you might have a pyrophone there:

https://londonist.com/2007/07/the_gas_organ

Had a similar issue with a power vented water heater before, low frequency resonance in the exhaust when it fired, added 3' of length to the exhaust which stopped it. Not easy to try with a direct vent.

kevster

I think I have finally found the culprit, don't know what to do about it, but hey, if any of you know! It has to do with the appliance pilot light area heating up. It pops once it gets up to a certain temp (no burner on), and if I put a fan and blow on the pilot/ignitor/thermocouple mount, the popping subsides as it cools down……..so wierd……

If I turn the burner on the popping gets much faster, and I need to turn it off in order for the fan to blow away the excess heat to bring the popping down.

The gas line into the pilot does heat up to over 100F which seems odd to me….but maybe that is normal.

Any ideas.