SSB & Propane Fume Detector Problem

[addimaui]

I am looking for some suggestions on how to resolve the following problem.

Within the last week or so, everytime I try to trasmit on my ICOM 710, the Propane fume detector (Xintex S-2A) alarm start beeping. Twice while I have pushed the silence alarm button, the SSB circuit breaker popped. DC current while transmitting generally did not exceed 15 amps, but when it flirted with 15 amps the breaker disconnected. I believe that one of the sensors on the detector is faulty. If I test sensor # 2, an amber light is shown, which seems to indicate a faulty sensor. Prior to this, the SSB has been flawless.

Unless other advice is given, I am going to disconnect sensor #2. I can't see how SSB operation would cause propane to leak.

Addison Gooding
S/V Koana

currently anchored off Provo in the Turks & Caicos

[Rick]

As convenient and pretty it is to have a circuit breaker dedicated to your SSB show up on your breaker panel, it is more reliable to have a 30Amp fuse from a battery post to deliver power to your SSB via #10AWG wires or larger.

Circuit breakers drop more voltage than do fuses and a good 30A fuse will not make a significant voltage burden when operating your SSB. Now, if you use the ICOM parts provided you already have fuses at the transceiver to protect from internal problems. Use both.

The better that your antenna is to being resonant on your frequency of operation (assuming a good antenna ground as well) the less problem you will have, in general, with nuisance interferrence from the rf output to various electrical components on the boat like with your propane detector. If you have a bad propane sensor it has nothing to do with the SSB causing a breaker to open. If you have very bad SWR on transmit the question is whether or not that could cause the destruction of a propane detector...guess it is possible, depending upon your installation.

[Alan Wheeler]

The only addition to Rick is, is it possible that a low voltage on your supply is occuring during transmit. If there is some fault with the SSB or you have a poor DC connection somewhere up stream, the voltage could be dropping enough to give your detector an erroneuose signal or operation.

[Rick]

separate the two circuits as previously described just to start.

[addimaui]

Thanks Rick and Wheels,

After spending more time, I find that the fault occurs when the refrigerator is running (6.5 amp). I assume the voltage drop under with the two loads trips the SSB breaker. (However, my link 2000 didn't show more than .05 to .10 volts dropped. Will check this out with the Fluke.) So for the meantime, I haven't lost transmitting ability.

Next job is to add a fuse block w/30 amp fuse and bipass the breaker. Still confused about this situation causing the propane detector to go to alarm status. RFI, EMF, maybe. The antenna wire passes within maybe two feet from the main propane sensor, but this doesn't seem to be the one going into alarm.

Addison

[markpj23]

Perhaps a bad / loose ground connection on the propane detector? If you can measure the voltage at the detector when you transmit that could also give you a clue. They all go into alarm for low voltage.

[hellosailor]

Addison-
You may have an RFI (radi frequency interference) problem. Alarm systems and sensors are known to trip when a high power radio transmitter is being used right up close to them. That could mean you need RFI supression near the propane sensor (sometimes a simple capacitor will do, other times a ferrite bead or choke is needed, neither is expensive) to stop a false trip.
But, if your diagnostics say the sensor is bad, it is time to replace it anyway. If the problem continues, add the RFI suppression.

You are blowing the 15A breaker quite simply because the radio has been improperly installed. According to Icom:
"Power Supply Requirement: 13.6 V DC +/-15%
Current Drain (at 13.6 V DC): Transmit (max. output power) 30 A"

That radio requires a dedicated 40Amp fuse or breaker direct to the batteries. Note that it DRAWS 30A which means it will blow a 30A fuse in very little time. It may not blow a 30A breaker as quickly--but it will eventually destroy one by "teasing" it at the full rating.

The RFI problem may also indicate that you have an SWR problem and inadequate grounding (or counterpoise). If you have an autotuner it may be installed incorrectly, that can cause RFI problems while hiding poor SWR. Since the power to the radio was improperly fused/installed, I would expect to find other basic problems like that. (It isn't all quite plug-n-play, not if you want it to really work right.<G>)

Also note that Icom expects the radio to work on 13.6VDC and they really mean 13.6, not 12V. Their radios often suffer performance problems with low voltage, and that means you really need a DC-to-DC converter (a "buck boost") to ensure the radio sees 13.6-14.4 volts when the alternator is not running.

Of course operating at reduced transmit power will also help avoid the problems, but that's not fixing anything, sometimes you'll want or need full power.

As Rick notes, you should be using heavy battery cables directly to the radio. You will find online calculators that tell you what cable size to use based on the number of feet (round trip, not one way!) to the battery. For instance, if the power cables need to be routed 25' to the battery, that's 50' round trip. For a 30A power drain and a voltage drop of 3% (reducing a typical 12.4V to an unstable 12.0 volts which your radio will NOT be happy with) you'd need something between a 4AWG and 2AWG battery cable. (Heavier for welding cable, no savings there.)

Another good reason to compromise (i.e. with 4AWG cable) and install a dc-to-dc converter right at the radio, so the line losses won't affect getting full power to the radio and you won't need wrist-thick cables to feed it.<G> Powerstream is one company that makes these converters, not terribly expensive ($150?).

That voltage drop in the cable can be critical for stable performance from battery power, and will affect your output even when running with the alternator. Your entire problem with the propane sensor *might* be from RFI because the radio is not getting enough voltage to operate properly. (It should only be that easy.<G>)

[Strygaldwir]

I use a seperate 30 amp breaker for my SSB. No issues on transmit. I'd expect 15 amp to trip when you are transmitting. Aren't the 710s rated for 300 watts? (300/12.5 = 24amps, no?)

Keith

[hellosailor]

The 710's are rated for 150W PEP emissions of tx, but you have to remember that is the OUTput and not the INput required to make it.

They are also rated at 13.6V, not 12.5V, and they are rated for 13.6V at 30A, totalling 408 watts input during transmit. At 12.5V that would mean 32.64 Amps drawn.

A 30A breaker typically will not open until something like 40-50A has been drawn for several minutes, so in theory it would hold for this radio. But in practice, you are consistently overheating the breaker and that will lead to it failing sooner and faster, especially if it is a thermal (rather than magnetic) breaker. Fuses have an advantage here, they will blow much faster and that's arguably a better way to protect the radio. Using a 30A breaker for a 30A load would violate every "rule" including rule of thumb for circuit protection.<G>

[Rick]

The ICOM specifications for maximum input current were placed there by some marketing guy who merely copied the fuse specification. The transmitter in the SSB mode is only rated for 150WPEP which will average 75 WAtts if speaking very loudly and continuously into the mike by a harried housewife. In the transmit mode the power drain will be typically less than 10 Amps. You will never blow a 30A fuse with this transmitter unless you short the supply wires. The fuses supplied by ICOM ARE 30A fuses and, by no means, do you need 40A fuses.

[Rick]

This transmitter IS rated to operate above 11.5V at specified output power. I can tell you that it will operate down to 10V but not at rated output power, not a bad deal. The design engineers at ICOM are not so misinformed that these units would only be operated at 13.6V and, in fact, are designed for battery operation with the attendant voltage fluctuations.

It is not economical or necessarily desirable in a boat to install a dc/dc converter merely in an attempt to keep the input voltage at 13.6V. Only very expensive dc/dc converter designs will function at sufficiently high efficiency over the entire input power range of the transciver an all modes (TX/RX and different modulations) so as to make them desirable. In fact, many such converters draw 2 Amps or more as a parasitic load just being turned on and delivering no power to the transceiver. Why unnecessarily drain your batteries listening to the radio?

The power output differences, in fact, are greater according to who is using the mic in SSB mode than is any battery voltage variation going to cause an SSB PEP output power variation. If you have access to a true output power meter try it yourself sometimes into a dummy load and you will be surprised at just how different operators cause radically different output power.

Again, these transeivers ARE designed to operate with the normal loaded lead-acid battery terminal voltges.