Transmitter plant ambient temps?

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RodeoJack
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Transmitter plant ambient temps?

Post by RodeoJack » Mon May 28, 2018 7:39 pm

I think this may be covered in an earlier thread. Feel free to redirect if you know where it is.

I'm currently dealing with a repair crisis, where a failed AC unit allowed a DX-10 to operate for several weeks in near-100 degree temps. That appears to have resulted in the final assault on already-aged filter caps. It's barely holding on while I wait for the delivery of a complete recap kit, That project is easily 4 or 5 years past due, if you go by the service bulletin on the subject.

Like processing, ambient temps seem to be a matter of personal judgment, rather than anything tangible. That said, what temps do you guys like to maintain in your buildings?

Much of what I take care of is specced to max into the low 120s, but getting even close to that has always proven to be a recipe for disaster.

Not having anything tangible to point to, I adopted the philosophy of a former mentor, who's opinion was that transmitters and associated gear would be comfortable in any environment that you'd also be.

That said, I don't get too worried about Winter temps that take a building into the low 50s, or Summer temps up to 85. Those have generally been my limits though. If I can keep a building stable at 70-75 or so, everything seems to be consistently happy.

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Deep Thought
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Re: Transmitter plant ambient temps?

Post by Deep Thought » Mon May 28, 2018 11:45 pm

Solid state equipment lifespan starts getting a lot shorter above 80°F ambient regardless of what the manufacturer says. It may be 20-25° warmer inside the box and those capacitors are gonna bake.

For tube rigs I like to see the stack exhaust below 120°F, which usually requires an ambient of around 80-85°. I know there are people who "get away with" much higher room temps even with solid-state transmitters and don't think air conditioning a transmitter building is cost-effective, but one prolonged heat-caused outage which requires multiple days of tech time to remedy can hit several multiples of a/c cost.

And then there was the building I encountered in southern Arkansas with no a/c, no exhaust fans (the plastic box fans employed had seized up) and a tube FM transmitter spewing somewhere around 5 KW in heat into the air because the RF coupling had failed but the plate overload had not been tripped. It took a half hour to cool the place down enough to stay inside for more than 5 minutes, and that was with a garage door open. Needless to say every piece of solid state equipment inside had died.
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ChuckG
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Re: Transmitter plant ambient temps?

Post by ChuckG » Tue May 29, 2018 12:24 am

Deep Thought wrote:
Mon May 28, 2018 11:45 pm
Needless to say every piece of solid state equipment inside had died.
The only equipment to survive a transmitter shack fire some years back were a pair of marti STL 10 receivers. No idea why.

A/C is rare in transmitter buildings up here in central WI, and many do not have heat either. Used to rely on the tube rigs for that, which are now in standby service. I regularly see building temps in the 40's during winter and upper 80''s in the summer. Below 40 and I'll run the aux into the dummy load for heat. What's that do for "plant efficiency"? lol. The equipment seems to survive, but I'd like a 10 degree swing a whole lot better.
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kcbooboo
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Re: Transmitter plant ambient temps?

Post by kcbooboo » Tue May 29, 2018 5:24 am

Of two sites I go to regularly here in Southern New England, one is cooled to around 74F and relies on the tube TX to heat the room in the colder months. It's fairly well insulated but with no trees around the building it definitely bakes in the hot summer. The other site is cooled to around 70F, which I consider to be too cold, and they have two 1,500w heaters running in the winter just to heat it up above 40. This is only a 1kw AM station and the TX heat output is negligible. In fact, the TX wouldn't care if it got down to 10F; it's all the support gear with computers and hard drives that don't like being cold.

I walked into one site a few years ago where the A/C compressor had popped its breaker. The over-temp alarm system was beeping loudly but the alarm panel wasn't wired correctly so notification never went out. Some other alarms were beeping; it was quite a racket. The room itself was 90F, the fan on the dummy load had turned on because its thermostat said it was hot (nothing was feeding the load either), the FM exciter had backed its power down and the TX followed to just below 50%. Once the breaker was reset and some fans were turned on to move 70F outside air into the room, things recovered after about half an hour, but they never found out how long it had been in this situation (possibly 3-4 days) because the remote control system had locked up due to the heat.

With all the alarms beeping, I completely forgot to turn off the burglar alarm when I opened the door, which added its beeping to the mix. The phone eventually rang when the chief engineer told me the alarm company had called the police who were on their way. That was the least of my problems. Luckily (to quote ObiWan in Episode 3), "I had the high ground" and the police would have had to get past the locked gate and then into the building. I wasn't a station employee but my name and phone number were on several call-out lists so I wasn't too concerned.

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Re: Transmitter plant ambient temps?

Post by TPT » Tue May 29, 2018 5:48 am

One of the problems with solid state transmitters is air flow. I have a pair of Nautel V1's that--when they worked--had constant problems with heat because of inadequate ventilation. The last working one had to be run with the covers off (usually on the floor--it was relegated to back-up use on loan to a local cluster).

I have one site in aa 60 X 40 former commercial garage--the transmitter run is 15 X 25. We put in central air for half the building and vented the main tube transmitter (Energy Onix ECO-4) through a hood into the adjacent garage. Works well in winter to keep the damp out of the garage, while the heat pump keeps the transmitter room comfortable. Now have an additional 3 solid state kilowatts running in the room for tenants on the tower. VS-1 with 800 watts TPO for a Class A, plus 3 translators--Gates air TPO 705 watts; BE STX 715 watts & BW broadcast at 295 watts. So far the A/C seems to keep up without much impact on the electric bill.

On the other hand have another site with a small (9X15) building with a single Nautel 10 kw FM. The NV10lt just doesn't seem to have much "pull" of air through it. Large window air conditioner (more like what you see in a hotel room) `doesn't seem to keep up. The Nautel is also vented through a hood--I had a blower installed near the outlet of the vent to the outside which seems to help air flow. At least there is not that much heat coming out of the transmitter--typically max of around 120 degrees.

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RGORJANCE
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Re: Transmitter plant ambient temps?

Post by RGORJANCE » Tue May 29, 2018 6:37 am

Here is another thing to consider. If you use a big exhaust fan to suck air out of the room, you create a negative pressure in the room which reduces the air density moving across the innards of the equipment. As your incoming air filters clog, you further reduce the room air density.

Use a forced air system that pushes air into the room thru filters. A single fan should be backed up by a second unit with separate air filtering. These are temperature controlled to produce more air forced into the room as temperature inside increases. I have used this technique in several locations. Both fans are over-rated for air flow so that if you sustain a failure on the first one, the second one will provide ample cooling.

Usually, equipment can tolerate quite a bit of heat as long as you move a sufficient amount of dense air over the components to exchange that heat.

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Re: Transmitter plant ambient temps?

Post by dbuckley » Tue Jun 05, 2018 4:29 pm

I remember being told about a semiconductor rule of thumb: every 10C extra temperature halves operational life.

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kkiddkkidd
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Re: Transmitter plant ambient temps?

Post by kkiddkkidd » Thu Jun 07, 2018 7:40 pm

dbuckley wrote:
Tue Jun 05, 2018 4:29 pm
I remember being told about a semiconductor rule of thumb: every 10C extra temperature halves operational life.
These days I see more problems with overheated capacitors and connectors than the actual semiconductors.

I have always used the rule of thumb that a decently cool (80's) degree tx room is better than one that zooms around from 65 to 95. Another rule of thumb is that if you are uncomfortably warm, so shall modern equipment be...
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dbuckley
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Re: Transmitter plant ambient temps?

Post by dbuckley » Sun Jun 10, 2018 2:26 pm

kkiddkkidd wrote:
Thu Jun 07, 2018 7:40 pm
Another rule of thumb is that if you are uncomfortably warm, so shall modern equipment be...
I hear you on that :)

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Re: Transmitter plant ambient temps?

Post by radio_guru » Mon Jun 18, 2018 11:59 am

Let me be quick to the point....One needs to consider UPS batteries first and foremost over the SS gear.

Lead acid cells designed for UPS service loose considerable capacity and life span when they get too hot or cold regardless of draw or charge state condition. While SS gear can tolerate temps below 30 and above 100F., UPS batteries are not as forgiving. They want to be kept at 60-75 deg. with a preference to about 65 deg. Go outside of that for any length of time, and you'll be replacing them shortly thereafter. BTDT.

And we all know how important UPS's are at TX plants these days.

RG

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Re: Transmitter plant ambient temps?

Post by Scott.Cason » Sat Jun 30, 2018 9:04 pm

RodeoJack wrote:
Mon May 28, 2018 7:39 pm
That said, what temps do you guys like to maintain in your buildings?
lower 80s for solid state transmitters. mid to low 70s for tubes. I also put temperature sensors at every transmitter site that starts calling out when the room temperature reaches mid 90s and starts shutting stuff down via macros in the remote control when the room temperature reaches 100.
LaGrange Communications - http://www.lagrange-com.com
Froggy 95.9 - http://froggy959.net/

RodeoJack
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Re: Transmitter plant ambient temps?

Post by RodeoJack » Sun Jul 01, 2018 9:14 pm

Scott.Cason wrote:
Sat Jun 30, 2018 9:04 pm
RodeoJack wrote:
Mon May 28, 2018 7:39 pm
That said, what temps do you guys like to maintain in your buildings?
lower 80s for solid state transmitters. mid to low 70s for tubes. I also put temperature sensors at every transmitter site that starts calling out when the room temperature reaches mid 90s and starts shutting stuff down via macros in the remote control when the room temperature reaches 100.
I'm doing something along those lines, but my macros reduce power before they get to the point where I consider shutting the transmitter down. So far, lowering the heat load tends to do the trick.

After having the caps bake out of a site where the AC failed, I do have a shutdown macro written into that RC. Fortunately, they repaired the old AC and added a new one that' keeps the room at a comfortable 75. Seems the downtime (they were off for 3 days before they called us in), coupled with the cost of overnighting a full cap kit, the 3rd major rebuild of the old AC, the new split unit, mowing down the waist-high grass and 3 trips across the state for my daughter and me made the requisite impression.

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Re: Transmitter plant ambient temps?

Post by kkiddkkidd » Wed Jul 04, 2018 5:29 am

RodeoJack wrote:
Sun Jul 01, 2018 9:14 pm
Seems the downtime (they were off for 3 days before they called us in), coupled with the cost of overnighting a full cap kit, the 3rd major rebuild of the old AC, the new split unit, mowing down the waist-high grass and 3 trips across the state for my daughter and me made the requisite impression.
The old, "you can pay me now, or pay me later" syndrome that seems to pervade radio.
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Re: Transmitter plant ambient temps?

Post by RFWarrior » Mon Jul 23, 2018 8:49 am

Semiconductor, electrolytics and fans all like room temp to be, well, room temp. Most fans, for example, are rated at a nominal 5 year life span at 40 degrees C. (104 deg F). For every 10 degrees C (18 deg F) that you decrease the temperature, the nominal life span doubles... so 10 years at 30 deg C (86 deg F), 20 years at 20 deg C (68 deg F). Obviously there's a point of diminishing returns as you get down near freezing and any lubrication starts to thicken...

On the alternate side, a lot of transmitters don't like to be below freezing - for the above reason... relays stick, any moisture in the air condenses, blowers slow down due to lubrication viscosity - my ideal site would be 65-70 degrees, all year round, positively pressurized with thermostatically controlled motorized louvers to allow exhaust air to dump into the room when heat is needed or to vent it outside in the case of an AC failure.

One other big gotcha is air flow direction - you can have an extremely well air conditioned and ventilated site, but if you're forcing air past the intakes of the transmitter at 90 mph, so that there's a negative air pressure in that area, the transmitter will still overheat. By the same token some (*cough* Bard *cough*) air conditioners are built upside down for broadcast - they take air in from floor level and send cool air out at ceiling height. In an office or home setting, this makes sense - the cool air spreads throughout the room and sinks, cooling the people quite efficiently. In a transmitter site, where gear takes cooling air in the front or rear and almost always spits warmer air out the top, you end up with a lot of circulation issues - bad airflow and incredibly inefficient cooling. If you have one of these setups, spend the 500-1000.00 with a sheet metal tech to redirect airflow and you'll see a noticeable difference in equipment temps.
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Scott.Cason
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Re: Transmitter plant ambient temps?

Post by Scott.Cason » Sun Aug 12, 2018 12:16 pm

RodeoJack wrote:
Sun Jul 01, 2018 9:14 pm
Scott.Cason wrote:
Sat Jun 30, 2018 9:04 pm
RodeoJack wrote:
Mon May 28, 2018 7:39 pm
That said, what temps do you guys like to maintain in your buildings?
lower 80s for solid state transmitters. mid to low 70s for tubes. I also put temperature sensors at every transmitter site that starts calling out when the room temperature reaches mid 90s and starts shutting stuff down via macros in the remote control when the room temperature reaches 100.
I'm doing something along those lines, but my macros reduce power before they get to the point where I consider shutting the transmitter down. So far, lowering the heat load tends to do the trick.

After having the caps bake out of a site where the AC failed, I do have a shutdown macro written into that RC. Fortunately, they repaired the old AC and added a new one that' keeps the room at a comfortable 75. Seems the downtime (they were off for 3 days before they called us in), coupled with the cost of overnighting a full cap kit, the 3rd major rebuild of the old AC, the new split unit, mowing down the waist-high grass and 3 trips across the state for my daughter and me made the requisite impression.
That macro was for the old Harris rigs I had. After installing new Nautel transmitters with HD, I now have the macro recall the preset without the HD signal. That reduces the heat load, and keeps the stations on the air while waiting on the HVAC techs to show up.
LaGrange Communications - http://www.lagrange-com.com
Froggy 95.9 - http://froggy959.net/

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