sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1A2 , 551A KSU Heat Tolerance Question

Who can tell me about practical heat tolerances for 1A2 systems, please? I have a 551A unit and would like to know if I can safely locate the KSU in my attic or garage. Although the garage is relatively cool, it gets hot up in the attic sometimes. But, the attic has a powered exhaust fan. I leave the thermostat at 95 degrees F so it doesn't pull too much power. Should I set the temperature lower? May a working 1A2 system be safely put in such places?

Comments? Witness?

Kind Regards,

Mark

95º F is a little hot. I would suggest a few degrees lower, or put it in the garage, just for peace of mind.

An attic fan thermostat set at 95 degrees only means that this is the cut-in (on) temperature. I can assure you that an attic in the Atlanta area in July will never fall below this temperature until long after the sun sets, if at all.

The 551 relies upon mechanical components and technologies that were developed back in the days when customers did what the telephone company told them to do with regard to environmental/electrical specifications. I can't tell you how many telephone "rooms" I have encountered that were wired/designed to Bell standards for just a large key system.

On the other side of that coin, I've seen many if not most 551's installed in garage environments. Honestly, I've only seen this to be the norm by Bell companies North of the Mason-Dixon Line. From my experience, most homes in those areas are older and if modern enough, they were pre-wired with a six-pair loop that originated in the garage. Many, many 1A2 tricks could be pulled with a six-pair loop, so the KSU ended up there by default.

In a garage in the South, I'd be concerned with the humidity factor more than anything.

The 551 Shoebox is pretty durable BUT like Arthur & Ed said 95+ is a little too hot.

I checked the BSP (SECTION 518-215-407 Issue 2, June 1981) and there was no mention of environmental conditions there, but somewhere there's probably a Generic environmental spec for all Key Systems. If I get a chance I'll look for it.

But I assure you that 95 deg. is going to be out of spec.

Sam

Thanks, guys. All good points. I've learned so much reading through the board and have put it to practical use, sort of.

Where shall we put the unit, then?

How about cold tolerances? The garage looks like a better choice but the garage will be in sub freezing temperatures for days at a time in the winter.

There's a closet in the garage. What if I put the KSU in the closet with the gas water heater? There's plenty of room and it will stay warmer in the winter. Would there by any realistic safety concerns (the obvious being gas/sparks, water/electricity) in the same closet?

I'm half finished wiring my backboard. The system works but it doesn't look like the nice photos you guys have posted.

Mark, my first thought is that I'd go with the garage closet. I'm not sure if local codes would preclude this (especially if the closet was put there for the sole use of the water heater). You might want to double-check that.

Frankly, electronics like cold temperatures a lot more than warm ones, so I'd say that placing it in the garage toward the back (closed) end would be best. That way you would avoid the temperature extremes and not risk the gas issue. Since the relays and interrupter contacts do make tiny sparks when operated, I'd stay away from any possibility of risk if there was a gas leak in an enclosed environment.

Feel free to post pics of your backboard if you'd like a professional and unbiased opinions or suggestions. We are here to help, not to insult.