Batboard

Does anyone have has the BTU/HR figures for the "typical" Motorola repeaters? IE: MTR2000 100W UHF 1160 BTU/HR

I have googled it to death & come up empty for the quantar & STR3000

Martin

Just out of curiosity, why would one need to know this? I assume that you are factoring this in for HVAC system design for use in a shelter.


If my assumption's correct, knowing the heat release numbers for a similar piece of equipment could be used in modified form for estimation purposes while being safely conservative. (BTU of other unit x 2). Also, if this is actually a published number, at what duty cycle of transmit is this heat number at?

jim wrote:Just out of curiosity, why would one need to know this? I assume that you are factoring this in for HVAC system design for use in a shelter.

If my assumption's correct, knowing the heat release numbers for a similar piece of equipment could be used in modified form for estimation purposes while being safely conservative. (BTU of other unit x 2). Also, if this is actually a published number, at what duty cycle of transmit is this heat number at?

Jim,
It is for a shelter HVAC calculation. As for the duty cycle 100%, CCS.

I would go for conservative engineering of the HVAC system, but also want to avoid short-cycling the units.

Martin

A 110W Quantar requires about 600W of power in, which means that about 400-500 watts of power have to be dissipated via cooling. According to the Glover "Pocket Reference," one watt is equal to about 3.4 btu/hr. So figure on the order of 1,500 btu/hr. cooling load on your equipment environmental system.

spareparts wrote:..., but also want to avoid short-cycling the units.

Martin

Good idea. There is a Cingular shelter at our FH. The thing must turn on and off 2 or three times in one minute. I don't know how it hasn't crapped out yet but it is annoying as hell to listen to.

nmfire10 wrote:

spareparts wrote:..., but also want to avoid short-cycling the units.

Martin

Good idea. There is a Cingular shelter at our FH. The thing must turn on and off 2 or three times in one minute. I don't know how it hasn't crapped out yet but it is annoying as hell to listen to.

To be honest, I'm cheap (as hell) and do not want to waste the electricity starting the HVAC compressors multiple times. And as you inferrred, making the unit crap out waay before it's time.

Martin

[quote="nmfire10"][quote="spareparts"]..., but also want to avoid short-cycling the units.

Martin[/quote]

Good idea. There is a Cingular shelter at our FH. The thing must turn on and off 2 or three times in one minute. I don't know how it hasn't crapped out yet but it is annoying as hell to listen to.[/quote]


Sounds like your talking about one of the wall hung air units on the typical concrete shelters. In the winter time the fan outdoors will short cycle. The compressor is probably running steady while this is going on. During the cold weather, it is normal for the outside condensor fan to come on and off like your descibing. As long as the compressor isn't doin't that.

Jim

Yea, it is one of those big wall hung units on the hut. Thing is, it does this 365 days a year.

Watt's don't convert exactly; it's watt-hours that converts to BTU. So, if your load is constant, the load in watts just happens to be the watt-hours.

Yes,

1 Watt Hour = 3.41 BTU

Then, in cooling tons:

1 Ton Cooling = 12,000 BTU / hr.

You'll also need to add in a factor for the temprature rise for the outdoor heat coming in through the walls and roof through the insulation. This is ofte a big number.

Don't oversize or undersize the unit. If you undersize, of course, it can't keep up, if you undersize it can cause the unit to short cycle or cause the coils to freeze up. It's a delicate balance.

Good Luck, Bob

Watt's don't convert exactly; it's watt-hours that converts to BTU. So, if your load is constant, the load in watts just happens to be the watt-hours.

Yes,

1 Watt Hour = 3.41 BTU

Then, in cooling tons:

1 Ton Cooling = 12,000 BTU / hr.

You'll also need to add in a factor for the temprature rise for the outdoor heat coming in through the walls and roof through the insulation. This is ofte a big number.

Don't oversize or undersize the unit. If you undersize, of course, it can't keep up, if you undersize it can cause the unit to short cycle or cause the coils to freeze up. It's a delicate balance.

Good Luck, Bob