VERY UNEVEN COOLING.! PLEASE HELP

STEAM DOCTOR

Good afternoon. The synagogue that i pray in on the high holy days has a serious issue with uneven cooling. The supply registers are all in the ceiling in the front of the room(it's a very large room; holds a few hundred people). They are approx 1/3 of the distance from the front of the room. The return registers are in the ceiling all the way in the back of the room. During the year when the synagogue is not that full the AC is adequate. The problem is that on the high holy days the room is packed to it's legal limit and the air movement is greatly affected. Typically  on these days there is a 20 degree difference between the front of the room and the back. If the people in the front are comfortable the people in the back will be sweating and if the people in the back are comfortable the people in the front will be freezing. To deal with problem they added ceiling fans a few years back. There are 3 fans (right to left )between the front wall and the supply registers, 3 fans in the middle of the room and 3 fans between the middle fans and the return registers. The idea was to help circulate the air around the room. This not helped at all and I'm fairly certain that the problem has gotten worse with the addition of the fans. There is no way that the synagogue administrators would agree to any expensive renovations. The one idea that I had was to disable the front  and middle fans. The logic behind this idea is that hopefully the rear fans will create a sort of sucking action due to the lower pressure resulting from the higher air velocity in the back of the room. Any insite that any one can share would be much appiciated. Thanx and a happy (Jewish) New Year to all.

nicholas bonham-carter

uneven cooling

why not try this for a while: leave the fan switch on the thermostat set to "ON" instead of to "AUTO". this may even out the temperature differences from front to back, as the fan constantly moves the air through the system. i do not think the cooling part of the system will run any more with this setting. during this experiment, you should turn off the fans. a couple of very accurate, and now inexpensive digital thermometers will tell you what the temperatures are front and back.

other things to check would be the location of the thermostat-could it be in bright sunlight streaming through a window or such? is the thermostat accurate? remember that a bump to it can throw it out of level, and out of calibration.--nbc

STEAM DOCTOR

thanx

I will give it a try. I don't think the thermostat is the issue. The thermostat has been replaced a number of times over the years without any effect on this issue. The cause of the problem is that the supplies are only in the front of this very large room. When the room is very crowded the air has trouble getting from the front of the room to the back. Thanks again!

STEAM DOCTOR

smoke

What do you think of using smoke to try to gauge the direction of air movement in the room

nicholas bonham-carter

gauging the airflow

just try the fan setting to begin with, using some digital thermometers to measure the temperature differences.

my point about the thermostats was not about their age, but placement and calibration.

is the temperature setting remaining constant, or is it changed before the services?

has the system received regular service, or at least had the filters changed [for good airflow]?--nbc

STEAM DOCTOR

airrflow

I don't think that there are any problems with the components of the system. The system works fine 362 days a year The only times that the above problems exist are on the two days of Rosh Hashanah and Yom Kippur. The only thing that is different  on those three days is that the room is filled to capacity and the the cold air can't make it from the front of the room to the back. There really is no good way to test anything because there is no balance problem on regular days and testing on the holidays  is out of the question due to religious restrictions on these days. 

STEAM DOCTOR

thermostat setting

During services the thermostat(which is in the hot back of the room) is set for 60 but since it's in the back the room temp reading dosn't go below the high 70's

nicholas bonham-carter

uneven cooling on holy days.

the registers in the ceiling may not be spreading the airflow enough so that all the cold air coming from them is hitting one small area [the north pole of the room].

different registers might help to spread out the air flow, as well as moving the thermostat to the cooler area of the room.

are there any strong lights which could be interfering with the temperature? a switch to CFL's or LED's may help. the point i wish to make is to reduce the time that the system is cooling, while a large number of people are in the room. it should be only their body heat which causes the compressor to run, not the lights.

other advice, may be also had by re-posting your question in the A/C section on this forum.

in the meantime just set the fan to constantly on, and if the A/C has been off before the service, turn it on earlier so that the thermostat is satisfied before people arrive.--nbc

nicholas bonham-carter

finally the summer is almost over!

as least, i hope your heating system is working for the temple........nbc

jpf321

it could simply be that ...

the system wasn't initially sized properly .. a properly sized system would have taken into account the MAX #of 98.6dF human bodies as the design cooling load.



be careful with the downward directed fans .. they may create a pressure wall or front that may keep the air from penetrating .. you may try to reverse the direction of the fans, if possible, in the front have them create an updraft and then use the fans in the back as a down draft .. it's just an idea.



i guess in this case, it pays to be early to the services :-)