HVAC Question

No problem.....the system is probably designed to supply fresh air 24/7....

No ,its supposed to cool down the room temperature and maintain the temperature.

Find another job. This project is doomed.

If the compressor runs all the time and the evaporator is icing, you're toast.

I hear they're hiring in the fracking (gas) fields in North Dakota.

More detail is needed in the description. Where would you locate the "central" thermostat? What other controls are there that can start, stop, and unload each package unit?

The only control here is the VAVs.As i mentioned ealier there is no thermostat ,no antifreeze sansor.The ideal location for thermostat is the central sitting area in the first floor.

That is not believable, unless the system design is plumb crazy to start with.

This is the truth of the matter,i was brought to this project fo final handover ,the engineers who did this are nolonger here ,they already resined,only one manager is still here ,but as you know ,some managers are not techinically sound .He is telling me to do my best without the required controls.

I'm sorry to hear that you have been stuck with a bad situation. I don't know the overall design of this system, but I don't see where another thermostat would help much. (But it depends on exactly what the suggested thermostat would control, and how.)

Most package units have pressure controls to govern start/stop/unloading of the compressor(s) and condenser fan(s). Is anything like that present in your packages?

You mention VAVs in the first floor. What is on the ground floor? Are the two packages separate from each other?

There is no any other controll device on these units other than these VAVs.In ground floo its a different system ,no VAVs its direct supply and return controlled by a central thermostat.

Has the situation been discussed with the HVAC equipment supplier yet, and if not, why not?

Explain to the manager that the HVAC specialists are the correct people to de-bug this installation, not someone who has been brought in at the last minute just to finish the job, and that if the job really needs to be finished and working correctly, the HVAC people will need to be there to do it. If the controls are really 'required', then it doesn't make sense to do one's best in their absence as it won't be good enough, as evidenced already.

So make the call, and get them in.

How about the unit's control panel itself, does it have some adjustable controls that would help?

The VAVs and a programmed delay timer for the compressor only.

What else has the forum not been told about this installation?

Why should the forum do the HVAC specialists' job for them?

This will work if FCU for each zone / room is available .

http://www.designbuilder.co.uk/programhelp/_vav.htm

If icing is observed - as you have said about anti freezing or some form of heating effect needs inclusion as an amendment or modification . Through client consultant or in Final handing over as Pending remark - you need to raise this aspect . If possible , let your authorities put forward this recent test run failure to the client so as to get sufficient time frame to overcome this technical factor .

VAV is supposed to control fan speed . Sensing circuitry is to be checked whether it really happens . If satisfactory , set point is to be adjusted to overcome icing .

If optimum performance in room / zone is not achievable - needs an amendment , please .