System can't maintain temperature/humidity

[Designer_82]

I'm working on a project where the building has a two pipe system with condensing boilers and an air cooled chiller.

There are very very old fan coil units throughout.

It's a dormitory type building with about 75 dorm rooms.

The owner is complaining that the system cannot really maintain temperature/humidity. (cannot provide sufficient heat in winter and maintain humidity in summer)

They said this system never worked well even on the first day it was installed.

I'm thinking it's undersized.

I know very little info. has been given so far, but any ideas on culprit? Or what other info can I obtain to help with this?


thank you

 

[TBP]

Were the air handlers originally designed for steam or higher temp hot water than what they are supplied with now?

 

[GT-EGR]

That question has way too many answers/possibilities

Heating - what temp is the hot water now, low condensing boiler temps of today are likely lower.

Cooling - can’t dehumidify properly without a reheat coil or at least fan speed control. Also how do they get ventilation, windows open? Is ventilation conditioned?

Owner needs to be a lot more specific - did none of them work, just certain exposures, what specific times of year, did they incrementally get worse over time. Did anyone ever diagnose if it’s the fan coil itself malfunctioning, or it’s controls, or it’s working fine and just not putting out enough heat/cooling

Is it a very old building with poor envelope?

Two pipe systems also by nature always have issues in shoulder seasons where you can only pick heating or cooling but you kindof need both depending on time of day

 

[LittleInch]

Boiler not big enough?
Pipes not big enough?
FCUs not big enough?
FCUs corroded / blocked / fans broken

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[nuuvox000]

Get the as-builts and go through the equipment schedule to look for any red flags. You can also do a rule of thumb calc to see if the boilers and chiller are in the ballpark as far as capacity. Start with the main equipment, pumps, boilers, etc. Clean strainers and take temperatures and pressures in the mechanical room. That would be a good starting point.

 

[EnergyProfessional]

So you have very little to non information, but you already know it is undersized? This knowledge is surprising. Based on the little information you provided the problem could be because of almost anything that ever could go wrong in design, installation, and operation.

 

[dbill74]

Is there a DOAS unit?
A 2-pipe system for a dormitory building? Would require the system to either heat or cool the entire building, odd choice for a design since the building could require heating and cooling simultaneously. Plus having reheat does wonders for humidity control.

You're going to need to do a deep dive into the design documents of the building to understand how it was designed, then you can better understand what it is not doing.

 

[MedicineEng]

The less info you provide, the more culprit possibilities it opens...

Dig a little further on the issue and if you want some meaningful input from the group you have to come with more information, otherwise we will just be guessing, with results just marginally more accurate than going to the tarot fortune teller.