2-pipe fan coil system

[joepilot]

Has anyone had any success fixing a 2-pipe fan coil system so that adjacent zones can have heating or cooling. I am working on an existing hotel with a 2-pipe system. They are OK spring summer and fall. However, in winter there is a problem when one room wants cooling and the next one wants heating.
I am looking for a successful case study or existing hotel that was renovated to solve a similar problem. This project is in southern California.

 

[walkes]

We are currently working on a similar problem. We are designing a conversion to a heat pump system. Removing the chiller adding a fluid cooler, revising the boiler loop and making some other modifications. Our approach doesn't take advantage of a core perimeter heat exchange to maximize the performance of the heat pump system, however each suite has the ability to go to heating or cooling as needed. (There may be some energy savings in the shoulder seasons)

The only other option I see would be to duct outside air into the fan-coil somehow.

 

[joepilot]

Thanks for the tip.
I was concerned about using water source heat pumps in this application because last time I did there was a significant problem. The units had a safety that would trip them off on low condenser water flow. This required a manual reset at the control panel on the unit.
Every time there was a power failure, about 2 times a week in Florida, all of the units would require a manual reset. This required getting up into the ceiling with a ladder for every unit in the builiding (about 150 altogether).
I have not specified a WSHP system in about 8 years. Has this issue been addressed?

 

[controlnut]

Joepilot - I saw a system like you described once... They had an energy management system that was supposed to disable control power for certain periods. One byproduct of this was that cycling the EMS system could also reset the units in mass. You might look at adding a reset relay to all units as they are installed. There are drawbacks to what they did, however. Units with a genuine problem would also be reset, causing a safety hazard in my opinion. I also don't know if they were switching the units in an approved manner. It might affect the warranty depending on the manufacturer. That is the only time that I have seen anyone address that problem. It is probably not an equitable solution, but maybe food for thought.
Regards

 

[friartuck]

Hi Joe Pilot

There are a few variants of two pipe systems. If the one you describe is a heat pump that can put out either chilled water ot low grade hot water (i.e. a changeover system) then you will have problems if your climate is not suitable for that type of system.

Some parts of the world have distinctive summer,winter periods and the system can be switched over from one mode to another. If the change is 'up and down', you might try electric re-heat at each FCU to 'smooth over ' the change.

In the UK we have a system called 'versatemp' which essentially is a two pipe system that circulates water at about 35C. The water passes through a cooling tower and a boiler system. (actually there are by-passes fitted so that they can be switched in and out of circuit)

The water then goes to each 'fcu' (which is in fact a water to air heat pump) The localised heat pump then decides if it needs to heat or cool. If it heats, it draws heat from the two pipe ring main, If it cools, it puts heat back in to the ring main.

They are quite energy efficient though a little noisy.



Friar Tuck of Sherwood

 

[ChasBean1]

Another option might be to split the services. Use the FCUs for cooling, run HW fintube at the perimeter. Do a control retrofit so that the thermostat runs either without overlap. A bit expensive, but cheaper than installing a four pipe system. OR (I hate to suggest this, but it is Southern Cal. and may not be in high demand), install electric baseboard heat below windows in each room...