Hydronic Heating and Cooling on a Ship

glycol mixtures hold on to air a lot better than plain water so you really need to have microbubble air separation.

if you have zone valves on each fan coil then balancing valves are maybe less important because the zones with more flow will satisfy first and shut off directing more flow to the zones with less flow. ideally you will balance it somewhat but zoning makes it less critical.

the air will cause you a lot more problems with circulation than not having balancing valves. ideally the piping would have been sized to provide rough balancing.

If they are repurposed AC coils they will have very small tube, high pressure drop

If the oump fund 24/7? There must be 3 way zone valves or a bypass somewhere

To size a pump you need gpm, head, and type of fluid

A freak drive may help dial in the gpm, but will not save much electricity or adjust as valves open and close

A correctly sized ECM circ may be less $$ than a drive

If the pump runs 24/7, I don't understand why it would it need a bypass? Isn't it just normal constant circulation? Constant circulation with only a 4° temperature difference because no fans were on at the time? Would @btkealy get more useful data running all the fans?

When I encounter a system with an air problem, I often leave the automatic feed water turned on. That way, as the air is eliminated from the system, the feed valve automatically replaces the lost volume and maintains adequate system pressure.

Since maintaining a conventional water connection is not an option in your system, (unless you have a really long garden hose) you could accomplish essentially the same thing by using a Pressure Reducing Valve connected to a pressurized Well X Trol WX-203 tank. The tank could be filled with approximately 25 gallons of the proper glycol mixture and the air side pressurized to about 60 PSI.

The pressure-reducing valve would then maintain the desired system pressure by feeding glycol from the storage tank as needed when air is eliminated or a small amount of fluid is lost. This would provide a reserve supply of properly mixed glycol without introducing plain water into the system.

Here is a diagram you can post in the boiler room:

Heat operation noted above

Cooling operation noted above:

This will help keep air out of the system by design. With less air occupying space in the HVAC piping, the system will contain more heat-transfer fluid and, more importantly, maintain better contact between that fluid and the heat-transfer surfaces throughout the coils, chiller, boiler, and piping.

I don’t know what percentage of improvement you would actually see. That would depend on how much air is being eliminated compared with the amount of air the system normally operates with. A system with only a small amount of entrained air may show very little measurable improvement, while a system with significant air pockets or air binding could improve considerably.

There is also the issue of additional wear and deterioration. Entrained air can contribute to noise, poor circulation, corrosion, and damage to pumps, valves, heat exchangers, and other system components.

Does each each fan coil has a thermostat controlled off/on valve on coil? Or is control on fan? If former there should be a shunt somewhere to allow some flow when all coils are off.

Has someone tried to compare cost of operating with glycol versus running some heat during cold weather? Water source heat pump?

I believe that OP is correct about over sized circulating pump. It almost always is the case. Often coils near circulator require a balance valve or constant volume valve to work as expected. Again OP is probably correct. 4° delta on chilled water is not nice. Too fast flow is noisy and tough on chiller.

some amount of outdoor reset would help keep the coils with the fan off because the zone is satisfied from overheating or overcooling by convection as much.

Some considerations about adding a VFD

Ideally you have a motor rated for inverter service.

You may not go below 50% or the motor will over heat

You would like your know the system curve, have it to lay over the pump curve

If you have a flat curve pump, depending on the system curve, you may run out of flow at the reduced speed

Do do some homework, get the pump data at the least, before you invest in a drive

A clamp on flow meter could give you good info,

Pressure reading across the pump is useful

Also the piping size will be what determines how many gpm you can flow before exceeding the 4-5 fps velocity where noise and wear become an issue

2”pipe is good for around 40 gpm, if 65-75 gpm is what you need??

The enginneringtoolbox online has all sorts of pipe flow data, gpm, velocity, pressure drop , etc.