A water source heat pump system is one of the most environmentally friendly and efficient ways of heating or cooling a building.
Water-source heat pumps work on the same principle as traditional air source heat pumps.
However, they do extract and dissipate heat by using a water source instead of from the air.
Excellent year-round temperature control is provided by all heat pump types.
The heat exchanger pumps heat during the winter months and removes it in the summer.
WSHP units are generally unobtrusive, quiet, and have very low maintenance requirements.
However, you still need to take care that the heat pumps have a consistent water supply that is sufficient throughout the year.
This guide will talk about everything you need to know about conducting preventative maintenance on your water source heat pump systems.
Water Source Heat Pumps
Hi. This is Eric Sorensen again with Servi-Tek Engineering and Facility Solutions. We're at another one of
our Orange County buildings, except this time we're talking about water source heat pumps. So there are
two different types of heat pumps. You've got waterside systems and you've got airside systems. In this
particular building, we've got a waterside system, which means we also have a cooling tower. Again,
we've got that term cooling tower. Cooling tower, there are three types. We have the evaporative
condensers, fluid coolers, which is what we have in this case, and then we have the open flow
condenser water cooling tower. So in this case, we've got a fluid cooler, we'll go out and we'll talk about
that in a little bit. Water source heat pumps are a unique type of system. Some people call them value-engineered,
but there are pros and cons to them.
And water source heat pumps, you typically have the unit hanging up in the overhead. Sometimes it's
above a T-bar drop ceiling. Sometimes it's just floating up in the air if they've got an open concept in
their space. You've got your condenser water flow in. Your condenser water flows in, that's actually your
cooling. So this is what's removing all of the heat from the building right here. So it's got an integral
compressor, refrigerant compressor. So that's causing the cooling in the system. And then that heat
that's being generated by that has to be removed. And it's being removed by the condenser water coil
that's going through the water source heat pump itself. That water is being removed and then it's taken
back to the cooling tower or the fluid cooler where that heat is removed. And then that water cycles
right back to the unit.
One of the critical things on these units is the strainer. So part of the preventative maintenance on the
water source heat pump is making sure that you clean these strainers quarterly, semi-annually. And then,
of course, they also have their filters built into them, up in the overhead. So if we were to see the side
of this unit, we would see their box pleated filters, where it's pulling the return air back up into the
plenum and then back through the cooling coils to be distributed back down into space. So one of
the unique things about the water source heat pump is that it's a standalone zone type system. Unlike
the larger central plants, or even some built-up DX systems, where you have a single point of failure
components, and if one of those components fails, your entire system goes down or your entire building
starts to heat up.
In this case, if this unit goes down, it's only this one area that's affected. And in a space like this, we
might have four or five or six of these units that serve the space. So that's the pros. Those are the
positives to a water source heat pump system. They are a little bit value engineered in the sense that
you're not putting in big capital equipment. You're popping in these units at eight to $10,000 apiece throughout the building.
And then you're feeding them back out with the condenser water line to the
cooling tower for the cooling. So if there is a failure, it's only in an isolated area. That's the positive. The
downside is, and we've had this happen on more than one occasion, these lines are sometimes tied to a
flexible line going into the unit. In fact, in most cases, tied to a flexible line going into the unit. And when
they rupture, an office space like this is underwater very, very quickly.
So you've got to be able to respond if you've got your maintenance or your engineer guys to come in
and get things mocked up, get the water isolated before you have to get into real money with the
restoration companies. So anyway, this is a water source heat pump building. This is a water source heat
pump system. You can have hundreds of these actually in a very large building. So that's a lot of
maintenance. Again, another one of the cons to water source heat pumps. This is an open space, but if
this was an occupied tenants' space, we would have cubicles, we would have desks, we would have
people. So accessing the equipment to actually do the maintenance or do the repairs can be difficult.
You've got to schedule with the tenant and then there are other issues with opening the overhead and dirt
and dust and things falling in occupied spaces.
So one of the downsides aside from the potential of flooding, other than that, it's a really good system.
Again, more on the value-engineered side, typically what we might see in smaller buildings, although we
will see them in a lot of high-rise condominiums, things like that, where they go ahead and put these in
the space. You might have one or two services in a high-rise condo, and again, cooling towers up on the
roof to remove the heat. So from there, we'll go out to the cooling tower or the fluid cooler.
When to Perform Maintenance on WSHPS
Don’t let months go by without doing a cursory check of your system and professional maintenance should be carried out at least once a year.
You can protect your heat pump systems from wear and tear by performing the following steps on your own. Consider using the following steps:
- Changing filters: Remove and replace air filters in your system quarterly, semi-annually, or at least once a year, depending on the environment.
- Check coils and fans: Fans and coils are prone to dust and grime buildup; therefore, clean them periodically for proper ventilation.
- Clean the fins: You may need to use a vacuum cleaner to clean the fins in the console units.
- Inspect outdoor pumps, boilers, and fluid coolers: Inspect and perform PM on the fluid cooler/cooling tower annually, ensure proper water chemistry, and that boilers and condenser water pumps are working properly.
- Follow HVAC instruction manual: Check the manual and follow all guidelines on the heat pump and HVAC operation
You can ensure that your system components run at peak performance throughout the year by following these simple maintenance tasks.
However, you should not ignore bringing in the professionals to have a look at your water source heat pump system periodically.
There are certain tasks that demand the attention of a professional. This holds true whether your system is installed commercially (condominiums, office buildings, etc.) or residentially.
The extent of the Maintenance Checklist
Proper maintenance is important for optimal operation in all heating and cooling systems.
The energy consumption difference between a well-maintained WSHPS and a severely neglected one can be as high as 25%.
It is important to maintain the system as per the manufacturer’s instructions.
You need to change and clean filters periodically. Dirty coils, fins, and filters can reduce airflow regardless of the type of system you have.
System performance gets decreased when there is reduced airflow which can then damage the compressor.
You need to make sure that you clean the coils whenever they appear dirty.
This should be done before the dirt turns to grime. You should also turn off the fan occasionally and clean it.
Several other things need to be addressed during your periodic preventative maintenance, such as ensuring proper condensate drain flow to avoid overflows and potential water damage.
There are some things that only professional technicians are trained to do.
You may not be able to discern the signs of damage or issues within your system.
Make sure you get a trained technician to look over your water sourced heat pump system at least once a year.
These are a few things the technician would do:
- Seal and diagnose duct leakage
- Inspect filters, ducts, blower, and coil for obstructions and dirt
- Verify correct refrigerant charge
- Verify adequate airflow
- Check for refrigerant leaks
- Lubricate motors
- Inspect electric terminals
- Clean and tighten connections
- Apply nonconductive coating to connections
- Inspect belts for wear and tightness
- Verify electric control when thermostat calls for cooling and heating are locked out
- Verify thermostat operation is correct
After The Maintenance
These are a few things you should do once a trained technician has checked your system to ensure that your system works the way it should.
- Set the system thermostat to run at a single temperature, as you may incur higher utility bills if you constantly adjust it–particularly in the winter.
- If you are using a setback type thermostat, limit setbacks to twice a day when you are sleeping or working.
- Make sure the thermostat is a setback to only 6% of the desired temperature.
- Refrain from setting the thermostat to below 65 degrees during the heating season. Low-temperatures can put undue pressure on the system.
- Setting a thermostat below 65 degrees can also cause indoor coils to freeze when using in cooling mode and cause unnecessary condensation.
- Always ensure that there is proper condenser water flow before cooling. Also, know that it runs for a short period after the units are scheduled to be off as the unit(s) will trip OFF on high head pressure and need to be reset if cooling water is not flowing through the unit(s) when called to run.
- Regularly check the outdoor heat pump. This is especially important during the winters when there may be excessive snow or ice buildup on or around the unit.
- Exterior units that are covered in snow or ice should be cleared promptly. Make sure you turn the thermostat to emergency off or a heat position to remove the ice and snow. You can also pour warm water over the system to melt the ice and snow; however, make sure you never use hot water.
- Do not knock or pick at the ice using a sharp object. You could damage the coils of the WSHP, cause an injury, or otherwise damage the unit.
- Turn the thermostat to regular heating when the unit is clear of snow and ice during cold weather. Call for a trained technician if the unit ices up again.
- Open-loop or closed-loop installations should never be under a leaking gutter. Water will drip on the exterior unit and freeze solid during a cooler climate. This will cause restrictions in access to air-source and may freeze the entire unit.
- Heat pumps in a water loop system should always be installed at least 4 – 8 inches off the ground, which helps keep the coils free from ice and snow and allows for proper drainage.
How Often Should You Conduct Preventative Maintenance?
Water Source Heat Pumps 2
So maintenance on the water source heat pump system is relatively simple, as long as you have access.
The unit has filters built into it that get changed out, usually box pleated filters, pretty straightforward.
Cleaning the coil is important, but one of the more important things to do is clean this strainer. If the
strainer gets clogged up, the flow starts to stop. When the flow starts to stop, the unit tends to overheat
and can trip off on what's called high head pressure.
So again, relatively simple unit, not a lot to do on the refrigeration circuit side. That's closed unless you
get a leak. There are some component repair issues to these if they fail. You can actually just change out
the compressor without having to change out the entire unit.
There are only a few points of connection on a water source heat pump. Your condenser water supply,
your condenser water return, your electrical connection, your ductwork, and then your condensate line.
So ductwork, depending on how the application is, can be some of this flexible duct, which you may not
be able to see from here, the silver flexible duct. Or it can be a rigid spiral duct, typically the application
for open space air distribution.
So from there, we'll move on to thermostats and the fluid core.
Preventative maintenance of water source heat pumps (WSHP) doesn’t need to be carried out often, as yearly maintenance is typical–similar to an air conditioning unit.
Always refer to the manufacturer’s pump maintenance checklist or guide regardless of whether your WSHP is an indoor or outdoor unit.
All maintenance activity should be performed by a trained and competent service provider who will take the time to inspect the system thoroughly and properly before diagnosing potential issues and repairing them.
Coil and filter maintenance has a significant impact on service life and system performance in heat source pumps.
Dirty coils, filters, and fans can limit the flow of air within the system.
This can cause the system to work on reduced performance.
This can also cause compressor damage, especially when the system is forced to run at reduced performance for extended periods.
Most WSHPs have a life expectancy of 20 – 25 years.
Water-source heat pumps have a shorter life expectancy as compared to air-source heat pumps since the compressor has less mechanical and thermal stress.
Air-source systems are also protected from environmental factors.
There is a one-year warranty on most ground-source heat pump units covering parts and labor. However, you need to check the warranty from the manufacturer–as many contractors offer extended warranties too.
How Water-Sourced Heat Pumps(WSHPS) Work
Air source heat pumps tend to get their heat from the outside air.
This is true even during cold months since cold air does contain a significant amount of heat.
The heat is used to keep your property warm during winter.
However, air-source heat pumps lose their efficiency as the outside temperature begins falling.
In contrast, a water-source heat pump extracts heat from water instead of air, such as a heated condenser water loop.
They work on the same principle as traditional air source heat pumps.
The heat is extracted by cycling water through loop systems.
This system has an intricate coil system of pipes at the bottom of the fluid cooler/cooling tower.
The water cycles through the pipes and is cooled by the cascading water within the fluid-cooled or heated by the hot water introduced to the tower and comes back to your property.
WSHPs are more efficient at cooling as opposed to heating.
Preventative maintenance can go a long way in keeping your system damage-free and running efficiently.
However, even with periodic maintenance and preventative service, your system is bound to malfunction and require repair.
The best way to avoid costly repairs is to take care of them before they exacerbate into something major.
These are a few things you should keep a lookout for in your water sourced heat pumps.
Typically, a visual analysis is performed for all components of the system to identify any leaks.
Bad Heat Pump
The heating mode in a WSHP is governed by a loop system.
Water or heat cannot circulate through the system if the pump stops working.
This can cause the system to lose its efficiency.
Most times the pump can be repaired with minimum expense.
However, in other cases, it may make more sense to just replace the entire heat pump.
Replacing the pump, condenser, or evaporator (as the case may be) could be the most economical solution if your system is old and keeps giving you trouble.
Issues with Heat Pump
There are a lot of reasons why your cooling mode won’t work or the system won’t maintain comfort zones within the building. Water sourced heat pumps can experience some problems.
- Bad contractors or dead capacitors
- Bad fan motor
- Refrigeration leaks
- Scaled/dirty cooling tower
- Tripped breaker
- Dead batteries in the thermostat
The system can be experiencing heat rejection issues as well.
Maybe, the boiler is not working as it should in heating mode.
Water sourced heat pumps rarely ever have unique problems.
The components are the same as traditional HVAC systems.
This means the system is plagued by the same typical problems as HVAC systems.
A clogged air filter is the simplest reason for a water sourced heat pump to be facing issues.
You would need to check the air filter when the system stops working as it should.
If it’s been a while, you should change the air filter before doing anything else.
Your HVAC system can be starved of air with dirty air filters.
There is a lot of heat transfer and clogged air filters don’t allow for air to be circulated within the system.
Why do We need To Maintain the Heat Pump System?
Your system is at a high risk of performance erosion like any cooling or heating technology if you don’t get it regularly maintained.
You don’t want your heat pump breaking down at inopportune moments and costing you tens of thousands of dollars in repairs.
Heat pump preventative maintenance can go a long way in helping you protect your unit from potential mechanical failure.
It also ensures that your system operates at high-efficiency levels.
Improving Energy Efficiency
You can enjoy a high Energy Efficiency Ratio (EER) from your open or closed-loop heat pumps by ensuring it operates properly.
Never resort to set back on a heat pump’s thermostat when it starts causing the backup heating to switch on.
Generally, backup heating systems tend to be more expensive in the long run to operate.
Your heat pump performance may get degraded if you use the indoor fan operation continuously.
This is unless the system makes use of a variable speed, high-efficiency fan motor.
You should consider operating the system on an auto fan setting. You should also consider installing a programmable thermostat.
These are a few ways you can improve the coefficient of performance (COP) in your WSHPS:
1. Water Regulating Valves
Heat pumps that have water regulating valves or solenoid valves allow for a variable flow pumping system.
They also cause a significant decrease in energy used for pumping and allow the pump speed to change as per demand.
WSHP system pumps are typically oversized. They represent a major base energy load. This allows for cost-effective improvements in the area.
This is especially true for pumps that need to operate continuously for satisfying a small portion of the building load.
Reducing the system pressure drop is another way of reducing pumping horsepower requirements.
The components (heat rejectors, strainers, heat pumps, and the piping) within a water sourced heat pump should be carefully selected for causing a minimum pressure drop.
2. Refrigeration Coupling
Another way to reduce the demand for supplemental heat is to the couple miscellaneous computer room or refrigeration units to the WSHP loop.
It helps in providing more efficient operation during summer months as opposed to air cooling machines.
This is true even for machines that reject heat for conditioning space.
3. Heat Rejecters
Closed-circuit coolers, cooling towers or heat rejecters can have increased efficiency by performing simple steps.
For instance, you need to select the initial unit carefully since it can have a significant impact on the fan horsepower.
Larger unit selection may cause less fan horsepower for a given heat rejection load.
In addition, there are many types of fan horsepower and heat rejecter requirements that can be tripled or doubled for a few styles to make them more efficient.
It’s necessary for fans to be allowed for part-load operation at limited horsepower ratings.
You can accomplish this by having several fans installed or staging fan operation.
You can also acquire this by using two-speed fan motors.
Brief Description of the Heat Pump Process
Heat pumps run a low temperature, low-pressure refrigerant within the heat exchanger coils through an external heat source.
In water sourced heat pumps it is through circulating water.
The fluid absorbs the lateral heat and boils. This is possible even when the outside temperatures are below freezing.
This is because the coefficient of performance (COP)tends to decrease with lower temperatures.
The resulting gas then gets compressed, which further helps in increasing temperature.
The gas is passed through heat exchanger coils where it condenses and releases latent heat.
The process works on repeat to ensure that your property maintains a comfortable temperature.
Water sourced heat pump system can be used both commercially and domestically for extracting heat from a building and cooling it.
A suitable water source is fundamental for water source heat pumps.
These systems are usually closed loop. Closed-loop systems have water within the pipe.
It’s crucial to consistently verify the integrity of your system and remedy any major flaws in the system.
New pump installations or replacements can be expensive.
Having preventative maintenance can help you avoid potential problems.