Hot water, happy customer
For a happy hot water customer, consider the following key points, Jon Palfrey, Rheem explains.
The following key points makes a list to have ‘top of mind’ when sizing, installing, commissioning or fault ﬁnding a water heating system.
EXTERNAL GAS STORAGE LOCATION
To ensure complete combustion at the burner for a gas unit, air pressure needs to balanced around the ﬂue terminal. Combustion byproducts need to leave the primary ﬂue in the direction of discharge ﬂow.
Installing the system against a wall that provides a clear area 500mm above and to each side of the water heater ﬂue terminal will create a zone of balanced air pressure that will provide complete combustion. A lack of balanced air pressure can create issues relating to sooting, pilot outage, yellow-tipped ﬂame and thermocouple durability, particularly if back pressure caused by high winds exists.
CONTINUOUS FLOW GAS SYSTEMS AND FILTERS
Regular checking of cold water supply inline ﬁlter strainers on gas continuous ﬂow water heaters is required to ensure un-restricted ﬂow downstream. If the cold water inlet ﬁlter strainer has silt or swarf, it creates a blockage which may mean the heater cannot function particularly if the water body assembly function cannot activate the unit’s sequence of operation.
Ensuring air is purged from a gas ﬁtting line and swarf from the water supply on all installations. If a gas pilot light won’t hold, always check the ﬁtting line to the gas water heater has been purged of air.
LAGGING/INSULATION Poorly insulated pipework and the associated branches creates heat loss increasing energy consumption driving up energy costs and signiﬁcantly increase the amount of time the customer has to wait for hot water.
A poorly or uninsulated hot water pipe line can lose three times the energy compared with a well-insulated pipe with 10mm of insulation. For example, an uninsulated 20mm diameter copper pipe can lose 30W/m compared with a well-insulated copper pipe which will only lose 13W/m.
When determining the size, discuss with the customer what their needs and expectations are for their new water heating system whether it is replacing an existing system or a new system for domestic or commercial applications.
Refer to manufacturer’s literature when choosing a domestic or commercial water heating system particularly when needing to provide allowances for applications where peak demand periods and temperature rise will equate to a system that will meet the needs of the building occupants.
INLET WATER PRESSURE
It is essential to conﬁ rm the inlet water pressure to the water heater particularly to a mains pressure storage gas or electric system and the associated TPR valve rating.
The 80% rule applies when determining the maximum cold water supply pressure into a gas or electric mains pressure water heater. For example, with a 1,000kpa rated TPR valve, 800kpa is the maximum cold water inlet pressure to the system. The key to allowing for the maximum pressure to a dwelling/building is to also allow for the time of the day as the inlet from the cold water mains will increase in pressure as local dwellings cease drawing water supplies.
MANIFOLD SYSTEM PRINCIPLES
When combining two or more water heaters whether mains pressure storage or continuous ﬂow, the principals of ﬁrst in and last out need to apply to ensure equal performance, consistent temperature and shared delivery from each system in a manifold.
- Header diameters for cold/hot to be equal.
- Branch diameters for cold/hot to be equal.
- Hydraulic water ﬂows “in one side, out the opposite”.
- Balanced performance per unit equals full delivery capacity from the system.
The manufacturer’s procedure to test, check, operate and discuss with the customer the function and safety requirements of the water heating system.
Remember to remind the customer to carefully read to re-lighting instructions on a domestic gas mains pressure system and to allow ﬁve minutes for unburnt gas to escape before attempting to re-light the systems pilot. Some manufacturers (including Rheem) have explanation videos available for end users to reference the safe re-light procedure.
Where damage to property can occur in the event of the water heater leaking, any water heater that has a volume capacity of 13.5L or more must be installed in a safe tray when positioned within a building. Construction, installation and draining of a safe tray must comply with AS/NZS 3500.4 and all local codes and regulatory authority requirements.
INLET GAS PRESSURES
The inlet gas pressure is critical to determine adequate pressure and supply to the appliance either when installing or servicing and maintaining the water heating system. The dynamic gas pressure measurement with all other gas appliances operating is the key to determining adequate supply downstream from the gas meter assembly.
Typically 1.1kpa for natural gas and 2.75kpa for propane gas is the required available gas pressure to ensure correct and reliable water heating system operation.
FLUING AND FIXED VENTILATION
Upper and lower ﬁxed ventilation with the minimum clear air space depending on the megajoul load of the system is needed to provide complete combustion. The ventilation of a room or an enclosure such as a cupboard, where the water heater is installed must comply with AS 5601 or AS/NZS 5601.1.
If the water heater is installed in a room or an enclosure, where the total thermal input of the water heater and any other gas burning appliance(s) exceeds 3MJ/h for each cubic metre of room or enclosure volume, an adequate air supply must be provided.
For eﬃcient water heater operation, allow two permanent openings into the room or enclosure, each of at least: 66,000mm2 for a 110MJ model water heater or 120,000mm2 for a 200MJ model system.
Customer and end user expectations for a water heater are to position it near to high demand areas to provide satisfactory hot water delivery outcomes. As near as possible to the kitchen sink is always a safe bet for best practice and customer expectations.
ACCESS FOR SERVICE AND MAINTENANCE
When installing a water heating system particularly a continuous ﬂ ow or mechanical instantaneous type, remember to allow access to service and maintain the system without the need for a ladder.
ADHERENCE TO INSTALLATION INSTRUCTIONS
No secret here… When installing a water heater for the ﬁrst time or after a long time it’s recommended to familiarise yourself with the installation instructions particularly relating to the manufacturer’s plumbing and commissioning procedures.
“Walk away from the job without your ﬁngers crossed knowing that you have installed and commissioned the system to the manufacturer’s and local regulator’s requirements and AS/NZS 3500.4.