Hot water warehouse unit heaters use the hot water from an existing hydronic system to provide heat to an isolated area.
A common example would be a workshop attached to an office space. Even if it's disconnected from the main office heating system, the workshop could still benefit from the heat generated by the office's boiler by way of a hot water warehouse unit heater.
Now that you've selected the application and fuel for your unit heater, it's time to choose those final specifications!
Choosing a Heat Exchanger Material
In some cases, you will have an option of choosing between two heat exchanger materials, steel or copper.
Steel is the standard material used for hot water heat exchangers and is known for its ability to reliably transfer heat over many years of use. Since steel has a high risk of corrosion when exposed to oxygen, it is best used in closed systems. If your hydronic system uses a supply of fresh water or is open to the atmosphere at any point, you'll be better off going with copper.
Copper is the counter to the corrosion issues that steel heat exchangers create. While copper is resistant to corrosion, it is relatively soft compared to steel. In a hot water application, though, this difference in strength doesn't manifest in any real way. The only downside to copper in this application is the additional cost. However, if you have an open system, a copper heat exchanger is definitely the way to go.
Choosing an Orientation
Because hot water unit heaters don't include a combustion site (i.e. a flame), they are available in more mounting and installation options than gas- or oil-fired unit heaters. Hot water warehouse unit heaters come in both horizontal and vertical orientations, and your application will dictate which makes the most sense for you.
In most cases, horizontal will be the orientation that provides the best comfort. Horizontal unit heaters blow air outward from one side of the room to the other.
Especially effective when placed at the far end of a room or in rooms with low ceilings, horizontal warehouse unit heaters will provide broad coverage across your entire space.
Vertical unit heaters direct heat downward and allow it to spread out horizontally through natural dispersion.
The primary applications for a vertical orientation would be spot heating or heating spaces with very high ceilings. By pushing air downwards rather than across, you can ensure complete coverage of your space before the heat rises back to the ceiling. If you know you're only working in one part of the room for the majority of the time or your ceiling is relatively high, vertical garage unit heaters would be a great fit for you.