What is the purpose of a balancing valve in a hydronic branch?
- To stop water from flowing backward in the branch
- To relieve pressure if the branch becomes isolated
- To shut the branch off quickly in an emergency
- To set the flow so each circuit gets its design gpm
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D. To set the flow so each circuit gets its design gpm
Water takes the easiest path, so short circuits would get too much flow and distant ones too little. Balancing valves add measured resistance so every terminal unit gets its design flow.
Reference: Hydronic balancing
In a closed-loop hydronic system that is full of water, what does the circulating pump have to overcome?
- The full height of the building plus friction
- Only the friction loss around the loop
- Only the full height of the building
- The fill pressure of the system plus friction
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B. Only the friction loss around the loop
In a closed, filled loop the weight of water going up is balanced by the weight coming down, so building height does not add to pump head. The pump only makes up friction. Height does matter for the fill pressure, which is a separate thing.
Reference: Closed-loop pump head
Two identical pumps are piped in parallel. Compared with one pump, what do they provide when both run?
- More head at about the same flow
- Double the head and double the flow
- More flow at about the same head
- The same flow at half the head
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C. More flow at about the same head
Pumps in parallel add their flows at a given head; pumps in series add their heads at a given flow. The actual gain depends on where the combined curve crosses the system curve, so it is less than double the flow.
Reference: Pumps in parallel and in series