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2 weeks ago | 
pmmag.com | John Siegenthaler
The availability of heat pumps has made it possible for those who design and install hydronic heating to expand their offerings to include cooling. One of the simplest approaches uses a single air handler with a chilled water coil, to supply a ducted forced-air distribution system. In “average” houses this approach, which provides single zone cooling, can be combined with multi-zone hydronic heating.
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2 weeks ago | 
pmmag.com | John Siegenthaler
Last month we began discussing direct-to-load hydronic heat pump systems. They combine a variable speed compressor with variable speed circulator to modulate both heat output and flow to match the needs of a distribution system without need of a buffer tank or hydraulic separator. Adding a boilerBoth air-to-water and water-to-water heat pumps are often combined with a boiler to serve as a supplemental and backup heat source.
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3 weeks ago | 
pmmag.com | John Siegenthaler
Radiant & HydronicsThe Glitch & The Fix The air-to-water heat pump has a nominal 4-ton (48,000 Btu/hr) heat output rating. It supplies an air handler as well as a heated concrete slab. At design load conditions the air handler is rated for 20,000 Btu/hr with a supply water temperature of 120 ºF. The slab is designed to release 20,000 Btu/hr when supplied with water at 105 ºF.
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3 weeks ago | 
pmmag.com | John Siegenthaler
The availability of heat pumps has made it possible for those who design and install hydronic heating to expand their offerings to include cooling. One of the simplest approaches uses a single air handler with a chilled water coil, to supply a ducted forced-air distribution system. In “average” houses this approach, which provides single zone cooling, can be combined with multi-zone hydronic heating.
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3 weeks ago | 
pmmag.com | John Siegenthaler
✕The GlitchA heating designer is asked to create a three zone radiant floor heating system using a single speed 5-ton (60,000 Btu/hr) geothermal water-to-water heat pump as the primary heat source, and a mod/con boiler as the auxiliary heat source. Because of the symmetry of the building, each zone will have a six circuit manifold station with nearly identical circuit lengths.
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3 weeks ago | 
hpacmag.com | John Siegenthaler
I’ve been known to throw out a rather sarcastic comment when the subject turns to using antifreeze in hydronic systems: “The only good thing about antifreeze is that it doesn’t freeze.” That quip was based on the facts that using antifreeze in a hydronic system: a.) adds to the cost of the system; b.) increases the pumping power required to achieve the given rate of heat transfer, relative to water alone; c.) decreases the heat storage ability of the system fluid; and d.) needs to be...
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1 month ago | 
pmmag.com | John Siegenthaler
One of the latest design approaches for air-to-water and water-to-water heat pumps is called “direct-to-load” piping. It’s based on the ability of a inverter-driven scroll compressor to operate over a wide range of speeds, and to handle on/off cycling when necessary, without the frequent inrush current demands associated with short-cycling a fixed speed compressor. The concept of direct-to-load piping using an air-to-water heat pump with it’s own internal circulator is shown in figure 1.
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1 month ago | 
hpacmag.com | John Siegenthaler
I was recently asked to review a proposed heating system for a school in which two electric boilers were being added to supplement the output of an existing gas-fired cast-iron boiler. The electric boilers were chosen to take advantage of low “off-peak” electrical rates. The system supplied four zones of low temperature water floor heating, all of which required the same supply water temperature at design load.
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1 month ago | 
pmmag.com | John Siegenthaler
Ask some average people you cross paths with this question: Have you ever heard of something called a heat pump? Chances are that many of them will say yes. Follow up with another question: Can you tell me what a heat pump does? Most of those who answered yes to your first question would likely say it does something that keeps a house warm in winter. Pose one more question to those who - so far - seem to have familiarity with heat pumps: Can you tell me how a heat pump works?
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2 months ago | 
pmmag.com | John Siegenthaler |Nicole Krawcke |Natalie Forster
In last month’s Heating with Renewable Energy column, we discussed piping options for multiple air-to-water heat pumps. The simplest approach — a 2-pipe header system — allows for staging and modulation of each heat pump, but it doesn’t allow some heat pumps to supply heating while others supply cooling. When simultaneous heating and cooling is required a 4-pipe header system with motorized valves allows any heat pump in the “plant” to be called into heating or cooling mode operation.
