JP2
New Member
Hi I'm Jeremy, and I'm looking for some advice on designing a properly sized heat pump system for home. I've learned a lot already from reading this forum but could use a little more specific advice for my situation. I hope this post is appropriate for the forum.
Here's the background about my house and situation: My house was built in 1996 is 1700 sq ft and is located in Seattle. It has an entirely open first floor living/dining/kitchen and three bedrooms on the second floor. Two adjacent bedrooms are about 110 sq ft and the master is about 250 sq ft with large vaulted ceiling. There is also a large landing/bonus area between the master bedroom and the smaller bedrooms. I calculated a heating load of 21,600 BTU using the calculator at http://hvac.betterbuiltnw.com/, which I read is the most accurate for sizing heat pumps. The house is currently heated by the original gas furnace. I am interested in switching to a heat pump for two reasons: (1) to gain air conditioning and (2) to free up the utility closet on the first floor that currently houses the furnace for other uses.
I had an hvac company out to give an estimate and they recommended a 36000 BTU daikin multizone with a 7k head in the two smaller bedrooms, a 9k head in the larger bedroom, and an 18k head on the first floor. They were not particularly concerned about oversizing because the inverter modulates the load. However, the inverter is limited in how much it can modulate the load.
After doing some research I discovered Neeps cold climate heat pump list. What a fantastic resource. I entered my location and heating design, and it actually looks like a 36000 BTU daikin Aurora --a different model than the hvac company recommended--may be best for my house because of its high turndown ratio: https://ashp.neep.org/#!/product/26570/28/22000/WA/727930/1. It looks like this model can modulate more than smaller models such that it can actually satisfy a greater percentage of the annual load in the modulating range. But since I'm just a curious homeowner, I wanted to get an expert opinion. Does this make sense?
The NEEP website focuses on the outdoor unit's ability to modulate. Will this be affected by the indoor head sizing? In other words, since the indoor heads are all oversized will that cancel out or reduce the benefits of the outdoor unit's large turn down ratio and result in significant short cycling? An alternative option that I have thought up is to put a 7k ducted unit in the unconditioned attic for the two small bedrooms to share, put a 7k ductless unit in the master, and then a 12k ductless for the first floor. That would at least make the demand each head satisfies more tailored to the room it serves. Will more right sizing the heads make a difference for the outdoor unit's ability to modulate and avoid short cycling?
If I can in fact get the performance the NEEP website suggests from the Daikin Aurora that seems like a pretty good option to me. It will more than satisfy the heating needs even if it's unseasonably cold without too much short cycling. But I want to make sure that is in fact realistic before proceeding. Would also love to hear any other ideas for my situation.
Thanks!
Here's the background about my house and situation: My house was built in 1996 is 1700 sq ft and is located in Seattle. It has an entirely open first floor living/dining/kitchen and three bedrooms on the second floor. Two adjacent bedrooms are about 110 sq ft and the master is about 250 sq ft with large vaulted ceiling. There is also a large landing/bonus area between the master bedroom and the smaller bedrooms. I calculated a heating load of 21,600 BTU using the calculator at http://hvac.betterbuiltnw.com/, which I read is the most accurate for sizing heat pumps. The house is currently heated by the original gas furnace. I am interested in switching to a heat pump for two reasons: (1) to gain air conditioning and (2) to free up the utility closet on the first floor that currently houses the furnace for other uses.
I had an hvac company out to give an estimate and they recommended a 36000 BTU daikin multizone with a 7k head in the two smaller bedrooms, a 9k head in the larger bedroom, and an 18k head on the first floor. They were not particularly concerned about oversizing because the inverter modulates the load. However, the inverter is limited in how much it can modulate the load.
After doing some research I discovered Neeps cold climate heat pump list. What a fantastic resource. I entered my location and heating design, and it actually looks like a 36000 BTU daikin Aurora --a different model than the hvac company recommended--may be best for my house because of its high turndown ratio: https://ashp.neep.org/#!/product/26570/28/22000/WA/727930/1. It looks like this model can modulate more than smaller models such that it can actually satisfy a greater percentage of the annual load in the modulating range. But since I'm just a curious homeowner, I wanted to get an expert opinion. Does this make sense?
The NEEP website focuses on the outdoor unit's ability to modulate. Will this be affected by the indoor head sizing? In other words, since the indoor heads are all oversized will that cancel out or reduce the benefits of the outdoor unit's large turn down ratio and result in significant short cycling? An alternative option that I have thought up is to put a 7k ducted unit in the unconditioned attic for the two small bedrooms to share, put a 7k ductless unit in the master, and then a 12k ductless for the first floor. That would at least make the demand each head satisfies more tailored to the room it serves. Will more right sizing the heads make a difference for the outdoor unit's ability to modulate and avoid short cycling?
If I can in fact get the performance the NEEP website suggests from the Daikin Aurora that seems like a pretty good option to me. It will more than satisfy the heating needs even if it's unseasonably cold without too much short cycling. But I want to make sure that is in fact realistic before proceeding. Would also love to hear any other ideas for my situation.
Thanks!
