Heat pump or separate heating and cooling

[ilameer628]

First let me say that this forum is beyond amazing. That said, I have tried to find answers to my many question and was only able to find answers to a few. Here it goes.

Background:
I have a 1930's all brick two unit house in Yonkers, NY, but I'm only concerned with the first floor right now. That unit has 2 bedrooms, a kitchen, a bath, a living, dining, and sun rooms, which add up to around 1100 sq ft. The living, dining, and sun rooms were all gutted and redone last year (They were originally plastered). The exterior walls were insulated with R-5 foam board, while the ceiling was insulated with R-20 for sound proof reasons. The bedrooms, having been done two years earlier, were not gutted, but the walls were framed out and insulated with R-11. I also had a 4.2 kw solar system installed on the roof.

I have a Weil Mclain EG-55-P1 natural gas boiler heating the whole house through steam radiators, but there are no cooling equipment currently installed. Which brings me to my options. I am exploring the possibility of adding some sort of centralized cooling but since I'm going to be implementing that, I figured I might as well explore a possible heating upgrade.

Option 1:
Get a mini split heat pump system (Mitsubishi Mr. Slim) installed. This would be a four zone system. The sun room and the living room would be combined into one zone while the other rooms will each be on individual zones. However, this would mean that the air handlers would most likely be wall mounted, which are somewhat intrusive.

Option 2:
Install mini ducts with a high velocity (HV) air handler or a conventional duct and air handler with some sort of heat pump. This raises the question of whether HV ducts are a better choice than conventional ducts. Everything I read about HV ducts states that they are less efficient than conventional ducts. But what is a good estimate (%) of how less efficient it is? And what is the respective cost difference?

With regards to the heat pump, I was thinking of a geothermal or a standard air source unit. At first glance, the geothermal route increases the complexity if used with a HV air handler, which would increase cost. But the increased efficiency is extremely appealing. The other possibility, air source, suffers from decreased heat pump efficiency in winter temperatures near or below freezing. Which brings up the topic of cold climate heat pumps. The only models I came across are the Hallowell Acadia and the Mitsubishi Zubadan. I believe Hallowell is out of business and the Zubadan series is not available in the US. Are there any other models that would perform well in those temperatures?

Option 3:
Use a duct system, either HV or conventional, as a common distribution source. But instead of having a heat pump, I would use a separate unit for heating and another one for cooling. Obviously this means that I will have three pieces of equipment and would increase cost and possibly maintenance.

Option 4:
Something that I have not thought of yet.

Heating/Cooling Load:
I was able to calculate the heating and cooling loads using the HVAC-CALC software in accordance with Manual J. After factoring in some of the insulation I will me adding, the heat loss is 34700 BTUs while the heat gain is 19950 BTUs. If I were to get a heat pump, what size would it be? Do I use the cooling load BTUs and be short on the heating side, or do I use the heating load BTUs and be over sized on the cooling side?

I would like to use electricity as the energy source in order to utilize my solar system. I know this is a lot of information all at once. All your help and advice is greatly appreciated.

Thanks.

- NG

[ilameer628]

Update

I have decided to eliminate high velocity ducts as an option. This is due to the fact that I will have access to the floor joists through the basement.

Does anyone know if Mitsubishi Zuba is available in the US?

[skippedover]

First let me say that this forum is beyond amazing. That said, I have tried to find answers to my many question and was only able to find answers to a few. Here it goes.

Background:
I have a 1930's all brick two unit house in Yonkers, NY, but I'm only concerned with the first floor right now. That unit has 2 bedrooms, a kitchen, a bath, a living, dining, and sun rooms, which add up to around 1100 sq ft. The living, dining, and sun rooms were all gutted and redone last year (They were originally plastered). The exterior walls were insulated with R-5 foam board, while the ceiling was insulated with R-20 for sound proof reasons. The bedrooms, having been done two years earlier, were not gutted, but the walls were framed out and insulated with R-11. I also had a 4.2 kw solar system installed on the roof.

I have a Weil Mclain EG-55-P1 natural gas boiler heating the whole house through steam radiators, but there are no cooling equipment currently installed. Which brings me to my options. I am exploring the possibility of adding some sort of centralized cooling but since I'm going to be implementing that, I figured I might as well explore a possible heating upgrade.

Option 1:
Get a mini split heat pump system (Mitsubishi Mr. Slim) installed. This would be a four zone system. The sun room and the living room would be combined into one zone while the other rooms will each be on individual zones. However, this would mean that the air handlers would most likely be wall mounted, which are somewhat intrusive.

Zuba is not currently available in the USA for some weird reason that's totally beyond my level of understanding. This is an excellent choice but with a couple of errors. You can have low wall units on a multi-zone system rather than high wall, thus looking more like radiation convectors than AC units. Or alternatively, if you've got a space for a small air handler, you can put in a mini-ducted unit that could put a supply in each of a couple of bedrooms or two supplies in one, as necessary by load analysis.

Option 2:
Install mini ducts with a high velocity (HV) air handler or a conventional duct and air handler with some sort of heat pump. This raises the question of whether HV ducts are a better choice than conventional ducts. Everything I read about HV ducts states that they are less efficient than conventional ducts. But what is a good estimate (%) of how less efficient it is? And what is the respective cost difference?

Glad you ruled this option out. I'm not a fan of HV systems. I prefer to install sound studio quiet systems. JMO.

With regards to the heat pump, I was thinking of a geothermal or a standard air source unit. At first glance, the geothermal route increases the complexity if used with a HV air handler, which would increase cost. But the increased efficiency is extremely appealing. The other possibility, air source, suffers from decreased heat pump efficiency in winter temperatures near or below freezing. Which brings up the topic of cold climate heat pumps. The only models I came across are the Hallowell Acadia and the Mitsubishi Zubadan. I believe Hallowell is out of business and the Zubadan series is not available in the US. Are there any other models that would perform well in those temperatures?

Interesting question with an interesting answer. Yes, Nordyne, Carrier/Bryant and soon others will all have high end, very high efficiency, variable speed heat pumps. What this means to you the end user is that the HP could be sized larger for heating because it will self regulate down to very small for cooling. In other words, normally we'd size a HP for the cooling season and it begins to run out of capacity around 30-35°F normally. With a variable speed unit, the real consideration for cooling is, does it slow down enough to cool and dehumidify properly. These variable speed units can actually slow down to 30% of full capacity, thus allowing for a larger HP that would have enough capacity to a much lower temperature. I've already seen one study where the system was sized at 1.5-tons for cooling but they used a 3.0-tons variable speed unit and it heated down to cold temps with adequate heat capacity and also cooled at less than 1.5-tons when in cooling mode. WOW! That's win-win, isn't it? So yes, there is an option and it's not in OZ, Dorothy!

Option 3:
Use a duct system, either HV or conventional, as a common distribution source. But instead of having a heat pump, I would use a separate unit for heating and another one for cooling. Obviously this means that I will have three pieces of equipment and would increase cost and possibly maintenance.

Option 4:
Something that I have not thought of yet.

Heating/Cooling Load:
I was able to calculate the heating and cooling loads using the HVAC-CALC software in accordance with Manual J. After factoring in some of the insulation I will me adding, the heat loss is 34700 BTUs while the heat gain is 19950 BTUs. If I were to get a heat pump, what size would it be? Do I use the cooling load BTUs and be short on the heating side, or do I use the heating load BTUs and be over sized on the cooling side?

See my paragraph above.

I would like to use electricity as the energy source in order to utilize my solar system. I know this is a lot of information all at once. All your help and advice is greatly appreciated.

Thanks.

- NG

Geo-thermal is another option and would be sized for heating if it's to be the sole source of heat (other than a toaster aux heater. This has the advantage of putting out full capacity down to the coldest temps but presently only come in 1-stage or 2-stage operation, with 1st stage being 67% of 2nd stage. So in order to size appropriately for cooling too, it gets a little dicey. On the other side, you can enjoy a federal tax credit of 30% of the ENTIRE installation if you put in a geo system and have until 2016 to enjoy that benefit. Hope this helps. Regards, SO