Mini Splits and Mono-bloc Question

jb9

Hello,

I am most likely going to use some kind of air source heat pump to heat water for a hydronic system I am installing. Load sizing aside, I don't fully understand the mono-bloc term that is used in some of the literature describing the units. I am building in a cold climate so I am carefully examining the COP (Coefficient of Performance) of the units (Chilltrix, Mitsubishi, etc). What is the difference between a mono-bloc and non-mono bloc unit? Why has the design evolved this way? Is one design better from a cost of ownership/maintenance or durability standpoint? I most likely will need an electric resistance boiler in series with whatever heat pump I select. Also, I am not a total refrigeration guru, but I do understand the basic evaporator and condenser components to the system... Feel free to give me a reading assignment or two if you think it will help. Also, if a heat pump is potentially oversized for the system, does the concept of short cycling death (as it is emphatically warned against) apply as much to a system using a heat pump? As we all know, combustion based boilers can die an early death due to short cycling.

Thanks in advance.

Paul S_3

Mono bloc air to water heat pump i believe means a packaged system...a mono bloc would require insulated water lines filled with glycol (prevent freezing) from outdoor unit to mechanical room ...non monobloc means its a split system and refrigeration piping work is required so if your not a "refrigeration guru" this isnt the way to go and a mono bloc would be used. To minimize short cycling you would need a buffer tank. Especially for the cooling side of it because the cooling capacity is oversized because you have to size the unit to meet the heating demand.

njtommy

A buffer would be great for have stored water for peak days and too eliminate short cycling. I believe most of these systems that you are looking at are VRF and modulating the compressors.

Check these out too. Daikin altherma

http://youtu.be/9lPjxnInwcQ

Paul S_3

how cold can these units operate at? would need some sort of auxiliary heat with design days around 10 F ? do they lose capacity? its air to water not like geo that's water to water that can extract more heat from the ground

Steamhead

Hatterasguy said:

That is fugly............!!

In Japan, the ones I've seen are usually installed in the rear, facing the alley or in a narrow walkway between buildings, so they aren't where people see them much.

njtommy

The Daikin is good for full btu out put down to 5f. Mitsubishi says there Hyper heat will run down to -10 with full btu out put.

SWEI

Fujitsu has low ambient versions rated down to -15F. ISTR Mitsu HH also claiming -15F? The standard units are good to about 5F, at a couple points lower than the 10F output.

For smaller houses with forced air and no NG availability, the current generation of mini-splits are real game changers.
The Altherma appears to be effectively EOL'd at this point in the US.

BobC

The problem (like steam) is making sure they get installed correctly, the devil is in the details!

Bob

SWEI

Lifecycle is also limited, at least in comparison with hydronic systems. Monobloc air-to-water designs can at least be replaced as a component rather than forklifing the entire system.

njtommy

Fujitsu puts pan heaters in there units too for the ones rated down to -15.

That is the nice part Swei. It's parts here and there an hopefully not entire unit. Lots of place now are going to this big VRV systems. With mutible systems installed if one item goes down the whole building does not lose cooling or heating. And with every School or building going to solar panels it silly not to use technology like this.

njtommy

No I haven't other then Economizers on chillers.
I would even consider r134a to be used or 404. Suction pressure would probably be around the 20 - 25 degrees regardless of refrigerant used. You need to try and keep your head pressure up around 100 degrees to keep the TXV working correctly. You can try with a comfort-cooling system or a medium temp refrigeration condenser IMHO.

I would really like to try this out my self.

jb9

So is it reasonable to assume that a mono-bloc is going to have a lower cost of ownership from a maintenance standpoint? Also, I should also add that I am only concerned about the heating capabilities of the heat pump I select. At a high level, what are the main considerations that should inform a design choice for a mono-bloc versus a non mono-bloc heat pump? Also feel free to throw some names of vendors out there so I can continue my research. I am aware of Fujitsu, Mitsubishi, Chilltrix, Spacepac and that's about it. I would also be interested to hear folks' experiences with particular brands.

Thanks.