Mitsubishi Zuba Central system and heat pumps

[IchBinKalt]

I have some quotes for the Mitsubishi Zuba system for our house and I have a few questions:

1 - from anyones experience, will the system work well on a 33 year old brick raised bungalow of 1,110 sqft and a heat load calc of 44,000 (ish) btu/h? The windows are mostly new, and the attic has been insulated from R11.9 to R50+. From what I have read online, it should be fine but...

2 - for the size of home, again from what I have read here, should I be getting an estimate on a York system as well?

3 - does anyone have one installed where I could get some info on yearly heating cooling costs and type/size of homes installed?

4 - what kind of longevity will the Mitsubishi's have? Similar to the r12 Ac units that ran for 20+ years? Are the heat pumps from York etc as good as they used to be?

Thanks a lot for any help, its just after years of living with a FAG system, and all the NAY sayers out there against the heat pumps, I need a little confirmation... of course the estimators said no problem, but I would love some real world figures, and they had installed so few that they had no testimonials for it.

[skippedover]

Well that's a new one on me. I've never heard of a Zuba system from Mitsubishi. In fact, I've never heard of a Mitsubishi central system. But then again, I'm in the USA. Could you be in Canada? Not all products are sold in both countries.

[IchBinKalt]

Just google it, and you will find the info on it from Mitsubishi... its finding information from other sources that is difficult. But after minutes on here, I have a local guy coming by tomorrow to take a look and quote me a price. He also has some testimonials which help as well...

[skippedover]

Well that's what I thought. It's a product only sold in Canada. So we down here in the lower 48 can't help you. Never have seen or heard of it.

[Tom Campbell]

Zuba looks VERY similar to the Nordyne iQ system (Broan). Different manufacturer of course, but very similar technology.

[mchild]

Zuba is a response to being able to replace an existing conventional North American type heat pump with the technology used for years now around the rest of the world - inverter driven compressors for operating efficiency and flexibility.

Mitsu is simply using a conventional style indoor unit and their hyper heat outdoor unit. The Mitsu hyper heat uses an oversized compressor to provide the high heat output at the single digit temps. In cooling more they limit the compressor speed to keep it at the nominal rating of 3 tons.

[Tom Campbell]

Zuba is a response to being able to replace an existing conventional North American type heat pump with the technology used for years now around the rest of the world - inverter driven compressors for operating efficiency and flexibility.

Mitsu is simply using a conventional style indoor unit and their hyper heat outdoor unit. The Mitsu hyper heat uses an oversized compressor to provide the high heat output at the single digit temps. In cooling more they limit the compressor speed to keep it at the nominal rating of 3 tons.

Oversize compressor for heating, but run it at 3 ton capacity for cooling. Hmmmm.

[DavidNJ]

Oversize compressor for heating, but run it at 3 ton capacity for cooling. Hmmmm.

I didn't realize that is how they did it but it makes sense. Might have worked better if it was multiple compressors though. They rate it at 40mbtu, but don't state the ambient temp. It is rated to -22F, but they don't give its capacity at that temp. They rate the COP as varying from 3.4 to 1.4; since power probably remains constant with 15%, that would imply it loses over half its capacity. It has optional electric resistance heaters up to 17.5kw (60mbtu). It would seem a hot water coil may be a better supplemental solution, although the Zuba may not have a control mechanism for it.

The 4-ton Nordyne can dip to 14mbtu at 60F while staying at 30mbtu at 12F. Ultimately that would come at a loss of modulation at low heating/cooling values. A conventional 2-ton is over 25mbtu at 60F.

[Tom Campbell]

I didn't realize that is how they did it but it makes sense. Might have worked better if it was multiple compressors though. They rate it at 40mbtu, but don't state the ambient temp. It is rated to -22F, but they don't give its capacity at that temp. They rate the COP as varying from 3.4 to 1.4; since power probably remains constant with 15%, that would imply it loses over half its capacity. It has optional electric resistance heaters up to 17.5kw (60mbtu). It would seem a hot water coil may be a better supplemental solution, although the Zuba may not have a control mechanism for it.

The 4-ton Nordyne can dip to 14mbtu at 60F while staying at 30mbtu at 12F. Ultimately that would come at a loss of modulation at low heating/cooling values. A conventional 2-ton is over 25mbtu at 60F.

I would go with a Nordyne if I could afford it, and that's why I'm trying to see if I can approximate the same heating effect by (mis) using an off-the-shelf 2 stage unit (different thread).

To the Original Poster - I'm not sure where BrockVegas is, but if you're looking for a similar US solution, check out Nordyne/Broan/Fridgidair.

[DavidNJ]

The question is: what are you trying to achieve? It doesn't look like an air-source heat pump maintains that much capacity in extreme conditions; does it really save operational costs when it is running at a 1.7 COP? If nat gas was $1.50/therm, electric would have to be around 9¢/kwh.

[Tom Campbell]

Just google it, and you will find the info on it from Mitsubishi... its finding information from other sources that is difficult. But after minutes on here, I have a local guy coming by tomorrow to take a look and quote me a price. He also has some testimonials which help as well...

Please let us know what you find out after meeting with the contractor, especially if any of the testimonials are available on public reviews websites. I'm assuming you are in Canada though, right?

[crmont]

Not "over sized" but able to ramp up the speed of the compressor in colder weather instead. Big difference.

[Tom Campbell]

Not "over sized" but able to ramp up the speed of the compressor in colder weather instead. Big difference.

From my understanding of DC vs AC motors, the DC motor in this kind of system is not only more efficient, but will likely hold up better over time than the AC motors used in traditional heatpumps.

I also understand from the above that it is not simply that it is designed for a larger capacity, so it must be either exceeding its capacity or perhaps it simply has a wider operating range than that of a standard AC motor at the lower end of the temperature spectrum? Does the "Ramping Up" involve a higher speed, or is it simply that a higher torque is required to achieve the compression needed lower temps? In either situation, does this mean that they would be going past the rated capability of the motor (or pump itself) to reach the output at lower temps? And would this have any impact on the longevity of either the motor or the pump?

[IchBinKalt]

Yes, I am in Canada... region V... my understanding is that it uses inverter technology to vary the pump output to match the load using a typically oversized unit in the AC mode but matches the heating mode. I believe that it only works if the house matches the output that it delevers. My place has been estimated at needing 43,572 btu/h at the most and a 1.5 ton AC unit. The mitsubishi is supposed to be able to ramp up and down between 25% and 100% output for both heating and cooling. So on paper, it should work for my house 99% of the time without needing the back up. It is also supposed to only suppliment what is needed if it is short... the system I was quoted so far (previous quote with no testimonials) included a 15kWh electric back up (I think that works out to a 51,000 btu/h back up - covering easily the load if the whole compressor fails). I would need clarification to weather or not that back up ramps up from say 2.5kWh to 15kWh...

I have been sent a testimonial from a customer of his (the contractor that is coming today) (no details will be given here on name etc), she went from oil of $3150 to an additional $593 electrical costs over the last year without the oil. I can assume she had air with the oil, so this number approximates the usage of the heating only. My consumption for a similar house to my new one was $991 (estimating out the fuel for DHW) for heating with a Trane XV95 2 stage ECM furnace. Her house is much newer and larger (3,000 sqft+ vs my 1,110, unless she has included the basement, where mine would be 2,220sqft) Does this mean my savings would be minimum approx. $400/year for heating? That would mean I would have a 5 year payback over a modulating Rheem furnace and 14.5 seer AC... (but funny enough, the Mitsubishi was quoted the same as the York and Tempstar systems that were quoted me)

Thats it for my rambling right now...

[DavidNJ]

This is Mitsubishi's claim:


The Technology Behind the Unequaled Comfort

The Hyper-Heating INVERTER outdoor unit uses flash technology which re-collects heat energy that is normally wasted in the flash process at the outdoor coil. This process helps the H2i systems overcome issues commonly associated with conventional heat pumps such as decreases in low-side pressure, refrigerant mass
flow rate and operational capacity.

The patent pending flash process cools the compressor allowing higher speeds at a lower outdoor temperature without overheating. This also allows increase in mass flow rate in the system providing phenomenal heating performance at low temperatures.

The Zuba fan coil is available with either electric heat or a hot water coil. It is rated at 44mbtu. Mitsubishi claims 100% capacity to 5F and 75% at -13F. They show 3 comparative examples in their brochure; the big gains are vs. electric resistance heating. Against natural gas the claims are more modest

http://www.mitsubishielectric.ca/en/hvac/PDF/zuba-central/Zuba-Central_Catalogue.pdf

[IchBinKalt]

With all the home renovations we will be doing, we just can't afford to put in the Zuba. Of that I am sad...

However, now I am looking at a couple brands of gas furnace, and am having a hard time with sizing. I have quotes from reputable installers for:

Trane - smallest 2 stage is the 60KBTU - but fires at its lowest at output ~40KBTU, and the modulating has not been recommended by the installer which would fire at output ~22KBTU as they are new and there have been issues with overheating.

Rheem - smallest modulating 60KBTU fires as low as output ~22KBTU and has been around for a while and comes recommended.

Goodman - smallest 2 stage is the 46KBTU which lowest fires at an output ~30KBTU and highest ~44KBTU - the cheapest, but a reputable company with quite a few satisfied customers (a relative, two coworkers and a friend have all had work (furnaces and repair) by them and are happy) are the installers, which is a factor considering the negative comments all over the web on Goodman.

The big question is: When I was looking at the Mitsubishi Zuba, it was agreed between installers that my house would easily be heated by the 40KBTU output of the Zuba. So now, with the gas furnaces I am at the mercy of looking at the manufacturers smallest furnaces, most of which are 60KBTU and up.

Would it not be best to buy the one that most closely matches the house? Like the Rheem or the Goodman? I would include the Trane modulating but the installer himself doesn't believe I should... wouldn't a 2 stage or modulating that fires well below my house rating be best?

[commerce48]

wouldn't a 2 stage or modulating that fires well below my house rating be best?

Yes. And the more you pay all the way up to the Zuba Central, the more comfort you will get. The ideal is to have your furnace exactly match your home's heat loss at any outdoor temperature. This means your furnace would be running all the time, using no more energy than is required. The fan would be running so slowly most of the time that sound and air currents (if the ductwork is well designed) that you will never know it is running. Only the Zuba will be able to do this at higher outside temperatures as only it can have very low outputs.

Two other alternatives for you. York/Luxaire/Coleman have the highest efficiency on the market at 98 percent. They have a 60 kbtu model that goes down to 35 percent, or around 21 kbtu.

If you can take a chance (your current furnace still works), Carrier is supposed to release a modulating unit this fall that is rumored to go down to 25 percent. If they continue to have a 60 kbtu model, the lowest output will be down around 14 kbtu (after adjusting for 95 percent efficiency). Several ifs, and this model will be the most expensive of your gas choices.

The Goodman will be fine, but a modulating furnace would be a significant step up. I'm in the same position as you, with a house with even lower heating needs. I'd love the Zuba, but can't get it in the US. So I'm waiting to see what Carrier comes out with.

[Peztoy]

I posted to a similar thread. At some point I'll be replacing my furnace and ac. I'm considering this Canada only Mitsu Zuba eh for the Toronto, ON area. Anyone out there have good things to say about it?

[dufour]

This is Mitsubishi's claim:



The Zuba fan coil is available with either electric heat or a hot water coil. It is rated at 44mbtu. Mitsubishi claims 100% capacity to 5F and 75% at -13F. They show 3 comparative examples in their brochure; the big gains are vs. electric resistance heating. Against natural gas the claims are more modest

http://www.mitsubishielectric.ca/en/hvac/PDF/zuba-central/Zuba-Central_Catalogue.pdf


I've seen the Zuba operate at -20C and output 43C. I'd say that is pretty amazing. What's more amazing than that is the fact that the defrost runs for only 3 minutes in roughly 6 hours of heating. I have one installed in my house and I've saved around $700 in heating over last year and this winter is much colder.

[crmont]

I've seen the Zuba operate at -20C and output 43C. I'd say that is pretty amazing. What's more amazing than that is the fact that the defrost runs for only 3 minutes in roughly 6 hours of heating. I have one installed in my house and I've saved around $700 in heating over last year and this winter is much colder.

Are you in Canada?

[dufour]

Yes,

I'm in Windsor Ontario- These are also used extensively in Quebec and across Ont. The Zuba is a Canadian innovation using an industrial based condenser and residential based air handler so I'm very confident in it's performance.

[Peztoy]

Correct me if I'm wrong. This is a variable capacity system that will ramp from 0 tons up to 3 tons. The indoor fan speed will adjust accordingly.
So this is a one size fits all system as long as you don't need more then 3 tons?

[dufour]

That is the basic idea. Lets say you calculated your heat loss at 45,000btu. You could still use a zuba provided you also installed a 10kw heater to cover the difference (45,000 - 36, 000 =9,000) The heater is designed so that the zuba will operate without any backup until it can no longer satisfy the stat. Only at this point will the backup come on to top up the difference.- very efficient.

[Peztoy]

In my case I'd like to use the hot water back up instead of electic duct heater. The hot water would have a variable speed pump.

Though a duct heater with scr's might not be to costly to operate. Would be easier to install.

[dufour]

If you want to go with hot water, you need to order the unit with the hot water installed - I don't think it is a variable speed pump though. What's nice with the electric backup is that you don't need to factory install - You can order without any backup, monitor the unit & if required add the backup later.