Mitsubishi Mr.Slim heat pump

[Buzzant]

Hi everyone
I have a Mitsubishi Mr.Slim heat pump 15 000 BTU
i am trying to find specs on it that mention it's minimum outside temperature shut off point cause mine shuts off at -10 celcius and i am wondering if making it shut off at let say -15 would damage it?

I have put it's sensor inside the box (where it is a bit warm) instead of outside, now all i have to do is keep a eye on it and see at what temp. it will shut off.

Thanks

[nike123]

Hi everyone
I have a Mitsubishi Mr.Slim heat pump 15 000 BTU
i am trying to find specs on it that mention it's minimum outside temperature shut off point cause mine shuts off at -10 celcius and i am wondering if making it shut off at let say -15 would damage it?

Yes it will, undone changes!

Spec: 14°F WB and 13°F DB

Use electric heater below -10°C. Efficiency of AC at that low temperature is very poor and you got similar result with electric heater.

[Buzzant]

Yes it will, undone changes!

Spec: 14°F WB and 13°F DB

thanks but where do you get this info. can you show link or something?

[nike123]

thanks but where do you get this info. can you show link or something?

I am service engineer and I have full HD of such data.

[Buzzant]

I am service engineer and I have full HD of such data.

I understand but i saw from a Sanyo data sheet that the minimum the compressor would work is -25C so i am looking for such data but for the Mitsubishi, i have a installation manuel but it doesn't say.

A Sanyo service engineer told me some of is customers were heating at -20C.

[nike123]

.................................

[Buzzant]

Big thanks man, its very nice and considerate of you.

[Buzzant]

Ok what i'm thinking is to test it, check it very closely and give some feed back, i don't think just a few degrees less (2 or 3 C) should effect the machine but could do quite a difference in the house, i have a cottage and it manage to heat up the entire second floor and lately the weather went down to -13C and it shuts off at -10C.

Your tough?

[AbsoluteWDJ]

I understand but i saw from a Sanyo data sheet that the minimum the compressor would work is -25C so i am looking for such data but for the Mitsubishi, i have a installation manuel but it doesn't say.

A Sanyo service engineer told me some of is customers were heating at -20C.

Sanyo heat pump carbon dioxide (CO2) natural gas system performs at lower ambient temperature. You have R410a refrigerant gas.

[Buzzant]

Sanyo heat pump carbon dioxide (CO2) natural gas system performs at lower ambient temperature. You have R410a refrigerant gas.

The Sanyo that the service engineer told me about some of is customers that were heating at -20C uses the exact same gas as the Mitsubishi, it's almost a carbon copy, it is his direct competitor here in Canada.

[Buzzant]

I am trying to find proof that making it work at a few degrees lower wont damage the outdoor unit.
Cause usually when it comes to degree control precision is not that precise, i don't think they would make it shut off at it's exact crucial point, they have to give a margin of error.

[Buzzant]

Hey guys look at what i just found, take a look at the service manual.

It is the same for the 12k or 18k BTU

Why the Mitsubishi should be different, the 2 machines are pretty much the same.


us.sanyo.com/HVAC-Single-Split-Systems-Wall-Mounted-Heat-Pumps/Wall-Mounted-Heat-Pump-12KHS71

[nike123]

I am trying to find proof that making it work at a few degrees lower wont damage the outdoor unit.
Cause usually when it comes to degree control precision is not that precise, i don't think they would make it shut off at it's exact crucial point, they have to give a margin of error.

There is no proof. Manufacturer has set cut out temperature after extensive testing and you should not do anything which will put it in danger.
And you just doing that.

[Buzzant]

Just put the www in front i cannot put url yet

[nike123]

Hey guys look at what i just found, take a look at the service manual.

It is the same for the 12k or 18k BTU

Why the Mitsubishi should be different, the 2 machines are pretty much the same.


us.sanyo.com/HVAC-Single-Split-Systems-Wall-Mounted-Heat-Pumps/Wall-Mounted-Heat-Pump-12KHS71

What makes you think that they are the same?

[Buzzant]

What makes you think that they are the same?

Come on man! i read the specs!

[Buzzant]

I have compare both very closely before a bought the Mitsubishi in the month of May 2009

[nike123]

Ok, then you are saying that manufacturer intentionally forbid operation at much lower temperature.
What would be his reason to do that, and in same time other manufacturer reason to not do that?

And what specification tells you that they are same? Quote, please.

[Gary]

Come on man! i read the specs!

You have two cakes made by two bakers. They are the same size and they both contain flour, therefore they must be identical, right?

It ain't necessarily so.

[Buzzant]

Ok, then you are saying that manufacturer intentionally forbid operation at much lower temperature.
What would be his reason to do that, and in same time other manufacturer reason to not do that?

And what specification tells you that they are same? Quote, please.

1- yes and they do that to protect them self, it's only normal.

2-Print both specifications sheets and compare side by side.

[Buzzant]

You have two cakes made by two bakers. They are the same size and they both contain flour, therefore they must be identical, right?

It ain't necessarily so.

I understand your point but cooking is not as an exact a science as are electronics and pressure control and such.

it's closer to compare two cars that are in the same cathegorie, you get the exact same qualities and performances but there different.

[Buzzant]

See guys i think that these days there is no mystery on how to make the best machine so they all make pretty much the same as they need to compete, same with cars and lots of other stuff.

I had also compare the fujitsu before buying and once again, pretty much the same

look here. but put the www in front

.ductless.ca/brochures/fujitsu/halcyon_06.pdf

Maybe i had my answer all along but wanted the personal experience of people?

[Buzzant]

Like i said previously, i will test it an post feed back.
All i did is put the sensor inside the box instead of outside so temp. will not differ that much!

[AbsoluteWDJ]

Mitsubishi have recently brought out a product called Zubadan heat pump, here in the UK. This unit operates in heating with ambient temperatures up to -25c. I've not yet seen one or even heard of anyone that has purchased this system but it appears they have the technology in place. I can only find 7.1kW - 10kW on a selected Mr slim range. Go to products & choose Mr Slim on the Mitsi website: http://www.mitsubishi-aircon.co.uk/d...i_electric.asp

[nike123]

1- yes and they do that to protect them self, it's only normal.

Than what is the reason that Sanyo doesn't protect itself?

2-Print both specifications sheets and compare side by side.

Are you kidding?
What is your profession or area of expertize? How much you know about refrigeration and air conditioning?

You still did not quoted what data tells you that these two units perform same at low temperatures.

[desA]

I am trying to find proof that making it work at a few degrees lower wont damage the outdoor unit.
Cause usually when it comes to degree control precision is not that precise, i don't think they would make it shut off at it's exact crucial point, they have to give a margin of error.

I'll give you the way to know for certain:

1. Open the outdoor unit - gain access to the compressor;
2. Install a temp sensor 150mm from the compressor exit, on the discharge line (the hot one);
3. Let the unit pull down & watch the discharge temp;
4. If temp exceeds 107-110'C, then you are pushing your unit too far.

It is possible that the manufacturer lets the compressor discharge run up a little higher on non-continuous load, but not too much higher.

Let us know how you get on.

[mad fridgie]

Mitsubishi have recently brought out a product called Zubadan heat pump, here in the UK. This unit operates in heating with ambient temperatures up to -25c. I've not yet seen one or even heard of anyone that has purchased this system but it appears they have the technology in place. I can only find 7.1kW - 10kW on a selected Mr slim range. Go to products & choose Mr Slim on the Mitsi website: http://www.mitsubishi-aircon.co.uk/d...i_electric.asp

In NZ I think this call Hypercore, basically a larger outdoor unit on a smaller indoor unit, lots of smarts in the electronics (keep the refrigeration balanced)
I believe (not seen) that they flood the evap at low temps and have a heater in the suction line to ensure there is some level of superheat/and load.
They are marketted as the same heatput across a full temperature range (the sales guy tried to say the same COP across the whole range, Bull Sh** if you ask me)
Buzzant, there is no mystery in refrigeration principle, I agree, but how these are applied is the mystery, with slight changes in controls , air flow, coil(s) configuration you can change the working enverlope of a system. You design to achieve best results at the designers conditions. Different manufactures design around these different conditions. Just because the sanyo is rated to -25 does not make it better across the whole range.
( Not saying sanyo is good or bad, just not the same)

[desA]

I believe (not seen) that they flood the evap at low temps and have a heater in the suction line to ensure there is some level of superheat/and load.

Interesting approach. Do they have a suction accumulator?

[mad fridgie]

Interesting approach. Do they have a suction accumulator?

All seem to have a small one acc, but I have never seen one these stripped down. maybe the heater is a combanation acc.

[desA]

Thanks MF.

Flashing off liquid carryover would either require a fairly hot heat source, or some sort of residence time... it takes a finite time & you'd need to be sure.

[Gary]

See guys i think that these days there is no mystery on how to make the best machine so they all make pretty much the same as they need to compete, same with cars and lots of other stuff.

I had also compare the fujitsu before buying and once again, pretty much the same

look here. but put the www in front

.ductless.ca/brochures/fujitsu/halcyon_06.pdf

Maybe i had my answer all along but wanted the personal experience of people?

If there is anything I have learned over the years, its that people believe what they want to believe, simply because they want to believe it.

Yes... you had your answer all along, and thats the problem. Rather than let the evidence lead you to the answer, you let the answer lead you to the evidence. If you started with the opposite answer, you would find the opposite evidence. All roads lead to 'you are right'.

[Buzzant]

If there is anything I have learned over the years, its that people believe what they want to believe, simply because they want to believe it.

Yes... you had your answer all along, and thats the problem. Rather than let the evidence lead you to the answer, you let the answer lead you to the evidence. If you started with the opposite answer, you would find the opposite evidence. All roads lead to 'you are right'.

Pretty deep man!

and thanks guys for the comments, keep them coming

[Buzzant]

I'll give you the way to know for certain:

1. Open the outdoor unit - gain access to the compressor;
2. Install a temp sensor 150mm from the compressor exit, on the discharge line (the hot one);
3. Let the unit pull down & watch the discharge temp;
4. If temp exceeds 107-110'C, then you are pushing your unit too far.

It is possible that the manufacturer lets the compressor discharge run up a little higher on non-continuous load, but not too much higher.

Let us know how you get on.

Than what is the reason that Sanyo doesn't protect itself?

Are you kidding?
What is your profession or area of expertize? How much you know about refrigeration and air conditioning?

You still did not quoted what data tells you that these two units perform same at low temperatures.

Before i buy i did print the specs. sheets of 3 different competitive heat pump and looked at them side by side to find that they all have pretty much the sames specs so!

Sorry mate but i am trying to clarify something, i'm not here to justify my self to frustrated people.

[desA]

Removed by desA...

[Buzzant]

Sorry DesA i did not want to quote you on that one, my mistake.

it was met for Nick 123

[desA]

^ No problem... I'll remove my post above, then.

If you have a chance, try & measure the temperature I suggested. This will be useful for all of us.

[Buzzant]

^ No problem... I'll remove my post above, then.

If you have a chance, try & measure the temperature I suggested. This will be useful for all of us.

Ok cool thanks, as for the test i am not equipped to do it so :-(

but what are your tough on me putting the sensor inside the box insted of outside so it wont be in the wind factor and will probably cut off a bit lower then -10C?

[Buzzant]

You know what guys?
I just put the sensor back where it belong and i am going to forget about it, i always like to push thing to their limit but if the risk of breaking it is to great it doesn't worth it, so i will live it be.

Thank you all for trying to help, peace out.

[desA]

^^ You cannot make a decision like that, without measuring the temperature.

As the other members have stated, each manufacturer sets up their systems differently. The difference between a reliable system & a blown compressor could be the few degrees you are wanting to over-run the spec by.

I simply would not take the chance, unless I was either experienced, or advised by the manufacturer...

[Buzzant]

^^ You cannot make a decision like that, without measuring the temperature.

As the other members have stated, each manufacturer sets up their systems differently. The difference between a reliable system & a blown compressor could be the few degrees you are wanting to over-run the spec by.

I simply would not take the chance, unless I was either experienced, or advised by the manufacturer...

I said (i put the sensor back where it belong)
thanks again man

[nike123]

B
Sorry mate but i am trying to clarify something, i'm not here to justify my self to frustrated people.

What makes you thing that I am frustrated?
I just tried to have argumented discussion, but I don't see any arguments from your side. And i am still not frustrated.

[Thermatech]

The Heat mode defost control stratagy has some impact on this minimum outside ambient temperature issue & different manufacturers deploy slightly differnt defrost stratagy.

For example
Mitsubishi Mr Slim split system heat pumps calculate an appropriate heat mode operation time untill the next defrost based on the lenght of time it took to complete the last defrost.

The minimum period of heating operation between defrosting is 20 mins when the last defrost took 15 min to complete.
If you look in the technical data books at the heating performance graphs you will see that at minus 10 - 12 deg C ambient the heat pump is doing arround 50 to 60 % heating duty only depending on other stuff like interconnect pipe length.

In practical terms as soon as the system starts heating mode in low abmient conditions the suction pressure is being reduced due to the frost forming on the outdoor coil. This makes the discharge temperature higher as the coil becomes more frosted.

At the Mitsubishi factories in Japan I know they do a lot of testing in environmental chambers.
So I would suspect that the Mitsubishi R&D engineers know that at minus 10 or minus 12 deg C the outdoor coil is going to be so heavily frosted within the minimum run time in heat mode that the compressor will be running at excessive discharge temp & will cause compressor damage.

Any way as stated before what is the point of a heat pump if it is in defrost for 15 mins & then heating at low heating performance for only 20 mins ?

In this case back up electric heating is needed.

Here in the UK we dont tend to get such extreem cold weather except in Scotland so this is not really any problem.

This is a global product & the manufacturer is only going to make a special design for very very low ambient conditions if there is a market & demand for such a product.

[Buzzant]

The Heat mode defost control stratagy has some impact on this minimum outside ambient temperature issue & different manufacturers deploy slightly differnt defrost stratagy.

For example
Mitsubishi Mr Slim split system heat pumps calculate an appropriate heat mode operation time untill the next defrost based on the lenght of time it took to complete the last defrost.

The minimum period of heating operation between defrosting is 20 mins when the last defrost took 15 min to complete.
If you look in the technical data books at the heating performance graphs you will see that at minus 10 - 12 deg C ambient the heat pump is doing arround 50 to 60 % heating duty only depending on other stuff like interconnect pipe length.

In practical terms as soon as the system starts heating mode in low abmient conditions the suction pressure is being reduced due to the frost forming on the outdoor coil. This makes the discharge temperature higher as the coil becomes more frosted.

At the Mitsubishi factories in Japan I know they do a lot of testing in environmental chambers.
So I would suspect that the Mitsubishi R&D engineers know that at minus 10 or minus 12 deg C the outdoor coil is going to be so heavily frosted within the minimum run time in heat mode that the compressor will be running at excessive discharge temp & will cause compressor damage.

Any way as stated before what is the point of a heat pump if it is in defrost for 15 mins & then heating at low heating performance for only 20 mins ?

In this case back up electric heating is needed.

Here in the UK we dont tend to get such extreem cold weather except in Scotland so this is not really any problem.

This is a global product & the manufacturer is only going to make a special design for very very low ambient conditions if there is a market & demand for such a product.

Big thanks to you
Ibought it mostly for cooling purposes but i find my self wanting to use it's heating capabilities to the max

[back2space]

Before i buy i did print the specs. sheets of 3 different competitive heat pump and looked at them side by side to find that they all have pretty much the sames specs so!

Sorry mate but i am trying to clarify something, i'm not here to justify my self to frustrated people.

Maybe similar specs but not same components, different compressors etc in each systems that will be rated to different dutys and capabilities.