Archive for April, 2013

Adding a Programmable Thermostat to Mitsubishi Mr. Slim Heat Pumps

As part of an ongoing energy upgrade of my 1930 home, I had four Mitsubishi Mr. Slim mini-split heat pumps installed (three MUZ/MSZFE09NA 9000 BTU units, and one MUZ/MSZ12NA 12,000 BTU unit.)

If price had been no object, I probably would have gone for Waterfurnace’s (TSX:WFI/OTC:WFIFF) Series 7 or Climatemaster’s Trilogy ground source heat pumps,  but my home’s existing heating is an oil boiler and radiators, and the Series 7 would require installing air ducts throughout the house.  The mini splits have the advantage that the refrigerant lines can run up the outside of the house, making them much easier to retrofit.

The geothermal systems I was quoted would have cost $50,000 to $60,000 (minus a $500 rebate from my utility), while the mini-splits cost $15,500 (minus a $2000 rebate.)

Because I’m also doing extensive insulation and air sealing, my heating bill is only about $2000 a year, even using oil at over $4 a gallon.  After using the air source heat pumps for two months, I expect these mini splits will approximately halve that.  The geothermal system would have done better, but even if it cut my heating bill by an impossible 100%, it would have taken 25 years to pay back my investment.  The mini-splits will have an estimated payback of about 13 years, which is not great, but both they and the geothermal system have the added advantage of giving me efficient air conditioning in a home that did not previously have it.  In New York’s Hudson Valley where I live, A/C is only useful for about 1 month a year, but it’s sure nice to have during that hot and sticky month!

In any case, I’m happy with the mini splits except for one thing: they have very limited programability, something I did not realize before I had them installed.  The best you can do with the included remote controller is set them to turn on and off once each during a given 24 hour period, and you have to manually set this up every day to use them that way.

There is an available programmable thermostat (Mitsubishi kit MHK1), but it is intended to be installed with the heat pumps, not after the fact.  My HVAC contractor offered to install them anyway, but he wanted $350 each, or a total of $1,400 for all four.  That’s not unreasonable, since the MHK1 retails for  $243, but it was more than I was ready to pay.

Since he told me he would have to figure out how to do the install from the documentation, and I had seen him struggling with the translated-from-Japanese when he was trying to figure out what was wrong with one of the units when it was first installed.  (It turns out two of the wires were reversed.)   I’m decent at that sort of thing, so I decided to give it a go myself.

There was one point where the documentation was completely unhelpful.  I figured it out eventually, but the rest of this post should save you a lot of trouble if you’re trying to do the same thing.

Installing Mitsubishi Programmable Thermostat Kit MHK1 on Mr. Slim Heat Pumps

  • Tools needed: Phillips screwdriver
  • Time required: 15 min (experienced) to 1 hour (first time).


Not only does the manual say to install the data cable before the heat pump is installed, there is no information about where the “CN105” connector on the control board is to be found, or even where the control board is.  None of the documentation I found online was any more helpful.  Eventually, I figured out where the control board and CN105 connector were, and how to get to them.  Here’s how:

Turn off the power to your heat pump at the circuit breaker.

Remove the horizontal vanes

Remove the horizontal vanes

remove screw covers

remove screw covers

Covers removed... screw locations circled

Covers removed… screw locations circled

After 2 screws holding the unit cover are in place, the cover can be removed by pressing in around the edges, and popping it off.

When the cover is removed, the bar containing the i-see and indicator lights may swing down.

When the cover is removed, the bar containing the i-See and indicator lights may swing down.

Don't panic, just hang it back on the two plastic hooks like the one shown here

Don’t panic, just hang it back on the two plastic hooks like the one shown here

Now remove the Emergency operation switch by pressing on the tab shown here

Now remove the Emergency Operation switch by pressing on the tab shown here

You can now remove the screw that holds the control board cover

You can now remove the screw that holds the control board cover and remove the cover to access the board.

These wires, too.

You’ll need to disconnect this wire to slide out the control board.


This wire, too.

Now you can gently slide out the control board and connect to the CN105 port, shown here.

Now you can gently slide out the control board and connect the control wire to the CN105 port, shown here, circled.  It’s located in the bottom back corner of the control board.

You’ll want to snake the control wire through the unit so that it’s hidden when everything is installed.   Make sure you’ve left plenty of slack on the control wire, so it does not pull off when you put the control board back.

Now you can reverse the above process to put everything back where you found it.

You can now connect the wireless receiver, and proceed as described in the installation guide.

You can now connect the wireless receiver, and proceed as described in the installation guide.

The rest of the manual was no harder to follow than these things usually are.

It took me a few hours to figure this out… hope I can save a few readers the aggravation.

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How to Get a Free Energy Assessment on a Home Before You Move In

Image TK note: I get a lot of submissions for guest articles at, most of which are off-topic (like this one.)  But this one from Whitefence Savings was a subject I’m interested in- understanding the energy use of a home before you buy, so I thought I’d post it here.

I paid for an energy audit of my home before I moved in, but was not able to get a free one… my utility required having an established account, and the current home owners had moved out a year before and were in bankruptcy.  The audits are inexpensive anyway… the most useful part for me was the infrared audit, although you should note that such audits work best when the house is being heated in winter or air conditioned in summer.

Walking through a house a few times while you’re thinking about making an offer on it will give you an idea of how much you like the house, but not an accurate estimate regarding its energy usage. You might notice the occasional drafty door or a window that needs sealing, but there’s no way to tell just how well-insulated or efficient a home is during a walkthrough. Have no fear! There is a way to eliminate unpleasant surprises regarding efficiency before it’s too late: get a free energy assessment on the home before you take the plunge into buying it.

Contact the Local Utility Company

The local utility company probably gives free assessments to its customers, or at least an average usage for the last calendar year or so. Though you are not their customer yet, the people currently living in the house are and will have access to that information. You would need to set up a time with the current owners for the assessment anyway, so you may as well see if they would be willing to speak with the utility company to have a free assessment done. From there they can share the results or allow you to be part of the process.

Schedule an Assessment with Energy Service Corps

Energy Service Corps is a group that has an overall goal of saving energy, saving the environment and saving you money. This is a great free option because they not only come out and assess the energy efficiency of your home, but they’ll also seal cracks around windows and doors to block drafts, change out your older bulbs for energy-saving models and make other small adjustments that will lower the cost of your utilities right away. As part of the assessment, they will give suggestions on other changes you should make to see greater improvements in energy efficiency. However, you should be aware they are limited in where they can go to provide their services.

Do It Yourself

You can do some informal assessments yourself. Ask the current homeowner about their energy usage, or call their utility company for an average use from the previous year. Keep in mind, this method will not tell you what areas of the house need updating or changing in order to create a more energy-efficient environment. Some ways you can assess the energy levels yourself is to feel along the walls for cool patches to determine where more insulation is needed. Along those same lines, feel along the windows and door frames and note where leaks are. Another thing you can do is peek into the attic to see about the state of the insulation. If it’s on the skimpy side, put that on a list of things that would need updating. If the basement is unfinished, check to see if the ceiling has any insulation which will impede the coolness of the basement from seeping up through the floors of your main level rooms. After your self-assessment is finished, you can determine if you need to hire a professional to determine if there are larger issues or be satisfied with your findings.

[ED note: Also see my own checklist for a DIY Energy Audit]

Know Why an Energy Assessment is a Good Idea

Before you move into a home, you’ll want to get an energy assessment so you can either know what improvements you’d like the owners to make as part of your offer on the house, or so you know what changes you’ll want to make once you do move in. Some things that are more serious, such as needing to replace windows and siding, may be more convenient if they’re completed before you start moving. Other, less pressing items such as caulking your windows or adding insulation to your attic, can probably wait until after you’ve purchased the house and moved in. Updating your home in small ways can lower your electric bills year round and impact the environment by lowering it’s carbon footprint.

Learn What Assessors Will Look For

Some assessors do tests to see how air-tight your home is. They mark where air leaks through, and can tell you the best way to eliminate those leaks. Others may do what is called a thermographic inspection that will measure the temperature levels along the walls of your home. This can be done indoors or outdoors depending, depending upon the season.

The most important thing to keep in mind is that, in order to increase the efficiency of the home and lower your energy bills, you must make the changes suggested by the assessor. Most changes that can be made to lower bills are relatively affordable and easy to do on your own. Don’t consider a house to be a lost cause just because it is not currently living up to it’s full potential in terms of efficiency, as you may be able to make small adjustments that have a big impact overall.


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