Monday, November 30, 2009

DIY heat exchanger for your shower

Update December 2011: You may now buy the new affordable DWHR unit for stand alone shower cabinets at the HeatSnagger Shop  (Norwegian link: Varmegjenvinner for dusj )

Update April 2011: Arthur and I have joined forces and are now working on a commercial, low cost DWHR unit based on this blog post. You may follow our progress at Meander Heat Recovery
Nov 2009:
I got an E-mail from Arthur Kimmels. He has come up with a DIY concept for a small shower heat exchanger, a drain water heat recovery (DWHR) unit. I really like the simplicity of this design. His mail speaks well for itself, so here it is:

Hei Svein,

With interest I read your blog about miljødusj I had been walking around with a similar idea of building a heat exchanger for the shower (before I read about miljodusj, but inspired by some products on the Dutch market), and after some months of thinking and building I installed it today. Attached you will find some pictures of the unit. It is built of wood, coated with fiber glass and polyester. It measures 85x32x12cm. The water channels have an inclination of approximately 1cm/m. The heat exchanger is built of ca. 4m copper, 12mm diameter and soldered together. It works as 'counterflow'. A disadvantage of this setup is the pressure drop/flow reduction due to the long PEX/copper/PEX length (ca. 8m), but I measured this to be within acceptable limits for my setup. The measured temperature increase at a flowrate of ca. 10liter/min was 23.3(out) -8.8 (in) or 14.5degC. Total material cost was ca. NOK 1500, including PEX tubes to and from the unit. (The thermometer in the picture measures at the in and outlet, I removed the 'indoor' sensor from the housing and soldered it to some wire.)
Feel free to add to your 'blog'.
Kind regards, Arthur Kimmels
Summary in Norwegian: Arthur har laget en enkel varmeveksler for dusj. Avløpsvannet fra dusjen brukes til å forvarme kaldtvannet som kommer inn i dusjen. Temperatur økningen på kaldtvannet er målt til 14.5 C. Det medfører at man bruker mindre varmtvann og dermed sparer energi. Spillvarme gjenvinning i praksis.

Monday, November 23, 2009

The most efficient way to boil water

This is a follow up of a great article by Pablo at the Treehugger where he tested the efficiency of different ways of boiling water. By bringing 350ml of 17°C water to a boil and measuring the energi used, he found the efficiency of using a pot on the stove to be 30.5%, a microwave 47%, and an electric kettle 81%.

I have been thinking of how to make coffee in the morning. I can use the drip brewer or the Frensh press pot. So I first repetead the Pablo test with our 2000W electric kettle. It took 77 seconds to bring the water the 83 C° up to a boil. Actually slightly shorter, but I timed it to the point where the kettle turned it self off. The specific heat of water is 4.180 kJ/kgK, which means that it takes 4,180 kWs to heat one liter one C°. Needed energy transfered to the water is then 0.350 l * 83C°*4.180 kWs which is 121.4kWs. The kettle averaged 2000 W and used 77 seconds, which is 154 kWs. From this I get the efficiency of my electric kettle to be 78%, which is close to what Pable got. Then I tried the drip brewer. It averaged 950 W and after 153 seconds it was done, but the next 15 minutes it turned it self on again four times for 6 seonds each time. So at the time of automatic shut off it had been running for 177 seconds. 168.2 kWs turns out to be an efficiency of 72%. I did this test with 350 ml so it could compare to Pablos test.
For us, a more realistic water use is typical 700ml, so after waiting for an hour, I redid the tests with twice as much water. The result from this was that the drip brewer was 95% efficient and the electric kettle 88% efficient. So for our family, the drip brewer is the most efficient way boiling water for coffee.

Summary in Norwegian: Det kreves store mengder energi for å varme opp vann. Derfor er det lønnsomt å være bevisst på hvordan man varmer opp vann. Konklusjonen fra denne testen er at en kaffe trakter er den minst energikrevende måten å lage kaffe på.

Sunday, October 18, 2009

Moving hot air from ceiling to floor

I have been contacted by a lady, Kari, that has a vertical pipe that she uses during the winter to move hot air from underneith the ceiling to the floor in her small house. It is about 8 ft tall, 4 inch wide and has a 7W fan inside the pipe. In her first year in the house she was often cold on her feet, but after installing the vertical air transporter her feet were much warmer. Before starting the fan in the morning she measured 18C (64F) three feet off the floor, and 13C (55F) at the floor. After running the vertical air transporter for 3-4 minutes the heat was distrubeted more evenly such that the temperature at the floor also was 18C (64F). She claims to have saved a lot on her heating bill by using this for one winter, comparing it to the heating bill from the previous winter. She has been trying to get Enova interested in the consept and get them to promote the consept as a general energy saver in Norway, but without much luck. So is this a working consept for saving energy?

I think it can be compared to using a celing fan. During the summer it blows cold air down at you and you feel cooler because of the wind chill factor. During the winter it can be reversed to slowly rotatet the air up and then down the sides of the walls. It must be done slowly so it does not create any noticeable wind chill factor, as it will make the air feel cooler. Slowly mixing the air evenly is known to save energy during the heating season. Energy Star: Using the Ceiling Fan Year Round It should not matter how you mix the air as long as it is done slowly. Kari measured as much as 5 C difference between floor and 3 feet up. I would think that in particulare a house with cold floor will benefit from mixing the air, as this will probably be where the highest difference is in vertical temperature. If mixing the air will help you lower the average temperature in the room with 5 C then the saving would be as if you turned down your thermosate with 5 C, which should give a noticeable difference on your heating bill.

Monday, August 31, 2009

Great savings with extra water heater insulation

We have under the kitchen bench a 120 liter / 2000W electric water heater from Several spots outside this was warm to the touch, as indicated on the picture. I called technical support at Oso and they could confirm that it was OK to add extra insulation anywhere, also including the plastic lid that cover the ectrical wiring inside. So I used some spare insulation material and wrapped some plastice aound it all, and taped it up. For the pipes I got special insulation to wrap around the pipes. I have previously measured the standby energi consumption to be 1,8kWh/day. With the added insulation it as dropped to 1,2kWh/day. (You can measure the standby losses by measuring the energy used for a weekend when you are not at home using hot water. Use a plug in meter and just read off how many kWh that has been used to keep the water hot when you where gone).

We have the heater set at 65 C. Our family of five use about 7-8kWh a day for heating water.

I noticed how the power cord to the heater got warm when it was on. I cut off 1,2m of it for an additonal saving og about 4W ( 2,4m wire, 1mm2 copper, and about 8A) when in use :-)

Summary in Norwegian: Kjenn på utsiden av din varmtvannstank. Er den varm kan du med enkle midler spare mye energi. Bruk det du måtte ha av isolasjonsmateriale (Glava e.l.) og pakke det inn i plast til slutt. Alle varmtvannsrør bør også isoleres. Besparelsen hos oss var 0,6kWh/dag. Du kan også spare noe ved å forkorte tilførsledningen til et minimum.

Sunday, August 30, 2009

Cleaning and checking the heat pump

We got an offer from Lier Everk to get a service agreement for our Panasonic CS-CE7GK air-to-air heat pump. For NOK 1200,- (about $200) they would come and clean our heat pump every 2nd year. I did some research and it looks like you easy can do this yourself.

The first part is to clean the coils of the unit. Turn off the power of the unit. Remove the filter. Vacuum any dust that can be seen. Use luke varm water and dishwasher liquid (Zalo) and just spray your indoor coils. Use a towel to collect excess water dripping from the unit. The outdoor unit is cleaned the same way. Spray on. Wait for a while for the dish washer liquid to disolve dirt. Then use a garden hose with low pressure and apply water in the opposit direction of the normal airflow. Be careful not to bend any coil fins. Let the unit sit for some hours to dry before turning on power.

The second part is to check that it still delivers the heat (or cold) that it should. According to the Pabasonic service manual the difference should be at least 14 C in heat mode and at least 8 C in cooling mode. I checked ours by setting the temp to 27 C. Inlet temp showed 23C and outlet 42C. A difference of 19C (The unit using 484W). Then for fun I set the additional "Powerful" mode. Inlet temp is then 23 C and out take 48 C. (The unit using 985W). A differance of 25 C. Outdoor temperature was 13 C. If the temperature difference is less than 14C you should check that all coils are clean. If cleaning does not help, it is time to call for service.

Summary in Norwegian:

Du kan enkelt rengjøre din varmepumpe selv. Vask ved å spraye på med lunkent Zalo-vann. Utdelen kan i tillegg spyles med hageslange med lavt trykk, aluminiums finnene må ikke bøyes. Det skal være en temperatur forskjell på minst 14 grader mellom luft som går inn i inndelen og luft som kommer ut av den ved normal drift.

Insulate your unused chimney

Some years ago we had a fireplace, but we never used it that often, and there was always a cold draft from it when it was not in use. So we sold the fireplace (and got space for a home movie theater instead..) and sealed off the chimney. Much of the draft was gone, but last winter I noticed that the chimney was still very cold when touching it. Both on the ground floor, but even more on the first floor. No wonder when all that cold outside air fills the entire chimney.
So in preperation for this winter I made a simple unused chimney insulation. I used a total of seven plastic bags, each filled with some insulation material. After tieing the top of each plasticbag, I connected them all together with a string. Using a long stick a pushed the first one about 4 m ( 12 ft) down the chimney.

Then I pushed the next one a little bit shorter, and the next even shorter, and so on until the last one finshed it off right at the top of the chimney. This should defenitely slow down any cold air trying to go down the chimney this winter. Should we decide to get a fireplace in the future I can easy pull all the insulation bags out of the chimney using the string that interconnect them all.

Summary in Norwegian: En ubrukt pipe er en kald pipe. Du kan isolere pipa ved å trykke plastposer med isolasjon ned i pipa. Hvis du forbinder dem alle med et tau, så går det greit å få dem opp igjen hvis du skal bruke pipa igjen.

Wednesday, March 4, 2009

Dryer balls save no energy

I stopped by Elkjøp in Sandvika and met this sign on my way to the cash register.

"Save energy, 25%, save money". This caught my interest, since I am always looking for ways to save energy. My first thought was that this is too good to be true. At the cash register I asked if they had some sort of proof that Dryer balls actually work, if not I would consider this being fraud. He told me to wait, and then left. After 10 minutes I had to go. I saw several customers buying Dryer balls at kr 199,- ($ 28) while waiting. Walking home I got really mad, and decided to get to the bottom of this. The day after I was back and bought my set of Dryer balls. The next morning I put it to the test.

In my test I used our normal family load of some towels, pants, T-shirts, underwear and socks. After washing and spin drying it, I used a digital scale to record the exact weight of the clothes. Then I threw them all in the dryer and set it on "cupboard dry". When the dryer stopped I measured the weight again. The difference is exactly the water removed, or how much drier the clothes are. The other part was to find the energy used. A plug in energy meter ( 36-2897 ) on the power cord of the dryer makes this task very easy. So I recorded the kWh used, and also room temperature, humidity, and the time for the dryer to finish. This I did first with no Dryer balls and then with Dryer balls. And then I repeated all this one more time for a total of 4 runs.

By dividing the energy used by the liter of water removed from the clothes, we get a number that can easy be compared. My four runs show results between 1.29 and 1.35 kWh needed to remove one liter of water. The average for the use of Dryer balls was 1.31 kWh/l and without was 1.32kWh/l. This is less than 1% difference, and a very clear conclusion that DRYER BALLS SAVE NO ENERGY.

On the they say that : "The 25% saving in electricity every time you use the dryerballs® in your drying machine is another terrific reason why dryerballs® is a winner for you and the environment, saving you money and substantially reducing energy consumption." The company backs this with a test report: "dryerballs® have been scientifically tested to ISO standards at an independent, fabric care laboratory". Robin Green at have managed to get hold of what is supposed to be this test report. You can read his review of it. In my opinion, it clearly indicates that there has never been any case with a possible 25% energy saving.

I have also tried to contact Dryer balls on all three info E-mail address I have found. The E-mails all get back with a "recipient failed permanently" message.

I give to you all the details in the tests I have performed. You will find the full recording of my test data here:
You can verify how the data was collected by looking at my video documentation of run 2 and run 3:

In March 2009 I will spend some time publishing my testresults, and contacting companies still selling Dryer balls. This product needs to be taken off the shelves!

I will visit Elkjøp again. They have a 30 day money back warranty, so I know I will get my money back. The challenge will be to have them remove it from the shelves.

Whereever you have bought your Dryer balls, take them back. Refer to this blog and ask for a full refund. If they do not give you a refund, go shop somewhere else.

In April the Norwegian Consumer TV Report program "FBI" got interested in dryer balls and made this TV program based on my test (Norwegian):

and this article (also in Norwegian) The conclusion was that Elkjøp now is giving everyone a full refund with or without a receipt. But they are still selling the product...

Summary in Norwegian:

Mars 2009: Elkjøp i Sandvika selger Dryer balls som jeg har testet meget nøye. De sparer overhode ikke noe strøm. Har du kjøpt noen så bør du gå tilbake og kreve kjøpe hevet basert på villedende reklame. Henvis til denne bloggen. Firmaet Enklere liv selger nå også " Tørkeballer - sparer deg og miljøet ". Etter det jeg kan se av bildet i deres helsides annonser i Budstkka og Aftenposten, så er dette samme produkt som Elkjøp selger.

April 2009: NRK Forbrukerinspektørene blir interessert i saken og sender "Tørkeballer fungerer ikke!" Se på nett-tv eller les artikkelen på . Lefdal og Elkjøp selger ikke lengre tørkeballer på nettet. Mange andre aktører har imidlertid kastet seg inn i et forsøk på å tjene noen penger. Ikke rart, når man kan kjøpe dryer balls i Kina for $0,66 (ved kjøp av 1000 stk + frakt) så man kan jo si at marginene gode. Imidlertid ser det ut til at salget går tregt, da prisene stuper. I utlandet får du nå nesten kastet dryer balls etter deg.

August 2009: Elkjøp selger igjen tørkeballer på nettet. De skryter fortsatt av opptil 25% energi besparelse. Andre steder har dempet ned dette med energi besparelse, og selger de mest som erstatning til tøymyknere. Det er helt klart markedskreftene som regjerer. Sløve konsumenter som ikke gidder klage på produkter som ikke virker gjør at Elkjøp kan profitere videre på tørkeballer.

Juni 2010: Det er ikke til å tro. I en liten slagskurv i hvitvare avdelingen selger de fortsatt trøkeballer. Innpakningen på dem så litt slitt ut. Mon tro om det er her de selger videre tørkeballer som kunder har returnert?

Februar 2013: Elkjøp fortsetter å svindle forbrukeren med tørkeballer. Nå  i grønn farge. Klart et tilfelle av hva man kaller å grønnvaske et produkt.

Sunday, March 1, 2009

Reduced water flow

When you reduce the flow of hot water you also reduce your use of energy. In our house we have two levels of water flow reduction. First our house is connected to the municipal water through a pressure limiting valve. It was probably originally put in because this areas may have too much water pressure, which can cause household appliances to malfunction. Safe pressure is usually less than 10 bar (145 PSI). We have turned this down to 2 bar (29 PSI).
In addition to this we have added faucet aerators on all outlets, except for the one at the bath tub. The faucet aerator introduces air into the flow of water coming out of the faucet. That makes it seem like more water is coming out, but it's actually using less water. I have installed two different types ( vannmengdebegrenser 30-9848 and 30-9849). The claim was that they will reduce the water flow with 40%. I have measured before and after the installation, and the reduction was almost exactly 40%. So whenever someone is washing their hands, less warm water will flow, and there will be a reduction in energy needed for heating water. Our kids often drink cold water straight from the faucet, which is not quite as comfortable to do with all the air introduced, so this is a slight drawback. They complained the first day, but did then get used to it.

Here is an article from EPA about water flow reduction:

Wednesday, January 21, 2009

Draft in a keyhole

One night going to the bathroom I noticed a small but cold draft. I was passing the doors the our children's bedrooms. They sleep with their windows open at night and this was a windy night. So I could feel this draft, but their door to the hall was closed. This puzzled me, but as I got closer to the door, I realized that the draft was coming out of the key hole! I used a piece of tape to stop the draft. It is almost invisible to the eye, and does help. It is common knowledge that any drafts must be stopped. No point in adding much new insulation to your house if the cold wind is blowing through it any how. In our living room I have also insulated the keyhole. Here I have used a bit of black electrical tape on the inside of the hole, and also a bit of insulation material behind that. This door separates our home movie theater from the rest of the house. So here the motivation was originally to sound proof the door, but it works for draft proofing as well.

Summary in Norwegian: På natten sover vi med åpne vinduer og dørene stengt til resten av huset. En vinter natt på vei til toaletet merker jeg at det kom iskaldt trekk i gangen. Det kom fra nøkkelhullet! En tape fixet problemet. Dette understreker hvor viktig det er at man finner kilder til trekk i huset og så tetter dem. Det kan like gjerne være en skjev dør eller dårlig tetting rundt vinduer som lager trekk.

Sunday, January 4, 2009

Insulate the trapdoor

Perhaps even more important than insulating the trapdoor is to make sure there are no drafts in between the ceiling and the trapdoor. Moist hot air finding the way into the attic during the winter season will condense. This will be a threat to wood beams and roof wall boards as they might rot. I have used a P-profile seal strip ( to make sure the trapdoor is properly sealed when closed.

Then I removed the ladder. For insulation I had some leftover Litex insulation that is self supporting and can be glued together. On top of this I added a 6mm plywood sheet before screwing the ladder back on top of this. I would think that the insulation now is at least twice as good as before, by judging the thickness of the insulation.

Insulate the attic

Insulating the attic is one of the best way to improve insulation with little effort, I have heard. The cost of getting insulation is limited and there are no structural changes that is needed. In theory it is just a matter of spreading out more insulation. I started out in one corner of the attic and moved around all the stuff we have up there as I added 7 cm sheets of insulation. I added as much as possible while still allowing air to circulate above the insulation. It was a lot of work. If I where to do it again, I would empty the attic completely, and then pay a company to come and blast insulation all over the place. A lot more easy, and probably slightly better when it comes to cover everything without any leaking cracks.

Summary in Norwegian: Jeg har etterisolert loftet. Skulle jeg gjøre det på nytt så ville jeg ha bestilt noen til å blåse ut isolasjon, for å krype rundt på et trangt loft var svært anstrengende. Men det ble veldig bra til slutt.