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Bosch Water Heater Cozy

1338 Views 15 Replies 4 Participants Last post by  takedown
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My wife made a cozy for the van water heater out of left over thinsulate. It's really hard to sew and work with thinsulate but it fits perfectly. Great job Jean!
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Bruce
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It looks so cozy! 馃

Would've been pretty cool to get before-and-after energy numbers... 馃榿
I went back and looked and I didn't save run any energy tests when I started it up, I just tracked the water temperature. But it would be informative to compare the insulated usage against what you got for your un-insulated heater. I'll wait a day or two for my tank to cool down and run a 24 hour test.

gregoryx tests as a bookmark...

I have a Cerbo GX/Multiplus too so I should be able to match your energy graph pretty closely
Bruce
I went back and looked and I didn't save run any energy tests when I started it up, I just tracked the water temperature. But it would be informative to compare the insulated usage against what you got for your un-insulated heater. I'll wait a day or two for my tank to cool down and run a 24 hour test.

gregoryx tests as a bookmark...

I have a Cerbo GX/Multiplus too so I should be able to match your energy graph pretty closely
Bruce
Super cool. Gonna have a market for water-heater cozies! 馃榿
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Boy I'm glad you asked about the energy usage, it forced me to chase down an issue I had noticed but didn't understand. I don't leave the water heater on all the time I just turn it on when I want hot water. But, the hot water seemed to cool off really fast, compared to when I had tested it with the water tank unconnected to the distribution piping. Preliminary electrical test results showed that I'm using at least twice as much energy as you (I can't show the graph as the Victron portal is down.) Here's a one-line diagram of my plumbing system, note the hot water re-circulation loop. This is so you don' t have to run the faucet and waste water to get to hot water:



I think that created a convection loop that pumps heat out the tank since the interconnect valve between the hot and cold water is open when the hot side is cold. The cold water piping coming out of the water heater was hot, which was my first clue what might be happening. When I closed the cold water valve to the water heater the piping cooled off and the time between reheats doubled. I've got a back flow valve coming from Amazon that I'll put in the hot water piping, I think that will break the loop. I'm also going to insulate the cold water piping. Then I'll test it again.
Bruce

P.S. The water cooling off too fast was what spurred the cozy.
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Boy I'm glad you asked about the energy usage, it forced me to chase down an issue I had noticed but didn't understand. I don't leave the water heater on all the time I just turn it on when I want hot water. But, the hot water seemed to cool off really fast, compared to when I had tested it with the water tank unconnected to the distribution piping. Preliminary electrical test results showed that I'm using at least twice as much energy as you (I can't show the graph as the Victron portal is down.) Here's a one-line diagram of my plumbing system, note the hot water re-circulation loop. This is so you don' t have to run the faucet and waste water to get to hot water:

View attachment 190969

I think that created a convection loop that pumps heat out the tank since the interconnect valve between the hot and cold water is open when the hot side is cold. The cold water piping coming out of the water heater was hot, which was my first clue what might be happening. When I closed the cold water valve to the water heater the piping cooled off and the time between reheats doubled. I've got a back flow valve coming from Amazon that I'll put in the hot water piping, I think that will break the loop. I'm also going to insulate the cold water piping. Then I'll test it again.
Bruce

P.S. The water cooling off too fast was what spurred the cozy.
Interesting find!

I wondered about the cozy - I thought I was seeing pretty good temperature retention for such a reasonably priced and sized device.

I've been surprised that while the initial heating is obviously longer now that we have the 4-gallon versus 2.5 gallon, the 24-hour heating is not very different - so more efficient, gallon-for-gallon. If we're using the van, I just leave it on as it's nearly the same energy to retain for 24 hours as it is to heat from ambient one time. To be fair, it retains a pretty good amount of heat if left off for 12 hours or whatever, so... it /would/ be more efficient to turn it off, obviously, but the difference is much less than expected.

I wish I could get a temp sensor inside the tank... 馃
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I used velcro cable ties to attach a Ruuvi tag to the pressure relief valve and then covered it with another thinsulate cozy. Then you can use your Cerbo to keep track of the water temperature.


It's close enough for me.


Bruce
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Victron portal is up, here's a graph of electrical usage from 11am 5/21 to 6pm 5/22. Wow, shutting off the re-circulation loop had a dramatic effect. The heat was coming on every two hours. Once I turned the shutoff valve to the water tank it didn't call for heat for eight hours.


More to follow...
Bruce
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Okay here's my final answer;
gregoryx 24 hour results:

My 24 hour usage with the cold water valve closed:

It looks like the cozy saved around 20% on energy use since the heater turned on four times instead of five.

Here's the 48 hour usage, the blue mark is where I closed the cold water valve to the water heater:

Plumbing, I've never liked plumbing. :cautious:
Bruce
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I used velcro cable ties to attach a Ruuvi tag to the pressure relief valve and then covered it with another thinsulate cozy. Then you can use your Cerbo to keep track of the water temperature.
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It's close enough for me.
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Excellent idea! I suspect if I use a hard-wired probe with a metal sensor it should be a bit closer / hotter. Oooo... and I think I may be able to do an "offset" for the temp to get it closer to internal. Great idea!

What temp / dial-position do you have the Bosch set to? We run as hot as possible on ours.



Okay here's my final answer;
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It looks like the cozy saved around 20% on energy use since the heater turned on four times instead of five.

Here's the 48 hour usage, the blue mark is where I closed the cold water valve to the water heater:
...
Plumbing, I've never liked plumbing. :cautious:
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That is pretty cool - probably a pretty close estimate of the improved efficiency of the cozy - assuming you're running hot-as-possible as well.

And almost extra funny that it was the recirc that was really the issue. But you now have the coziest water heater around! 馃榿

Funny thing is... I sort-a like the plumbing in the van - where I can easily access things and readily repair them. In the house, though... tearing apart walls and floors? Ugh. Hate that. 馃槒
Yup, got that dial cranked up to 11.
Bruce
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Yup, got that dial cranked up to 11.
Bruce
Don't let the drummer near your van.
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Yup, got that dial cranked up to 11.
Bruce
Where's that heavy-metal "like" icon?

馃
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I just added the back flow preventer and that seems to have broken the convection loop. At least the cold water piping isn't hot like it was before. I'll see how long it stays warm after heating the water and turning the inverter off.
Bruce
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Looks like the backflow preventer did the trick, the tank temperature dropped 30F from when I heated it up at 0815 yesterday to this morning at 0530. I can live with that.


The Case of the Missing Heat is closed.
Bruce
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