Hotwater Insulation for a modern (already insulated) cylinder

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timmmay

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#604438 3-Apr-2012 12:02

cshaun:

My understanding is that's reasonably common too. My ceiling gets incredibly hot - would almost think you'd need less insulation. Though not sure how cold it gets during the night. I think the biggest negative would be it's more difficult to get at when anything needs to be done.

Thanks, I might look into that for my renovations. It does get pretty cold up there in winter, much colder than the body of the house.

cshaun

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#604444 3-Apr-2012 12:06

gzt: The standards state: "The delivered hot water temperature at any sanitary fixture used for personal hygiene shall not exceed: 55 C* and "the storage water heater control thermostat shall be set at a temperature of not less than 60 C to prevent the growth of Legionella bacteria".

In practice this means a tempering valve (automatically mixes hot and cold water) is required to ensure the (minimum) 60?C storage temperature is always a maximum of 55 C when it arrives at the tap.

The standards indicate it is acceptable to supply higher temperatures to kitchen appliances and laundry appliances. The standard also needs to be applied when installing new showers/basins/etc.

* but must be 45 C for early childhood centres, schools, old people's homes, institutions for people with psychiatric or physical disabilities, hospitals.

Yip well aware of the 60 C. And understand not exceeding 55 C.

So the 55 C is a maximum not optimum. And like I said I'd think the lower it is the less wasted heat in the pipes.

So optimum = low as possible while still giving you hot enough water for anywhere you use it.
(Keeping in mind you may sometimes be adding hot water to colder water in a sink or bath to increase the temperature. This may completely outweigh losses in pipes meaning you may want it at 55 C.)

Jaimita

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#604446 3-Apr-2012 12:06

cshaun:
Jaimita: If you are looking at saving money from hot water: Make sure your cylinder is set at 60 degrees and coming out of the tap at 55 degrees. If it is set hotter you are wasting money and you risk burning yourself (even more so if there are little children or older folk living in or visiting the house).

Also if you have a big enough cylinder you may profit from putting it on nightrate. There may be a fee to set that up. Test whether your cylinder is big enough by switching off in the morning and switching back on at night. Do that for a week, and if you don't run out of water you may benefit from the nightrate setting.

Thanks yes good advice - should have mentioned that too I guess. I set it to 60 degrees yesterday.

Why 55 degrees specifically out at the tap?

I guess the lower this setting will result in less heat loss in the pipes on the way to the tap? So low as possible but high enough for washing dishes and anything else you may want hot water for.

If you set cylinder at 60, it will come out at app. 55 degrees at the tap. Setting lower than 60 degrees, there is a risk of Legionnaire's.

cshaun

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#604450 3-Apr-2012 12:10

Jaimita:
cshaun:
Jaimita: If you are looking at saving money from hot water: Make sure your cylinder is set at 60 degrees and coming out of the tap at 55 degrees. If it is set hotter you are wasting money and you risk burning yourself (even more so if there are little children or older folk living in or visiting the house).

Also if you have a big enough cylinder you may profit from putting it on nightrate. There may be a fee to set that up. Test whether your cylinder is big enough by switching off in the morning and switching back on at night. Do that for a week, and if you don't run out of water you may benefit from the nightrate setting.

Thanks yes good advice - should have mentioned that too I guess. I set it to 60 degrees yesterday.

Why 55 degrees specifically out at the tap?

I guess the lower this setting will result in less heat loss in the pipes on the way to the tap? So low as possible but high enough for washing dishes and anything else you may want hot water for.

If you set cylinder at 60, it will come out at app. 55 degrees at the tap. Setting lower than 60 degrees, there is a risk of Legionnaire's.

Any reasonably new cylinder does not give you the option of setting it below 60 C (because of Legionnaire's like you mentioned). Mine for example can be set anywhere from 60 to 70 C.

So really should be on the lowest (60 C) to reduce heat loss or if you're running out of hot water and instead of buying a bigger unit turn the temperature up and mix more cold water with it.

gzt

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#604456 3-Apr-2012 12:18

cshaun:
gzt: It is unusual to have an electric cylinder outdoors. What was the reason for that installation style?

Yes all used to be all indoors. But putting them outdoors is becoming far more common now days. Primary reason being space - why have it indoors when it doesn't need to be. And I guess they feel insulation good enough to put it outside now.

Yes, it will definitely be rated for outside use. I'm sure it will meet the same loss standard we discussed earlier, which will mean a far higher insulation value is present in the cylinder to meet the same standard.

I don't recall ever seeing any wraps designed for outdoor use.

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cshaun

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#604468 3-Apr-2012 12:36

gzt:
Yes, it will definitely be rated for outside use. I'm sure it will meet the same loss standard we discussed earlier, which will mean a far higher insulation value is present in the cylinder to meet the same standard.

I don't recall ever seeing any wraps designed for outdoor use.

Good point - didn't really think of that. Haven't wrapped on before or had chance to look at the wrap. You don't think it will have the same lifespan outside?

Mine is under the house. So can't imagine the rain getting to it. It's fairly well sheltered.

gzt

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#604490 3-Apr-2012 12:59

I doubt wraps are designed or tested to withstand UV (and wind/rain conditions). In a dry sheltered position underneath a house that would not be a problem.

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gzt

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#604678 3-Apr-2012 18:25

cshaun: My understanding is that's reasonably common too. My ceiling gets incredibly hot - would almost think you'd need less insulation. Though not sure how cold it gets during the night. I think the biggest negative would be it's more difficult to get at when anything needs to be done.

timmmay: Thanks, I might look into that for my renovations. It does get pretty cold up there in winter, much colder than the body of the house.

My feeling is the new roof cavity cylinder I wrapped years ago was underspecified for the task, hence the massive improvement when I wrapped it.

The roof itself was uninsulated, which is typical (even where the ceiling is insulated).

IMHO, the correct specification for that environment would have been something like this:

http://www.rheem.co.nz/hot-water-cylinders/product/91330025/

- I'm guessing cshaun has something similar.

[Edit: I'm making an assumption these outdoor ones have more insulation to meet the same standing loss standard. I see this one is rated for 3 - 5 people in a moderate climate and 2 - 4 people in a cold climate. I'm guessing the input water temperature makes the biggest difference in that rating (rather than purely a higher standing loss in cold climate areas)]

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timmmay

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#604688 3-Apr-2012 18:37

Looks expensive, but well specified! The roof cavity is pretty much outside, in terms of temperature.

cshaun

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#604706 3-Apr-2012 19:23

gzt:
- I'm guessing cshaun has something similar.

My model number is: 91218015
http://www.buildspace.co.nz/files/HWC_OptimaElectric_Rheem.pdf

gzt

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#604738 3-Apr-2012 20:14

timmmay: Looks expensive, but well specified! The roof cavity is pretty much outside, in terms of temperature.

Yeah, I'm still not sure if the 'Grade A' spec is an absolute measure or can also represent an improvement in insulation when specified for outdoor use. EECA says this spec is AS/NZS 4692.1.2005 with the test standard AS/NZS 4692.2:2005. (with 'alternative' test methods in NZS 4602:1988 and NZS 4606:1989).

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cshaun

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#604842 3-Apr-2012 23:02

gzt:
timmmay: Looks expensive, but well specified! The roof cavity is pretty much outside, in terms of temperature.

Yeah, I'm still not sure if the 'Grade A' spec is an absolute measure or can also represent an improvement in insulation when specified for outdoor use. EECA says this spec is AS/NZS 4692.1.2005 with the test standard AS/NZS 4692.2:2005. (with 'alternative' test methods in NZS 4602:1988 and NZS 4606:1989).

Almost seems like an absolute measure the way the product mentions indoor/outdoor. Doesn't seem to push the fact that if it's "outdoor" it would be better.

cshaun

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#605107 4-Apr-2012 15:00

Had just thought that perhaps having a wrap on it especially outside might cause condensation or something along those lines which could be bad.

So figured I'd just phone Rheem and see what they have to say. Talking to their sales team who also asked someone technical did think condensation with a wrap may be an issue (no wrap it just runs off I guess). She'd also said she'd never come across someone wanting to insulate an outside cylinder.

Supposedly is no grading anymore - all cylinders now must meet certain insulation criteria (basically old A grade I think).

Bah maybe just go with the flow and leave insulating it. Will just do the pipes - even though seems like there may be a benefit.

Thanks for all the input - at least there's bit more info/thought on the matter now for the next person that's interested.

Niel

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#605229 4-Apr-2012 18:34

Just finished building a house, today had the CC inspection. Our plumber said moderm cylinders are so well insulated that people tend to have to add a space heater to the linen closet to get enough heat to prevent mould.

We have copper pipes out of the cylinder, changing to plastic in the walls/ceiling. The copper helps to warm up the cupboard.

If your cylinder is set to a lower temperature you will run out of hot water sooner. The extra power consumption from a small increase in temperature of a modern cylinder is so minute that you will not notice it. The tempering valve will regulate the temperature to 55 degrees for safety, and if you had work done in the past few years then you should have had one fitted. Except if you have copper pipes throughout the house, then avoid a tempering valve if you can even if you insulate the pipes. Maybe fit a tempering valve at the taps that matter rather than a single master tempering valve.

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#605280 4-Apr-2012 20:12

We have a 12 year old cylinder in the ceiling space above the shower.
In summer I have the shower mixer set at 5.30 and in winter I have to move it around to 6.30 to get the same temperature.
The cylinder is warm to touch so I am going to fit a insulating wrap over it in the next few weeks.

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