Converting to main pressure and gas.

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5047 posts

Uber Geek

#1598121 25-Jul-2016 11:47

Talkiet:

caution: Gas hot water is NOT Mains pressure in most places. It's better than a low pressure HWC, but in nearly all places the mains pressure exceeds the capability of the Gas heater units, so the hot water pressure is lower than if you had a true mains hot water system.

I got a Gas system and it's good, but if you want the "cut you in two" mains pressure then Gas won't cut it (Sorry, I had to!)

Cheers -N

Thanks Neil, does the pressure come down to the particular unit you install? E.g a 27L unit will give higher pressure on a single tap than a 16L unit?

Talkiet

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#1598128 25-Jul-2016 11:53

Paul1977:

Talkiet:

caution: Gas hot water is NOT Mains pressure in most places. It's better than a low pressure HWC, but in nearly all places the mains pressure exceeds the capability of the Gas heater units, so the hot water pressure is lower than if you had a true mains hot water system.

I got a Gas system and it's good, but if you want the "cut you in two" mains pressure then Gas won't cut it (Sorry, I had to!)

Cheers -N

Thanks Neil, does the pressure come down to the particular unit you install? E.g a 27L unit will give higher pressure on a single tap than a 16L unit?

Not sure about the designations (27L and 16L) but yes, I believe that the more powerful the unit, the higher volume of water it can heat per second, which translates into higher pressure. I got the largest residential one I could and it's still well short of the cold water pressure.

(I got Gas because my existing HWC was in the middle of the house and a mains HWC requires a drain to outside which meant significant extra cost (probably concrete cutting)

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

darylblake

1162 posts

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#1598131 25-Jul-2016 11:55

I had a 1960s home. And only had a small place for a hwc. I ended up getting my mate (who is a plumber) to come and fix it when it burst and he suggested putting it outside. This freed up extra room in the house and ended up being brilliant.

I ended up purchasing a new Main outdoor Rheem HWC and new valves (about $400ish for the valves alone). He re-did all the piping and the water pressure, it was amazing. I did end up using a lot of extra water over the next couple years because the pressure was quite high. I put some water restrictors in my shower, which did lower the pressure a bit but it definitely cut the power bill down and was well worth it. Your power bill will probably go up a bit by going with mains pressure, because you will find you use more hot water, however I loved the showers. But if you get gas then it might be a different story.

You also need to make sure that the taps in your house will handle mixed pressures otherwise some might need to be changed.

Good luck.

Smithy100

180 posts

Master Geek

#1598245 25-Jul-2016 15:08

We did the same recently... then for an added bonus turned the former hot water (cylinder) cupboard into a pantry. Win!

lissie

495 posts

Ultimate Geek

#1598392 25-Jul-2016 17:34

If there is gas in your street it's quite likely you can get a free connection - in Wgtn the price of bottled gas is sgnificantly more than a network connection - even allowing ofr the daily fee.

Yes a bigger capactiy Rinnai makes a difference - in our last place it was about 16l (cheapo developer) and anyone in the shower knew if any other hot water was turned on. Now with a 27l you can run the washing machine and not know it in the shower. The price of the larger unit is nominal compare to the costs of install

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PhantomNVD

2619 posts

Uber Geek
Inactive user

#1598403 25-Jul-2016 17:49

Paul1977:

Talkiet:

caution: Gas hot water is NOT Mains pressure in most places. It's better than a low pressure HWC, but in nearly all places the mains pressure exceeds the capability of the Gas heater units, so the hot water pressure is lower than if you had a true mains hot water system.

I got a Gas system and it's good, but if you want the "cut you in two" mains pressure then Gas won't cut it (Sorry, I had to!)

Cheers -N

Thanks Neil, does the pressure come down to the particular unit you install? E.g a 27L unit will give higher pressure on a single tap than a 16L unit?

With a 27L/m Rennai 'Califont' in my new home (completed March this year) the how and cold 'full pressure' are both really FULL pressure, and the excellent SatinJet shower heads are the only reason it doesn't "cut me in 2". the kids regularly splash the bathroom basin all over when they open the tap too far. excellent pressure even when BOTH showers going.

mcraenz

1140 posts

Uber Geek

#1598501 25-Jul-2016 20:27

I also understand that the units have more oomph when running on natural gas from the street vs LPG bottles. The litres/min figure is at a 25 degree rise. So not hot enough for a shower in many cases.

I'm looking at the 32 l/min 60kW unit but I'm going to struggle with the clearance regulations. The house has to many windows!

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Paul1977

5047 posts

Uber Geek

#1599117 26-Jul-2016 15:43

Well, gas not available on my street so will definitely be bottled. Out of interest, is mains gas available anywhere in Christchurch?

Sounds like it's worth paying a bit extra for the larger units to improve pressure too.

Paul1977

5047 posts

Uber Geek

#1599119 26-Jul-2016 15:45

@Talkiet Do you still live in Christchurch? If so, who did you get to do yours? Do you get the bottles swapped, or to they come and refill them in place?

Talkiet

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#1599141 26-Jul-2016 16:52

Paul1977:

@Talkiet Do you still live in Christchurch? If so, who did you get to do yours? Do you get the bottles swapped, or to they come and refill them in place?

I do. I forget who installed mine... It was Joe Average plumber and he did an OK job. Not great (he didn't replace the unequal pressure mixer and there was a leak afterwards which he came back to fix). I have 2*45KG bottles with a nice automix/cutover valve... I go to the Nova energy site once every 2-3 months (when the indicator tells me one bottle is empty) and put my customer number in a field and hit OK. They come out and swap the bottle within a few days and I get an invoice in my email. So, so, SO easy.

Cheers - N

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

Paul1977

5047 posts

Uber Geek

#1599148 26-Jul-2016 16:59

Talkiet:

Paul1977:

@Talkiet Do you still live in Christchurch? If so, who did you get to do yours? Do you get the bottles swapped, or to they come and refill them in place?

I do. I forget who installed mine... It was Joe Average plumber and he did an OK job. Not great (he didn't replace the unequal pressure mixer and there was a leak afterwards which he came back to fix). I have 2*45KG bottles with a nice automix/cutover valve... I go to the Nova energy site once every 2-3 months (when the indicator tells me one bottle is empty) and put my customer number in a field and hit OK. They come out and swap the bottle within a few days and I get an invoice in my email. So, so, SO easy.

Cheers - N

I suppose a weekly check to see if one of the bottles is empty isn't too inconvenient... I am lazy though.

Scott3

3970 posts

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#1599316 26-Jul-2016 23:01

Street gas (natural gas - north island only) is much cheaper than bottle gas (LPG)

Street gas is generally the best (cheapest per energy and most convenient) if available, and not too expensive to get connected.

Both have a monthly fee (connection charge or bottle rental) - Unless you do BBQ bottles - where gas is even more expensive

For just hot water, It is likely that your cost savings from using gas won't cover your fixed monthly fee.

All mains pressure systems (correctly sized gas instant, gas cylinder, electric cylinder, solar, heat pump) give the same shower quality.

We are electric only here (despite gas in the street). I don't miss gas we had a the old place, as we only just broke even with pretty much all savings getting eaten by monthly connection fee.

Note your lines fees will go slightly when you get rid of the controlled load (electric hot water cylinder).

Paul1977

5047 posts

Uber Geek

#1599621 27-Jul-2016 16:33

Scott3:

Street gas (natural gas - north island only) is much cheaper than bottle gas (LPG)

Street gas is generally the best (cheapest per energy and most convenient) if available, and not too expensive to get connected.

Both have a monthly fee (connection charge or bottle rental) - Unless you do BBQ bottles - where gas is even more expensive

For just hot water, It is likely that your cost savings from using gas won't cover your fixed monthly fee.

All mains pressure systems (correctly sized gas instant, gas cylinder, electric cylinder, solar, heat pump) give the same shower quality.

We are electric only here (despite gas in the street). I don't miss gas we had a the old place, as we only just broke even with pretty much all savings getting eaten by monthly connection fee.

Note your lines fees will go slightly when you get rid of the controlled load (electric hot water cylinder).

Thanks Scott. Not really looking at it for savings, just for improved hot water pressure and capacity. Converting to a larger cylinder with mains pressure isn't an option because of space limitations.

Talkiet

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#1599628 27-Jul-2016 16:47

Scott3:

All mains pressure systems (correctly sized gas instant, gas cylinder, electric cylinder, solar, heat pump) give the same shower quality.

(My bold)

Is that really true in all places? remember some places have very high mains water pressure. Here in Chch I think 600Kpa at times (from what I could find on the council site). Are there any residential gas heaters that would sustain that? A quick look at the Rinnai site shows the largest units they have give a 25C rise for up to 37 litres per minute. CCC state 0.42litres/second so that's 25 litres per minute. A little guestimathematics and I get about 37C at 0.42l/sec. I guess that's pretty good but it's not at the 50C I thought that a hot tap would give... (and what a Mains HWC would give)

Remember, that's the biggest unit I could find on their site - a more sensible residential unit was rated at about 75% of that.

Cheers - N

[edit: for comparison my Rheem27 (from 2013) is rated at 16.7litres/min with a rise of 40C]

Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

mdf

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#1599640 27-Jul-2016 17:54

Talkiet:

Scott3:

All mains pressure systems (correctly sized gas instant, gas cylinder, electric cylinder, solar, heat pump) give the same shower quality.

(My bold)

Is that really true in all places? remember some places have very high mains water pressure. Here in Chch I think 600Kpa at times (from what I could find on the council site). Are there any residential gas heaters that would sustain that? A quick look at the Rinnai site shows the largest units they have give a 25C rise for up to 37 litres per minute. CCC state 0.42litres/second so that's 25 litres per minute. A little guestimathematics and I get about 37C at 0.42l/sec. I guess that's pretty good but it's not at the 50C I thought that a hot tap would give... (and what a Mains HWC would give)

Remember, that's the biggest unit I could find on their site - a more sensible residential unit was rated at about 75% of that.

Cheers - N

[edit: for comparison my Rheem27 (from 2013) is rated at 16.7litres/min with a rise of 40C]

Yep, but that it would be a Niagra Falls-scale tap if 25L/min is coming out. You can set the temperature of a continuous hot water unit higher than that, you just don't get as high a flow rate. From what I gather (but this is all anecdotal so take it with a pinch of salt), the litres per minute/25 deg rise figure is all to do with showering, which is probably the highest flow rate in regular daily use. And a 25 deg rise (38-40-ish deg) is the temperature most people shower at. 10 L/min is an efficient shower, so a 37L/min unit is nearly 4 efficient showers going at once (or at least 2 inefficient ones). So that's a big unit. Most domestic ones are in the teens or twenties /min range I think.

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