Instant electric hot water

Forums › Home Workshop DIY › Instant electric hot water

timbo1604

102 posts

Master Geek
+1 received by user: 1

#151986 12-Sep-2014 10:48

Have a small backpackers hostel (max 20 guests) and only a 135 litre hot water cylinder so looking at instant hot water systems. Gas isn't an option and I'm not keen on replacing the cylinder.

I've found this http://www.insapipe.com/hotstream.htm which looks ok as the tapware/rose is a lot more robust than the standard electric showers. It's an 8kw unit, not sure what kind of pressure I'll be able to run the hot water at though.

Also looked at this http://www.trademe.co.nz/building-renovation/plumbing-gas/water-cylinders-heaters/auction-778134761.htm which looks like it attaches to the water supply and I can use the existing shower hardware. It's an 8.5kw unit and caps pressure at 3.5l per minute, is that enough for a reasonable shower?

I'm wondering if anybody may be able to let me know if they've used anything similar in the past and are there any better options than what I'm looking at? I'm keen to keep installation costs as low as possible.

I don't know much about anything but I'll give it a go.

1 | 2

153 posts

Master Geek
+1 received by user: 15

#1127092 12-Sep-2014 10:56

Checkout http://www.myheatworks.com/ looks like a pretty cool system that complements what you already have. You can increase number of units if/when needed to boost capacity.

I'm thinking about one for our kitchen that is a decent distance from the low pressure cylinder so takes a long time to get hot water running.

gcorgnet

1096 posts

Uber Geek
+1 received by user: 273

ID Verified

#1127097 12-Sep-2014 11:09

KShips: Checkout http://www.myheatworks.com/ looks like a pretty cool system that complements what you already have. You can increase number of units if/when needed to boost capacity.

I'm thinking about one for our kitchen that is a decent distance from the low pressure cylinder so takes a long time to get hot water running.

Could anyone shine some light on how this system works? The website doesn't really explain..

timbo1604

102 posts

Master Geek
+1 received by user: 1

#1127100 12-Sep-2014 11:11

gcorgnet:
KShips: Checkout http://www.myheatworks.com/ looks like a pretty cool system that complements what you already have. You can increase number of units if/when needed to boost capacity.

I'm thinking about one for our kitchen that is a decent distance from the low pressure cylinder so takes a long time to get hot water running.

Could anyone shine some light on how this system works? The website doesn't really explain..

And also where to find in NZ please :)

I don't know much about anything but I'll give it a go.

KShips

153 posts

Master Geek
+1 received by user: 15

#1127104 12-Sep-2014 11:18

https://www.kickstarter.com/projects/1132758406/heatworks-model-1-your-next-water-heater has a bit more information.

They can be brought from the site although the NZ shipping is $160US which seems a lot? Might pay to check with them first.

lxsw20

3689 posts

Uber Geek
+1 received by user: 2174

Subscriber

#1127113 12-Sep-2014 11:30

If anything like the electric showers I have used in the UK, they are useless lowest of low pressure. If you're lucky you will feel a light mist of water.

nickb800

2735 posts

Uber Geek
+1 received by user: 829

Trusted

#1127128 12-Sep-2014 11:52

My flat has an 8kW electric instant hot water system. Its low pressure, works alright if you have an 'eco' showerhead.

The main consideration for you would be supplying sufficient electricity to the units - for a 8kw unit you'll need a thick dedicated line from the switchboard to the shower (just like a stove/oven), and if you have multiple units you'll need to review your mains supply - 8kw is roughly half of a standard 63 amp residential service. The lights in my flat dim when you turn the shower unit on.

Edit: I'm not a sparky, but my guess is that with 20 guests you would be far better off upgrading your HWC than installing several on-demand units, as you will need a significant current to feed multiple 8kw units in the morning when everyone (or at least several people) are having a shower. A HWC essentially spreads this demand across 24 hours thus needs less peak current

Dyson

Shop now for Dyson appliances (affiliate link).

gundar

488 posts

Ultimate Geek
+1 received by user: 80

Trusted

#1127184 12-Sep-2014 13:32

I must say that I back up the inline electric heaters as being poor experiences. I have used one before and I found I had to lower the pressure of the shower in order to have a warmer shower. It wasn't great on it's best day. That was a long time ago, so maybe things have changed since then.

When I saw this thread, I remembered that I had seen an article a few days ago about hot water recovery: http://www.econation.co.nz/heat-recovery.html this link explains how it works although it looks like the efficiency of the system will depend a lot on who installs it and how they use it but in your case, where there are a number of showers happening at about teh same times of day, a system such as this might actually pay off well.

I have no idea who installs or sells these, but it sounds like something that would work for your scenario.

wellygary

8810 posts

Uber Geek
+1 received by user: 5287

#1127200 12-Sep-2014 13:42

Given that this is a kickstarter project and is only available for pre order, I would steer clear until there have been some real world reviews or what the flow artes are like, and whether it functions well with Mains pressure etc.

The whole notion of something that allows "wifi controlled hot water" just screams over complication to me,

Gas infinity systems used to ( and I think its still an option) come with remote temperature controls so you could get real hot water to wash the dishes or cooler to wash your hands, in the end I haven't seen a new install with them in years, most people just use a mixer tap to adjust the temp to what they want.

timbo1604

102 posts

Master Geek
+1 received by user: 1

#1127215 12-Sep-2014 13:50

wellygary: Given that this is a kickstarter project and is only available for pre order, I would steer clear until there have been some real world reviews or what the flow artes are like, and whether it functions well with Mains pressure etc.

The whole notion of something that allows "wifi controlled hot water" just screams over complication to me,

Gas infinity systems used to ( and I think its still an option) come with remote temperature controls so you could get real hot water to wash the dishes or cooler to wash your hands, in the end I haven't seen a new install with them in years, most people just use a mixer tap to adjust the temp to what they want.

Hi. Sorry I'm not sure exactly what you're referring to as a kickstarter project or wifi controlled hot water. Is it the heat recovery systems?

I don't know much about anything but I'll give it a go.

wellygary

8810 posts

Uber Geek
+1 received by user: 5287

#1127217 12-Sep-2014 13:53

http://www.myheatworks.com/
https://www.kickstarter.com/projects/1132758406/heatworks-model-1-your-next-water-heater

timbo1604

102 posts

Master Geek
+1 received by user: 1

#1127224 12-Sep-2014 13:55

wellygary:
http://www.myheatworks.com/
https://www.kickstarter.com/projects/1132758406/heatworks-model-1-your-next-water-heater

aha! cheers

I don't know much about anything but I'll give it a go.

Dyson

Shop now for Dyson appliances (affiliate link).

graemeh

2080 posts

Uber Geek
+1 received by user: 226

#1127234 12-Sep-2014 14:08

Hot water heat recovery sounds like it might be a good idea but I've read recently that in practice it just isn't worth attempting.

In large scale hot water systems they often use gas instant hot water heaters to heat water before it goes into a cylinder for storage and use. Perhaps something like this might work for you (obviously with electric instant heaters).

timbo1604

102 posts

Master Geek
+1 received by user: 1

#1127238 12-Sep-2014 14:15

graemeh: Hot water heat recovery sounds like it might be a good idea but I've read recently that in practice it just isn't worth attempting.

In large scale hot water systems they often use gas instant hot water heaters to heat water before it goes into a cylinder for storage and use. Perhaps something like this might work for you (obviously with electric instant heaters).

That's a very good idea but wouldn't flow rate be a problem? If the heater caps at 3.5 litres per minute and the tapware draws 8-11 litres per minute.

I don't know much about anything but I'll give it a go.

graemeh

2080 posts

Uber Geek
+1 received by user: 226

#1127266 12-Sep-2014 14:58

timbo1604:
graemeh: Hot water heat recovery sounds like it might be a good idea but I've read recently that in practice it just isn't worth attempting.

In large scale hot water systems they often use gas instant hot water heaters to heat water before it goes into a cylinder for storage and use. Perhaps something like this might work for you (obviously with electric instant heaters).

That's a very good idea but wouldn't flow rate be a problem? If the heater caps at 3.5 litres per minute and the tapware draws 8-11 litres per minute.

You'd have to find a better electric heater or use more of them.

In the large scale system they had something like 3 x Rheem instant heaters (about 24 litres/min) and 2 large cylinders. They looked like 300-400 litre cylinders to me. This was feeding about 45 apartments. I don't know what temperature they were set at.

Depending on where you are and what time of year you are busy solar water panels may help too.

It really is a job for an expert to come up with a system that suits your circumstances.

Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#1127278 12-Sep-2014 15:10

Short answer - don't.

Most electric instant water heaters only give quite a low flow rate. As others have said. Also they normally don't have any real temp control. This means you control the temp by varying the water flow. In a hostel situation this will be a nightmare, as when other people turn taps on when someone is in the shower the water temp will vary massively.

Easiest upgrade for you will be to replace the element in the cylinder with a larger one. Go with a 5 or 6kW element. Your current element is probably only 2kW. Meaning it will take 4 hours to reheat the cylinder. A 6kW element will only take about 1.4 hours to reheat the same cylinder. And it would be less likely to run out due to the faster reheating rate. Of course you will still need to upgrade the cable running to the cylinder. But you would have to do that anyway if you got an electric instant water heater.

1 | 2