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Author Topic: General Instantaneous water heater installation questions  (Read 8412 times)

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Offline Rodza1

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General Instantaneous water heater installation questions
« on: April 02, 2012, 05:53:57 PM »

Hi all,

Was out and about today and i saw a Bosch 25e highflow that was recessed into a wall cavity,only about 20mm of the front,mainly the front cover was protruding from the wall,it had a galvanised finned cover underneath that was screwed to the exterior plastered type wall surface for access to the isolating valves. Above the appliance say about 250-300mm i noticed an oval shaped externally mounted outside light fitting slightly bigger than a can of coke. Was looking in 5261 under minimum clearances for flue terminals to electrical fittings and the only reference was to an electrical meter or fuse box. It did have a small say 30mm angled flashing above the recessed hole the appliance was in as possible heat deflection although it was not in any way covering or obstructing the external front flue outlet. I dont think its dangerous how it is but want to know what others think and if it is in breach of the code,as i will then go tell that particular homeowner the lights got to be moved,or removed.

Also just out of interest for myself, have put in quite a few water heaters of the instantaneous type in the last few years and i have been asked on more than one occasion even when ive been on a property for a un-related plumbing or gasfitting matter why they turn on for a second or so when a cold tap inside the home is operated. The best answer i can come up with for them is usually something along the lines of the drop in water pressure on the appliances inlet valve causes a momentary pre-cycle start up as it adjusts itself to a much lower operating pressure,followed by theres not much that can be done etc... Can anyone put me on the right track??

Comments and opinions would be well recieved,always enjoy learning something new as often as possible

 8)   8)

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Offline aboutgas

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Re: General Instantaneous water heater installation questions
« Reply #1 on: April 02, 2012, 08:54:31 PM »
When you say the light fitting is above the unit is it wall mounted or mounted to the surfeit?

As for the drop in pressure and the unit starting for a moment or two there is 2 ways to look at the problem
1 check to see where the cold feed is plumbed into the system as it should have the priority feed

2 or the other solution I have used for a quick cheep fix for customers is to put a non-return valve in the cold inlet line below the unit this stops the pressure dropping of and should stop the unit trying to start when not required
Unless the moral improves the floggings will continue

Offline Rodza1

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Re: General Instantaneous water heater installation questions
« Reply #2 on: April 02, 2012, 11:25:18 PM »
Thanks for the tip, it seems logical that either of those ideas would prove effective. It happened to me once ages ago but was at a random house just the other day and the client queried me about it out of interest and was sick of not knowing without a doubt what causes it.Thanks for the reply.

Yeah there is no soffit,just fascia board and spouting etc...the light is actually mounted on the wall above the recessed appliance, 250-300mm above. Had to take a second look when i walked past and its had me thinking. When running the appliance i went outside and had a look out of interest ,the flue gas doesnt seem to affect it at all,the heat in the flue gas pushes out not up etc and the plastic body of the light remains dead cool but the big thing is...is it suppose to be there or not?


Offline Rodza1

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Re: General Instantaneous water heater installation questions
« Reply #3 on: June 22, 2012, 11:10:26 AM »
??? Anyone?

Offline Plumber

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Re: General Instantaneous water heater installation questions
« Reply #4 on: June 22, 2012, 12:05:07 PM »
Any chance you can post a pic?
Please note that the advice I am giving is only my opinion and not necessarily a fact.  Please refer to our terms and conditions.

Offline Rodza1

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Re: General Instantaneous water heater installation questions
« Reply #5 on: June 22, 2012, 07:16:55 PM »
ok, i could do that. give it a week and i will see what i can do!     cheers

Offline Rodza1

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Re: General Instantaneous water heater installation questions
« Reply #6 on: August 17, 2012, 12:11:39 PM »
Went past so stopped and photographed this installation today. As ive recently been on the property I dont want to be burnt for something someone else has done. Cant find anything in NZS 5261 that says it cant be there. I tested it while I was on site a few months ago as I said in an above post and the heat from the exhaust port doesnt in any way heat or warm the plastic light in case anyone was wondering. It stays dead cold. I think it should go, it just doesnt look right being that close.

What do you guys think?   

Offline Thunderhead

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Re: General Instantaneous water heater installation questions
« Reply #7 on: August 17, 2012, 12:43:08 PM »
most easy thing to do is phone BOSH directly and ask them the clearances they require around there flue.

As it is a power flue then all of the heat is going out in front of the fixture...i remember my tutor at tech saying that to make sure there was 600mm clearance in front of and of these units just cant remember him saying anything about above...as the heat is thrown out from the machine and you cant find anything in the codes about it and you have done testing and found the light remains dead cold when in full afterburn mode then i wouldnt worry about it too much

Offline Thunderhead

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Re: General Instantaneous water heater installation questions
« Reply #8 on: August 17, 2012, 12:46:50 PM »
i actually would be more worried about burning my face as i walked past it when its was in operation perfect head height??? :P

Offline Rodza1

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Re: General Instantaneous water heater installation questions
« Reply #9 on: August 17, 2012, 12:54:58 PM »
Yeah good idea, Oh its not too bad. Bit higher exhaust than the average mans head height I think. Seen far worse in this city lol

Offline Badger

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Re: General Instantaneous water heater installation questions
« Reply #10 on: August 17, 2012, 12:55:21 PM »
let me know what Bosch says mate about clearences, this is the  exact same model as I got on the one charge, which is bollox. Do me a favour while your talking to bosch can you ask specifically about under a openable window.

As far as it firing with the cold turned on....I had one that the owners had put both hoses off their washing machine in to a "y" fitting and hooked them to the one tap for the water, so it may be a crossed/joined hot to cold supply??
You can't choose who you are.....but you are the sum of your choices.......

Offline Rodza1

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Re: General Instantaneous water heater installation questions
« Reply #11 on: August 17, 2012, 12:59:33 PM »
Thats ridiculous, they sound like a couple of hill billys badger. Ok I will see what I can find out. Cheers

Offline Badger

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Re: General Instantaneous water heater installation questions
« Reply #12 on: August 17, 2012, 03:46:52 PM »
with banjo's ;)

Offline NZMoose

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Re: General Instantaneous water heater installation questions
« Reply #13 on: August 21, 2013, 08:18:14 PM »
NZS:5601.1, figure 6.2 requires a minimum clearance of 200mm below any eaves, balconies and OTHER PROJECTIONS

I'd suggest your light (and that flashing if it's in front of the flue terminal level) are other projections.

Also be aware that unless the cut where the flashing sits is sealed, it's an opening into a building.

2 reasons to advise the owner his installation is non-compliant.


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