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Offline foggy

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Rinnai temperature fluctuations
« on: August 07, 2014, 06:51:19 PM »
Looking for any advice, new installation Rinnai VT26 feeding 2 bed house. Problems with temperature fluctuations on shower mixers, some information:
Heater working correct, been checked by Rinnai no issues with gas pressure or flow, keeps a constant 55C
House has 20mm RMC limiting valve, 20mm feed direct to Infinity and 20mm to within 1m of showers, cold to house taps tees of feed to Infinity
Shower mixers and hand pieces have no flow restrictors fitted
If you run another tap whilst using the shower you get a noticeable drop in temperature, if more taps are turned on the temp drops right off
It seems to me that the cold is over pressuring the hot at the mixers, limiting valve been checked and adjusted
The Rinnai is located approx 15m away from bathrooms ( builders bright idea) so i'm thinking that the pressure loss through the unit and pipework and the flow modulation when the unit running full capacity is possible cause
Was thinking of installing a flow restrictor on the cold supply to showers

Any idea's?

Linkback: https://www.plumbers.nz/instantaneous-water-heaters/67/rinnai-temperature-fluctuations/1728/
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Offline integrated

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Re: Rinnai temperature fluctuations
« Reply #1 on: August 07, 2014, 07:30:53 PM »
Quote from: foggy on August 07, 2014, 06:51:19 PM
Looking for any advice, new installation Rinnai VT26 feeding 2 bed house. Problems with temperature fluctuations on shower mixers, some information:
Heater working correct, been checked by Rinnai no issues with gas pressure or flow, keeps a constant 55C
House has 20mm RMC limiting valve, 20mm feed direct to Infinity and 20mm to within 1m of showers, cold to house taps tees of feed to Infinity
Shower mixers and hand pieces have no flow restrictors fitted
If you run another tap whilst using the shower you get a noticeable drop in temperature, if more taps are turned on the temp drops right off
It seems to me that the cold is over pressuring the hot at the mixers, limiting valve been checked and adjusted
The Rinnai is located approx 15m away from bathrooms ( builders bright idea) so i'm thinking that the pressure loss through the unit and pipework and the flow modulation when the unit running full capacity is possible cause
Was thinking of installing a flow restrictor on the cold supply to showers

Any idea's?



you need flow restrictors everywhere - depending on mixer brand & type this can be set at the mixer - if the mixers are not adjustable settable flow type then throw restrictors in the shower head and sink/whb mixer spouts - they are readily available these days


that's crazy having that unit so far away and it will be chewing through the juice


you have checked the filters aye?
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Offline foggy

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Re: Rinnai temperature fluctuations
« Reply #2 on: August 07, 2014, 09:29:08 PM »
Mixers have no restrictors in, can't access. Shower head had restrictor built in but was noisy on full flow so removed, no difference either way.
All other tapware is new and has standard flow rate, nothing special, yeah did check every filter
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Offline integrated

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Re: Rinnai temperature fluctuations
« Reply #3 on: August 07, 2014, 11:07:52 PM »
hmm - I know what you mean they can be noisy - maybe partial blockage or kinked pipe?
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Offline bowtieboy

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Re: Rinnai temperature fluctuations
« Reply #4 on: August 08, 2014, 07:59:25 AM »
i agree with Intergrated, you need to flow restrict all the tap ware, what is happening is the shower is not preferentially piped and other taps are.

good flow restrictors don't make noise if fitted correctly. i would start with 12 litre ones on the shower and ensure you have mains pressure perlators on all other taps,

also just check your incoming water temp, this time of year the rinnai will reduce that flow rate way lower with the cooler water coming in, this is why you will have an unbalance it your shower mixer, having said that what type of shower mixer is it ? some are just rubbish :o and wont be helping things.
regards
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Offline foggy

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Re: Rinnai temperature fluctuations
« Reply #5 on: August 09, 2014, 10:12:18 AM »
The shower mixers have been piped up 20mm hot within half a meter and the kitchen is furthest away from Infinity, the mixers are Hansa
Think it just comes down to the location of the Infinity and the pressure loss and yeah the cold is colder this time of year.
This is what happens when builders/customers decide on the location of the Infinity and the plumber didn't point out the possible problems.
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Offline mini g

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Re: Rinnai temperature fluctuations
« Reply #6 on: August 12, 2014, 05:04:00 PM »
Think the main problem will be the pressure difference between hot and cold. The hot is restricted through the infinity and the cold will over ride it to some extent through mixer taps. You will need to fit another limiting valve to the cold and adjust it down to match the hot pressure. Measure it at the wash machine with a couple of gauges. Unless the shower mixers are of the venturi type they need equal pressure to get a good mix. Basin taps can be restricted down quite bit as can the sink if it is the tap which causes the most complaints. The showers should be restricted to 9 litres. Remember the infinity will prioritize temperature over water flow and can only heat X amount depending on in coming temperature so the more controlled the flow out of the taps the better the infinity will cope.
Hope some of this helps.
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Offline robbo

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Re: Rinnai temperature fluctuations
« Reply #7 on: August 13, 2014, 08:35:34 AM »
hi guys, it`s common to install a `limiting 'valve on the incoming main so as to limit all outlets to the same pressure and is adjustable, so if this is not the case you will need to fit one. As a matter of interest 15mm pipes to all outlets is fine, with high pressure i would not pipe 20mm to anything except the hot water cylinder, cheers 
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