rinnai gas cailfont under temp

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tweake

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#324099 26-Feb-2026 18:47

we got a new gas califont at work the other day.

model NB56kWe its set up on a ring (runs our heat exchanger) with a circulation pump (not controlled by the califont).running off bottles, installed by pro gas installer.

the problem is it runs cool. set it to 55c and it runs at 50c. i have a tap on on the hot side so can take a cup of water to check. also there is built in temp gauge. both measurements the same. also tried reading the performance data. it seams to indicate that its reading the temps as 55c input and output. however my instructions are for a different model so i might be reading it wrong. so at the moment it looks like the califont thinks its on the correct temp but its actually its down by 5c.

what makes matters worse is i need to run it at 85c and its only outputting 75c when set to 85c (not a gas performance issue, it stops due to thermostat).

@WWHB anyone got a service manual for these?

tweake

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#3465542 27-Feb-2026 18:12

ok partly solved i think.

i found the booklet on ring mains. it says that the unit uses the incoming (cold) side temp sensors and shuts the gas off 5c before target. no idea why, that would mean a lot of the time you never get the correct temp hot water out of the tap unless you draw lots of water.

i suspect these are not really designed for closed loop systems.

the 75c when set to 85c is my fault. you have to actually unplug the controller when setting 85, not just select fixed temp. otherwise its meant to only be set to 75c if a controller is plugged in. funny enough the controller did actually say 85c and outputted 75c like it was set to 80c. something funky in the programming i think.

so i'm probably going to have to wire in a switch to disconnect the controller to be able to run it at 85c and get 80c hot water (which is hot enough for what we need).

i also wonder what would happen if a resistor was added to the temp sensor to make it think the returning water was 5c cooler.

insane

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#3465555 27-Feb-2026 20:38

Could be to stop cycling on/off. Have always wondered how you can circulate infinity hot water with another pump... Perhaps this is how, or you circulate it through another unheated hw tank to increase the volume in circulation.

tweake

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#3465558 27-Feb-2026 20:52

insane:

Could be to stop cycling on/off. Have always wondered how you can circulate infinity hot water with another pump... Perhaps this is how, or you circulate it through another unheated hw tank to increase the volume in circulation.

not sure, it doesn't seam to short cycle when it has no load. it sits on temp very well, the control system is pretty good. if its fine at 50c when you select 55c, why not have it do 55c when you select 55c.

its friday and i'm tired. way to much new stuff this week.

WWHB

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#3465826 1-Mar-2026 16:42

If you have a controller the temperature cannot be set above 75c. If you want 85c just disconnecting the controller won’t do this you have to adjust the settings inside the unit itself. 85c is the hottest setting. The service manual shows how to do this but it’s really supposed to be a Gasfitter that does this

Saor Alba

tweake

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#3465828 1-Mar-2026 17:04

WWHB:

If you want 85c just disconnecting the controller won’t do this you have to adjust the settings inside the unit itself.

the 75c setting and the 85 setting is exactly the same. the only difference is if the controller is connected or not. when i get a mo i shall test just unplugging it. if thats successful i'll look at fitting a switch so i don't have to open the cabinet each time.

i was hoping the service manual might have some more info.

"if you want 85c......." thats the interesting bit because you can't actually get the temps you want in this setup as it will only produce 5c colder than you set it to. from what i'm finding its also not the only brand that does this. would love to know why.