Rinnai boiler won't fire up when I turn on the hot tap

[Natson Bo Janley]

Hi all - hoping somebody can help with this problem - apologise in advance if i garble on a bit.....

So, i have a Rinnai boiler, pilot light lights fine.

When I open the hot tap in the kitchen sink the boiler fires up and warm water comes out - this used to be hot, but now only warm. 

When I open the hot tap in the bathroom or switch on the shower - the boiler doesn't fire up at all. The shower used to fire the boiler fine and the water would get really hot and stay this way with the pump out running, after a while, this would only stay lit and hot with the pump switched off - now nothing. 

I recently had a leak from a broken kitchen tap

The water pump used to periodically sound like it was starting up for no reason - every few hours it would grind over, but this has stopped since I replaced the kitchen tap.

 

any/all help and advice appreciated.

 

many thanks!

 

 

[Mad Harold]

Sounds like the diaphragm has hardened with age.

This is a rubber thing connected to the gas valve and water pressure pushes the diaphragm opening the gas.

If Mike The Boilerman is online,I am sure he will know.

[system 4-50]

How exactly did you change the kitchen tap? What components of the system did you affect/disturb? What exactly was the fault with the tap?

 

[rusty69]

I don't know the answer, but how is the general flow rate from both the hot and cold taps? Comparing the kitchen to the bathroom and the expected pump delivery rate. Can you remove the shower hose? Does this improve things?Have the taps got one of those silly screw on filters that is blocked?

[Natson Bo Janley]

thanks all! 

flow rate is good from both hot and cold - no filters. Makes no difference with the shower hose removed. 

The kitchen tap had a broken part inside which meant it could not seal - I simply replaced like for like. The hot water issue has gone on much longer than the leak.

 

sorry - i'm not very technical!

[rusty69]

4 minutes ago, Natson Bo Janley said:

thanks all! 

flow rate is good from both hot and cold - no filters. Makes no difference with the shower hose removed. 

The kitchen tap had a broken part inside which meant it could not seal - I simply replaced like for like. The hot water issue has gone on much longer than the leak.

 

sorry - i'm not very technical!

Stick around, there will be more knowledgeable replies forthcoming. It sounds to me like a probable boiler part worn out,or a pipework restriction  Hopefully Mike will be along soon. I think he had a Rinnai at one time.

[Richard10002]

I had a similar issue with my Rinnai and the shower. To my logical mind, it felt like a water pressure issue, but people here and ybw.com suggested it wouldn’t be. Eventually I found out how to increase the pressure on my water pump, and increased it enough to solve the issue, then reduced it a bit, so it still worked.

 

Shower works fine now.

[Arthur Marshall]

My Rinnai cuts out if I try to run the shower and the tray pump at the same time, not enough power to run both and get enough pressure through the heater. Worse when the battery is low, not so bad if engine's running. 

Could there be a blockage in the water supply hose? 

[MtB]

2 hours ago, Mad Harold said:

Sounds like the diaphragm has hardened with age.

This is a rubber thing connected to the gas valve and water pressure pushes the diaphragm opening the gas.

If Mike The Boilerman is online,I am sure he will know.

 

I don't really. Never felt I fully understand instantaneous water heaters. Mine does stuff I have no explanation for and even Morco tech can't answer my questions. 

 

But yes I had a Rinnai water heater for a couple of years. Endless trouble and it eventually went in the skip. Your symptoms are typical of a perforated diaphragm inside the water section. I'm pretty sure Rinnai don't support this water heater any more so a new appliance will be needed. The new Morco equivalent water heater has a flue hole 2" away from the Rinnai flue position, so fitting it will be a right beach of a job...

 

 

[Natson Bo Janley]

Many thanks all.....looks like I'll have to call the experts in! 

 

[MtB]

19 minutes ago, Natson Bo Janley said:

Many thanks all.....looks like I'll have to call the experts in! 

 

 

Err.... we ARE the experts!!

 

 

 

[Natson Bo Janley]

?.... of course! When can you pop round!

[Richard10002]

1 hour ago, Natson Bo Janley said:

Many thanks all.....looks like I'll have to call the experts in! 

 

If you can find the adjuster screw on your water pump, I would increase the pressure, and see if this makes a difference. It's a simple fix if it works. If it doesnt, make sure you note how many turns of the screw you have made, so you can return it to its original position.

 

I increased mine quite a lot, and it worked. I then reduced the pressure until it just didnt work. I then increased the pressure a bit, by bit, until it worked.

[MtB]

41 minutes ago, Natson Bo Janley said:

?.... of course! When can you pop round!

 

Like i said, it can't be fixed. It needs a new diaphragm that is not available.

 

Prolly best to call Rinnai and double check first though in case I'm wrong. 

 

 

[Richard10002]

Paloma Bob has a refurbished one for sale:

 

https://www.ebay.co.uk/i/123700088680?chn=ps

 

[Richard10002]

Spares ?

 

https://gasproducts.co.uk/water-heaters/rinnai-genuine-water-heater-spares/rinnai-58e-gas-water-heater-spares.html

 

Gas Control Valve Assembly:

 

https://gasproducts.co.uk/water-heaters/rinnai-genuine-water-heater-spares/rinnai-58e-gas-water-heater-spares/rinnai-58e-gas-control-valve-assembly.html

 

Dont know if this is where the diaphram lives?

[Arthur Marshall]

If you live on the boat, then it's obviously a real problem as it's been in constant use. If you don't, though, and the boat's not been used much over the winter, it may well be either water pressure or dirt in the boiler. 

One problem I've had is the pipe from the water tank gets a bit rusted or clogged (at the tank end) and this lowers the pressure enough to cause Rinnai problems. And this time of year, I can't get very hot water anyway as the water in the tank is so cold. 

[Ex Brummie]

What temperature setting do you have the heater set on? If you have it set for a 'good' flow, there may be too much water passing through the heater for the output to heat properly, especially when the water temperature is as low as it will be at present.

Is your shower control a thermostatic mixer? If so, you could have problems there.

[Arthur Marshall]

1 hour ago, Ex Brummie said:

What temperature setting do you have the heater set on? If you have it set for a 'good' flow, there may be too much water passing through the heater for the output to heat properly, especially when the water temperature is as low as it will be at present.

Is your shower control a thermostatic mixer? If so, you could have problems there.

Good point about the shower mixer. My Rinnai will only run if the shower is solely connected to the hot supply. Any other tap on and the pressure is too low. Even the tray pump can lower the power level enough, too.