Hot water problems with Grant 90 Oil Combi Boiler

[hazelside]

Hi

I have a problem with the boiler overheating. ((Its fine with the central heating running, but with 'Hot water only' selected it doesn’t deliver any hot water.)) ((= duff gen, please see below

When the boiler is set to constant, or when the central heating is running via the control panel, the water is luke warm at best. After an overheat reset, it comes out hot for 5 secs, then nothing or just luke warm.

The boiler seems to be heating the water inside the tank, but nothing coming out.

Can anyone help me out, as no water and three kids, is getting to my wife.

Many thx

Richard

 

[oilman]

Probably diaphram on diverter valve, possibly blending valve too.

I have a problem with the boiler overheating. Its fine with the central heating running, but with 'Hot water only' selected it doesn’t deliver any hot water.

This makes no sense. Does it overheat? If so when? Is there air in the top of the boiler? Is the automatic air valve open?

When the boiler is set to constant, or when the central heating is running via the control panel, the water is luke warm at best. After an overheat reset, it comes out hot for 5 secs, then nothing or just luke warm.

Are the radiators hot?

Who chose a combi boiler?

 

[hazelside]

Ok scrap my first post.

I have tested the boiler and come up with the following

The radiators do not get hot. Pre or post zone control valves.

The pump is running on Constant setting on boiler. It doesnt run on Timed Heating, even when room stat temp has not been reached.

I opened the tap and lovely boiling water for about 5 to 10 secs, then back to nothing.

Air emittence valve seems to be open. Boiler will overheat between 5 to 10 mins. I will time the intervals and report back.

Any ideas, or something else i need to check.

Im starting to smell, and need a shower soon

p.s i hate combi boilers, but dont have the money to get rid

 

[oilman]

When you open the tap for say 30 secs, does the boiler fire?

If boiler doesn't fire, it's the diaphram. If it fires it's the blending valve.

If the rads are cold, it sounds like the pump is not pushing water round. Have you bled the system of air?

You don't have to replace the boiler. Install a water tank, and arrange to heat it from the heating side as if it was a normal boiler, connect the hot tap pipe to the cylinder, and dispense with the combi side.

 

[hazelside]

Hi

Thx for all your info.

Ok some radiators are hot, i must have an issue with the two i have been checking.

So pump is working ok.

Ok when i run the hot tap with the boiler on Hot water only, nothing happens apart from hot water for the usual 5 to 10 secs. I removed the microswich unit on the front of the diaphragm and can manually pull the rod to simulate the diagragm movement. When i do this we get lovely boiling hot water.

So my question is, is it the diagrapm or something else feeding it.

I'm extrememly grateful for all your advise.

Richard 01892 653581, if you need to run me through any testing.

 

[oilman]

If you have the microswitch removed, measure how far the pin extends when you have the hot tap open. It should be 11mm.

 

[hazelside]

Hi again

The pin doesnt extend at all. only if i pull the pin out do i get lovely hot water, so whats the verdict.

Rgds

Richard

 

[oilman]

Diaphram.

 

[hazelside]

Hi OilMan,

Vertual hug on its way, thx so much for all your help

I will get one asap and make the wife happy

Many many thx

Richard

 

[oilman]

It's not that sort of diaphram

 

[hazelside]

PMSL, that did make me chuckle.

ok one last question. does the diapragm live inside the diverter valve ?. i.e

this

live inside this

and why doesn't the water pressure push it over to allow the hot water through, just so i can understand the dam thing a little more.

Cheers

Richard