Oil boiler overheating my water

Hi Plumbers,

I'm having a problem here with my boiler, it’s heating my hot water in the tank to temperatures where I can’t touch it. If I turn the temperature down on my boiler it doesn’t seem to make a difference but the radiators definitely don’t get warm enough so I’m guessing that works. I have turnt my hot water tank thermostat down on two occasions and it hasn’t made a difference so could it be that’s broken.

I’ve attached photos and any help would be appreciated!

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Wearb

Perhaps its your immersion heater not switching off. Turn it off and see if that sorts it.

asdfg22

https://www.boards.ie/discussion/2058276205/oil-boiler-overheating-my-water

just confirm what type of boiler, assuming its oil turn the stat down to lowest possible setting and gradually bring up until heat comes on, fiddle around with the stat and check tank and rads each time it cuts out. Are the top of the rads getting warm? i think it may be that the setting is too high on the boiler or the stat may be faulty. i dont think its the tank.

Its the pic that is sideways i expect.

I do not see an immersion heater?

greasepalm

I would ask are there taps on the tank to regulate the heat going in ?

On my gas central heating i was not aware of a tap on the tank in hot press about 2 feet down from top and rads were cold as water in tank was getting heated first and all that was needed was to regulate wind in the tap to restrict the flow and make rads get hotter and might this be your situation. You might also be able to reduce your oil burner but not sure.

Any more photos of pipework and your gauge as it looks low?

Hi, the immersion is off at the wall haven’t used it in the 2+ years of being here but it does work, haven’t tested if it overheats the water still though so that could be an idea

Hi, it’s a warm flow utility 70 I presume as that’s the only stamp on it and it’s oil yes.

the radiators all heat up perfectly, it’s only the hot water that seems to just keep cooking itself, the boiler thermostat is on 2.5/5 and definitely works as i turn that down when the weather is milder and the rads don’t heat up as much, but again the water just keeps getting hotter as the boiler fires on

Wearb

https://www.boards.ie/discussion/comment/120009467#Comment_120009467

Turn it off at the board. It should have its own breaker.

Are you loosing pressure? The gauge (though blurry) looks low.

asdfg22

https://www.boards.ie/discussion/comment/120009433#Comment_120009433

I think the gate valve on the bottom will control the flow but would not recommend doing anything without having a plumber on-site.

Yeah I do loose pressure very very slowly, I have to top it up beside the gate valve every now and again, I top it up back to 1 when I notice it’s gone below it

That’s the balance valve I believe I have played around with it and lowering the amount of water into the the tank does get my rads up to heat faster but doesn’t stop the water in the tank getting way over tank, I might just go ahead after Christmas and replace the thermostat and see where I’m at then

greasepalm

Okay so you have adjusted the balance valve in and noticed rads get hotter.

Have you closed that valve and maybe opened it 1/4 - 1/2 turn on then recheck water temp from hot tap.

Maybe you might get a boiler or plumber to offer advice.

The balancing valve is currently only opened half a turn so if I’m thinking rightly it’s only allowing minimum amounts of water into cylinder anyway.

yeah I’m going to have to keep trying for a plumber, ive been after one for about 4 months as there’s none local that’s why I’m on here as a last resort😅

thanks for all your help everyone

have a great Christmas!

greasepalm

As the only thing to heat your water is the boiler and at a 1/2 turn on is very little if it is restricting the flow. If turned off as in fully in does it heat up as much.

I would google up your boiler and download a pdf file to see parts and might show adjustments as wondering if its on max and needs to be turned down a notch or 2 and your balance valve also coming in to use.

Iderown

May not be any help to you ML - the thermostat for the hot water cylinder here (we have a two zone system) is hidden under the cylinder insulation. It is about half-way down the cylinder. There is an electrical connection to it.

Is the white coloured cable just about visible in one of your photos connected to the immersion heater in the cylinder?

declan b

You have a faulty cylinder stat, post a picture of the cylinder stat if you can

Hi Declan,

I’ve attached photos of my stat, would I be right in saying that this stat would only control the heat of the immersion and not through the boiler?

Hi Iderown,

I only have the one stat at the top which I assume is for the immersion, this might be the problem as there’s nothing telling the boiler to stop heating the water possibly

I’ve just had the heat on with the valve opposite ways as in 1 turn from fully open instead of fully closed, rads taken longer to heat and water still too hot too touch, I’ll try it again with the valve completely closed and see where we’re at then. I’ll also download the PDF and have a read through it next time I’m on the toilet😅

I really appreciate the help!

youtheman

If you don't have a 'zoned system' then you don't have actuated valves and a cylinder thermostat. I assume this is the case.

If you water is heating up too much via the boiler then I suspect your 'pump overrun thermostat' is faulty. This is designed to cut out the boiler when the water coming back from the radiators and cylinder is too hot. Sounds like yours is not working.

Hi you the man 🤯

I have a two zoned system, the first zone is downstairs and the second is upstairs which includes my hot water, meaning I have no controls to only heat hot water with the boiler. Where would this thermostat be located do you know?

jimf

do you ever need to reset the high limit button on the boiler stat

No, never had to Jimf!

youtheman

If your cylinder is tied in with your central heating upper zone then you have no cylinder thermostat. As far as the boiler sees it your cylinder is just another 'heat exchanger' on the same loop as all the radiators. So it looks like your cylinder is heating up preferentially, i.e. before you radiators heat the room and the thermostat on the wall closes the zone valve. So you need to 'balance' that zone such that more water goes to the radiators and less to the cylinder. There should be a gate valve on the coil to the cylinder. You need to close that valve in some more (not full closed).

greasepalm

https://www.boards.ie/discussion/comment/120011990#Comment_120011990

That looks like a standard emersion element that can adjust via the red dial and only for heating the water via emersion and on/off switch on the wall and should not any bearing on water too hot as its switched. I do hope there was a safety cover over that and held on with a screw.

Last time I had the balance valve open about 1.5 turns, I’ll try it with just half a turn now thank you!

Hi greasepalm,

yeah I figured, there was a cover but it was blank so I removed it for the photo. Thanks so much for your help

asdfg22

it appears there are flow restrictor valves on the rads and that the water can flow freely to hot water tank. I would be inclined to open the valves on all rads and use this as a start point.