Hot Water Coming On With Heating

[Fayecb]

Hi,
We've just moved in to a property that has an Ideal Mexico 2 Boiler downstairs, a water tank in a cupbaord upstairs and in the loft 2 water tanks, a large one and a smaller one. When we moved in they had both the heating and water on constantly and the thermostat turned down for the radiators when not required. We had an electrician upgrade the old thermostat with a Nest but now when we put the heating on the radiators get boiling hot and can't be controlled. If we just have the heating on then we can control the temp ok. We called the electrian back who then said it was the boilers fault and an issue with a valve. We've had someone to look at the boiler and no valve can be found. Well and truly stuck and don't know where to turn. Any help would be much appreciated. Thank you

 

[Last Plumber]

Hi,
We've just moved in to a property that has an Ideal Mexico 2 Boiler downstairs, a water tank in a cupbaord upstairs and in the loft 2 water tanks, a large one and a smaller one. When we moved in they had both the heating and water on constantly and the thermostat turned down for the radiators when not required. We had an electrician upgrade the old thermostat with a Nest but now when we put the heating on the radiators get boiling hot and can't be controlled. If we just have the heating on then we can control the temp ok. We called the electrian back who then said it was the boilers fault and an issue with a valve. We've had someone to look at the boiler and no valve can be found. Well and truly stuck and don't know where to turn. Any help would be much appreciated. Thank you

Is this a gravity hot water, pumped heating system or fully pumped? If you don't know that can you see how many pipes leave the boiler? 2 or 4 normally (not including gas).

 

[Fayecb]

Is this a gravity hot water, pumped heating system or fully pumped? If you don't know that can you see how many pipes leave the boiler? 2 or 4 normally (not including gas).

Hi we have a round red and black pump near the boiler does that help?

 

[exedon2]

Some clear pictures would be useful tho given type and age of boiler you probably have gravity hot water which will come on ever time boiler is powered up.
At the moment with the Nest you have probably added mud flaps to a tortoise!
You need a competent heating engineer, system at very least needs converting to fully pumped eg S plan.

 

[Fayecb]

Some clear pictures would be useful tho given type and age of boiler you probably have gravity hot water which will come on ever time boiler is powered up.
At the moment with the Nest you have probably added mud flaps to a tortoise!
You need a competent heating engineer, system at very least needs converting to fully pumped eg S plan.

I'll get some pics when I get home. Is this a big job changing the system to an S plan? Thank you

 

[Last Plumber]

Hi we have a round red and black pump near the boiler does that help?

Not really. Most systems alive at the moment will have a pump.
The photo's of the boiler would help a lot. If you have gravity hot water, it will always heat up when the boiler is on. You wouldn't be able to have heating only.
Let me see the photo's of the boiler and I will be able to tell you more about it. Did you keep the old programmer in and just have the thermostat replaced?

 

[Fayecb]

Not really. Most systems alive at the moment will have a pump.
The photo's of the boiler would help a lot. If you have gravity hot water, it will always heat up when the boiler is on. You wouldn't be able to have heating only.
Let me see the photo's of the boiler and I will be able to tell you more about it. Did you keep the old programmer in and just have the thermostat replaced?

Hi we changed the programmer to the heat link one. I've a drawing on how the old system was wired up. Here are some pictures. Thank you

 

[Last Plumber]

Hi we changed the programmer to the heat link one. I've a drawing on how the old system was wired up. Here are some pictures. Thank you

Can you take a photo from further back so we can see all the boiler and pipework in the cupboard

 

[Fayecb]

Can you take a photo from further back so we can see all the boiler and pipework in the cupboard

 

[Last Plumber]

From here it does look like it is gravity hot water, pumped heating.
What is the boiler stat behind the drop down door set to and are there photos of the cylinder in the airing cupboard?

 

[Fayecb]

From here it does look like it is gravity hot water, pumped heating.
What is the boiler stat behind the drop down door set to and are there photos of the cylinder in the airing cupboard?

 

[Last Plumber]

I would turn that stat down to 3 1/2 or 4, try it and the domestic hot water should cool a bit but you do want to store it at 60 C.

I don't know much about nest but you need a 2 channel programmer set to 10 programmes and you will be able to use hot water only or hot water and heating. You will not be able to use heating only. If the nest is capable, fine. Someone else will need to tell you that as I don't use them.

You could have it changed to an 'S' plan if you really want to but your boiler is 20 to 25 years old now and that cylinder looks the same or older. If you can manage with it I would do that until you are ready to replace the boiler and address it all then. The boiler doesn't look to have been serviced in a while and there are signs of leakage/corrosion around the area where the heat exchanger sits on the combustion chamber box. That could be products of combustion seeping through or a water leak past or present but it needs looking at if you want my advice.

I have only seen photo's and an experienced heating engineer on site will tell you more and advise you accordingly.

 

[Fayecb]

I would turn that stat down to 3 1/2 or 4, try it and the domestic hot water should cool a bit but you do want to store it at 60 C.

I don't know much about nest but you need a 2 channel programmer set to 10 programmes and you will be able to use hot water only or hot water and heating. You will not be able to use heating only. If the nest is capable, fine. Someone else will need to tell you that as I don't use them.

You could have it changed to an 'S' plan if you really want to but your boiler is 20 to 25 years old now and that cylinder looks the same or older. If you can manage with it I would do that until you are ready to replace the boiler and address it all then. The boiler doesn't look to have been serviced in a while and there are signs of leakage/corrosion around the area where the heat exchanger sits on the combustion chamber box. That could be products of combustion seeping through or a water leak past or present but it needs looking at if you want my advice.

I have only seen photo's and an experienced heating engineer on site will tell you more and advise you accordingly.

Thank you, do you think we can still use the thermostat if we had both the hot water and heating. That's how it was when we moved in but we'd just turn the thermostat down and the radiators would go off. We can't do that at the moment.

 

[Last Plumber]

Thank you, do you think we can still use the thermostat if we had both the hot water and heating. That's how it was when we moved in but we'd just turn the thermostat down and the radiators would go off. We can't do that at the moment.

It depends on how he's wired it really. You want a switch to turn the boiler on and a thermostat to turn the pump on to have it as was.

 

[ShaunCorbs]

Needs ripping out and starting again as it’s gravity hot water eg no pump nest can’t be controlled like this

 

[Timmy D]

Needs ripping out and starting again as it’s gravity hot water eg no pump nest can’t be controlled like this

Can’t you just wire the nest hot water s/l to the boiler and leave it permanently on.

Then wire the nest heating s/l to the pump?

 

[ShaunCorbs]

You will get back feeding eg pump will come on as you have a live at the boiler

 

[Timmy D]

You will get back feeding eg pump will come on as you have a live at the boiler

Still can’t wrap my head round this.

So you’ve got the boiler s/l connected to the nest HW s/l. You set the nest for continuous HW.

Boiler is on, cylinder is being heated. Pump is off, heating circuit is cool.

We then connect the nest heating s/l directly to the pump. We turn the heating on, the pump starts up and heats the heating circuit. We don’t need to send a demand signal to the boiler s/l as the HW demand is already there.

What am I missing? How’s it gonna back feed? Through the nest?

 

[ShaunCorbs]

Yes you will have to link both heating and hot water at the nest or boiler eg run two wires

as say you just connect the pump to heating but as you just have hot water on the live / call to the boiler would go back to the nest heating and power the pump

can’t leave hot water on as it wouldn’t turn off potential over heat the cylinder

also part g of building regs require you to have a thermostat on the cylinder

 

[Timmy D]

Yes you will have to link both heating and hot water at the nest or boiler eg run two wires

as say you just connect the pump to heating but as you just have hot water on the live / call to the boiler would go back to the nest heating and power the pump

can’t leave hot water on as it wouldn’t turn off potential over heat the cylinder

Understood.

Just seen this Link

 

[king of pipes]

As Shaun says it needs a re pipe and controls upgrade to a s plan you cannot separate the heating and hot water the way it is now . Kop

 

[Timmy D]

As Shaun says it needs a re pipe and controls upgrade to a s plan you cannot separate the heating and hot water the way it is now . Kop

I agree that it should be s-planned.

Have a look at the link I posted. If you connect the cylinder stat inline after the “2” tee on the “L” to “6” wire, you get control of the system. Heating or hot water wouldn’t back feed.