Why is bathroom radiator connected to hot water tank

[Zaffy]

I have an old oil fired central heating system.
I keep the hot water/central heating permanently on all year round. And at this time of year the thermostats on the radiators are set to zero or one/two.
Because the water is constantly on it means the bathroom radiator that is connected to the hot water tank is always hot, and at this time of year, it can be uncomfortable.
I understand it is not advisable to turn the bathroom radiator off. Therefore, in the summer, I turn the whole system off and use the immersion heater to heat the hot water instead. On talking to several non-plumbers and indeed one plumber, they seem to think I am mistaken and the radiator can indeed be switched off when heating the water with the oil boiler.
Q.1. Have I after all these years misunderstood my set up?
Q.2. What would happen if I turned the bathroom radiator off while heating the water tank with the oil boiler?
Q.3. Am I wasting money with the bathroom radiator having to be permanently on?
Q.4. Boiler works fine, but is it time to have a completely new system?
Q.5. Why does no one else have this system?

 

[Dotty]

Your heating system was originally solid fuel with the heat source being a back burner in the fire. If it wasn't it was plumbed in by a guy who always plumbed them that way.

Because the heat generated by the back burner was uncontrollable, it was, and in some cases still is, advisable to install what is known as a heat leak radiator, usually in the bathroom.

The boiler you have now is a controllable heat source, you can set a temperature for it to turn off at, and control it by means of a time clock. It also has a limit switch for when the temperature rises to an unsafe level.

This means you no longer need a heat leak radiator.

Turn it off.

I wouldn't worry about getting the system replumbed, or at least modernised, until such time as you're looking at a new boiler.

 

[Zaffy]

Dear Croppie, Thank you for your answer. Because I do not know what I am talking about, I have to refer to other articles such as this.
What is a heat sink radiator & why should you have one? - Trade Radiators

 

[joni os]

It used to be common practise to have bathroom radiator on same pipework as coil in DHW cylinder. This ensured somewhere to dry towels even when central heating was turned off.
Such a set up would imply primary flow to DHW and rads can be separated. In the absence of motorized valves this could be gravity DHW and pumped central heating or even a two pump system now rarely encountered. As above rad could have been heat sink for solid fuel system.
Without major works to your system, it may be possible to introduce controls allowing for both DHW off boiler and the comfort of your environment. Take advice from a local heating engineer who services your boiler.

 

[Zaffy]

Joni, thanks for your answer. I think my system is gravity fed, open vented. I have had a few engineers over. One said 'just turn rad off' but two engineers said 'rad has to stay on'. None offered a solution.

 

[Zaffy]

Because I have from various sources a 50-50 answer as to whether I can turn the bathroom radiator off, I rang Potterton.
The boiler is a Potterton Statesman 90/110. Twenty-years-old.
Potterton tech department said 'this particular boiler does not have a bypass and the radiator should stay on.'
However, I am still not sure if this is the definitive answer because other professionals question this. Someone (not an engineer) suggested I should have a plumber attach some sort of thermostat so then I could turn the radiator off.

 

[Best]

Because I have from various sources a 50-50 answer as to whether I can turn the bathroom radiator off, I rang Potterton.
The boiler is a Potterton Statesman 90/110. Twenty-years-old.
Potterton tech department said 'this particular boiler does not have a bypass and the radiator should stay on.'
However, I am still not sure if this is the definitive answer because other professionals question this. Someone (not an engineer) suggested I should have a plumber attach some sort of thermostat so then I could turn the radiator off.

You are asking the wrong people. Someone on the end of a phone, - or on this forum cannot see your pipework setup and are only going by your very vague and non technical description.
Potterton technical might be someone who reads from a book tbh, and could be totally wrong. Boiler only would require a bypass valve or rad in certain circumstances, mainly if all circuits can close.
Here is the answer, - firstly, does your boiler have separate pipes on gravity just to heat the cylinder without a pump? If it does then a rad off that circuit can be turned off on oil system.
But if it is an all pumped system then having all rads turned off except bathroom, or including bathroom would be fine providing the system can always pump continuously around the cylinder coil (no cyl therm valve fitted for example) and if it can't pump over into your expansion tank, as yours is a open system you say.
A lot of systems were designed wrong and at risk of pumping over as vent pipe is on positive side of pump.
This is why you need to be certain what system design you have.