Gravity HW system issue

[BrianR1939]

I have an old heating system - pumped CH and gravity HW.
Hot tank has a thermostat and I have a British Gass MyHome remote thermostat and transmitter for CH.
The main timer is set to ON for CH so that remote MyHome can work. This of course means that linked WH controll sets to ON.
Problem is When remote CH is set to OFF CH is imobilised BUT HW still calls for HW and fires boiler - even when tank stat is set to min.
Have checked stat and it does show open circuit when set low and closed circuit when set high so stat is working.
How do I stop maintaing a tank of hot water when I am away from home but want to maintain internet control of my CH system.
BrianR

 

[I Like Sleeping]

Get it wired up correctly.

 

[45yearsagasman]

Thermostat on the cylinder indicates something other than a simple gravity HW system. You sure you're describing your system correctly?

 

[Dan Robinson]

C-Plan?

 

[BrianR1939]

Thermostat on the cylinder indicates something other than a simple gravity HW system. You sure you're describing your system correctly?

Yes that is exactly how it is Pete
Have seen some diagrams on this site which show gravity systems exactly how mine is.
System 30 years old and had a hot tank stat then! 7 years ago B Gas replaced boiler and tank still using the old stat fastened to side of HW tank via a cut out in the insulation.

One reply said get it wired correctly - presume B Gas know what they are doing! and they wired it up!

My qquestion is should the HW tank stat stop the boiler firing if it set to lowest temperature and with CH set to off.
If it should then clearly there is a fault somewhere. Maybe it has always been wired incorrectly?

 

[bellairaphon]

Sure you don't have a zone valve?

 

[BrianR1939]

Sure you don't have a zone valve?

The HW system does NOT have a zone valve.
There is one in the CH circuit that I had fitted a few years ago to segregate upstairs and downstairs radiators.
But as I say the 28mm pipe for HW goes to and from cylinder with nothing in the line.
Thanks for your reply.
If more info helps here goes.

Boiler is B Gas 380 RD1 fitted 7 tears ago
Timer for CH/WH
Zone vale to split CH upstairs / downstairs.
Room stat downstairs for control of CH temp
Water tank stat to control temp of HW (when CH is off) wires from tank stat go into the manual CH/HW linked timer.

So1 with CH timer off and HW timer set to ON. Should the tank stat block the boiler from fireing when syat is set to minumum ??

Thanks

 

[Agile]

Dont ask us!

Just turn the cyl stat down when the tank is warm and see if boiler goes off.

BUT, does the pump run when the hot water is being heated?

I suspect that it DOES and if so then it is not a gravity system !

Tony

 

[BrianR1939]

Dont ask us!

Just turn the cyl stat down when the tank is warm and see if boiler goes off.

BUT, does the pump run when the hot water is being heated?

I suspect that it DOES and if so then it is not a gravity system !

Tony

Tony
When tank is warm and stat turned down the boiler continues to fire on and off to keep temp up. NO the pump for the CH systemt does NOT run.

As I said earlier - with CH OFF and HW set for ON but with stat set to minimum boiler fires and heats tank to very hot (temp of boiler stat setting).

It IS a gravity system

thanks

 

[Agile]

In that case get it wired up correctly so the stat turns off the boiler when the cyl is up to temp.

However, I don't think that boiler is meat to be used on a gravity flow system without a pump!

Tony

 

[DP]

A timer for Gravity HW will give you control you seek.
Function now would be HW timer calls, boiler fires. Demand over, boiler now switches off

CH calls, pump runs. HW activated to run boiler

Get a 28 mm installed in gravity loop. It will give you better control of HW heating

What you need to realise is that for HW, boiler only fires and circulation to cylinder is non mechanical. During CH, pump is run to circulate water to radiators, but boiler needs to be activated also, that is what will confuse most part changers that look after your boiler

 

[gas112]

7 years ago it would not have been allowed to fit a gravity HW boiler.
So either been in longer or boiler possibly has built in divertor valve for splitting HW and CH and pipework looks like gravity system

 

[BrianR1939]

In that case get it wired up correctly so the stat turns off the boiler when the cyl is up to temp.

However, I don't think that boiler is meat to be used on a gravity flow system without a pump!

Tony

Agile - I think you have identified the problem and it would seem the stat may have been wired wrong by B Gas when the boiler was changed 7 years ago. And maybe the boiler they installed was not suitable for Gravity feed system without pump.
I will take it up with them.

DP - sound comment , however as the CH has to be set to ON to enable remote control of heating via Internet the HW (being linked via the timer means that HW canot be set to off. But thanks for your advice.

Gas112 You will see from the tread that the system was installed about 30 years ago - it was only the boiler that was changed 7 years ago. Maybe B Gas should not have fitted this particular boiler!

Thanks to all contributors.
I have referred the matter back to B Gas as it does seem that they may have wired the system incorrectly or advised that a punp would need fitting.

NB All of this only came to light when I took up their MyHome remote central heating system.
I was away for 10 weeks and remotely turned the heating OFF due to the hot weather. Tank stat had been turned off knowing I would be away. When I returned I found I had a tank full of very hot water.
Hence my drive to have no hot water when the CH is not calling for heat.

As a point of interest to you guys I will let you know what B Gas come up with as a solution.

 

[gas112]

I read system fitted 30 years ago but if you live in england or wales from april 2005 8 years ago only condensing boilers should have been fitted and none of them where gravity boilers.

Just checked your boiler is a rebadged ideal classic capable of gravity and def not a condensing boiler

 

[BrianR1939]

Gas112,
Yes it is a rebadged Ideal boilerl. Model Number 380 RD1 which according to the manual is suitable for gravity HW systems.

Having read all of the advice given on this forum and as an electrical engineer I am now convinced that the stat has always been wired incorrectly and that the line feed from the timer for boiler ignition is going direct to the boiler instead of being routed to the boiler via the HW tank thermastat contacts.

Thanks again to everyone.