Heating timer oddness

[Aragorn84]

We've recently moved into a new place and i've been tweaking the heating timing to get the system working as efficiently as possible, and i've come across something i've never seen before.

The Boiler is an Ideal Classic RS360, and its controlled by a Siemens RWB9 timeclock, plus a room stat in the hall. Theres a vented hot water cylinder in the upstairs bathroom, with a cold header tank above it.

We dont use much hot water in the evening, so i was trying to shut the water off at say 8pm, but run the heating until 10, however the time clock wouldnt let me. After lots of head scratching, i noticed that if i flip it to manual and select hot water, only the hot water fires up as you would expect. If however if i select central heating, both the heating and hot water LEDs come on....

My previous system had complete control over both zones whenever i wanted it.

I've searched around trying to find a circulating pump and/or some motorised zone valves, however the boiler is in the kitchen and i fear the valves are behind the cabinets or wall or something.

I've also noticed the hot water doesnt get very hot, so i was wanting to fit a thermostat and hopefully manage to get better control over the hot water temperature by turning the boilers output up a bit, but if the time clock wont let me control the hot water seperately then i presume this wont work either.

Any tips?

 

[D_Hailsham]

You probably have a pumped heating/gravity hot water system. You can usually tell by the number of water pipes connected to the boiler. If there are only two, it will be fully pumped; but if there are three or four it will be pumped CH and gravity HW.

When you have a pumped/gravity system you are restricted as to what you can do. You can run the hot water on its own in the summer; but in the winter you have to have both heating and hot water on at the same time. This is because you can't stop the water circulating through the heating coil of the HW cylinder. The heating pump is off in the summer and this acts as a valve preventing circulation through the radiators.

If you have a pumped/gravity system and want to have independent control over CH and HW times and temperatures, you have two choices: convert to fully pumped or, retain gravity HW but install a C Plan system.

The conversion to fully pumped will cost more than the C Plan, but be more efficient.

Either change will require a new timer as the RWB9 is a single channel timer. i.e the CH and HW times are the same.

 

[Aragorn84]

Cheers for that.

I've had a quick look at the boiler (its boxed into a kitchen wall so its hard to see) but it appears to have four pipes coming out the top of it, two at each side, and probably some more out the bottom, but i cant see those very well. That would seem to follow with what your saying, however unusually, the pipes are all 22mm, whereas the convention for gravity HW would generally be to use 28mm pipe?

Might this account for the poor hot water temperature? Should i try turning the main boiler control up a bit to get some more heat into the water?

Thanks

 

[D_Hailsham]

I've had a quick look at the boiler (its boxed into a kitchen wall so its hard to see) but it appears to have four pipes coming out the top of it, two at each side, and probably some more out the bottom, but i cant see those very well.

Definitely a gravity HW system. Unusual for the HW pipes to be 22mm. As you say, they are normally 28mm. Turning the boiler temp up will help - but the room thermostat will still turn the boiler off when the room is up to temperature, even if the HW is not up to temperature. That's why you need to consider updating to fully pumped or C Plan.

 

[picasso]

Definitely a gravity HW system. Unusual for the HW pipes to be 22mm. As you say, they are normally 28mm. Turning the boiler temp up will help - but the room thermostat will still turn the boiler off when the room is up to temperature, even if the HW is not up to temperature. That's why you need to consider updating to fully pumped or C Plan.

why would the room stat turn off the boiler when the hot water is calling,? the boiler would still be controlled from the hot water on connection on the programmer and should run until the boiler stat turns it off.

 

[D_Hailsham]

Definitely a gravity HW system. Unusual for the HW pipes to be 22mm. As you say, they are normally 28mm. Turning the boiler temp up will help - but the room thermostat will still turn the boiler off when the room is up to temperature, even if the HW is not up to temperature. That's why you need to consider updating to fully pumped or C Plan.

why would the room stat turn off the boiler when the hot water is calling,? the boiler would still be controlled from the hot water on connection on the programmer and should run until the boiler stat turns it off.

Don't know what I was thinking of! The OP has a two-channel timer, so you are correct. But the OP still needs to consider a fully pumped or C Plan if he wants independent time and temperature control.

 

[picasso]

Don't know what I was thinking of! The OP has a two-channel timer, so you are correct. But the OP still needs to consider a fully pumped or C Plan if he wants independent time and temperature control.

agree with you there, I would hate to see his gas bill