CHP (Combined HeatPower) and a Cylinder

[Art Deineka]

Hello,

I have recently moved to a place with CHP heating.

the controls have a Thermostat powered by "Heat Exchange" switch,
and a cylinder powered by a switch called "Cylinder"

I programmed thermostat to only turn on in the evenings, and kept both switches ON at all times, thinking that heat would only come when programmed.

To my surprise Cylinder itself is warm at all times, even when Thermostat says "off", and hot water is also available at all times!!

Can somebody please explain how it's supposed to work, and why I get hot water, when I don't expect it - and how to run it cost efficiently, so I don't get million pound bill by the end of month.

Also why does Cylinder has it's own switch, isn't it just a container for hot water? or is it warming it up somehow?

 

[Riley]

Welcome to the forum. I may be missing your point but I would assume that your cylinder is heating via an immersion heater. This would be turned on and off by a switch

 

[Worcester]

Chp systems work best when the heating unit is running 24x7 - which unitvis it - the baxi one?
Note we have come across a few of these systems plumbed in completely incorrectly

There should be a set of operating instructions and a hydraulic diagram in the handover pack which explains it all . If its a baxi their technical helpline can be really good

 

[snowhead]

The cylinder is most likely a Thermal store being constantly heated by the waste heat produced by the CHP.

If so then the domestic hot water (water through the taps) will be instantaneously heated within the Thermal store, not heated and stored.
DHW will always be available, providing the CHP has enough capacity.

 

[missplumb]

As Worcester said, chp units work most efficiently when running continuously, therefore generating power all the time. I would also agree with it probably a thermal store rather than a cylinder.

 

[Worcester]

P.s. you are getting paid for the electricity you generate through a feed in tariff aren't you, they should have gone through that when you bought the house.

Generally chp units would appear to tne uninitiated to be undersized as they are designed to run constantly at a an efficient output and put excess over demand into a store that is then used when heat for heating or hot water is needed

It works very differently from either a system or combined boiler though looks the same go here for more info and user guides
Ecogen

 

[Art Deineka]

Hi All

thanks for quick replies,

the cylinder is "Unvented Indirect Cylinder",

it's the Cylinder switch that turns on thermostat, not the "Heat exchange" switch
Why did they put two separate switches, and do I ever need to have them on them separately?

if 24x7 is most efficient way, then why is there "On" position in thermostat for hot water, if I get hot water even when thermostat says "Hot water Off".

I also attach image of the cylinder