Help to improve my central heating...

We've recently moved into a new house which has a Concord WRS boiler, gravity fed hot water with pumped central heating. There are TRV's on all of the rads but no motorised valve. Everything is controlled by a Danfoss 102 mechanical programmer.

I have a couple of issues with it, the main being the innacuracy of the programmer, trying to get it to come on exactly when I want is proving tricky, and occasionaly if I override the controller during the day it seems to forget to heat the water the following morning
The other is that the house is a detached house with concrete floors so once it's cooled down it can take an hour or so before the rooms start to warm up.

The whole lot is going to be replaced in the next year or two when we extend so I don't want to make huge changes to the exising setup but i think I have two options to try to improve it.

The first is to replace the controller with an electronic version, giving better control over when the heating comes on.

The second is to add a room stat, I had a programmable one in the old house which would allow the heating to drop down while we were at work, then heat the house in the evenings and weekends. I think I could add a wireless stat to the existing setup and leave the danfoss on constant. I'm confused about what would happen in the summer when the stat isn't calling for heat, how would the boiler know to heat the water?

Am i missing anything else here?
Thanks

The boiler is old and inefficient and it has no proper controls.

Everyone dreams of an extension. They dreams are often just that for a long time.

My advice would be to replace the boiler for a new efficient system now and benefit from the 30% lower operating costs.

Dont forget the loft insulation, windows and if possible cavity walls and floor insulation.

Tony

Thanks,

We have >30cm loft insulation, cavity wall insulation and brand new double glazing where the windows aren't going to be junked when we extend. I think the house is insulated pretty well.

If we do replace the current setup it won't be until next spring when we can live without heating while it's being fitted.

Are new boilers really that much more efficient then the current thing? I kind of like it just due to the fact that it still works after 25 years.

kingderik said:

The first is to replace the controller with an electronic version, giving better control over when the heating comes on.

The second is to add a room stat, I had a programmable one in the old house which would allow the heating to drop down while we were at work, then heat the house in the evenings and weekends. I think I could add a wireless stat to the existing setup and leave the danfoss on constant. I'm confused about what would happen in the summer when the stat isn't calling for heat, how would the boiler know to heat the water?

Am i missing anything else here?
Thanks

Click to expand...

I'm assuming the gravity fed hot water tank already has a thermostat which just fires up the boiler when the water temperature is low.

A room thermostat if added to the system would need to both fire up the boiler AND start the pump so the water circulated through the radiators.


These two functions should operate independently now using the old programmer.

With a standard gravity system control, in the summer, when only HW is on, the boiler is turned on continuously and heats the water to a temperature controlled only by the boiler thermostat setting. With the programmer set to gravity mode, the HW output is turned on with CH. So you don’t want to set the programmer on constant as the boiler will cycle continuously. It is possible to interlock the system with a tank thermostat as shown here:

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This has the advantages that, when you are not using the heating, the hot water temperature is controlled by the setting of the tank thermostat and it prevents the boiler from cycling. When the heating is running, the water temperature will also depend on the boiler setting because the tank thermostat is overridden by the CH thermostat.

So long as your existing programmer switches on then you can control the heating as you suggest with a programmable thermostat to give variable temperature control through the day. I have just fitted a Honeywell CM907, which has very good control characteristics and is simple to use. Much better than the Horstmann I had before. The wireless version is the CMT927.

If you are upgrading your entire system in the near future I suggest you investigate weather compensation control – I reckon it’s the future. See http://www.viessmann.co.uk/downloads/6pp Weather comp.pdf
Many boiler manufacturers now offer weather compensation control. Do a search on this forum for further info.