Help me understand our central heating!
Comments
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Thank you, i will try lowering the boiler temperature then until i strike a happy balance.
Our house is not a very warm house, end of the row with with 3ft thick walls, the loft is well insulated and earlier this year we had the central heating system installed along with new windows and doors fitted which should go a long way to help keep the heat in compared to previous years gone by.0 -
I designed the system to handle radiators and underfloor heating, plus two hot water cylinders, so it has four zone valves, with a 230V Honeywell two channel programmer, AND a zero volt Glowworm Climastat programmer. Way beyond the Gas Safe engineer's comfort zone, so he called Glowworm. They actually sent an engineer. He didn't understand it, but at least he didn't say no.
What output temperature do you set your boiler to?
I have a Worcester CDi Combi to service heating as well as an unvented cylinder through a Y-plan. The Combi's Eco temperature is about 40. However this is not sufficient to heat my cylinder which has temperature set to 60. So I increase the boiler's output temperature to 70 (nearly maximum). But based on discussion in this thread, this is apparently not optimal. Is there any way I can improve it?0 -
What output temperature do you set your boiler to?
I have a Worcester CDi Combi to service heating as well as an unvented cylinder through a Y-plan. The Combi's Eco temperature is about 40. However this is not sufficient to heat my cylinder which has temperature set to 60. So I increase the boiler's output temperature to 70 (nearly maximum). But based on discussion in this thread, this is apparently not optimal. Is there any way I can improve it?
I don't understand what you mean by an unvented cylinder which 'has the temperature set to 60'
unless you mean the immersion heater is switched on and set to 60C.
An unvented cylinder - like any other hot water cylinder - will simply heat up to the output temperature of the gas boiler. e.g my boiler is set to provide hot water to my unvented cylinder at 50C and that is the maximum temperature it will reach. If I turned the boiler down to 40C, or up to 60C, that is the temp the cylinder will reach. Naturally the immersion heater is switched off.0 -
Many thanks Cardex for your response.
Unless I misunderstood, my cylinder (Santon Premier Plus 210L) has two thermostats: one for direct/immersion and one for indirect/boiler. Both are set at 60 degrees (manufacture recommended temperature). Like you I normally use indirect/boiler to heat the cylinder. The indirect thermostat will turn on the boiler on demand and turn it off when the water reaches 60. I used to rely on it to start/stop boiler, which seemed to have worked fine (the cylinder has good insulation). My old boiler has the output set to 80 so it can bring the cylinder to 60. But if the output of boiler is 40, it can never take the cylinder to 60, which means that boiler will be on all the time. Because of this, I have to add a timer to control the cylinder's demand for indirect/boiler. I am still not sure what's the recommended way to control the cylinder's demand though, thermostat as I had before or timer as I'm having now? Do you use a timer for your cylinder?0 -
What output temperature do you set your boiler to?
I have a Worcester CDi Combi to service heating as well as an unvented cylinder through a Y-plan. The Combi's Eco temperature is about 40. However this is not sufficient to heat my cylinder which has temperature set to 60. So I increase the boiler's output temperature to 70 (nearly maximum). But based on discussion in this thread, this is apparently not optimal. Is there any way I can improve it?
The Glowworm has a free hand to optimise for condensation as much as possible, forcibly fixing a boiler output temperature is unnecessary.
Obviously, to maintain a room temperature of 20 degrees, the boiler needs to vary output to match heat loss.
For domestic hot water, its amazing! In order to heat the cylinder water, the boiler output needs to be higher, but it doesn't need to be 85 degrees if the cylinder water is at 18 degrees. So the Glowworm outputs at say 55 degrees to begin with, so it can still condense, but increase to 85 degrees near the end. I assume it measures the return flow from the cylinder so it can work out how hot the cylinder water is.
The cylinder stat is an electrical contact relay.
When the cylinder water temperature is below the set point, in your case 60 degrees, the relay closes, and makes contact. In a normal setup, this means a "demand for heat" to the boiler.
Obviously, for heating a cylinder, you will need very hot output, whereas you want nice and low output for central heating, to encourage condensation.
For really ancient no-condensing boilers, it is possible you had just one boiler output, which is used for both, but these days, you need to tell the boiler it's working on heating a cylinder, or keep it low for central heating.
With a combi, the default set up is NO CYLINDER, so I suspect it will only do condensation friendly low temperature output, UNLESS you went to the manufacturer's training course, and know the "other" way to wire it.
Having a cylinder and a combi is a non-standard set up.
Maybe you had a one trick pony plumber who cobbled together a system based on partial knowledge. Just ask: "How does the boiler know it's heating hot water, and not central heating?"0 -
Thank you very much Pincher for the indepth explanation. Much appreciated.
When I first had the heating system installed many years ago, I was aware that Combi + Unvented Cylinder is not a standard setup. I wanted a bit flexibility that I would still have hot water even if one of them fails (HW from Combi services ground floor taps plus a shower) but missed the point that the two circuits need different output temperature:-(
Seems I have no choice but set the boiler output to be high (70) in order to service both heating and cylinder. Hopefully that will not shorten the boiler's life.0 -
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