how hot do you run you CH boiler

Just found the manual for my Ideal Logic:

"The Logic + Combi is a high efficiency combination boiler which is most efficient when operating in condensing mode.

The boiler will operate in this mode if the CH temperature control (C) is set to the ?e? position (economy mode) or below. This control should be set to a maximum for very cold periods".

Annoying Worcester do not have a simple weather comp option for theirs (you have to have the fancy controller and that precludes using your own heating controller, according to them).

I oversized my rads as much as possible and I have been able to run on

Thanks for that, interesting. And I hadn't realised such systems had a collection of sensors.

OT but loosely relevant, I use my CH as 2 zones - upstairs and downstairs. I'm really not going to replumb to add a properly zones system, and I was wondering if it's possible to isolate the upstairs zone with a three way motorised valve - simply cutting out the upstairs 'circuit'.

A single switch would be easier than faffing about with 4 TRVs each evening.

on 12/01/2019, dennis@home supposed :

My stat is in the hall and it is generally set to a lower temperature than we desire in the living room next to it.

Generally, if our hall is below temperature, other parts of the house will be too. So in practise it works pretty well.

It is a compromise of cost versus ideal with considerable extra complexity. Ideal is a zone per room, a temperature sensor per room and the means to use the data/ decide which rooms should be what temperature at what times of day, maybe to include occupation sensors. The boiler coming on if any zone requires heat input.

That's not a stat problem that's too much heat capacity in the radiators.

The stat stops the flow but the stuff in the rad is too hot.

You need to have low water content rads.

IIRC one of the add on controllers allows for different temps when running HW and heating but I don't recall which.

dennis@home explained :

I agree, it was originally installed when the place had a much higher heat loss. Single glazed, no CWI, not much insulation in the roof and quite air leaky. But its a cost v benefit v need. Only one rad has needed to be changed and that swapped for one half the capacity, in the hall. The original boiler was around 32Kw, the new one 18Kw. The guy I got to install it, even suggested that was probably borderline too big, but I specced it.

Too much capacity has the advantage that - Nudge the stat up a couple of degrees and it hits the selected new temperature very quickly. Then once up to temperature, it barely ticks over.

dennis@home brought next idea :

It would have to be something which interacted directly with the boiler and Vailant said there was nothing able to do that, when I spoke to them. The boiler has the built in interfaces for the fancier control systems, I understand, but little detail to be found about these extra systems.

Yes ;-)

The boiler knows what it is heating - you get a Tap logo pop up on its LCD rather than a radiator logo. The information is conveyed over its eBus rather than with a discrete input.

Also like many boilers, it can adjust its power output based on a number of criteria including flow and return temps etc.

ISTR that when I was looking for system boiler's that could do split temp, there were some options for some of the WB boilers.

(I also considered paring a combi with an unvented cylinder, so one could have fast potable DHW to the kitchen which is on a long pipe run)

I was not that keen on the idea that some times it would otherwise deliver 70 degree water to the taps.

Having a TMV on the cylinder output is a bit of a compromise, since it means you don't have the benefit of running the very hot water through all the pipe work like you would with multiple TMVs at every point of use.

In the end I went for a high flow TMV, and set it at max temperature (about 55 IIRC). That allows for some heat loss in the pipes and still delivers water hot enough you can mix in some cold at the point of use - giving shower valves etc a bit more control.

This is what I do. The boiler is in the downstairs loo at the back of the house, and I see it frequently!

You must have rather oversized rads?

John Rumm was thinking very hard :

I just have one TMV, on a toilet wash basin. I put that in so kids could use the single tap I installed, to wash their hands un-supervised, with no risk of too hot water.

in the hall way

works OK in my current house which is, presumably, balanced properly

tim

Many CH installers would probably argue that is the case... but it can make a system less nice to live with. Especially if you have rooms that don't get adequate flow until nearly all the other rads have throttled on their TRVs, or worse, never get to set temp because the main stat has turned the whole system off.

Nope

they are tiny

they are on all day

The house is well insulated

Why do you think that wouldn't work?

tim

Probably no more sensors, than any other zoned system (i.e. one for each stat, plus the external one), but the fact that it can read actual temperatures from each does open up some more possibilities.

You could do, although a pair of two port valves is the more common way of doing it. It does depends a bit on how the pipework is done. Some systems are easy (say where pipework for each floor of rads is run under the respective floor), and some very difficult (say where all the pipework is under the upstairs floor, and then branches both up and down to feed rads).

Indeed - or even a timer / programmable stat for each floor.

That was my 'understanding', but not what was stated in the admittedly dumbed down instructions, which talked about the startup procedure as "lighting the boiler", as if it has a pilot light rather than igniting the gas as required.

The physical size depends on the demand in that area.

Anything can work. But there is an ideal figure for rad temp for best efficiency.

I downloaded the manual and it omits the critical "or below".