How to set a boiler flow temperature

UnsureAboutthis

I've looked on the net/forums and none the wiser.

How do I set the boiler temperature on my boiler
It is a Valaint Eco Tec 831 Plus.

There is a knob to turn up and down the hot water temp - I get that as easy to use

The flow temp has a knob next to it with a minus/plus sign.  I set it to 57 I think when I started it this morning and when the heating has settled it is shows 50 atm.  Is the flow temp set as I turn the flow knob and see a number, EG 57 in my case and then when it fires up it goes up and then comes back down to 50 and fires again

My OH was cleaning the cover on Sunday and we think they accidentally moved it to a lower setting ie 40, and our rads came on then turned off even at the highest settings on TVR and now at 57C working ok, I think

The central thermostat we kind of ignore and set at the same temp as heating is adjusted via TVR's

I hope I've been clear - What I want to know please is, how to set the flow temp when heating is on and the nuber I see, is that the flow temp but then it varies up and down within limits.

danthemoneysavingman

My (unrequested) opinion is to just leave it as is. Seems you'd have more luck swimming uphill. The benefits are marginal either way

ThisIsWeird

A flow temp between 50 and 57 is nicely in the condensing range, with your return temp most likely then being in the mid-40s. Your boiler will therefore be operating pretty much as efficiently as it can, so cooool.
In the current mild weather -12-ish around here - it will hopefully heat your house well. If we get another cold spell, you may find it struggles, in which case temporarily turn it up, and back down again when you can - for max efficiency.
The output temp will fluctuate as the burner fires up and down to maintain and match demand - I don't think that is unusual. The 'set' flow temp is probably in between these two temps as it slightly overshoots, backs off, undershoots... It's referred to as 'hysteresis', I understand.

mexican_dave

Yes, the "hysteresis" is all about fuel efficiency. Is like driving a car: braking gently up to traffic lights and stopping at the white line, rather than slamming the brakes on at the last moment and overshooting the white line. In this analogy the white line is the temperature you boiler is aiming for. Your boiler has not expended any more fuel than necessary (braking gently, up to the whiteline). Whereas if it had no hysteresis it would run full blast and overshoot the temperature it was aiming for wasting fuel (braking at the last moment). Hope that helps.
TRVs can fight with your boiler due to poor feedback from the room 'stat. In older houses the room stat was placed in the hallway (coldest room) the trouble with that is you enter your house on a cold day, you let in a draught and your boiler kicks in, probably for longer than needed, wasting fuel. Many room stats are now fitted in the room where people spend more time (lounge?) and the stat triggered less by draughts, leading to better fuel efficiency. But the radiator in the selected room (lounge?) should NOT have a TRV, but an ordinary rad valve. That way the boiler gets more accurate feedback on what's going on, better fuel efficiency.

UnsureAboutthis

Cheers all!
The rad without the TVR is the rad on the top landing as the full blast from it keeps other rooms slightly warmer.
All other rooms are controlled by TVR's
The thermostat is in the hall near the door and turned all the way up as we knew we'd use the TVR's for the heating levels
The sitting room is bif about 28 feet by 16' max and we have the rads on high near where we sit and lower levels on tv, and dining table sides - works for us

It is warm outside compared to the last few weeks.  I sincerely appreciate the good help/guidance provided here and thank you for your time.

markin

Unless they have smart TVR's directly controlling the boiler you don't want the boiler trying to hit 30c in the corridor, it must be firing constantly 24/7?

You don't want the boiler over heating turning off and then coming back on after just 10min.

UnsureAboutthis

markin said:

Unless they have smart TVR's directly controlling the boiler you don't want the boiler trying to hit 30c in the corridor, it must be firing constantly 24/7?

You don't want the boiler over heating turning off and then coming back on after just 10min.

Sorry, I'm not understanding this.

The boiler ASFIK id not firing constantly. We have a rad without a TVR on top landing. When heating is on, there are several rads always on mid or full blast.

I assumed the boiler would only kick in out the heating when tvr demanded it. I have noted in warmer weather certain rads do turn on and off at the set levels of TVR's

So do I really need to turn down the central control uit set at max - it is one of those manual things and not the electronic digital display and I am aware it is connected to the boiler in some way

PS: Sorry, I get it I missed the post above yours.
Thanks you all.

Albermarle

UnsureAboutthis said:

markin said:

Unless they have smart TVR's directly controlling the boiler you don't want the boiler trying to hit 30c in the corridor, it must be firing constantly 24/7?

You don't want the boiler over heating turning off and then coming back on after just 10min.

Sorry, I'm not understanding this.

The boiler ASFIK id not firing constantly. We have a rad without a TVR on top landing. When heating is on, there are several rads always on mid or full blast.

I assumed the boiler would only kick in out the heating when tvr demanded it. I have noted in warmer weather certain rads do turn on and off at the set levels of TVR's

So do I really need to turn down the central control uit set at max - it is one of those manual things and not the electronic digital display and I am aware it is connected to the boiler in some way

PS: Sorry, I get it I missed the post above yours.
Thanks you all.

A modern boiler can turn down its power output, or modulate it in the jargon.
In other words a 15 KW boiler can turn itself down to say 5 or even 3Kw once the system has heated up.
So as long as some of the rads are hot/TRV open, the boiler should be fine even if the thermostat was turned right up.
An older boiler would probably keep switching itself on and off as it got too hot.