Valliant Eco tec Plus 937 cond combi CH problem

[Andyk78]

Sorry for the outburst, just have a million an one jobs to do at the house and was hoping the heating would be a bit simpler and a case of turn it on and heat will flow freely. Wasn't ready for heating curves/weather compensators and pressure valve adjustments
Thanks for all help given though its appreciated, and hope I can get to grips with the system otherwise it may land itself on eBay!!!

 

[D_Hailsham]

However the radiators just don't get hot enough?

So you immediately think there must be something wrong, which is understandable if you have been used to a system where the boiler is either on or off and the rads are boiling hot when it's on - even in warmer weather.

If you think about it you need a lot of heat when it is very cold (below 0°C) and very little when it is warmer (10°C). A standard on/off boiler can only take this into account by staying off for longer in the cooler weather.

A weather compensation system knows exactly how much heat is required because it knows the outside temperature and the required inside temperature and can adjust the boiler output accordingly. This means the radiators will be hotter in cold weather and cooler and the mild weather. They will also stay at a more constant temperature.

As for the heating curve, it's really the installers job to set this.

If your house is getting up to the required temperature, I would leave well alone. Unfortunately the extremely cold weather seems to be over, so you will have to wait until next winter to find out if the curve is correctly adjusted.

 

[scoobydo123]

It is easy, just set the heat curve to say 1.6 and set the times you want the heating at y. Outside this time you set a lower temp for economy.

If it doesn't maintain the temp you are comfortable with then try upping the heat curve, and/or reducing flow to the radiator where the stat is.

It should be a good system if radiators sized correctly dont get rid

 

[Andyk78]

Thanks guys, I will try and stick with it, just that looking back to a few weeks ago when we was round there it was cold in the house and felt as cold as it did outside almost? I noted that the cat was sat on top of the radiator in the hallway....Jesus if the cat which has has a full coat of fur can't get warm then there little hope for us

 

[ALEC1]

There are several benefits to these controls, including comfort, reliability and efficiency... Correctly set up they really are fit and forget.. Indeed it may already be ready to go...

Why not see you get on over then decide...

 

[Andyk78]

Will do, just to finally confirm do I still need to adjust the pressure to 1.2bar then?

 

[ALEC1]

Yes its a good idea too, although it may not be necessary, it depends how many floors up your highest radiator is!

as water is heated it expands, hence the rise in pressure...

 

[D_Hailsham]

As water is heated it expands, hence the rise in pressure...

Which is why you need the system cold when you adjust the pressure. This then sets the minimum pressure.

 

[Tipper]

The heating curve should be set to reflect the heat demand of the building which is basically how well insulated it is.

1.6 for a UK house is way too low unless it is super insulated like some continental homes. I find 2.5 is reasonable for my averagely insulated 1990s town house but have been running 2.8 this year because I like HEAT to come from my radiators!

Basically the heating curve sets the circulating temperature at a proportion above the outside temperature. There is a reference curve graph in the instruction book.

Oh, and the programmer has a temperature sensor in it so the controller compares inside and outside temperatures and sets the circulating water temperature accordingly.

 

[ALEC1]

In fairness tipper it will only sense room temperature if programmed too, and the heat curve reflects levels of insulation AND heat emmitter type..

I find 1.6 fine for terrace houses in London, higher for detatched...


The controls work around room temperature, not flow temp..if your getting a room temp of about 21c if thats what you want, the heating curve absolute number doesn't really matter..its all about comfort..

 

[Tipper]

But I've found that a low curve means the house takes up to two hours on the morning to go from the setback temp, 16C, to 21C!

It's much better with a higher curve. I think others have advised this too.

 

[ALEC1]

well the lower curve will keep the boiler operating at a higher efficiency for longer...

and a two hour heat up time isn't really that long, at the end of the day with this equipment you have many ways of running it...

 

[Andyk78]

Just to throw a spanner in the works here, I didn't notice any sort of sensor outside the house which I thought would be needed to work with this wether compensator thing? Or am I wrong here and an outdoor sensor not required?

 

[D_Hailsham]

But I've found that a low curve means the house takes up to two hours on the morning to go from the setback temp, 16C, to 21C! It's much better with a higher curve.

well the lower curve will keep the boiler operating at a higher efficiency for longer

The correct curve shouldn't be a matter of guesswork. It will be determined by the temperatures used when the system was designed.

It the system was designed for a 70C flow when -3C outside and the selected heating curve provides 60C at that temperature, of course the house will take longer to heat up and may never reach the required temperature.

Of course a house will take longer to heat up if the radiators are not giving off the expected amount of heat due to the lower flow temperature of a low curve. It could also be due to the radiators not being sufficiently oversized to provide extra heat for quicker warm up. (That's nothing to do with installing larger radiators to account for the lower output when working with a 20C differential.)

The only time you should need to experiment with the heating curve is when WC is added to an old system. But even then some heat loss calculations and finding, from catalogues etc, the output of the existing radiators will give you enough data to calculate the required water temperatures.

 

[Andyk78]

Also we are adding a downstairs wc and upstairs ensuite when we get to this I suppose our plumber can sort out the heating curves etc at that time and have the system running properly. Just want it to perform well now before these additions are made. Should we have an outsoor sensor? I will have another good look when I'm there for it if we should but couldn't see anything.
Also going back to my earlier question about the flue being upside down as per the web picture ours is the other way round from the one showed, will this need turning round and will it have any negative affect on the system how it is currently fitted/performing.

Additional info: The house is a 4 bed semi detached with just a ground and 1st floor.

Edit: just called valliant tech support and they have give me the following info which may help others other if anyone ever stuck:

Adjusting the bar pressure as follows: turn the left grey nob a quarter turn first then the right one until hear the water flowing in and press the minus button to show the pressure reading and get it up to about 1.3 bar then close the grey nobs

Setting the heating curve as follows: press “P” AND HOLD FOR 10 SECONDS –ISH until the spanner icon appears. Then press the dial in and search through for heating curve “HC” set this to 2.8 then hold “Button down again to exit the menu.

If the heating curve setting doesn’t appear in the menu then it is not a wireless weather compensator model and just a programmable room thermostat.

If it is a wireless weather compensator then there should be an outside probe sensor fitted somewhere …. Need to look for this as without it will not work as it should do.