Vaillant Ecotech Plus No Heating when hot water is on

[Harry Bloomfield]

Thank you very much for that. Annoying as my other systems have never had that limitation. I had hoped there would be something on the VRC 470f controller under the installer level settings that I could change.

I replaced the boiler with a Vaillant, but originally running on my old control system. The old boiler just had a single flow temperature setting, irrespective of supplying CH or HW. With those old controls, the new Vaillant only permitted one flow setting, because it could know what system it was supplying.

Within a month, I installed and upgraded to the VRC 470f with remote out door sensor. Once installed, I found it could only do one or the other.

It was also my first system with this limitation too and I was a bit surprised, though in practise it is not a big problem to have the CH not available for the 20 minutes worst case it takes to reheat the cylinder. When I first set it up, I had it heat the water just at the times it would normally be used - a single 30 minute boost at 4pm, then use the manual boost for the occasions when a bath was needed. That scheme made the loss of CH noticeable, so I now have it set to keep the cylinder hot from 10am to 6pm. The brief boiler occasional runs to reheat the cylinder are not then noticed.

 

[MikeJS]

I replaced the boiler with a Vaillant, but originally running on my old control system. The old boiler just had a single flow temperature setting, irrespective of supplying CH or HW. With those old controls, the new Vaillant only permitted one flow setting, because it could know what system it was supplying.

Within a month, I installed and upgraded to the VRC 470f with remote out door sensor. Once installed, I found it could only do one or the other.

It was also my first system with this limitation too and I was a bit surprised, though in practise it is not a big problem to have the CH not available for the 20 minutes worst case it takes to reheat the cylinder. When I first set it up, I had it heat the water just at the times it would normally be used - a single 30 minute boost at 4pm, then use the manual boost for the occasions when a bath was needed. That scheme made the loss of CH noticeable, so I now have it set to keep the cylinder hot from 10am to 6pm. The brief boiler occasional runs to reheat the cylinder are not then noticed.

Yes, it is a nuisance more than a problem. I have a Power Diverter from my Solar Panels that diverts excess to my immersion so I get free hot water on mostly sunny days. That means I do not want to heat the water using gas until near sunset (and the temp on the immersion is set higher than the temp for gas heated hot water). In the winter months the hot water from the gas is timed to come on at 1630 to 1730 and this ensures we have a full tank of hot water ready for the evening showers and other uses. Unfortunately, this invariably gives a slight clash in winter time if my wife needs the CH on before 1730.

Glad of the information - thank you.

 

[Harry Bloomfield]

Sorry I did not realise you had read the instructions and understood how your system works oh wait you haven’t ? Easier to ask on a forum than take the time to read a user guide.

Vaillant instructions are not well written and in some cases they contradict themselves. For instance they suggest that with the remote outdoor sensor, that the time will be derived from Hamburg. In the EU perhaps, they are fitted with that version, but not in the UK. Nowhere did they implicitly say that the CH cannot be used simultaneously with a call for the HW. So it's no surprise the OP is confused and asking questions here.

 

[MikeJS]

Sorry I did not realise you had read the instructions and understood how your system works oh wait you haven’t ? Easier to ask on a forum than take the time to read a user guide.

Thank you so much for your helpful answer. Why are you even bothering to reply if you cannot or will not help?

FYI the instructions consist of around 5 booklets and not a single one appears to say that hot water and CH cannot be supported at the same time. Given my past systems have be able to do this I thought I may have missed something. I therefore hoped that someone more knowledgable (and I do not mean you!) could help.

 

[ianmcd]

I am still not sure that you cant set this up to do what you want, @ScottishGasMan will know, I know your controller was withdrawn

 

[MikeJS]

I am still not sure that you cant set this up to do what you want, @ScottishGasMan will know, I know your controller was withdrawn

I live in hope!

 

[Harry Bloomfield]

I am still not sure that you cant set this up to do what you want, @ScottishGasMan will know, I know your controller was withdrawn

Not that I am aware of, it would defeat the whole principle of the boiler carefully matching itself to the CH demands and demand for heat of the building itself, via the flow temperature.

 

[fixitflav]

Not that I am aware of, it would defeat the whole principle of the boiler carefully matching itself to the CH demands and demand for heat of the building itself, via the flow temperature.

Agreed, with weather compensation the adjusted flow temperature could be below the cylinder stat setting, so has to have separate CH and HW, with HW preference, reverting to higher control-stat setting in HW mode.

I’ve always had W-plan (without weather compensation) and never found HW preference a problem, even many years ago with 3 youngish kids. I just leave HW on 24/7.

On a general note, I see on the internet that either/or diverter valves (eg Honeywell V4044) are available, as needed for a weather compensation set-up. Last time I had to change the valve, only needing the body, I could only get a complete mid-position V4073. I still have the actuator, £10 to anybody who wants it!

If retrofitting weather compensation to a system with mid-position valve, I assume it’s necessary to somehow eliminate the mid-position. Or change the actuator. On S-plan, need to arrange HW preference, probably by adding a relay, as discussed on this forum a year or so back.

 

[ScottishGasMan]

I have this Vaillant in a pressurised system and have the VRC 470f controller. Heating works perfectly on the timer as does the hot water. However, I cannot have hot water and central heating on at the same time. Normally not a problem as it is rare for us to need both on. However, at the moment my wife is recovering from an op and needs more heating! If the heating is switched on before the hot water is due to come on via the timer then the hot water does not heat up. Conversely, if the hot water is already on the rad will not heat up. My previous systems in other houses could always do both. Is this a fault, a setting issue or a feature?

Weather compensated controller so it's priority hot water. As has been said, for the time being, stick the hot water on 24/7 so its only topping up the cylinder rather than recharging it from cold, it will hold the heating off for less time this way, or if a cylinder of hot water does you for the day, time it to come on during the night, thats what I do with mine, but it depends if your cylinder is big enough for your useage.

The other consideration is your heating schedule, weather compensation works best replacing heat as its lost rather than heating up from cold every day, so having an on temperature of say 21 degrees, and a set back of 18 degrees, leaves far less work to be done by the heating than having set back of 15 say, where it needs to build up 6 degrees in the house to get you warmed back up.

 

[MikeJS]

Weather compensated controller so it's priority hot water. As has been said, for the time being, stick the hot water on 24/7 so its only topping up the cylinder rather than recharging it from cold, it will hold the heating off for less time this way, or if a cylinder of hot water does you for the day, time it to come on during the night, thats what I do with mine, but it depends if your cylinder is big enough for your useage.

The other consideration is your heating schedule, weather compensation works best replacing heat as its lost rather than heating up from cold every day, so having an on temperature of say 21 degrees, and a set back of 18 degrees, leaves far less work to be done by the heating than having set back of 15 say, where it needs to build up 6 degrees in the house to get you warmed back up.

Thank you for replying, I will probably leave my system as it is currently set as most days the solar heats the hot water so I only want the gas to top it up on the greyer days. I’ll get my wife to put an extra jumper (or 2) on!

 

[Harry Bloomfield]

On a general note, I see on the internet that either/or diverter valves (eg Honeywell V4044) are available, as needed for a weather compensation set-up. Last time I had to change the valve, only needing the body, I could only get a complete mid-position V4073. I still have the actuator, £10 to anybody who wants it!

If retrofitting weather compensation to a system with mid-position valve, I assume it’s necessary to somehow eliminate the mid-position. Or change the actuator. On S-plan, need to arrange HW preference, probably by adding a relay, as discussed on this forum a year or so back.

My original system pipework and valve is designed for either/or /or both together, with a mid position valve. Prior to my installing the Vaillant controls, it would do mid position and both together. After, it would only select HW or CW, never both together.

Yes, suppose it could be bypassed, using a relay powered by a room stat, but as said we would not notice much cooling of the place in the 20 minutes needed to reheat the cylinder.

 

[fixitflav]

My original system pipework and valve is designed for either/or /or both together, with a mid position valve. Prior to my installing the Vaillant controls, it would do mid position and both together. After, it would only select HW or CW, never both together.

OK, sounds like the weather compensation software takes care of eliminating the mid-position. But can you have CH without HW? Because you can't with W-plan, it's HW only or HW + CH. And I assume it's the same if weather compensation is retrofitted to W-plan (not that it would be a problem).
In that case, ScottishGasman's suggestion of calling for HW at night only works if you don't mind having no CH when HW is not called.

 

[ScottishGasMan]

OK, sounds like the weather compensation software takes care of eliminating the mid-position. But can you have CH without HW? Because you can't with W-plan, it's HW only or HW + CH. And I assume it's the same if weather compensation is retrofitted to W-plan (not that it would be a problem).
In that case, ScottishGasman's suggestion of calling for HW at night only works if you don't mind having no CH when HW is not called.

Its one or the other regardless. HW only or HTG only. Never both.

 

[Harry Bloomfield]

OK, sounds like the weather compensation software takes care of eliminating the mid-position.

No, the compensation has nothing what so ever to do with the mid-position, no relationship at all. The compensation just helps the boiler decide how much heat it needs to produce and when, to just meet your set room temperature, with no wasteful overshoot.

Rather than burning flat out until the stat is satisfied, it approaches the set temperature knowing to ramp the output gradually down as the set temperature is approached.

Once at temperature, it just gently maintains that temperature, with no wild swings or creaking of pipes as the heating cuts in and out. All because the boiler has feedback rather than the boiler being simply on or off.

But can you have CH without HW?

Yes, the only thing you cannot have, is both at exactly the same time. The boiler serves and satisfies the HW needs first, then the CH last.

 

[picasso]

So setting the hot water on times on the programmer is too simple a solution for the op ?