Vaillant VRC 400 - won't heat the room, can't program

[madmanu]

Hi,
I'm not a heating professional. I'm only a poor homeowner who moved into his new house to discover that it is inhabited by a monster called Vaillant vrc 400.

First, there was something called a 'BMU error', then FP75. Very intimidating. A service call later from someone suggested by vaillant based on postcode, and 85 quid lighter, the boiler works now. purportedly. It just doesn't heat the rooms. The expert reset the programs (turned everything off and then turned it on) and I have no clue what is going on. What is 'set room temperature'? what is heating curve? why do I need to know about these things? Why can't I say I need the room at 22 C and go to sleep?

Anyway, the temperature on the panel in the lounge is 13, it has gone up to 16 now but I and the wife are shivering in our winter coats. Please help. I've tried everything.

 

[gas4you]

BMU error is just saying the boiler has faulted and locked out.

F75 is notorious fault with these.

More often than not a faulty pressure sensor, but can also be aggrevated by muck in the system.

 

[Onetap]

Why can't I say I need the room at 22 C and go to sleep?

You can; read the manual; here it is.

http://www.vaillant.co.uk/stepone2/data/downloads/b2/42/00/VRC_400_Installation_and_user_guide.pdf

 

[madmanu]

Why can't I say I need the room at 22 C and go to sleep?

You can; read the manual; here it is.

http://www.vaillant.co.uk/stepone2/...C_400_Installation_and_user_guide.pdf[/QUOTE]

I have, actually. Care to point out how?

 

[Onetap]

I have, actually. Care to point out how?

I don't know without reading the manual. I don't know the VRC 400, I have a VRC 430, which is better.

You'd like me to read the manual and the explain to you how to do it, at 22:35, free of charge?

I fear you will be disappointed with me. I'm going to bed.

How about you read the manual and then explain to yourself how to do it?

 

[madmanu]

I don't know without reading the manual. I don't know the VRC 400, I have a VRC 430, which is better.

You'd like me to read the manual and the explain to you how to do it, at 22:35, free of charge?

I fear you will be disappointed with me. I'm going to bed.

How about you read the manual and then explain to yourself how to do it?

So you haven't read the manual but you know the answer's in there? You are in a hurry to go to bed but not hurried enough to post a comment here, telling me to read a manual, which you know has the answer to my question without having read it yourself? What does your boiler 'being better' have anything to do with anything?

How about you don't comment at all if you're not ready to help? I didn't know this was a paid forum.

The manual says turn the button on the right and this will change the H1 and H2 temperatures. It also says these temperatures are only valid if you've turned a particular setting on in installer mode. It doesn't explain what set temperature does or how you should change the heat curve to get the best results.

What you can do, free of charge, is go to sleep and don't come back to this topic. Works for me and works for you. Jeez.

 

[Agile]

I have to admit that sometimes I have to read the instructions!

But thats usually a situation where I am getting paid for the time!

However, there is a ray of sunshine in your cold life! Thats the learned D Hailsham!

He is retired and has a pension/investments to live on and has the time to read instructions and advise those who are blind/lazy/unable/installed by a cowboy/or anything else!

Maybe the curve needs upping? What about 2.6 ?

Tony

 

[madmanu]

I have to admit that sometimes I have to read the instructions!

But thats usually a situation where I am getting paid for the time!

However, there is a ray of sunshine in your cold life! Thats the learned D Hailsham!

He is retired and has a pension/investments to live on and has the time to read instructions and advise those who are blind/lazy/unable/installed by a cowboy/or anything else!

Maybe the curve needs upping? What about 2.6 ?

Tony

I finally got that from the internet... There's a 100 quid for anyone who can show me where the manual says the curve needs upping or what the curve does.

Thanks for all the help and lovely comments.

 

[Agile]

This is all for free!

The curve is a factor by which the coldness outside has to be matched by warmth inside to crete a comfortable living temnperature.

Two examples!

Its cool out side at +10° so the rads inside have to be at 55° inside to create a stable 21° indoors.

Then it gets colder after midnight and goes down to +2° outside. When its so cold outside the temperature of the rads has to go up to 75° to give the same 21­° inside.

So the curve is set by a "factor" which you can set to adjust the rad temperature compared with the outdoor temperature to achieve the desired indoor temp. Got it?

This factor varies between different properties and is mostly dependent on the size of the rads and the insulation or heat loss of the property. Its mostly a try it and see. Gas4U suggests 2.6 as a good starting point but this needs to be adjusted on a try it and see basis to achieve the desired 21­° or similar comfort temperature.

In your case its not hot enough so increase the curve to about 50% higher as a starting point.

If you can understand this then give me a press of the thanks button. If you dont then tell us what you dont follow.

Tony

 

[gas4you]

Have you got the rad stat on the boiler set to maximum?

 

[Onetap]

So you haven't read the manual but you know the answer's in there? You are in a hurry to go to bed but not hurried enough to post a comment here, telling me to read a manual, which you know has the answer to my question without having read it yourself? What does your boiler 'being better' have anything to do with anything?

What you can do, free of charge, is go to sleep and don't come back to this topic. Works for me and works for you. Jeez.

I have read it but some time ago when I last had dealings with one. It made sense to me then.

I helped you by posting a link to the manual, assuming that any fool could figure it out with the written instructions and the programmer in front of him/her. Obviously I assumed wrong.

The relevance of the VRC 430 is that it is a later generation of the Vaillant weather compensator programmer and programming is similar, but better explained.

The curve gives the boiler flow temperature setpoint for any given outdoor air temperature, as measured by the outside sensor. An older, less-insulated building needs a higher curve/flow temperature than a modern well insulated building. The user manual doesn't explain this, since it should have been set by the heating professional who installed it (see below). I suggest you don't mess about with it, or record the setting if you must. I doubt that it's relevant to your problem. You will find it explained in one of John Siegenthaller's excellent articles, somewhere on the internet (a Septic; they call WC 'outdoor reset').

When I last enquired about the price of one of these, the Vaillant merchants told me they'd never, ever sold one. Few UK heating professionals have experience of these or understand weather compensation. I understand WC & analogue controls better than most domestic heating contractors, the result of 15 years experience of commercial controls (BMS).

There was a question asked on here recently about a VRC 400; some well-informed, respected posters answered it. Sadly, their answers were wrong.

Bye.

PS. Good luck.

 

[JoeMar]

So you haven't read the manual but you know the answer's in there? You are in a hurry to go to bed but not hurried enough to post a comment here, telling me to read a manual, which you know has the answer to my question without having read it yourself? What does your boiler 'being better' have anything to do with anything?

How about you don't comment at all if you're not ready to help? I didn't know this was a paid forum.

The manual says turn the button on the right and this will change the H1 and H2 temperatures. It also says these temperatures are only valid if you've turned a particular setting on in installer mode. It doesn't explain what set temperature does or how you should change the heat curve to get the best results.

What you can do, free of charge, is go to sleep and don't come back to this topic. Works for me and works for you. Jeez.

i understand your are cold and frustrated, but this sort of attitude isnt going to get you much help on here...

 

[D_Hailsham]

I'm only a poor homeowner who moved into his new house to discover that it is inhabited by a monster called Vaillant vrc 400.

Anyway, the temperature on the panel in the lounge is 13, it has gone up to 16 now but I and the wife are shivering in our winter coats.

The VRC400 is just the boiler controller. When you say the "panel in the lounge" are you referring to the VRC400 or something else? The VRC400 can be installed in the boiler or in the room. This affects how it works.

What is 'set room temperature'? what is heating curve? why do I need to know about these things? Why can't I say I need the room at 22 C and go to sleep?

Set room temperature should, I would have thought, be self explanatory: it's the temperature you want in the room. So, if you want the room to be at 22°C, the Set Room Temperature is 22°C.

Heating Curve is a bit more complicated to explain, but here goes.

The VRC400 is a weather compensating controller. This means it takes account of the outside temperature when deciding how much heat the boiler needs to produce to maintain the Set Temperature. The amount of heat required is proportional to the difference in temperature between inside and outside. So if you need 16kW to maintain a temperature of 21°C when the outside temperature is -1°C, then you will only need 8kW when the outside temperature is 10°C.

Connected to the VRC400 is an external sensor which measures the outside temperature ( it will normally be about half way up a north facing wall).

Obviously not all houses require the same amount of heat. The heating curve is the method used to fine-tune the system for each particular house. What it actually adjusts is the temperature of the water leaving the boiler; the radiators will therefore vary in temperature and give off less or more heat as required.

If you are only achieving a temperature of 15 - 16°C, the heating curve is set too low. i.e the water temperature is too low.

So you need to set the required room temperature and monitor what temperature is actually reached. If too low, set the curve to a higher number and vice versa. You may have to experiment.