Boiler overheating?

[David937]

Hello,

My boiler seems to be overheating when supplying the attic zone (one radiator) the boiler fires up and the flow temperature on the display escalates rapidly (sometimes more than the set value) and shuts off. This whole process lasts around a minute and continues until the room has reached temperature. I am worried that this may result in excessive gas bills.

This does not happen when the boiler is heating the other zone (10 radiators and Myson Kickspace) independent of the attic or with the attic.

What is wrong?


Your help is greatly appreciated.

 

[David937]

Strange, no replies, all must be fed up with me I suppose.

 

[muggles]

Ckeck the lockshield on the rad (I'm ssuming here that you have one valve that has a wheel head that you can turn and one that's just got a plain cap, you need to open the plain cap one) if it's closed too much that could cause it. Seems odd that you have a seperate zone for just one rad though :S

 

[David937]

Will try that, the lockshield is half open.

 

[D_Hailsham]

My boiler seems to be overheating when supplying the attic zone (one radiator) the boiler fires up and the flow temperature on the display escalates rapidly (sometimes more than the set value) and shuts off. This whole process lasts around a minute and continues until the room has reached temperature. This does not happen when the boiler is heating the other zone (10 radiators and Myson Kickspace) independent of the attic or with the attic.?

Sounds as if the boiler's output is much too high to run just one rad. What boiler do you have - make and model?

Are the two zones controlled by their own thermostats and motorized valves?

 

[Deleted member 105431]

have you range rated the boiler using d0 in the menu? Why have you got 1 single rad as a seperate zone? seems daft to me.

 

[malkie]

get a by pass fitted close to the boiler,what boiler is it

 

[David937]

The boiler is a Vaillant ecoTEC+ 937, the range is 12kw-28kw.

It has been range rated to 25kw.

We have zoned the attic (bedroom) because at night the temperatures drop drastically and heat is required.

 

[David937]

My boiler seems to be overheating when supplying the attic zone (one radiator) the boiler fires up and the flow temperature on the display escalates rapidly (sometimes more than the set value) and shuts off. This whole process lasts around a minute and continues until the room has reached temperature. This does not happen when the boiler is heating the other zone (10 radiators and Myson Kickspace) independent of the attic or with the attic.?

Sounds as if the boiler's output is much too high to run just one rad. What boiler do you have - make and model?

Are the two zones controlled by their own thermostats and motorized valves?

Yes, there are Honeywell 2 port valves if that matters.

 

[simond]

I have never seen so many posts about one persons boiler. We were even treated to pictures of it - I assume the poster thought we hadn't seen one before.

If you zone off just one radiator the boiler will modulate down and cycle, that is to be expected.

 

[D_Hailsham]

The boiler is a Vaillant ecoTEC+ 937, the range is 12kw-28kw.

Even when it is running at the lowest output, it will be producing maybe 10kW more heat than is actually required, so the boiler will cycle rapidly just to keep the flow and return temperatures within range.

We have zoned the attic (bedroom) because at night the temperatures drop drastically and heat is required.

Insulation?

Yes, there are Honeywell 2 port valves if that matters.

Just confirming that there was an interlock when only the attic rad was on. I trust you do not have a TRV on the attic rad.

get a by pass fitted close to the boiler,what boiler is it

Don't see how that would help.

 

[Deleted member 105431]

The boiler is a Vaillant ecoTEC+ 937, the range is 12kw-28kw.

It has been range rated to 25kw.

We have zoned the attic (bedroom) because at night the temperatures drop drastically and heat is required.

range rate it using d0 to 20kw and set the flow temp to 70deg c this will help but to have 1 rad as a zone is daft.

 

[David937]

I did reduce the output less than 25kw but the house took very long to get warm. Flow temp is set at 70 degrees.

The system works great, it's just that I get worried when things like this happen, I like to learn new things.

As for the pictures, I put them for people like me; before I got my heating I wanted to see how this boiler would look installed.

 

[Deleted member 105431]

I did reduce the output less than 25kw but the house took very long to get warm. Flow temp is set at 70 degrees.

The system works great, it's just that I get worried when things like this happen, I like to learn new things.

As for the pictures, I put them for people like me; before I got my heating I wanted to see how this boiler would look installed.

to have 25kw going to 1 loft radiator the boiler will cycle and you will get very rapid temp rise. A progressive temperature rise over a longer period at lower flow temps is far more efficent than a quickly heating system at a higher output and flow temp. Consider weather comp (vaillant 430) cavity wall insulation and draught proofing. (hopefully you already have double glazing and loft insulation)

 

[David937]

So basically I should be setting the flow temperature as low as possible.

I have loft insulation and double glazing and draft proofing.