My boiler has just been slapped with a - "Danger Do Not Use" Warning Notice

[Deleted User]

Having thought about the OP’s situation overnight, I need to address some of the issues raised. Firstly, when I had concerns about my new build boiler, I got the manufacturer to service the boiler. Yes, this cost me about £40 more than the ‘man-in-street’ but I did end up with a replacement heater exchanger and fan. The OP has to give the builder and his sub-contractor the chance to put things right; however, it might be worth pushing for a Baxi engineer visit/inspection to give more leverage.

The size of a combi boilers is usually based on the HW requirement not what is needed for CH. People complain when hot water isn’t near instant. This means that the boiler is over-specified for CH and it will be less efficient that a smaller boiler. All modern boilers have a built in modulation ratio which effectively reduces the boiler output as the home heating demand falls. A 40kW boiler might have a 5:1 ratio which means it will modulate down to 8kW whereas a 24kW boiler might modulate down to c.5kW. Does this matter: yes, it means that there will be frequent boiler cycling and increased ‘wear and tear’. Does the OP have any re-dress, I doubt it unless the original build design specification required a smaller boiler.

A final thought. It is summer which is not a good time to test a boiler because of the high internal air temperature. Did the boiler engineer ask for all the TRVs fitted to the 11 radiators to be turned to the fully open position? If not, many of the radiators will have effectively been shut off from any boiler flow. Given recent summer temperatures, it is possible that the boiler flow was just to one or 2 radiators and via the Automatic Bypass. It follows that the return flow temperature would quickly reach the boiler shut off temperature and the boiler would shut down. Occam’s Razor.

OP - I know what you are going through at the moment: my sympathies. My wife was treated for Hodgkin’s Lymphoma a few years back. 

GunJack

[Deleted User] said:

GunJack said:

Take it up with the housebuilder and NHBC, not another local plumber - they may try and use that to wriggle out of fixing it at their cost. And be firm.

The NHBC warranty doesn’t kick in until Year 3. The builder is responsible for rectifying all defects for the first two years - even if the work was carried out by a sub-contractor. Based on my recent experience, sub-contractors can get very grumpy when they are forced by the builder to rectify mistakes.

This is true, but worth keeping them informed as they may put pressure on the builder to rectify within the 2 yrs. They wouldn't like to have to get involved further down the line with a dispute over one of their members.

Ultrasonic

Mstty said:

I am not sure you will get the housebuilders to change the boiler

Surely if the boiler is actually unsafe to use there should be zero debate?

Mstty

Ultrasonic said:

Mstty said:

I am not sure you will get the housebuilders to change the boiler

Surely if the boiler is actually unsafe to use there should be zero debate?

This was taken out of context and not with the flow of the thread Ultrasonic.

Having read the which article you must give the opportunity to put things right all the things mentioned so far by the OP service engineer visit can be put right.

The out of context grab of text was to do with the fact they have fitted a 40kWh combo boiler which the OP thinks has cost them more to run and is quoted by their service engineer as oversized.

So the point is I don't think they will replace the 40kWh boiler with a smaller one or reimburse the OP additional running costs for the past year but they will have to fix what is there.

Ultrasonic

Mstty said:

Ultrasonic said:

Mstty said:

I am not sure you will get the housebuilders to change the boiler

Surely if the boiler is actually unsafe to use there should be zero debate?

This was taken out of context and not with the flow of the thread Ultrasonic.

Having read the which article you must give the opportunity to put things right all the things mentioned so far by the OP service engineer visit can be put right.

The out of context grab of text was to do with the fact they have fitted a 40kWh combo boiler which the OP thinks has cost them more to run and is quoted by their service engineer as oversized.

So the point is I don't think they will replace the 40kWh boiler with a smaller one or reimburse the OP additional running costs for the past year but they will have to fix what is there.

I've read the thread and my understanding was that the boiler being too powerful is part of the reason that it is unsafe to use?

Mstty

Ultrasonic said:

Mstty said:

Ultrasonic said:

Mstty said:

I am not sure you will get the housebuilders to change the boiler

Surely if the boiler is actually unsafe to use there should be zero debate?

This was taken out of context and not with the flow of the thread Ultrasonic.

Having read the which article you must give the opportunity to put things right all the things mentioned so far by the OP service engineer visit can be put right.

The out of context grab of text was to do with the fact they have fitted a 40kWh combo boiler which the OP thinks has cost them more to run and is quoted by their service engineer as oversized.

So the point is I don't think they will replace the 40kWh boiler with a smaller one or reimburse the OP additional running costs for the past year but they will have to fix what is there.

I've read the thread and my understanding was that the boiler being too powerful is part of the reason that it is unsafe to use?

Certainly over powered but not necessarily unsafe or against any rules or regulations if fitted properly.

If you can find the regulations where a 40kw combi boiler should not be fitted to a 3 bedroom home by law then I will certainly review my opinion and that would certainly help the OP taking their case to the housebuilder,👍

GSDMum

Ultrasonic said:

Mstty said:

Ultrasonic said:

Mstty said:

I am not sure you will get the housebuilders to change the boiler

Surely if the boiler is actually unsafe to use there should be zero debate?

This was taken out of context and not with the flow of the thread Ultrasonic.

Having read the which article you must give the opportunity to put things right all the things mentioned so far by the OP service engineer visit can be put right.

The out of context grab of text was to do with the fact they have fitted a 40kWh combo boiler which the OP thinks has cost them more to run and is quoted by their service engineer as oversized.

So the point is I don't think they will replace the 40kWh boiler with a smaller one or reimburse the OP additional running costs for the past year but they will have to fix what is there.

I've read the thread and my understanding was that the boiler being too powerful is part of the reason that it is unsafe to use?

Sorry if I've misled, the 'Do Not Use' notice is about the flue issue. Having an oversized boiler isn't a safety issue as the boiler cuts out. Although because of the oversize the engineer can't test the omissions for servicing the boiler - perhaps there should be a safety issue here?

[Deleted User]

I doubt that there is anything wrong with the boiler, and given that developers have to jump through hoops to get NHBC sign off, I also suspect that there is nothing wrong with the foam that has been used.

As I post, my downstairs thermostat is showing a reading of 22.1C. The service engineer will have asked the OP to turn up the CH thermostat to get the boiler ready for its testing mode. As my home TRVs are set in the range 13 to 21C based on the rooms that we use, how many of my 14 radiators would actually start to heat if my CH was turned on? I guess that a handful might get warm.

A 40kW boiler at maximum flow is pushing out a lot of hot water which will quickly heat up the  water in the very restricted piping up to the maximum flow return temperature. When this temperature is reached, the boiler will shut down as it is designed to do. My suspicion is that the boiler is cutting out on test before the test measurements are completed because the heating area is restricted due to ambient temperature:  this doesn’t mean that the boiler has a fault.  My premise is easily tested by turning all radiator TRVs and the thermostat to maximum temperature, and then turning the boiler on. Then time how long before the boiler cuts out. 

GSDMum

[Deleted User] said:

Having thought about the OP’s situation overnight, I need to address some of the issues raised. Firstly, when I had concerns about my new build boiler, I got the manufacturer to service the boiler. Yes, this cost me about £40 more than the ‘man-in-street’ but I did end up with a replacement heater exchanger and fan. The OP has to give the builder and his sub-contractor the chance to put things right; however, it might be worth pushing for a Baxi engineer visit/inspection to give more leverage.

The size of a combi boilers is usually based on the HW requirement not what is needed for CH. People complain when hot water isn’t near instant. This means that the boiler is over-specified for CH and it will be less efficient that a smaller boiler. All modern boilers have a built in modulation ratio which effectively reduces the boiler output as the home heating demand falls. A 40kW boiler might have a 5:1 ratio which means it will modulate down to 8kW whereas a 24kW boiler might modulate down to c.5kW. Does this matter: yes, it means that there will be frequent boiler cycling and increased ‘wear and tear’. Does the OP have any re-dress, I doubt it unless the original build design specification required a smaller boiler.

A final thought. It is summer which is not a good time to test a boiler because of the high internal air temperature. Did the boiler engineer ask for all the TRVs fitted to the 11 radiators to be turned to the fully open position? If not, many of the radiators will have effectively been shut off from any boiler flow. Given recent summer temperatures, it is possible that the boiler flow was just to one or 2 radiators and via the Automatic Bypass. It follows that the return flow temperature would quickly reach the boiler shut off temperature and the boiler would shut down. Occam’s Razor.

OP - I know what you are going through at the moment: my sympathies. My wife was treated for Hodgkin’s Lymphoma a few years back. 

 Thanks Dolor, I do hope your wife's now fully on the mend. 

Our CH system appears to be split, upstairs and down, both were working when the boiler was tested. Not sure if the hot taps were running as we just let the engineer and his mate get on with his job. Surely such an oversized boiler wouldn't have been on the house spec? The house was purchased because it's supposed to be energy rated as 'B' with the potential to be an 'A' if we install solar panels. 

This brings up another question, would the energy rating be affected by having an overly sized boiler? I suspect this could be an issue.

I've received an email from the developer saying someone will call me at the first instant next week to arrange a visit. So presently I'm just trying to gather thoughts on the stance I should take.

Thanks everyone for helping

GSDMum

[Deleted User] said:

I doubt that there is anything wrong with the boiler, and given that developers have to jump through hoops to get NHBC sign off, I also suspect that there is nothing wrong with the foam that has been used.

As I post, my downstairs thermostat is showing a reading of 22.1C. The service engineer will have asked the OP to turn up the CH thermostat to get the boiler ready for its testing mode. As my home TRVs are set in the range 13 to 21C based on the rooms that we use, how many of my 14 radiators would actually start to heat if my CH was turned on? I guess that a handful might get warm.

A 40kW boiler at maximum flow is pushing out a lot of hot water which will quickly heat up the  water in the very restricted piping up to the maximum flow return temperature. When this temperature is reached, the boiler will shut down as it is designed to do. My suspicion is that the boiler is cutting out on test before the test measurements are completed because the heating area is restricted due to ambient temperature:  this doesn’t mean that the boiler has a fault.  My premise is easily tested by turning all radiator TRVs and the thermostat to maximum temperature, and then turning the boiler on. Then time how long before the boiler cuts out. 

Thanks for your good explanation. Now (I think) the ball is rolling, it'll be interesting to see how the developer tests the system and what his explanation is. 

I hear what you say about the NHBC, although I'm a bit surprised they missed the flue pipe not being cemented. With the foam being used, the engineer was afraid the wrong foam was used and it would be a fire risk (believe the foam has to be supplied by the boiler manufacturer), though I'm not sure how anyone could possibly tell - perhaps sometimes you've got to take things on trust.

Pretty sure the boiler doesn't have a fault, except it appears to be far too big. With energy bills not coming down soon, think it's important that the heating system is as efficient as possible.