BOXT - any good ?

Lorian

Or £100 refer a friend from an existing customer. Obviously can't give out codes on here. I have had two boilers installed by boxt and both nicely done and tidy. One even included an extra day of two engineers for an extra long run of 28mm copper gas pipe all at no extra cost.

I do have another to do soon though and as someone else has pointed out Worcester direct is quoting me quite a lot cheaper than boxt at present.

MouldyOldDough

Worcester Greenstar 4000 30kW

BOXT - £2445

Worcester direct - £2600

MouldyOldDough

What about radiators - how do I know when they need replacing ?

Ours are minimum 30 years old - none leaking and minimum rust stains around bottom seams.

FreeBear

At 30 years old, they probably used an 80°C flow temperature as the basis for sizing the radiators. Modern installations use 70°C or even 60°C which means slightly larger radiators for the same amount of heat. Lower flow temperatures means the boiler is pushed further in to condensing mode for better fuel efficiency. At 80°C flow, you'll probably get around 86% efficiency. Get the flow temperature below 60°C, and efficiency could get as high as 98% (more correctly, it is the return temperature that is important, so 40-50°C is the target to aim for).

If you measure the room size and area of the doors & windows, punch the numbers in to this calculator - https://www.stelrad.com/basic-heat-loss-calculator/ - Set the Delta-T for 40°C for a flow temperature of 60°C (return of 40°C). Stelrad appear to be fairly generous on their calculations which isn't a bad thing. When I used it, I still oversized most of my radiators by about 30%. Ended up getting quantity discount on 1000x600 type 21 radiators and fitted them myself to keep costs down.

MouldyOldDough

FreeBear said:

At 30 years old, they probably used an 80°C flow temperature as the basis for sizing the radiators. Modern installations use 70°C or even 60°C which means slightly larger radiators for the same amount of heat. Lower flow temperatures means the boiler is pushed further in to condensing mode for better fuel efficiency. At 80°C flow, you'll probably get around 86% efficiency. Get the flow temperature below 60°C, and efficiency could get as high as 98% (more correctly, it is the return temperature that is important, so 40-50°C is the target to aim for).

If you measure the room size and area of the doors & windows, punch the numbers in to this calculator - https://www.stelrad.com/basic-heat-loss-calculator/ - Set the Delta-T for 40°C for a flow temperature of 60°C (return of 40°C). Stelrad appear to be fairly generous on their calculations which isn't a bad thing. When I used it, I still oversized most of my radiators by about 30%. Ended up getting quantity discount on 1000x600 type 21 radiators and fitted them myself to keep costs down.

Thanks - i meant, how will we know when the rads need physically replacing ?

FreeBear

MouldyOldDough said:

FreeBear said:

At 30 years old, they probably used an 80°C flow temperature as the basis for sizing the radiators. Modern installations use 70°C or even 60°C which means slightly larger radiators for the same amount of heat. Lower flow temperatures means the boiler is pushed further in to condensing mode for better fuel efficiency. At 80°C flow, you'll probably get around 86% efficiency. Get the flow temperature below 60°C, and efficiency could get as high as 98% (more correctly, it is the return temperature that is important, so 40-50°C is the target to aim for).

If you measure the room size and area of the doors & windows, punch the numbers in to this calculator - https://www.stelrad.com/basic-heat-loss-calculator/ - Set the Delta-T for 40°C for a flow temperature of 60°C (return of 40°C). Stelrad appear to be fairly generous on their calculations which isn't a bad thing. When I used it, I still oversized most of my radiators by about 30%. Ended up getting quantity discount on 1000x600 type 21 radiators and fitted them myself to keep costs down.

Thanks - i meant, how will we know when the rads need physically replacing ?

Measure up the room sizes & window area. Put the numbers in to the online calculator I linked to.

Measure your existing radiators, and you can get a rough idea of their output at Delta-T 50°C (flow temperature of 70°C). Multiply the number by 0.75 to get the rating for a Delta-T 40°C (60°C flow temperature).

Any radiator that is coming out as too small compared to the calculated size should be replaced. If you have any rooms that are always too cold an/or difficult to heat will benefit from larger radiators - Might pay to oversize those by 20% of the calculated size.

MouldyOldDough

FreeBear said:

MouldyOldDough said:

FreeBear said:

At 30 years old, they probably used an 80°C flow temperature as the basis for sizing the radiators. Modern installations use 70°C or even 60°C which means slightly larger radiators for the same amount of heat. Lower flow temperatures means the boiler is pushed further in to condensing mode for better fuel efficiency. At 80°C flow, you'll probably get around 86% efficiency. Get the flow temperature below 60°C, and efficiency could get as high as 98% (more correctly, it is the return temperature that is important, so 40-50°C is the target to aim for).

If you measure the room size and area of the doors & windows, punch the numbers in to this calculator - https://www.stelrad.com/basic-heat-loss-calculator/ - Set the Delta-T for 40°C for a flow temperature of 60°C (return of 40°C). Stelrad appear to be fairly generous on their calculations which isn't a bad thing. When I used it, I still oversized most of my radiators by about 30%. Ended up getting quantity discount on 1000x600 type 21 radiators and fitted them myself to keep costs down.

Thanks - i meant, how will we know when the rads need physically replacing ?

Measure up the room sizes & window area. Put the numbers in to the online calculator I linked to.

Measure your existing radiators, and you can get a rough idea of their output at Delta-T 50°C (flow temperature of 70°C). Multiply the number by 0.75 to get the rating for a Delta-T 40°C (60°C flow temperature).

Any radiator that is coming out as too small compared to the calculated size should be replaced. If you have any rooms that are always too cold an/or difficult to heat will benefit from larger radiators - Might pay to oversize those by 20% of the calculated size.

Sorry - but still not what I was looking for

I want to know how to tell whether radiators are rusty on the inside and need replacing due to failure... 

FreeBear

MouldyOldDough said:

FreeBear said:

MouldyOldDough said:

FreeBear said:

At 30 years old, they probably used an 80°C flow temperature as the basis for sizing the radiators. Modern installations use 70°C or even 60°C which means slightly larger radiators for the same amount of heat. Lower flow temperatures means the boiler is pushed further in to condensing mode for better fuel efficiency. At 80°C flow, you'll probably get around 86% efficiency. Get the flow temperature below 60°C, and efficiency could get as high as 98% (more correctly, it is the return temperature that is important, so 40-50°C is the target to aim for).

If you measure the room size and area of the doors & windows, punch the numbers in to this calculator - https://www.stelrad.com/basic-heat-loss-calculator/ - Set the Delta-T for 40°C for a flow temperature of 60°C (return of 40°C). Stelrad appear to be fairly generous on their calculations which isn't a bad thing. When I used it, I still oversized most of my radiators by about 30%. Ended up getting quantity discount on 1000x600 type 21 radiators and fitted them myself to keep costs down.

Thanks - i meant, how will we know when the rads need physically replacing ?

Measure up the room sizes & window area. Put the numbers in to the online calculator I linked to.

Measure your existing radiators, and you can get a rough idea of their output at Delta-T 50°C (flow temperature of 70°C). Multiply the number by 0.75 to get the rating for a Delta-T 40°C (60°C flow temperature).

Any radiator that is coming out as too small compared to the calculated size should be replaced. If you have any rooms that are always too cold an/or difficult to heat will benefit from larger radiators - Might pay to oversize those by 20% of the calculated size.

Sorry - but still not what I was looking for

I want to know how to tell whether radiators are rusty on the inside and need replacing due to failure... 

Without a borescope, you can't really see if the radiators are rusting on the inside. But if the enamel is flaking off and there is rust along the seams (particularly at the bottom), it would be prudent to fit new radiators. Replacement radiators can be had for as little as £30. Bigger ones in the £80-120 range, although the price jumps considerably for sizes over 1200mm wide.

MouldyOldDough

How do "inline scale reducers" work?
Surely the limescale must go somewhere?
BOXT recommend that I fit one

FreeBear

MouldyOldDough said:

How do "inline scale reducers" work?
Surely the limescale must go somewhere?
BOXT recommend that I fit one

I've looked for scholarly articles on these devices, and have yet to find anything. I suspect they are like those magnets that people used to clip round the fuel lines in their cars to get better MPG.

I'm in a hard water area, and when I swapped to a combi boiler last year, I cut open the old copper water tank to see how much scale had accumulated in the 40 odd years it had been in use. Quite surprised to find very little - Best described as a thin, light coating. As the DHW was never steaming hot, I concluded that it was the reduced temperature was the main factor. In comparison, the kettle needs regular descaling, but the water is (nearly) always heated to 100°C where as hot water from the tap was rarely above 50°C.

Viessmann and the boiler installer recommended fitting a scale reducer, so for the sake of £15, one was fitted. One less reason for a warranty claim to be rejected. Running the DHW at 45°C should keep limescale deposits to a minimum.