Enough heating output?

[David937]

Hi there,

Yes I know your getting tired of all the problems we have...

When it is very cold in winter the downstairs rooms and one upstairs bedroom will never be warm enough, I have heard that all homes should be able to reach 21C within an hour when it is -1C outside.

So we called the company who installed the system back.

They said that the heating should be more than sufficient; two rooms have radiators with an output of 2135W, the kitchen has a 1500W Myson kickspace and a small radiator which has a heat output of approximately 730W, the passage has a radiator with an output of 1600W, the living room has a radiator which has an output just over 1600W and the porch has a 600W radiator.

We don't mind the porch being cooler but the living areas all struggle to get over 19C on cold winter days, we have the thermostat set at 19.5C-20.0C and the flow temperature is at 82C on cold days.

Since the heating engineer insisted that the output should be enough he said that we could get a bigger radiator in the living room but we would have to pay.

I was thinking that the radiators are not giving out their full output due to the lack of 22mm pipework; starting from the boiler there is 3 metres of 22mm pipework and the rest is 15mm, all the downstairs radiators are fed from a single drop of 15mm pipework.

Could this be the problem?

 

[D_Hailsham]

When it is very cold in winter the downstairs rooms and one upstairs bedroom will never be warm enough, I have heard that all homes should be able to reach 21C within an hour when it is -1C outside.

Those temperatures are not the "law" but just what heating engineers use when designing a system. You have a Vaillant Ecotec Plus 937, if I remember correctly. This can produce 28kW for central heating (37kW for hot water), which should be more than adequate - unless you live in a barn or castle.

two rooms have radiators with an output of 2135W, the kitchen has a 1500W Myson kickspace and a small radiator which has a heat output of approximately 730W, the passage has a radiator with an output of 1600W, the living room has a radiator which has an output just over 1600W and the porch has a 600W radiator.

That's 10.3kW if I read your info correctly. But what about upstairs? You have not included those rads.

the living areas all struggle to get over 19C on cold winter days

Then the system has not been sized correctly. If you use the EST Boiler Sizing Wizard, you can find out the central heating requirement of your house; but deduct 2kw from the final result (built in allowance for a hot water cylinder). Your radiators should add up to this, although more will not do any harm. Provided they total less than 28kW, the boiler will be large enough.

Since the heating engineer insisted that the output should be enough he said that we could get a bigger radiator in the living room but we would have to pay.

If you relied on the engineer's advice as to what size rads you needed in each room to achieve a named temperature and the room does not reach that temperature then the problem is down to the engineer. If larger rads are required then he can legitimately charge you the cost of the new rad, less an allowance for the old wrong sized one. But he should not charge any labour for removing the old and installing the new rad.

starting from the boiler there is 3 metres of 22mm pipework and the rest is 15mm, all the downstairs radiators are fed from a single drop of 15mm pipework.

10.3kW flowing through 15mm pipes may be OK, it depends on the flow/return temperature difference. It's right on the upper limit if the difference is 11°C; but OK if the difference is 20°C. Fortunately your boiler is designed to work with a 20°C differential, so 15mm pipes are OK.

The rads, however will not be delivering their stated output but about 15% less. This could be contributing to your cold house.

You say the flow temp is 82°C, what does the diagnostic display say it is (d.40)? What is the return temperature (d.41)?

Did the engineer give you anything in writing showing how the rad sizes were calculated?[/quote][/url]

 

[JohnD]

; two rooms have radiators with an output of 2135W

that might be plenty, but you do not say how big the room is, what outside walls it has, what insulation and draughtproofing, how big the windows are, if they are double glazed, if you have a draughty floor or chimney, if you leave the internal door open.

 

[David937]

You have a Vaillant Ecotec Plus 937, if I remember correctly.

Yes, you are correct.

That's 10.3kW if I read your info correctly. But what about upstairs? You have not included those rads.

The upstairs radiators all equal to 6.5kw, this is including a towel rail...I have checked the specs for the towel rail.

10.3kW flowing through 15mm pipes may be OK, it depends on the flow/return temperature difference. It's right on the upper limit if the difference is 11°C; but OK if the difference is 20°C. Fortunately your boiler is designed to work with a 20°C differential, so 15mm pipes are OK.

The rads, however will not be delivering their stated output but about 15% less. This could be contributing to your cold house.

The difference when I last checked on d.40 and d.41 was only 9C, but the boiler was not running at 82C then as it was early spring, IIRC it was running at 70C. Three of the upstairs radiators are teed of the 22mm pipework.

Did the engineer give you anything in writing showing how the rad sizes were calculated?

No, nothing was given, all he did when he came to measure everything up was use the existing non-convector rad sizes and made some radiators K2 or P+. He said it will be OK as new radiators have much higher outputs.

 

[David937]

that might be plenty, but you do not say how big the room is, what outside walls it has, what insulation and draughtproofing, how big the windows are, if they are double glazed, if you have a draughty floor or chimney, if you leave the internal door open.

Point taken, I have just been to measure one of the rooms with a 2135w rad.

The French double glazed doors measure 2m x 2m.

The room measures 3m x 3m and has cavity wall insulation.

Internal door left closed.

Draught proofed.

No chimney as this is an extension to the living room which has no cavity wall insulation or cavity walls and has a gas fire..however we don't feel any draughts from the fire place.

Need any more information?

 

[D_Hailsham]

That's 10.3kW if I read your info correctly. But what about upstairs? You have not included those rads.

The upstairs radiators all equal to 6.5kw, this is including a towel rail...I have checked the specs for the towel rail.

So you have 16.8kW total rads, which means that the boiler is more than adequate. So the question now is: are the rads large enough?

The difference when I last checked on d.40 and d.41 was only 9C, but the boiler was not running at 82C then as it was early spring, IIRC it was running at 70C. Three of the upstairs radiators are teed of the 22mm pipework.

If the system is running with a 9°C differential, then 15mm is certainly not large enough. Though the real question should be why is it not running with a 20°C differential?

... all he did when he came to measure everything up was use the existing non-convector rad sizes and made some radiators K2 or P+. He said it will be OK as new radiators have much higher outputs.

Typical.

In your reply to JohnD's questions you wrote:

... the living room which has no cavity wall insulation or cavity walls

So it's an old house with solid walls. How old? Any double glazing or draught proofing? What about loft insulation - how much? Do you have a cellar? If so is the underside of the ground floor insulated?

If none of these things have been done there will be a large heat loss.

Have you used the EST Boiler Sizing Wizard to check you heating requirement? You should divide the house into two, original and extension, and then add the results together. Please let us know what answer it gives.

Ultimately the installer is responsible, under the Supply of Goods and Services Act 1982, for providing you with a working system which meets your requirements. The problem, in many cases, is that nothing is in writing; so it's difficult for the customer to prove what was required. You may need to get advice from your local Trading Standards Department.

 

[David937]

If the system is running with a 9°C differential, then 15mm is certainly not large enough. Though the real question should be why is it not running with a 20°C differential?

The chap that came to quote etc, said that we should run the system all year at 82C and the differential should be 11C, I told him that the return must be below 55C..or is 57C for the boiler to condense, but he thought I was stupid and said as long as there is an 11C differential the boiler will condense.

So it's an old house with solid walls. How old? Any double glazing or draught proofing? What about loft insulation - how much? Do you have a cellar? If so is the underside of the ground floor insulated?

If none of these things have been done there will be a large heat loss.

Have you used the EST Boiler Sizing Wizard to check you heating requirement? You should divide the house into two, original and extension, and then add the results together. Please let us know what answer it gives.

Ultimately the installer is responsible, under the Supply of Goods and Services Act 1982, for providing you with a working system which meets your requirements. The problem, in many cases, is that nothing is in writing; so it's difficult for the customer to prove what was required. You may need to get advice from your local Trading Standards Department.

We called an insulation company and they told us our house is probably 100 years old.

Double glazing and draught proofing is present.

There is loft insulation (12 inches).

There is no cellar.

I will have to see if I can figure out how to use the EST boiler sizing wizard.

Thanks for your input.

 

[Agile]

My learned colleague, D Hailsham, appears to have put insufficient weight on the evidence when the claimant stated in his evidence that the whole of the downstairs, which amounts to over 10 kW is supplied from a single 15 mm flow pipe.

The usual rule of thumb employed by those who do that work is that 15 mm can only carry about 3.5 kW.

We will need a suitably qualified expert to measure the flow and return pipe temperatures of each of the downstairs radiators.

One wonders why a matter pertaining to central heating is being brought before us during the summer!

Tony

 

[D_Hailsham]

The chap that came to quote etc, said that we should run the system all year at 82C and the differential should be 11C, I told him that the return must be below 55C,or is 57C, for the boiler to condense, but he thought I was stupid and said as long as there is an 11C differential the boiler will condense.

The man was talking out of his proverbial! You are quite correct. The temperature depends on the exact composition of the gas but is around 55°C, lower is safer so let's say 50°C

our house is probably 100 years old.

My last house was a 3 floor 5 bed Edwardian semi, built in 1905. Solid 13 inch walls. mainly original windows, nine foot ceilings etc. It was heated by a floor standing 23kW Potterton Diplomat. The house was always nice and warm.

Double glazing and draught proofing is present. There is loft insulation (12 inches). There is no cellar.

That all helps.

I will have to see if I can figure out how to use the EST boiler sizing wizard.

It's not difficult

 

[D_Hailsham]

My learned colleague, D Hailsham, appears to have put insufficient weight on the evidence when the claimant stated in his evidence that the whole of the downstairs, which amounts to over 10 kW is supplied from a single 15 mm flow pipe.

The usual rule of thumb employed by those who do that work is that 15 mm can only carry about 3.5 kW.

It all depends on the maximum allowed flow rate, which is really determined by the acceptable level of noise generated by the water flowing through the pipe. See Small bore heating systems.

In any case I said that 10kw was too much for 15mm with an 11°C differential but OK if it was a 20°C differential, which the OPs boiler is designed to use.

We will need a suitably qualified expert to measure the flow and return pipe temperatures of each of the downstairs radiators.

You don't need to be an expert to use a thermometer!

One wonders why a matter pertaining to central heating is being brought before us during the summer!

Because he wants to get it sorted before next winter? Doh!

 

[David937]

I don't have a thermometer to measure the radiator flow and return temps but I can tell you that when the system is running the radiators are too hot to touch.

 

[namsag]

D halisham says not law but the books state definition of Central heating is the ability to raise room from to 21 degrees when minus one outside .
Which is why people use rad calculators to get the smallest rad they can to achieve this.
If it doesnt do this it is then defined as back ground heating .

As you say new rads did he use existing pipework and did rooms get hot enough before.

Its really simple you have bought central heating and as such you should have it, if rooms not getting hot enough then its down to installer and you should not pay a penny for bigger rads.


Also use a proper stat to measure temp of room not a cheapo thing

 

[David937]

I use the Honeywell CM927 to measure the room temps.

As you say new rads did he use existing pipework and did rooms get hot enough before.

Yes existing pipework was used, he told us their was no need for any new pipes.

The rooms never used to get hot enough, the upstairs has improved but nowhere else has. We told him that the house doesn't get warm enough and he said it should be OK once the new system is installed.

 

[snb]

have you checked the required heat input for your rooms yet?

1600w for a lounge either means you have exceptional insulation or a very small lounge.

the average lounge 5.5m x 3.5m with cavity wall insulation would require around 1800watts but if you wanted to have 50 degree return temp then this means you need rads with around 3600 watts output.

because of size and cost implications and the fact that we often don't need to increase from -1 to 21 then you would opt for a rad size in between around 2700 watts and then most of the year you could have the return temp around 50 to 55.

every installer has slightly differing ideas but i know that i always want to fit the smallest rads because of cost but would always be cautious as nothing worse than an upset customer for the sake of a few quid on each rad.

 

[David937]

1600w for a lounge either means you have exceptional insulation or a very small lounge.

the average lounge 5.5m x 3.5m with cavity wall insulation would require around 1800watts but if you wanted to have 50 degree return temp then this means you need rads with around 3600 watts output.

The lounge is 4m x 4m with an extension that is 3m x 3m, the extension has a 2135w radiator and the older part has a 1600w radiator.