NIBE F205 boiler - please help!

[itspaul]

At a cost.

Well cop is 3.3. So a properly designed and maintained system should give out 3.3 kW of heat for ever 1 kW of electricity used according to man data.
http://www.nibe.co.uk/nibedocuments/10591/031977-1.pdf

 

[jasonoldy69]

Ideally, you need to know the heat loss in each room. However, the total heat loss in the flat should be enough You can find this out by using .

Information on typical radiators can be found on page 44 of

Post the information.

Flow and Return Temperatures

The flow temperature is the temperature of the heated water leaving the boiler and travelling to the radiators.
Heat is extracted from the water by the radiators, so the water temperature leaving the rads and returning to the boiler is lower. This is the return temperature.

The output of a radiator depends on the temperatures of the water entering and leaving the rad. So this is standardised at 75C flow and 65C return. If different temperatures are used a formula is used to calculate the rad output.

Bare in mind, this boiler is ventilating the property 24 hours a day, most of which is unrecovered. This is why homes with EAHPs are unable to maintain a decent temperature.

 

[Misha]

Ideally, you need to know the heat loss in each room. However, the total heat loss in the flat should be enough You can find this out by using Baxi Whole House Boiler Size Calculator.

Information on typical radiators can be found on page 44 of Stelrad Catalogue

Post the information.

Flow and Return Temperatures

The flow temperature is the temperature of the heated water leaving the boiler and travelling to the radiators.
Heat is extracted from the water by the radiators, so the water temperature leaving the rads and returning to the boiler is lower. This is the return temperature.

The output of a radiator depends on the temperatures of the water entering and leaving the rad. So this is standardised at 75C flow and 65C return. If different temperatures are used a formula is used to calculate the rad output.

Great - thank you so much for the info and the links.

 

[Misha]

It's also important with these systems that the circulating pump is working correctly and the flow rates are not to high

How will I know if the circulating pump is working correctly?

One of my radiators (the largest one) gets hot at the top but stays cold at the bottom? I've been told that is because the water flows through a pipe at the top of the radiator and then flows out of the radiator at the bottom. Does that sound right to you? Also, something I noticed today. The temperature gauge on the F205 said the temperature was 50 degrees. The TRVs on all of the radiators (one rad doesn't have a TRV) were completely closed at that point and the thermostat was on 14 degrees. I didn't use any hot water, and I opened all of the TRVs. The temperature on the gauge went down to 40 degrees in about 10 minutes. Should that happen?

 

[doitmyself]

Great - thank you so much for the info and the links.

So where are the results of your research?

 

[doitmyself]

One of my radiators (the largest one) gets hot at the top but stays cold at the bottom? I've been told that is because the water flows through a pipe at the top of the radiator and then flows out of the radiator at the bottom. Does that sound right to you?

Some systems do have one pipe connected to the top and the other to the bottom, but this is move prevalent on the continent. In the UK it is normal to have both pipes connected to the bottom.

However, heat rises, so the top of a rad will always be warmer than the bottom.

The temperature gauge on the F205 said the temperature was 50 degrees. The TRVs on all of the radiators (one rad doesn't have a TRV) were completely closed at that point and the thermostat was on 14 degrees. I didn't use any hot water, and I opened all of the TRVs. The temperature on the gauge went down to 40 degrees in about 10 minutes. Should that happen?

If all TRVs closed no heat is being removed from the water by those rads, which leaves one rad to give off any heat. So the water temperature (return) will not drop very far. As soon as tyou open the TRVs the rads give off heat, and the return temperature drops. The boiler then heats the water up.

Did the temperature stay constant at 40 or did it rise?

 

[jasonoldy69]

Well cop is 3.3. So a properly designed and maintained system should give out 3.3 kW of heat for ever 1 kW of electricity used according to man data.

In theory, yes. In practice, it's nowhere near COP 3. It's closer to 1.5 in most cases.

Don't forget, this a Swedish product installed in standard British housing. Swedish homes are 1000% more air tight. The fact they've needlessly punched "fresh air inlets" in these homes, reduces air tightness further.

If you called NIBE UK today, and asked them to confirm the COP value, I guarantee you won't get a straight answer.

 

[jasonoldy69]

NIBE EAHPs will be featuring on BBC again, this year.

I may be able to post more news regarding current and future NIBE installations, in the coming weeks, hopefully to the delight of thousands of unhappy users.

 

[Misha]

So where are the results of your research?

Sorry about the delay. I haven't calculated anything yet as I have no idea what size the property is. When someone visits me, we'll get a tape measure out to measure everything. I had a look at the radiator catalogue, but I couldn't find a radiator like mine.

 

[Misha]

Some systems do have one pipe connected to the top and the other to the bottom, but this is move prevalent on the continent. In the UK it is normal to have both pipes connected to the bottom.

However, heat rises, so the top of a rad will always be warmer than the bottom.


If all TRVs closed no heat is being removed from the water by those rads, which leaves one rad to give off any heat. So the water temperature (return) will not drop very far. As soon as tyou open the TRVs the rads give off heat, and the return temperature drops. The boiler then heats the water up.

Did the temperature stay constant at 40 or did it rise?

The temperature did rise eventually. i'm confused; I didn't think the water for the rads came from the hot water cylinder. I thought it was only water for taps that came from the hot water cylinder...

 

[jasonoldy69]

The temperature did rise eventually. i'm confused; I didn't think the water for the rads came from the hot water cylinder. I thought it was only water for taps that came from the hot water cylinder...

The unit has a cylinder, with another hot water cylinder wrapped round it (double-jacket).

If I'm right in remembering, the inner cylinder feeds water for the radiators, the outer one is your domestic hot water store.

 

[Unregistered]

The unit has a cylinder, with another hot water cylinder wrapped round it (double-jacket).

If I'm right in remembering, the inner cylinder feeds water for the radiators, the outer one is your domestic hot water store.

Ohhh. So which cylinder does the gauge relate to?

 

[jasonoldy69]

Ohhh. So which cylinder does the gauge relate to?

I guess the gauge on the f205 is domestic hot water.

P.S. I'm sorry about the private messaging. This rotten site only lets you store 1-2 messages at a time.

 

[Misha]

I guess the gauge on the f205 is domestic hot water.

P.S. I'm sorry about the private messaging. This rotten site only lets you store 1-2 messages at a time.

No worries about the private messaging.

I thought it would be measuring domestic hot water. That's why I got so confused when the temp dropped as soon as I turned the rads on.