is this boiler too small?

[matz]

sorry another topic and another question, we're on a mission to sort out our heating and hot water

We had a Valiant eco 415 condensing boiler non combi installed new 2 yrs ago, pro install at cost of £2100.00.

Whilst trying to work out what to do re. upgrading our DHW supply I've just added up the radiators in our 4 bed detached house - 13 rads equalling 71900BTU inc hot water at 6800btu. As i understand it the Boiler is rated at around 55,000BTU

did they put in a big enough boiler?

 

[Dan Robinson]

Whats your insulation and glazing like?

My 4 bed (with large ground floor) ticks over quite nicely on 15kW.

I do have mine set for hot water priority though.


Double glazing, cavity walls etc.,

 

[matz]

UPVC double glazing throughout
cavity wall bead insulation
loft insulation a bit skimpy!
concrete floors
1980s build

forgot to say I calculated the BTUs based on 60degrees output from the rads

have to say though that compared to previous boiler, the rads are not as hot - they are hot but not almost burn your hand hot and the house aint as hot when in a cold spell.

 

[Dan Robinson]

Rads don't need to be blazing hot though.

Does the house have to be HOT.... surely 21 degrees or thereabouts should be the aim.

 

[JohnD]

did they put in a big enough boiler?

Is your house cold in the winter, when the boiler is running flat out?

 

[BigSnoopy01]

are you calculationg the rads on an 11degree drop or 20?

 

[JohnD]

You do not calculate the heat loss of a house by adding up the size of the radiators.

 

[D_Hailsham]

You do not calculate the heat loss of a house by adding up the size of the radiators.

Agreed. You use the Whole House Boiler Size Calculator to size your boiler.

You have 19kW of rads and a 15kw boiler. Assuming the pump has been set to give a 20C difference between the flow and return temperatures, the boiler will stabilize at a flow temp of about 72C, return of 52C.

When you say that you calculated the rads for a 60C output, which temperature are you referring to?

 

[matz]

wow, happy to be corrected here seems like I have it totally wrong! re. the heat of the house - try telling my missus it doesnt need to be baking hot!
so I'm assuming the boiler size is ok then? The rad output temps were taken from a site selling radiators...

 

[JohnD]

did they put in a big enough boiler?

Is your house cold in the winter, when the boiler is running flat out?

You tell me.

 

[D_Hailsham]

try telling my missus it doesnt need to be baking hot!

I know what you mean. My wife used to worry when the rads were only luke warm: not anymore. She soon learned that how warm she felt was the important criteria.

The rad output temps were taken from a site selling radiators...

Can you post a link to the site? Some unscrupulous sites still use historic methods which will overstate the output of a radiator.

 

[Dan Robinson]

Mine complains that are floor doesn't get hot (underfloor heating). Daft mare doesn't appreciate the difference between half a square metre of radiator and 70 square metres of heated surface.

Will they ever learn?

 

[matz]

try telling my missus it doesnt need to be baking hot!

I know what you mean. My wife used to worry when the rads were only luke warm: not anymore. She soon learned that how warm she felt was the important criteria.

The rad output temps were taken from a site selling radiators...

Can you post a link to the site? Some unscrupulous sites still use historic methods which will overstate the output of a radiator.

http://www.plumbworld.co.uk/single-panel-single-convector-3792-22940

I calculated the output per square mm on a radiator type then multiplied it up by the size of each of our rads.

 

[matz]

did they put in a big enough boiler?

Is your house cold in the winter, when the boiler is running flat out?

You tell me.

all I can say to you is when theres a bitter cold period, the room stat in the hall is set at just over 20 maybe 22, the rads are hot but not red hot, the house does not feel hot enough compared to previous properties I've lived in but that maybe due to everyone sat on their arses in t shirts lol.

Also, the boiler appears to keep cutting out as soon as it reaches a temperature limit on its own rather than the room stat cutting the boiler off. I can watch the boiler water temp rise up on the dial then cut off - I think the boiler temp cut off is 70degrees from memory but may be wrong...

 

[JohnD]

loft insulation a bit skimpy

so insulate the loft and I expect it will be enough. Use the whole house heat loss calculator to find out what the house would typically lose.

You can balance your radiators as well.

Thermostat should be in your main living room, not in the hall.