40kw Boiler in 3 Bed Bungalow

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s00tie

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Had a quick search on the forum and couldn't find anything specific to my question so here goes..

We've been renting a 3 bed detached bungalow for about a year now and regardless of what we've tried (balancing rads, turning thermostat down, turning CH boiler temp up or down, turning DHW boiler temp up or down we're seeing crazy energy bills.

It's come around to renewal time and I've taken the usage from Npower and it shows about 35,000 kwh for the year which is staggering. I'm seeing projections of circa £2-3k as an estimate from suppliers which is worrying.

We use a Nest thermostat set to 20.5 and during Winter months we see about 6 hours of calling down to nothing during the warmer months. From overnight lows of around 16 - it takes the heating about an hour to get up to temp.

House feels just about right at 20.5

I ran a rough calculation for the rads output and saw it to be about 12kw

What I'm concerned about is whether this is just down to the boiler (Baxi DuoTec 40) being way oversized for the property.

We've had the landlords plumber check and service the boiler who reported everything was fine although I'm not sure how thorough he was to be honest.

Any advice or suggestion would be very welcome - happy to answer any questions.

Thanks in advance!
 
Does the meter meaure in Cubic Metres or Cubic Feet and does the bill refer to measuring in same units as the meter.

One cubic metre = 35 cubic feet

Imperial meters measure 100 cubic feet as one unit
Metric meters measure 1 cubic metre as one unit

Burning one cubic metre of gas will register as one unit on a metric metre and as 0.35 units on an imperial ( cubic feet ) meter.

Hence a bill could be approc 3 times the correct price
 
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I take it you have a combi boiler?
It’s never really a good idea to oversize your appliance but regardless if it’s to big for your property or not it shouldn’t cost you anymore to run.
Maybe you have a small gas leak? I would assume that your service engineer did a gas safety inspection aswell as making sure your boiler was working correctly?
 
high flow rate combi = higher running cost.

Assuming its a :censored: combi
 
Thank you for the replies, see if I can answer some of them :)

Yes it's a Condensing Combi and regarding the volume measurement, looking on the front of the smart meter it's showing gas in m3. The bill also references m3 supplied so at least they add up.

We did have a very minor leak at the meter when we first moved in, but that was resolved and yes - you'd hope the engineer would have checked for other leaks. Have to say though, when we've been away with heating off - the usage hasn't increased so if it is a leak it's either very minor or it's only when the boiler is running.

During the winter months, I was seeing a daily cost of around £6 just for Gas. The boiler is the only gas appliance we have, everything else is electric. We don't run the shower for too long, fill the bath rarely and the washer / dishwasher all use cold water.

I'm wondering if I should have an independent engineer come take a look to be honest. I'm still skeptical on how well the plumber serviced / checked it.

Something I have noticed which is interesting is with the DHW set to 55 (a number we've tended to use elsewhere) the flow reading at the boiler when the hot tap is running shows about 68. We have to set the dial to 45 in order for it to deliver hot tap water at about 55.

I've also watched the boiler operate whilst the CH is on (I know - this is what my life has come to!) but I won't bore you with the tests/result unless someone asks :)

I'm happy to answer any other questions or run any tests that will help find out what's happening. It's important I get this right as we're planning on staying here for a while.
 
How old is the bungalow? If you were to get it up to a comfortable temperature on a cold day and then turn off the heating, how quickly does it lose the heat? Some bungalows are diabolically insulated because it's so awkward to retrofit compared to a traditional house with simple attic space.
 
s00tie said:
Something I have noticed which is interesting is with the DHW set to 55 (a number we've tended to use elsewhere) the flow reading at the boiler when the hot tap is running shows about 68. We have to set the dial to 45 in order for it to deliver hot tap water at about 55
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You misunderstand what the display is showing.
 
It's 40Kw for the hot water only to give quicker bath filling or running a couple of showers.
In heating mode the boiler will modulate its power output but being such a high Kw for hot water means it will cycle more especially when the heating demand is lower. Is the heat getting away from the boiler? Does it cycle excessively? TRVs on the bedroom rads?
 
Gasguru said:
It's 40Kw for the hot water only to give quicker bath filling or running a couple of showers.
In heating mode the boiler will modulate its power output but being such a high Kw for hot water means it will cycle more especially when the heating demand is lower. Is the heat getting away from the boiler? Does it cycle excessively? TRVs on the bedroom rads?
Click to expand...

All rads that are calling heat up at about the same time so yes, heat is getting away. TRVs are on the bedroom rads and set at 2 (max is 5).

If I set CH temp lower (say 50) then it cycles a lot. It's currently set to 65 and seems to stay on longer and cycle less - I can hear the flame reduce in power as the water heats up to about 68 and then the temp holds steady at 65.
 
garyo said:
How old is the bungalow? If you were to get it up to a comfortable temperature on a cold day and then turn off the heating, how quickly does it lose the heat? Some bungalows are diabolically insulated because it's so awkward to retrofit compared to a traditional house with simple attic space.
Click to expand...

Think it was built in the 70s - insulation isn't great (big bay window on one side and patio door on other which both can feel cooler).

I'd say during winter, once the temp gets up to about 20.5 the heat will come on about every hour for 10 mins or so to maintain, I don't think leaving the heating off after a warm up in the morning would be an option.
 
s00tie Do you have a current epc for the property if so what is mentioned ? some properties are exempt but just asking.

Usually the landlord,on renewal of a rental contract has to ensure the property meets the current MEES standards,its in your favour to check.

Otherwise,pack up your pots and pans and find alternative lodgings,sorry thats life ;)

:)
 
Is it single storey with an attic and able to be well insulated, or the chalet type with inaccessible areas of roof with no insulation? If it's the latter than some are really really bad. Effectively the ceiling/floor void between ground and first floor levels is exposed to the outside.
 
garyo said:
Is it single storey with an attic and able to be well insulated, or the chalet type with inaccessible areas of roof with no insulation? If it's the latter than some are really really bad. Effectively the ceiling/floor void between ground and first floor levels is exposed to the outside.
Click to expand...

It's a single storey with an attic. There is good amount of loft insulation up there and some of it is boarded.

The property isn't draughty and stays relitively warm in winter and nice and cool in summer so although I believe the heat loss isn't great because of it's open plan nature, big double glazed bay window and sliding double glazed patio door - I don't think it's terrible either.

I'm convinced that considering the amount of time the boiler spends heating to supply the central heating, the boiler is consuming more gas than it should be doing.

In theory - if the house isn't particularly well insulated and we've got an overrated boiler, what would the general consensus be on temps - should I be putting the heat almost to max so rads are getting 70/75 degrees, go lower and for longer maybe 50/55 or keep in the middle with 65?
 
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