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Hi,
I've just had a Baxi Duotec 28 fitted. I've got 7 radiators and the plumber said for this 2 bedroom bungalow it should be fine.
Because it's winter I've had the the thermostatic valves fully open. All the radiators seem to get quite hot but I've found that shutting off a couple of radiators has made things a bit warmer.
Silly question maybe but should that be expected? I would have thought this boiler would be more than ample. The plumber said it would be.
I was thinking of replacing a couple of single radiators with doubles but I'm not sure if that would make things worse.

Is it normal for properly spec'ed boiler to do this?

Thanks.
 
This is also going to lead to the question, - is the system properly balanced?
If it was all out of balance, shutting certain radiators off can put others more in balance, if you understand my meaning.
Did you notice some radiators were more hotter to the touch that others?
Cold weather shows how bad some heating systems are balanced or piped.
 
Hi, I've just had a Baxi Duotec 28 fitted. I've got 7 radiators and the plumber said for this 2 bedroom bungalow it should be fine.

The boiler can pump out 28kW, more than 7 (typical sized) radiators would be able to dissipate. This means you probably have a controls/balancing issue, which the original installer should sort out for you.

If you want to do a bit of sleuthing yourself, start by reading your gas meter at hourly intervals when the heating is on, you're not using hot water and you feel cold. From the amount used per hour, you can convert to the number of kW that is being used to heat your bungalow.

Also note whether the boiler firing continuously or whether it seems to be cycling on and off frequently.
 
Hi all. Thanks for the replies.

Stat is set to 80. These are almost all single radiators.

Boiling is pretty much continuously on.

When the system was installed, the bathroom radiator was luke warm. He then balanced them and they've all been a similar temperature since but the ones in the living room seem a bit hotter. I know the insulation is bad in the house and I suspect that is a big part of it but when the radiators became hotter I thought it might be that instead.

The plumber did say the boiler was the same as he had in his house and would be powerful enough to power my house and the one next door.

I'll certainly start checking the meter. I don't think it's as economical as it should be.
 
I'll check but from I remember seem to be hot all the way through the radiator. Maybe just not hot enough.

Can the plumber adjust the CH output on a combi?
 
I'll check but from I remember seem to be hot all the way through the radiator. Maybe just not hot enough.

Can the plumber adjust the CH output on a combi?

There are a range of adjustments a competent heating engineer can make but they should start with the basics, e.g. measuring the flow and return temperatures at each radiator and working logically from what that tells them.
 
Hi,
I've just had a Baxi Duotec 28 fitted. I've got 7 radiators and the plumber said for this 2 bedroom bungalow it should be fine.
Seven rads will be about 10-12kW, which is near the lowest output from your boiler (8.7kW). That's OK in the winter when it's very cold, but don't be surprised if the boiler turns on and off a lot when it gets warmer.

Because it's winter I've had the the thermostatic valves fully open.
That's not necessary. A TRV is fully open if the room is below the required temperature and only starts to close when room is up to temperature; it will only close completely if the room temperature is about 2C above the setting. If the room cannot get up to temperature the radiator is too small.

Just set the TRV to 4 and leave it to do its job. If you feel too cold, turn TRV up a fraction, and vice versa.
 
They were replaced with similar sized radiators. As far as I know he didn't do a heat loss calculation. There are a couple of concrete floors so that made it difficult.
I may get another plumber round for his advice.
 
The Baxi Whole House Boiler Size Calculator (set DHW to zero) will tell you the total heat loss from your house, but not the room by room loss. Compare that with the total output of your rads.

Condensing boilers work more efficiently when the return water temperature is lower, i.e. below 55C, meaning a flow of 70-75C. But this has to be compensated for by larger output rads, e.g. a type P+ instead of a K1 . This is because a rad output are temperature related.
 
80f/26C is very hot!
Try dropping a bit so perhaps everywhere becomes more even, rather than one room being 80 and others at 70 and feeling 'cooler' even though 70f is usual design temperature and enough to sit in a tee-shirt!
 
There's no room stat. The plumber thinks they're unnecessary and thinks the heating is best controlled by TRVs.

Then your plumber needs to go back to college, it is a regulation requirement to install a room thermostat to help stop interlock and the boiler from cycling, and you do not have a TRV in the same room as the room stat. As Chuck says you need a new plumber who knows how to do things properly.
 
Your Baxi Duo-Tec 28 will do job easily. You need time and temperature control to provide ‘interlock’. This is achieved through having a programmer/room stat installed. This should have been done at time of installation in accordance with part L of the building regulations (conservation of fuel and power).
If rads have been properly balanced and all air vented out of the system then rads should be the same temperature. If TRV’s are closing down while testing, open the windows or remove TRV heads.
If you’re still cold then either you need more loft insulation or your radiators have been sized incorrectly.
BTW you shouldn’t need a flow temperature of 80! I set all my boilers to 73 in winter and 65 in spring and autumn.

Dan :)
 
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