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Dextrous63
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13-09-2018, 07:45 AM
11

Re: Gas Combi Boiler

Originally Posted by fender ->
Very odd......

Combi's are used all the time with microbore. The heating will only have a flow of circa 1.5 bar.

Was it an apprentice heating engineer that said that?
Even if the hot water outlet to the taps was in microbore (which would be extremely odd!!!), these pipes and joints are more than capable of taking pressures up to 9 bar at 60%. according to Hep2o's own speccs (http://www.tglynes.co.uk/downloads/t...erformance.pdf).

Maybe the engineer used this fact and ALL of the wet pipework was in 10mm and the supply to the house is over 9bar?
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13-09-2018, 11:21 AM
12

Re: Gas Combi Boiler

Originally Posted by Lindyloo ->
What a blissful summer! My gas bills are incredibly low. Now we're beginning to see a few evenings with lower temperatures. Tonight the temperature inside my home is 20 C and as I walked through the door I heard my gas boiler fire up..............which is the second or third time I've heard that. WHY? I'm not running a bath or kitchen sink - so I can't see a reason for the boiler to fire up............
Any ideas please?

We have a gas combi boiler but are able to turn off the heating switch until it is required, and just have the hot water on.
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Dextrous63
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13-09-2018, 12:31 PM
13

Re: Gas Combi Boiler

Just had a google. One suggestion, which seems to make sense is that they go through a hot water pre-heat cycle intermittently.
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fender
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13-09-2018, 06:37 PM
14

Re: Gas Combi Boiler

Originally Posted by Dextrous63 ->
Just had a google. One suggestion, which seems to make sense is that they go through a hot water pre-heat cycle intermittently.
They do. It's to stop legionella being an issue.
The pre heat cycle kills it off.
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fender
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13-09-2018, 06:40 PM
15

Re: Gas Combi Boiler

Originally Posted by Dextrous63 ->
Even if the hot water outlet to the taps was in microbore (which would be extremely odd!!!), these pipes and joints are more than capable of taking pressures up to 9 bar at 60%. according to Hep2o's own speccs (http://www.tglynes.co.uk/downloads/t...erformance.pdf).

Maybe the engineer used this fact and ALL of the wet pipework was in 10mm and the supply to the house is over 9bar?
Hot & cold would still be 15mm / 22mm as appropriate.
Even if the mains inlet is high, you'd just fit an adjustable pressure reducing valve inline. Only the heating should branch off in microbore.
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13-09-2018, 07:41 PM
16

Re: Gas Combi Boiler

Originally Posted by Dextrous63 ->
Just had a google. One suggestion, which seems to make sense is that they go through a hot water pre-heat cycle intermittently.
Only if it's turned on Dextrous. If you are running your boiler on 'Economy' that function is turned off, as Fender pointed out some posts ago.

I still believe it's because the thermostatic controller is hovering close to the activation point.....
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13-09-2018, 07:44 PM
17

Re: Gas Combi Boiler

Originally Posted by Dextrous63 ->
Just had a google. One suggestion, which seems to make sense is that they go through a hot water pre-heat cycle intermittently.
I stated that but maybe very badly in post 5.

It might be the case as some old Combis do is just to keep the Hot water in the Combi hot and fires for a few seconds so you have almost hot water out of your tap
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Dextrous63
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14-09-2018, 06:26 AM
18

Re: Gas Combi Boiler

Originally Posted by fender ->
Hot & cold would still be 15mm / 22mm as appropriate.
You'd have thought so, but who knows what might have been installed in realspeed's house I think 10mm is used in caravans and some dodgy cowboy might have thought it's be a good idea to put it in a house!!!!
Originally Posted by galty ->
I stated that but maybe very badly in post 5.
So you did, as indeed did Morty in post 2.
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Dextrous63
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14-09-2018, 06:28 AM
19

Re: Gas Combi Boiler

Originally Posted by OldGreyFox ->
Only if it's turned on Dextrous. If you are running your boiler on 'Economy' that function is turned off, as Fender pointed out some posts ago.
Wasn't aware of that, thanks.

Originally Posted by OldGreyFox ->
I still believe it's because the thermostatic controller is hovering close to the activation point.....
Entirely reasonable explanation too
Originally Posted by fender ->
Hot & cold would still be 15mm / 22mm as appropriate.
You'd have thought so, but who knows what might have been installed in realspeed's house I think 10mm is used in caravans and some dodgy cowboy might have thought it's be a good idea to put it in a house!!!!
Originally Posted by galty ->
I stated that but maybe very badly in post 5.
So you did, as indeed did Morty in post 2.

Anyway, the main thing is that it's perfectly normal and nothing to worry about!
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15-09-2018, 09:00 AM
20

Re: Gas Combi Boiler

Phew - glads that sorted - sounds like grand designs re-visited! but well done lads we have enough tradesmen to build a house here! Morticia can you erhm organize tea and sannies please?
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