Can running hot water tap when mains water is turned off (and subsequently drained) damage boiler?

[Mmcgar]

Hi all

I'm not sure if the title makes sense but basically today I was getting some work done. The plumber isolated my mains and drained the system down by opening multiple taps however I noticed afterwards that one of the taps opened up was a hot water tap.

My concern is the combi boiler will have kicked in to heat this water but as the mains was isolated the flow would have decreased until there was no water for the boiler to heat I'm not sure if this is an issue or not but I'd guess it works by a heat exchanger that is intended to have a constant flow of water over it I'm not sure of the ramifications of removing the water when the heat exchanger is operating. The boiler seems to be working ok in regards to producing hot water and heating rads however I did note that there was a distinct squealing noise from it when I used it

Also, on a side note, can anyone explain to me how the boiler knows to start producing hot water Is it a flow meter inside it that detects hot water tap is open and then directs the boiler to start heating it?

 

[45yearsagasman]

how the boiler knows to start producing hot water

What make/model boiler would that be?

 

[Mmcgar]

What make/model boiler would that be?

Hi it's a Worcester greenstar

 

[ianmcd]

you are worrying about nothing, the boiler only senses water flowing

 

[Mmcgar]

you are worrying about nothing, the boiler only senses water flowing

Hi, thanks for the reply, hopefully your right.
My concern is the boiler is behaving a bit different from normal It's entirely possible that it's been this way for a while but I have only noticed now because I'm paying attention to it.
I've been testing it out over the last hour or so and I'm not convinced the internal temperature sensor is functioning correctly

 

[ianmcd]

Thought this was coming, you have a boiler fault and looking to get it sorted FOC , shutting off the water supply to the boiler is exactly the same as closing a hot tap as far as the boiler is concerned, it will not affect anything to do with the boiler

 

[Mmcgar]

Thought this was coming, you have a boiler fault and looking to get it sorted FOC , shutting off the water supply to the boiler is exactly the same as closing a hot tap as far as the boiler is concerned, it will not affect anything to do with the boiler

Hi I'm not sure what you mean. Are you saying I have a boiler fault that I'm looking to get fixed free of charge and using the mains being shut off as an excuse for this? Apologies if I've picked you up wrong but I can assure you that's not the case, I was originally looking for a bit of reassurance from people more qualified than myself that the boiler trying to heat water that wasn't there wouldn't cause any issue. Also if you mean free of charge in regards to blaming the plumber for this again I can assure you that this isn't the case.
Since this has drawn my attention to the boiler I have noticed that the temperature sensor isn't behaving normally as I said its entirely possible it's being doing this for a while and I've not noticed it

 

[ianmcd]

what do you mean by isnt behaving normally

 

[Mmcgar]

what do you mean by isnt behaving normally

Basically it's not changing much Normally the boiler modulates on /off while its running, you can see it reaching temperature then switching off to cool down before kicking back in again, but tonight the temperature just stayed the same 75 degrees while it was on earlier with no modulation of the boiler. Since then the temperature hasn't dropped much (now at 65) when usually it drops quite quickly

 

[ianmcd]

well it is working normally now that is how it is supposed to work, a boiler modulating means that it is like a car accelerator, if you need to speed up or the boiler needs more input then the boiler increases the input, once it gets there it runs less to keep a constant temperature, a boiler going on and off is not efficient , this is called Cycling not modulating

 

[opps]

Thought this was coming, you have a boiler fault and looking to get it sorted FOC

A tad harsh...

Did the milkman of human kindness forget to call at your house this morning

 

[ianmcd]

nope just knew at the on set that the boiler had a problem