question on water pressure in combi

[wowthisistuff]

Hi
My installer told me the optimum water pressure on guage of the worcester 38cdi boiler should be 1.25. However i see worcester say it should be 1.5, i wonder why the descrepnacy? Also i note that as the water temperture goes up in the central heating system the pressure rises to 1.8. Is this ok? This also leads me to the question of at what point should the pressure reading be taken, hot or cold? Is there actually an operating range to be observed? tx.

 

[Dotty]

It'll be fine. WB make a recommendation based on lab conditions and a clean install. your guy is the man on site.
A rise of 4-6 bar as the system heats up is pretty much standard.

Have a nice evening, watch the box and don't be afraid to ask us again should you get any worries.

 

[drip-dry]

At the back of the the boiler ,there is an expansion vessel,this takes care of some of the expansion of the water as the heating system heats up,the Worcetser use a min size expansion vessel,this is why on Worcester's we lowly engineers recommend at cold setting of 1 to 1.25,it just allows a bit more tolerance in the expansion ratio,if you are topping off at 1.8 bar when the system is fully up to tem,you could increase the cold setting a little to the 1,5 bar but no need and your engineer is correct in his advise to set around 1.25bar when cold

 

[rpm]

It'll be fine. WB make a recommendation based on lab conditions and a clean install. your guy is the man on site.
A rise of 4-6 bar as the system heats up is pretty much standard.

Have a nice evening, watch the box and don't be afraid to ask us again should you get any worries.

Did you mean a rise of .4 - 6 bar?

 

[wowthisistuff]

im curious then with the desired range being below too why the red doesnt start till over 3? what is happening in the 2-3 range that is undesirable but not enough of a problem to be showing as red in the guage?

thanks for the replies.

 

[lame plumber]

It'll be fine. WB make a recommendation based on lab conditions and a clean install. your guy is the man on site.
A rise of 4-6 bar as the system heats up is pretty much standard.

Have a nice evening, watch the box and don't be afraid to ask us again should you get any worries.

and at 3.5 bar your prv will work fine, dropping the pressure to zero. Dont worry about croppie, he is commercial, doesnt understand white goods ps a rise of 1.5 bar to 2.5 is about the norm, if your standing pressure is around 1 bar. you only need a higher standing pressure cold if your house is
over two stories

 

[Dotty]

I meant 0.4-0.6 bar. smart arse......

 

[Dotty]

Did you mean a rise of .4 - 6 bar?

I did, yeah. I've consumened roughlly 0.7 bar of whisky lol....

 

[lame plumber]

I meant 0.4-0.6 bar. smart arse......

oh I thought commercial meant bigger pressures and stop checking out my rear

 

[rpm]

I did, yeah. I've consumened roughlly 0.7 bar of whisky lol....

Fair enough, didn`t want the OP to say he`s pressure gauge didn`t go that high. lol