Biasi 24s overheat switch tripping

[Agile]

Yes, lime scale so DS3 ( sulphamic acid ) is appropriate to treat it.

As explained above its not very soluble so several goes will be needed.

Tell us how you get on. Newgas is very interested in this!

Have you seen what temperature its tripping at? Watch the gauge until you hear the click ( or feel the pin come out ). Its actually hotter than the indicated temperature because of the position of the sensor.

When you have fixed it I will tell you how to reduce the CH power as this being mis set will have contributed to the scaling. Its often resulting from incorrect commissioning.

Tony

 

[DP]

Temperature gauge showing 70 during hot water delivery would suggest boiler is functioning correctly while hot tap is running. It would also suggest main heat exchanger and HWHE are both in reasonable condition if hot water delivery and gas rate is correct

 

[Homesafe]

If the plate heat exchanger was totally clean then the temperature on DHW would not be as high as 70° C.

Tony

someone has to be wrong here, that conflicts with the Mr. T's answer.

 

[Agile]

I have to disagree with DP here.

Perhaps he does not visit many of these boilers?

In any case no boiler than I can think of would have a primary temperature of as high as 70°C during normal DHW delivery.

Tony

 

[DP]

You want to bet?

Can proove it as well!! Can post pictures to proove the point.

 

[Homesafe]

well i never Mr . T. wrong

 

[twgas]

Agile (London) v. DP (Glasgow)
Probably a better match than D(anger)M(ouse) v. Bg

 

[kevplumb]

$1 on danny

 

[Homesafe]

$1 on danny

you have a lot of faith putting a "whole" dollar on

 

[kevplumb]

$1 on danny

you have a lot of faith putting a "whole" dollar on

alright $1.55 or £1 bet

 

[DP]

When Flowmatic was in production, went to Shuna Street (home of Vokera in Glasgow) for training. Boiler, 20/ 80 was set up for flow rate of 9.5l of water at hot tap, burner pressure being correct and HW stat at max. Temperature rise of 35 degrees C.
Were told the temperature gauge should indicate 70. It did.

Water at the cold tap during winter often is just above freezing. Have often set the hot water delivery just by observing the primary temperature.

Have used this procedure on other makes as well including Biasi 24 and 28S. (6 clients)

 

[Agile]

Have used this procedure on other makes as well including Biasi 24 and 28S. (6 clients)

Biasi 24s are popular boilers in the London area and particularly in rented property as they used to be one of the cheapest to buy.

I go to about 10 per month to repair them and feel that I am very conversant with their operating parameters.

They use a stainless plate heat exchanger which have a good thermal transfer and are used in current combi boilers.

They cannot be compared with the older designs using a copper coil in a steel pot which have lower heat transfer and need a higher temperature differential.

Tony

 

[DP]

They cannot be compared with the older designs using a copper coil in a steel pot which have lower heat transfer and need a higher temperature differential.

Tony is this your thought or based on fact?

 

[Agile]

Thats based on my observations.

It also seems to be supported by what you were told at Vokera and by your own observations in the field in respect of the 20-80.

It would also match mine as well although I dont take much interest in the exact measurements on older design boilers because its not very important for me and many are quite sludged up by now.

Tony

 

[Homesafe]

i thort we wus gonna haw a slug fest but i reconn it aint hapnin,

just fizzled out like a usless firework (spit's out mouthfull of backi spit)

correct me if i'm wrong anyone, but during DHW demand on most

modulating boiler's the boiler is on full gas rate meaning flow temp. will

be high ie 70/75 and the as temp. of required DHW is reached it modulates down or am i way off.