Biasi boiler pressure

[logo5961]

Looking for some advice. This is the 1st winter we have had in this house. It is heated by a Biasi M90F 28S feeding 7 rads over 3 floors. The last 4 digits on the boiler are 1103 which i understand means built in 2003, but the rads in the system look older making me think they were not installed with this boiler. The rad valves are not TRV's. All the rads get nice and hot. what is concerning me is the boiler pressure. The cold pressure shows 1 BAR when the system is running this pressure climbs to 2.3 BAR (the boiler at our previous house did not get anywhere near this high). The boiler does not fly up to this pressure but rises steadily and does not drop rapidly when the stat switches the boiler off. also there is no kettling.

Is 2.3 BAR a normal pressure for this boiler or is it too high?. If it is too high what could be the cause and is there any way too get it to where it should be

We have no history of this systems water treatment although having cracked open a couple of rads the water looks pretty clear.

Thanks in advance

 

[charri421]

Sorry i can't answer your Q, but can say my Biasi combi (2005 Garda HE on a new 7 rad system) sits a 1bar cold, upto 1.4 if running very hot.

It would suggest you may have any issue - sorry I can't be more helpful..

 

[ACOperson]

1 bar cold pressure is OK.

When water is heated it expands and in a sealed system this means that the pressure rises.

2.3 bar is quite high but not presently a real problem, the expansion vessel is probably undercharged.

Do a search on this forum for expansion vessels and you can decide if you want to have a go at charging yours yourself

 

[Agile]

Either the expansion vessel is damaged ( unusual ) or it needs recharging.

See the FAQ for instructions on recharging.

A common problem on your model is that the installer does not set the boiler output power to match the CH requirement.

You can see how to do it in the book but if its not kettling then it may already be set OK.

Tony

 

[logo5961]

Thanks for the quick replies. I will check and if needed recharge the expansion vessel this weekend and see if that solves the problem. Also will give it a dose of system restorer and then some fresh inhibitor to see if that helps any

 

[Agile]

Just solve the one problem with the EV.

Its not necessary to add anything. If you must add inhibitor then you have to use the same make!

Tony

 

[logo5961]

ok thanks Tony, just downloaded the manual off Biasi's website to get EV info

 

[Agile]

No ! You have to get the instructions on repressurising the EV from the FAQ section on this web site.

Tony

 

[logo5961]

Thanks again Tony i have read the instructions in the FAQ just wanted to make sure i got the pressure right

ps the Biasi manual has a fairly good explanation on how to repressurise the EV

 

[Agile]

You may think so but if you followed them as written you could end up not doing it properly. It does not actually tell you how to repressurise it!!!

I recommend 0.9 Bar in the EV ( as measured with the system open! ) and 1.5 bar cold in the system.

Tony

 

[logo5961]

Tony, diagnosis spot on. EV showing virtually nothing on foot pump pressure gauge but no water came out of the EV valve when pressed so diaphragm appears ok. Followed FAQ instructions and your suggested settings on recharge left it an hour to make sure no pressure drop. Refilled system as you suggested (0.5 BAR more pressure than it was set before). Boiler now running 2 BAR top pressure (so system pressure now rises only 0.5 BAR instead of the 1.3 BAR it did before) and the whole system seems a lot quieter.

Once again many thanks for all the assistance

 

[Agile]

Its still slightly more temp rise than expected ( 0.3-0.4 ) although that depends on the water content of your rads.

You probably did not properly check for water on the air side. That has to be checked with the system pressurised !!!! You let ALL the air out whilst at least 0.5 Bar pressure in the system.

If no water coming out then repressurise with the system open to the atmosphere ALL THE TIME while you are pressurising it.

Tony

 

[logo5961]

Thanks again Tony i think i may have depressuried before i checked the valve for water. I isolated the boiler via the flow and return on the boiler stop taps but kept the primary circuit drain cock open while i repressurised and for the hour i left it standing to see it the pressure dropped to make sure i did not just pressurise a sealed boiler. More water did come out of the drain cock when i recharged the EV The house is a victorian house with ceilings about 10 ft from the floor. I wonder if the precharge needs to be a bit higher, it says in the manual the stated precharge is based on the maximum height differrence between the PRV and the highest point in the system being 7 metres. The boiler is in the kitchen and the highest point is the rad in the converted loft bedroom. It must be close to if not more than 7 metres height difference. Would this cause the slightly higher pressure rise. Either way i will redo the recharge in the morning on a cold system

Many thanks again

 

[logo5961]

Released air in EV while still pressurised. definately no water air side of EV. Recharged EV and repressurised system bled rads. Boiler pressure reading same as yesterday, but far better than originally. I will give it a couple of weeks and if still running ok get the boiler serviced to make sure output matches CH requirements. Thanks again Tony for all your help and advice