Restricted flow across boiler

[mikepmk]

Boiler: Worcester Bosch Greenstar 24RI - installed summer 2006 !
Heatstore: Boilermate II

Symptoms were boilermate not staying up to temperature when C/H on, escalating to boiler only staying on for a minute or so at a time, then boiler only came on for 5 secs = no H/W or C/H .

Have contract with BG - blamed Boilermate being scaled , walked away. Also brought in WB & the guys who installed the boiler, both of whom said probably scaled up Boilermate. Went as far as agreeing with a company to replace Boilermate with Megaflo.

In the nick of time, finally found someone who understood Boilermates and he quickly diagnosed restricted flow in Heat Exchanger caused by crud in system.
Flushed thru the boiler and it all worked.

BUT: How do we stop this happening again?
Will a Powerflush remove all crud from whole system?
Are there other types of flushes that would be better?
What will stop crud re-appearing?
Is there a fundamental design flaw that means the type of heat store and the way the water routes round the system will always mean some crud exists and the narrow pipes of the boiler are therefore likely to block?

 

[Agile]

I dont think that you have correctly explained what was done to cure the problem! I expect it was the secondary heat exchanger on the store.

Many people dont seem to understand stores and their problems!

Lime scale is deposited when the temperature of the water is above 65°C. Most stores are run close to the manufacturers recommendation of 80°C although if this is done the efficiency of a condensing boiler is much lower. At 80°C scaling is inevitable.

Although the capacity of the store and the radiator temperature will be reduced, my recomendation is to run the store at about 70°C as this will greatly reduce scaling on the DHW side.

In addition time the store to heat earlier than the CH is required by say 20 minutes if you dont already have it on 24/7

Many parts of Buckinghamshire do have pretty hard water and a scale reducer is advisable on the mains water supply. I would only recommend a polyphosphate ( combimate ) or a permanent magnet type. Others have different views and manufacturer's claims are not usually achieved!

In my opinion the scaling is inherent in the recommended operating conditions but by careful consideration of how its operated this can be minimised. There is a lot of controversy particularly from arm chair experts!

Its also essential in my view that the water in the store is strongly dosed with 1% inhibitor. Not just a single 1 litre bottle!

Tony

 

[mikepmk]

The flushing was done by connecting the machine to the pipes leading to & from the boiler. The Boilermate heat store wasn't affected.

 

[gas4you]

After system has been correctly flushed you could have a boiler buddy similar fitted to remove any c*** in system that may occur.