Sealed system or open system

[tally100]

I have a boiler and thermalstore which needs replacing, 2 companies have been out to quote 1, wants to put in a sealed system with Vaillant boiler and unistor and power flush before fitting
2, wants to put in a system boiler and new vented tank so as not to have to alter pipes too much (didnt mention flushing system and said would be done in a day)
Which is best system regarding reliability and usage - 4 bed house 3 kids
neither has priced yet but want a good system


Thanks

 

[Agile]

Any properly designed system should work.

None will work if the system is not totally clean. Even if they say they will powerflush then many dont!

Has the unvented person measured the water flow rate into the property?

You cannot make a choice based on such minimal information.

Tony

 

[Softus]

None will work if the system is not totally clean. Even if they say they will powerflush then many dont!

Surely power flushing is primarily a show for the customer?

 

[tally100]

neither rgi measured the water flow,in fairness i had to change grundfos pump last year as it was screaming with iron filing and c**p in it.

 

[gas4you]

I have a boiler and thermalstore which needs replacing, 2 companies have been out to quote 1, wants to put in a sealed system with Vaillant boiler and unistor and power flush before fitting
2, wants to put in a system boiler and new vented tank so as not to have to alter pipes too much (didnt mention flushing system and said would be done in a day)
Which is best system regarding reliability and usage - 4 bed house 3 kids
neither has priced yet but want a good system


Thanks

Sealed system with the Unistor will give the best performance as long as you have good incoming mains water pressure at least 3-4 bar and ideally you will need a 22mm cold mains supply to the cold inlet on the unistor.

Although not mandatory the powerflush is a must. Normal draining of the system will clean it approx 60% powerflush done correctly will clean about 90-95%. Powerflush is needed to ensure longevity of the new boiler and the manufacturers warranty will be dependant on the cleanliness of the water in the system. If a heat exchanger fault develops (highly unlikely) the first thing a manufacturer will do on call out is test the water in your system. if found to be dirty then you have no warranty. Go with the Vaillant installer if the price is right and you feel confident with them.

 

[sm1thson]

Go with the Vaillant installer if the price is right and you feel confident with them.

Id at least get another quote first, infact another 2 as the two you have arent like for like, but as gas4you says you want someone you can be confident with (ie not just the cheapest)