sealed or open boiler for central heating

aliby21

I am having a new boiler, already know I want conventional rather than combi, and with vented hot water cylinder, but have now come up with the question of a sealed system or open for the central heating part. I'd just assumed it would be open with second tank in the loft, and my gut instinct is that I'd prefer this. I don't like the sound of having to monitor pressure, and faff around with topping up. There was a hot water tank in the loft, so space is not an issue. However plumber is heading towards a sealed system one. Any input from those who know about these things would be very much appreciated.
(it is an oil boiler, going in the garage)

Alex1983

As long as you have no heating pipes in concrete floors then I would make the system sealed.

MikeEngTech

I!!!8217;m not even goinng to read the post and say sealed. If your pipes can!!!8217;t take a sealed system then your need more pipes. If you don!!!8217;t solve it now then it!!!8217;s going to be a bigger issue down the line. The only reason for open vent is for cost and it!!!8217;s a major compromise.

MikeEngTech

I mean you need new pipes if they can!!!8217;t take sealed system pressure.

Owain_Moneysaver

Sealed.

You have a slightly greater risk of a leak on a pressurised system, but in a sealed system the water volume is limited, so the damage resulting from a leak is finite.

With a header tank, a leak could be unnoticed for a long time and cause a lot of damage somewhere hidden. Also, a header tank is more vulnerable to freezing or to a ballvalve failure and flooding in the loft about the ceiling.

MikeEngTech

exactly. I'm frequently up against British Gas for quotes and their salesmen scare the clients about sealed systems to sell them a cheap open vent job. It's scarier what damage can be going on without you knowing about it with open vent. Some plumbers don't like sealing old systems because they can't be bothered with the agro and just want a quick sale. I explain that they are under greater pressure but if you have leaks or very weak pipes then keeping it open vent isn't wise. Normally it's people who aren't planning on staying long just don't want to uncover problems but they have the interests of their wallet short term and not the property long term in their minds.

aliby21

Thanks for replies. Have to say I am still not convinced. I try and follow the KISS principle, and a sealed system seems to be adding complexity to a method for heating that has worked very well for a long time. Can't see any way in which it is that much better that would make it an obvious choice. Will try and get the plumber to convince me!

SuzieSue

aliby21 wrote: »

Thanks for replies. Have to say I am still not convinced. I try and follow the KISS principle, and a sealed system seems to be adding complexity to a method for heating that has worked very well for a long time. Can't see any way in which it is that much better that would make it an obvious choice. Will try and get the plumber to convince me!

Yes, I agree with you. I have an open vented system and don't want to change either. I was always aware about the risks of pipes freezing in my loft, but some of the other replies about other types of leaks in the loft have concerned me, although perhaps they are more relevant for older houses. My house is 20 years old and so the systems is relatively modern.

aliby21

SuzieSue wrote: »

Yes, I agree with you. I have an open vented system and don't want to change either. I was always aware about the risks of pipes freezing in my loft, but some of the other replies about other types of leaks in the loft have concerned me, although perhaps they are more relevant for older houses. My house is 20 years old and so the systems is relatively modern.

I will still have a cold water storage tank in the loft, whichever boiler system I go for, as I am sticking with vented water cylinder. It is only the smaller F&E tank that is made redundant with a sealed heating system. If I was worried about pipes freezing in the loft I could always remove the loft insulation

SuzieSue

aliby21 wrote: »

I will still have a cold water storage tank in the loft, whichever boiler system I go for, as I am sticking with vented water cylinder. It is only the smaller F&E tank that is made redundant with a sealed heating system. If I was worried about pipes freezing in the loft I could always remove the loft insulation

Oh, ok, in which case I can't see the point.

That is why I haven't added to the insulation in my loft since the house was built as I don't want it to get too cold up there and also it might cause condensation.

I am only really concerned about the pipes freezing if we have a prolonged power cut when it is very cold but we don't have overhead electricity cables so hopefully it won't happen.