is a sealed system better for central heating?

[Brooster]

Sorry - householder here, but I've spent a day on the internet trying to answer this question for myself without any luck, so if any of you are able to give any pointers I would be one happy lady!


We are undergoing a major refurb including underfloor heating in a new extension, new boiler etc.

We currently have conventional gas boiler with a gravity-fed system, with a
shower-pump for the showers. Current hot water works okay for us, central
heating not warm enough - but I think that's a combination of sludgy rads, too
small rads, old inefficient boiler and complete lack of insulation (all to be
addressed as part of refurb).



However, builder is now saying we need to swap to pressurised system (involving expensive megaflow, new 25mm mains water feed, and a whole bunch of new pipework/re-routing all totalling up to £10k of extra work without the cost of new boiler and rads etc) otherwise our central heating will never be satisfactory and won't cope with the U/F heating etc.


As a heating ignoramus, I'm confused - I understand the benefits of a megaflow/pressurised system for the hot water but will a sealed system really
make a difference to the central heating??? Can't find anything on-line that suggests this. Loft space etc not an issue. All tips/opinions gratefully received - thanks

 

[Gray0689]

My best advice to you is get a plumber in to look at the work you may need or may not as a builder is not really in a position to tell you what you need
If you post up your location a member may be able to help you out

 

[Gray0689]

A sealed heating system is better as water heats better under pressure

 

[Howsie]

Cost doesn't sound right to me based on what you've said but there could me more to it. I'd get another quote from a plumber if I were you. I've known a couple of builders try to add profit to a job by suggesting additional work once the bulk was under way.

 

[kay-jay]

Get an independent heating engineer out to assess your system.
From your description it sounds as if you just need a powerflush and a couple of larger rads to get your heating jumping again.

 

[kay-jay]

Also a decent plumber can convert your existing heating system to a sealed system and it shouldn't cost much more than a couple of hundred depending on your location but only if it is permitted in the boiler manufacturer instructions

 

[Brooster]

Thanks for all the advice from everyone - really helpful.

We still have the original old lead smallish bore mains pipe so think there is prob not sufficient pressure currently to just convert (if I've understood sealed systems correctly) - so I think a big part of the cost is replacing the mains feed (and paying Thames Water their cut too I expect). But the builder has quoted what seems like a hefty fee (£4250 excl) for disconnecting the existing hot water cylinder and tanks and re-routing for new system. I'm not sure how much work this involves to know if this sounds way too much??

Time to call an independent plumber/heating engineer methinks...

 

[mikegas]

Post some details here [DLMURL="http://www.ukplumbersforums.co.uk/im-looking-plumber-gas-engineer/"]I'm looking for a Plumber or Gas Engineer[/DLMURL]

 

[Griffo]

In brief the advantages of sealed sytems are space saving as you mentioned and they tend to stay cleaner and more efficient over time.

As long as system flushed properly at changeover the sealed system doesnt allow contact with oxygen via the air above the expansion tank or via water pumped over the expansion pipe so less air introduced into the system means less corrosion from the iron elements of the system, ie rads.

 

[Bronze_tap]

Thanks for all the advice from everyone - really helpful.

We still have the original old lead smallish bore mains pipe....
Time to call an independent plumber/heating engineer methinks...

Do REPLACE LEAD pipe. No point of slowly poisoning yourself&yours childrens! Lead has a long term ***ulative action (like mercury) :-( Quite efficient enzymes inhibitor...

But go for GOOD INDEPENDENT bloke(s). Cut out the middle man.

Since your's system is gravity CH -> I expect most of the pipework to be of a GOOD SIZE, so it just needs flushing, and a few bigger rads. No need of pipe replacement. Also make sure rads are under the windows and not to high above the ground. Depending on the condition of your's boiler, it may or may not needs replacing (or just a good cleanup/configuration).
I would certainly keep the indirect HW, cylinder, if you are happy with it. Combis usually are less reliable/convenient if someone is taking shower and washing dishes at the same time..

Also read this for some system cleanup tips: http://www.ukplumbersforums.co.uk/c...olution-how-do-proper-cheap-job-yourself.html


As for sealed/open system - if well dozed with good inhibitor there is not very much difference in corrosion rate + a spoon of engine oil on the CH expansion tank water surface (to seal off oxygen)... Also it is easier to maintain, so I would leave thing open + Fernox inhibitor.
PS: Also some independent sole traders like if someone gives them a hand during radiator handling/trench digging, so it may help with the pricing.