8xRadiator and microbore replacement

[alexrowstock]

Hi,

We've just moved house and the heating system is made up of 8 rads without convector "fins" on them plus a fair amount of microbore pipe (although there is a 22mm spine down the centre of both floors of the house and some 15mm spurs). I want to change all the rads for modern convector ones plus get rid of all the microbore (the guy who's going to fit the new boiler said this was a sensible pre-requisite before putting the new boiler in).

The questions I'd really like some help with (so far!) are:

* If I drain the system, can I leave it drained for long-ish periods of time without affecting the parts of the heating system that will remain?

I think the answer is "yes" - I'm intending to change all the rads and powerflush the system before refilling, so I think the worst that can happen is that the old rads will get rusty shortly before they go off to radiator heaven Be keen to hear from you if I've missed something and am being dumb.

* Am I OK to continue to use the hotwater from the combi-bolier while the C/H system is drained?

This one I'm less clear on - I'm hoping that the two circuits (domestic H/W and C/H) are sufficiently isolated inside the boiler that I *can* do it. Again, sage advice in advance to stop me doing something stupid would be *much* appreciated. It's an old-ish Worcester Bosch 35 CDI (non-condensing).

* I've inherited a second hand towel rail from a friend who's recently upgraded his b'room from posh to really posh. There's a small amount of rusty deposit around the connectors. Fine to plumb in if the system is going to be powerflushed and filled with decent inhibitor, or steer clear and buy a new one?

Really not sure on this one, so voices of experience welcomed...


Also - keen to hear from anyone who's tried this type of thing before. I think it's a pretty straight forward job - drill the joists in the right place, plastic pipe & push fit connectors and check the system with an air pressure tester before refilling - but any helpful/cautionary tales welcome.

Thanks folks

 

[muggles]

First question - yes, you can leave it drained for as long as you need to

Second question - the short answer is no, it won't work. In some boilers you can get away with linking the flow and return pipework to create a loop with no rads on, then filling that, the main issue with doing this is how to make sure you've got the air out of the pipework in the boiler, and I can't remember off-hand whether there's an auto air vent on your WB anywhere (and even if there is it might not work...). Best to avoid doing it if you can really.

Third question - Depends really on how old it is and how well the previous system it was on was looked after. Some new towel rails have rust deposits in them where they've been pressure tested, so it's not necessarily a bad thing. If you're worried about it, get your installer to pressure test it.


Advice - take your time with plastic, use good stuff not cheap stuff, and pressure test it well, failure rates tend to be higher with plastic than copper. If you scratch the pipe as you're pulling it through, it'll leak in the fitting. If you don't cut it dead square it may also leak. Cut it with the proper tool, not a hacksaw.

Pressure testing with air is a controversial topic, as air is elastic and can be compressed, a fitting blowing off can be quite dangerous if you're standing in front of it, as it'll go off like a giant air rifle. Water is much safer but of course will get your house wet if you get a leak, so there's pros and cons to both.


Just out of interest, why are you having the boiler changed? Has it broken down beyond economical repair, or did you just fancy a new one? What's it being replaced with?

 

[mysteryman]

You can close the central heating isolation valves on the boiler and drain the radiator circuits, and get hot water as normal. Just make sure the central heating stays off!

Plastic is OK when fitted properly.

 

[alexrowstock]

Thanks for your replies - both really helpful

Boiler replacement is partly because it's ~15 years old and has already needed a new PRV since we've been here, but also because I want to replace the combi with a heat only boiler, hot water tank & thermal solar/log burner system. I did *briefly* investigate the new modulating combi-boliers that are used in conjunction with a hot water tank, and as yet a bit undecided...any thoughts on that one?

Many thanks again both.

 

[muggles]

If you want to do all that I hope you have very deep pockets! Not quite sure what you mean about the "new modulating combi-boilers in conjunction with a hot water tank". All modern boilers modulate, and have done for some years so it's hardly new. Maybe you're talking about storage combi boilers that have a small hot water store within them????