Replacing House Central Heating System

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Bailes1992
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Replacing House Central Heating System

Post by Bailes1992 » Mon Oct 19, 2015 2:34 pm

So this last few weeks has just reminded me how totally useless my central heating system is.
The system is piped up to the landing in 22mm and then a small manifold where all the central heating pipes come back to in 8mm microbore. The flow is rubbish, the whole system is loud and due to the way the pipes have been shoved in under the joists it makes a horrific banging meaning we can't leave the central heating on for long periods of time because it gets bloody noisy.
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It's a massive shame because I have a 9 month old 32kw Viesmann boiler and I just don't feel like we are getting the most from it. The boiler certainly can't be condensing properly as the flow is so poor.

So come spring next year I'm going to have to drain the system, rip it out and put all new in.
I'm also going to look into re-insulating my attic and try and find out how well my current cavity is insulated, if at all.
I'm hoping to reuse the majority of the radiators, especially in the bedrooms. I'm hoping I will only have to buy 3 new radiators.

I have a fairly large kitchen (with a non insulated roof I have to sort out), however it has one piddly radiator in it.
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I would like all the pipes hidden so will probably move the current radiator to under the TV as that's a stud wall, may consider replacing it with a bigger rad. I'm also hoping to go back to back with another radiator in the living room to minimise pipework. I think a radiator by the door wouldn't go amiss either. Was thinking of one of those tall but skinny units you can get.

In my living room I have two radiators, both 1200 x 600 singles. I want to keep one of the radiators in front of the window where it is now but fit a far larger double rad. Can I bury heating pipes in concrete? How would I go about insulating the pipes before fitting? Bare in mind I want to minimise the depth of the chases.

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I need to sit down, calculate my houses heat losses and work out exactly how much heat I need for each room, however I would rather go far too big than have too little. I need to see how the current rads stack up and see what needs to be replaced. With any luck I'm hoping to just purchase a tall radiator for the kitchen, a new chrome rad for the bathroom and a large double rad for the living room.
Pipework I was planning on running two 22mm heating pipes from the front to the back of the house and then pipe in 15mm down to each radiator. That should improve flow significantly.

TRV's or 'Zoning'?
A) Now I would like to have zones with separate stats. What I actually want is one controller that I can set the temperature on and 2 or 3 stats in the house that can just turn on the required area. Is there a system that would allow me to do this?
B) My other option would be to have an old fashioned controller to do the On/Off of the heating but then have 3 standard thermostats, one for the kitchen, living room and the entire upstairs. Just use 3 temperature two port valves to control where the heat goes. Is this too complicated for a house? Is this the engineer in me going nuts? :lol:
C) Have 1 stat in the coldest part of the house and have TRV's everywhere else. Basic but more expensive than option B.

Anyone plumbed their house themselves? I'm quite happy installing pipe and will even test it up to 1bar with my compressor before I fill it up with water. :roll:
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Re: Replacing House Central Heating System

Post by steve_earwig » Mon Oct 19, 2015 3:34 pm

No, I've never re-plumbed an entire house but I've changed stuff, moved radiators, re-plumbed a couple of bathrooms, that sort of thing. I quite enjoy plumbing :supafrisk:

I think calculating what you actually need for each room and adding a little is the way to go.

A few things I have learned (in no particular order):
Never reuse a fitting (even if you've run out of new ones and want to finish, it's false economy)
End feeds are fine, providing you can get all the way around them (I've used solder ring but I never trust the amount of solder in them so end up adding some anyway). You may have to make metal shields to protect your woodwork and/or bounce flames to the bit you can't reach.
Flux is your friend.
Don't forget drain cocks!
For long runs or more than one radiator it really needs more than 13mm, there's probably a rule for that somewhere.

I wouldn't put anything in concrete, the Croats are fond of doing that but it all ends in tears when the inevitable happens.
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Re: Replacing House Central Heating System

Post by lozz » Mon Oct 19, 2015 3:39 pm

Just take all the micrabore out and replace with plastic..
The plastic pushfits are really simple to work with.

Have a look on the plumbers forum ..you will pick up some good info on there.
As for materials ..avoid the likes of b and q ..wickes etc you will be fleeced..
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Re: Replacing House Central Heating System

Post by Welly » Mon Oct 19, 2015 4:05 pm

You can bury 15mm copper into the blockwork of a wall and plaster over them, it's just more work, difficult to insulate without it affecting the plasterwork (cracking/shrinkage) but would benefit from the copper tube being wrapped in PVC gaffer tape before the wet finishes are applied. Nice thing about digging the pipes into the blockwork is you can have them emerge right where the rad valves are for a neat finish.

Controls-wise I find the following most effective for me:

Enable the heating to run all day from 07:00am to 10:00pm but under the control of a programmable digital room stat; these have 7-day programmes and you can pick 4 different temperatures you'd like at any time of each day. Fit TRV's on all rads except the Bathroom and you should have a nice tweakable system. I have the house ticking over at 19deg all day and then it ramps up to 21deg before we all get home. I like a warm house cos I'm a puff. Similarly on Sat/Sun mornings you don't want the heating to come on too early so I have it on a delayed start via the stat.

Your Kitchen extension would benefit from the plasterboard ceiling being removed and two layers of Celotex Board cut to fit inbetween the joists but not touching the underside of the roofing ply (an air gap there is preferable) and even better a vapour control layer on the warm side of the insulation (poly sheeting) stapled to the joists. Some flat roofs will form condensation on the undersides when there's a layer of snow on top etc. and obvs when cooking the 'wet' air can condense in the void above the ceiling. You can approach Celotex's technical people to do a 'condensation risk' for you free of charge and they will give you a detail of how it should be done.

Of course a heating system works in conjunction with the home insulation so loft insulation, cavity wall and double-glazing all go hand in hand.
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Re: Replacing House Central Heating System

Post by Bailes1992 » Mon Oct 19, 2015 4:18 pm

Cheers guys, looks like one stat in the kitchen and TRV's it is. Will be the easier install as it's only one flow and return rather than having to run 3 flows and 1 return through the house.
Is there any reason I can't fit a TRV in the bathroom?

I'll probably get most of the gear from screwfix. I have a trade account with them but I'm a qualified electrician so have no issues getting trade accounts with local merchants.

My preferable method of filling is chases is filling the chase in 99% with a dryish cement mix and then a very thin skim of filler.
If I move the radiator in the kitchen and one in the livingroom so they are back to back on the stud wall then I will only have to chase two radiators.

I'll ensure that the pipe in the wall is one piece with no joints, just a 90° at the bottom that should be easily accessible should I ever get any issues. I would love to use a proper pipe insulation over the pipes but the chase would have to be deeper than I think I would be happier with. Maybe I'll cover the pipes in electrical tape and fill the chase with expending foam, cut the foam back and then fill over it with cement and a final skim of filler.

I'm definatley going to have to pull the kitchen ceiling down and get some insulation up there. I'm convinced there's nothing in there at all at the moment.
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Re: Replacing House Central Heating System

Post by lozz » Mon Oct 19, 2015 4:26 pm

It might sound daft but do you live in a hard water area..
If so have it flushed.

It might solve the problem.

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Re: Replacing House Central Heating System

Post by Welly » Mon Oct 19, 2015 4:32 pm

Try not to put the stat in the Kitchen, when you cook it will turn off the Heating elsewhere/upstairs.

Stats need to be in a coolish area not overly populated and away from other heat sources. Seeing as you don't seem to have a Hallway I would go for that bit of wall under the 'open' staircase in the lounge and fit a TRV on the Kitchen rad.
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Re: Replacing House Central Heating System

Post by benczuk » Mon Oct 19, 2015 4:55 pm

Or get a wireless one you can move about till you find the optimum spot
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Re: Replacing House Central Heating System

Post by Bailes1992 » Tue Oct 20, 2015 10:14 am

We have a Viesmann wireless stat/timer unit at the moment. I'll probably try fit it on the wall between the living room and the kitchen.
Would love separate stats but it's a stupid idea in a 2 up 2 down. :lol:
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Re: Replacing House Central Heating System

Post by steve_earwig » Tue Oct 20, 2015 6:38 pm

You could get 4 and cover the whole house!

Which reminds me, I really need to get my old boiler serviced :shock:
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Re: Replacing House Central Heating System

Post by GingerMagic » Tue Oct 20, 2015 10:39 pm

I like your house Sam, although you need to find a good electrician to tidy up the wiring to the telly....

I have microbore in my house ( 3 bed Victorian semi ) and although it wouldn't be my first choice of pipe work it seems to do the job okay - certainly not bad enough to warrant ripping it out to replace with 15mm.

I hear through the builders grapevine that plastic pipes and speed fit may not be the future after all, some people are replacing it with copper - maybe do some Gooogling?
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Re: Replacing House Central Heating System

Post by dummysock » Wed Oct 21, 2015 9:00 am

Hi

Cement and plaster are corrosive and so any pipework has to be wrapped in corrosion resistant material.

Plastic or copper pushfit fittings all have a rubber sealing washers.. They may be guaranteed for 10 years, but rubber when it gets hot and cold dries out and perishes and then leaks. So if you only want it to last for the duration of the guarantee OK, but copper soldered joints last forever.

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Re: Replacing House Central Heating System

Post by benczuk » Wed Oct 21, 2015 9:11 am

+1 for not using plastic. We had them fitted in the bathroom of my sisters house when she was at uni and they succeeded in drenching the kitchen ceiling twice in 3 years
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Re: Replacing House Central Heating System

Post by Doggy » Wed Oct 21, 2015 1:00 pm

Soldered copper, (with extra solder on the integral solder fittings), is the only guaranteed long-term solution.

Avoid micro bore if possible.
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Re: Replacing House Central Heating System

Post by teamster1975 » Thu Oct 22, 2015 10:11 am

Bailes1992 wrote:Is there any reason I can't fit a TRV in the bathroom?
There has to be a flow through the pump, otherwise you get a lovely water hammer sound should all the TRVs close!
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