Planning heating/Plumbing from scratch..

[thompo]

Hi guys,

Having finally had our sub floors laid we are in a position to start thinking about plumbing. Currently the only pipe work we have is a 15mm copper main through the kitchen wall (giving approx 22l/m), flow and return going to 1 rad in conservatory, pipe work for backboiler and all original pipework in the loft conversion and the old toilet soil pipes

Ive rang quite a few local plumbers but many are too busy (1-3month waits!), dont want a full house to do or dont know anything about thermal store systems .

So im thinking of having a go myself and get someone to make connections where required and commission everything when done (found a guy busy with new builds for next few months but willing to call in to keep me right and test everything)

Its a bungalow with 2 rooms upstairs,
Water draws - me + other half, no kids for while
1 bath, 1 shower,1 hand basin,1 toilet, kitchen sink, wash machine.

Heating -
UFH throughout groundfloor, 6/7 zones
1 Rad in Conservatory
1 Rad in Utility room
1 Towel rail in bathroom
2 Rads upstairs

Heat sources -
Old oil boiler - will be changed for modern condensing down the line
Would like to utilise back boiler to make a contribution to CH when fire/stove is going
Add solar panel down the line

Given the above desires im looking at a system based around a thermal store to give flexibility and mains pressure DHW.

Planning on using Polypipe 22mm "pipe in pipe" under the insulation so there are no joins under the floor and problems should be easily rectified. Then use distribution manifolds to connect 15/22mm to outlets.

As for the existing copper id like to solder extensions and run them back to a manifold or striaght into the heating circuit if sensible.

Thermal store will be beside the bathoom with the shower being the shortest pipe run and kitchen being the farthest for DHW. Boiler will be about 1m from thermal store but in an exisitng outdoor boiler house. Im hoping by keeping the pipe runs short it should minimise losses and give good response.

So my basic plan of attack is:

Figure out what our main supply pipe is from the water meter, if MDPE trace exisiting copper and replace with MDPE, if not replace the whole thing and have it checked for compliance before filling in and connected by someone qualified.

Run 22mm for the hot/cold water to sensibly located manifolds in kitchen and bathroom
Figure out rad/back boiler circuit
Fit UFH Manifold
fit Insulation and UFH pipework
Fit Thermal store and check it all works before pouring the screed.

Does this sounds right?

Untitled

• thompo
• 12 Feb 2013
• 4

 

[thompo]

Jay'sus That was a long post, if you cant be botherd reading it all, skip to last few lines lol

Apologies

 

[virgilns]

Is the bungalow a new build? the reason i ask is that I've been advised to steer clear of UFH for my place due to thermal loss (an old 100yr old solid brick build)...water UFH just won't be man enough as a primary heating source. great for well insulated new builds, but not for me.

I'd be interested to hear your thoguhts on solar though...have you costed it?...been looking myself with eh the idea of fitting a dual circuit unvented cylinder but starting to doubt the cost savings...depends on how long you plan to stay in the home of course, but i wonder if the money I spend on the panels/system would be better spent on insulation. Just as green if I cut the gas I use by half by keeping the heat in rather than generating it cheaply but letting it al out the roof! Still undecided though...if I spend 3 grand today and save £300/yr it'll take me 7.5yrs to get my money back (assuming fuel costs rise 10% yr on yr)

Can you explain your pipe in pipe under insulation plan?...presume just for the runs to rads and underfloor loops? as by putting the pipe in a pipe for the UFH you'll be insulating the floor form the loop defeating the object....

For me, zones are the way I'm thinking...the more the better (within reason) 5 beds an ensuite and up to 3 baths over two floors plus the downstairs living gives a lot of combinations I'd like to be able to turn on/off automatically or at a moment's notice. do-able but not automatable by TRVs...

There's a lot to think about with heating these days!

 

[thompo]

Thanks for the reply and some good questions,

Bungalow is an old 1930's solid brick building (60m²) with a more modern cavity walled extension (40m²). We are fitting 100mm insualtion to the floors and 75mm interally to all external walls and fitting as much as feasible in the roofspace conversion, using 75-100mm kingspan board where we cant get decent depth of wool due to the conversion. All walls - floor junctions will have 25mm upstand insualtion to prevent bridging.

Going on the vastly upgraded insulation (currently 50mm wool in some parts of the loft only!), most people we have spoke to reckon it should be fine with underfloor provided ALL insualtion is done. Some have suggested we go with tighter UFH pipe spacings to ensure it will work at the expense of pipe/pumping but if not required we can offset the excessive pipe by running a lower flow temperature..

Solar tbh is just something im considering down the line, prefer to spec the option now and not use it rather than have to replace the tank later if it becomes more affordable / i find a cheap used panel. Friend has it on his new house and reckons for his family wife and 3 kids, his panels provide all his DHW between April and October he is ideally situated for solar so he gets maximum gains.

Pipe in pipe is purely for water/rad circuits, UFH will be 16mm Pex-Al-Pex ontop of the insualtion and covered in 50mm "ThermaFlo" screed.
Interestingly i came across a company that offer UFH using an insulated pipe in pipe design to allow radiator flow temps in the UFH circuit but not over heat the floor. Means you pump less water because it hotter (smaller bore pipes) and removes the need for blending valve and extra pump if mixing rads and UFH.
google Rotex system 70

We have approx 100m² on the ground floor, 80m² that can be used as heat surface planning 6-7 zones to fill this + rads on a seperate zone to give maximum control.

Thankfully were mostly on 1 floor with only 2 rads upstairs, that probably will we switched off most of the time (main bedroom is on ground floor).

Cheers Neil

 

[thompo]

Was thinking last night

Given that a thermal store is more or less a heat bank for the boiler and other heat sources. With a heat exchanger to give DHW,

Is it possible to plumb a plate heat exchanger to the boiler flow and return directly to make what is essentially a DIY combi?

Probably a hugely inefficient use of the boiler but would it be ok for a few months? Would allow us put off the 1.5k for the tank till over the summer and use money now on better/more thorough insulation and get us in a few months early and save on rent.

Do you think this would pose any significant issues down the line when fitting a proper Thermal store?

This is my thinking

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• thompo
• 6 Feb 2013
• 1

 

[SimonH2]

Is it possible to plumb a plate heat exchanger to the boiler flow and return directly to make what is essentially a DIY combi?

Probably a hugely inefficient use of the boiler ...

Don't see why not, it's more or less all a combi is anyway. It'll be no less efficient - or only a little if you have the boiler flow temp set at a reasonable value.

 

[RWhites]

I can't comment on your PHE idea, but just thought I'd chip in... I've recently fitted a thermal store married with a condensing gas boiler, piped for a solid fuel stove gravity input (not yet activated), and with a solar thermal input coil for when I get around to fitting a panel (hopefully this year!).

I've also fitted the Honeywell Evohome system as the primary heating controller, with 8 zones controlled by the HR80 radiator valves.

Our previous hot water system was a gravity heated, gravity fed system that produced not much more than a dribble at the tap (not much head). Now, despite a relatively low mains water flow rate, our hot water is awesome (by comparison anyway).

It was expensive, but overall I'm absolutely delighted with it.

I can't wait to get around to fitting the solar thermal. I've been looking at the www.solarproject.co.uk website. Do you have any you've seen at reasonable prices?

 

[SimonH2]

There's also Navitron and they have an active forum. However, should you venture onto the forum, beware that it's inhabited by some "interesting" types, including some of the admins. I'm banned from there for (to paraphrase) questioning those who have an unshakable belief that all we need is more windmills, and smart metering will mean that we'll just adjust our usage to suit

I put a thread on there about the thermal store install in my flat.

 

[Norcon]

Rotex system 70

They state its more for larger open space commercial situations.

I'd expect it to be more difficult to lay and a real pain in a domestic property.
Also its bound to slow down the response time between the water flow temperature in the internal pipe and the finished screed temperature.
That maybe doesn't matter if the flow temp is constant but many are compensated and you want the fastest response available.

I'd also expect it to be nearly double the price of most normal pex pipe manufacturers.

Compensated flow temp and a gypsum based flow screed are a good partnership for ufh combined with single wall pipe imo.

Haldane and Fisher in Newry beside you supply the Rehau system.
Probably one of the best out there and well tried and tested in the commercial field.
Then you have AJ Plumbing who supply the mlcp system.

Rotex wrote

The design feed temperature in System 70 Industry is max. 70 °C, whilst in conventional underfloor heating systems the upper limit is mostly at approx. 50 °C.

You would also have to question the wisdom of a 70c flow temp when just about everyone agrees that lower tempertures promote higher efficiencies in modern condensing boilers.
And also less heat loss on pipe runs outside the heated area with lower temperatures.

Thats particulary important where some boilers are situated 10m and more from the property and ground buried f&r is used.

 

[thompo]

Thanks for repiles and useful info

Im only 2 mins from AJ plumbing (Ballynahinch) so they are likely to be my supplier provided they are competitive on the UFH, coming in good with all the main pipe work, fittings and cylinder etc so far.

Couldnt see the benefit of the System 70 myself apart from its easer/cheaper to tie into existing rads, definately be sticking with normal pipe, (pex-al-pex or pert-al-pert) to keep the low flow temps etc.

Sent drawings for quote on the Rehau kit but on response yet, will see how it goes.

Navitron looks like a good source source for info, lots of good ideas floating about, some just arent practical or cost effective for my situation. Will check out your thermal store thread

Cheers

 

[Agile]

Was thinking last night

Is it possible to plumb a plate heat exchanger to the boiler flow and return directly to make what is essentially a DIY combi?

This is my thinking

Untitled

• thompo
• 6 Feb 2013
• 1

As there would be no effective temperature control to the DHW a temperature controlled mixer would need to be used.

But those systems can bew prone to lime scaling in hard water areas.

Tony

 

[thompo]

Cheers Tony,

We are quite lucky in that we are in a soft water area so not expecting too much trouble

Had a plumber out last night to spec up a thermal store and he reckons its not going to be practical for what i want to do. He reckoned a 300l tank would be required which is close to 6'x2' which i will struggle to fit with associated pipework in the area i would like it to go.

Stove/ fire is too far away (15m) from the tank and were going to struggle to get the height difference for gravity circulation to work and the required pipe work is likely to cause backflow of heat from the tank to the stove without careful use of valves.

He suggested an unvented cylinder with oil and solar, use a room heat only stove with ducts to distribute warmed air throughout the other rooms, or just open doors etc.
He thought thermal store is great where you have a constant low level heat source such as heat pump or good solar array. keeping it warm but when using heat and DHW at maybe say 6-8am and 6-9pm its not as efficient as unvented.