Heating and Plumbing Design

[Auchlossen]

Well my build has actually started and going up - see http://auchlossen.blogspot.co.uk/

tho the focus at the moment is on the garage and 'studio/office', for construction strategy reasons.

Here is my first take on heating and plumbing design, and I am looking forward to some expert critique to update the useful info on Ebuild which has guided the strategy.

The general principle is Keep It Simple.

• House is PH 96m2 single storey 2BR.
• There is also a separate studio 36m2 with autonomous electric based supplies for heating and HW, with shower/wc/basin and sink.
• There will also be PV in the garage/studio roof - 12 panels 3kW - and I am considering a Sunamp for HW for the house, so need to get my head around the economics of this.

Space Heating is by [sun sometimes!] combi gas boiler, UFH with small 50l buffer tank;

I have rejected a wood burning stove; also no thermal store for HW. [Thanks JSH]

Cooling by UFH and MVHR.

HW by mains gas combi.

I propose 10mm radial pipework from HW/CW manifolds in the Utility Room where boiler etc is based for most items, 15mm for bath. Maybe some of them will need to be co-supplied?

I am looking forward to some cutting comments, thanks in advance.

PS I found this Edraw freeware a bit of a pain to use.

 

Edited July 25, 2016 by Auchlossen
re-inserting pdlumbing diaagram

[Auchlossen]

Bump.

Given the interest over on ebuild, I am surprised none shown her as yet, but would be pleased to see comments.

I had an accidental meeting today with an advisor from Home Energy Scotland, who was doing a home visit to a friend whom I was visiting at the time. So I have arranged a review of my heating/HW plans which will be useful.

I see that I have included in schema neither the Dishwasher nor the washing machine, which will be branched off the sinks in K and U respectively, and should prob be in 15mm.

[PeterW]

Dishwasher and washing machine can both be 10mm - they work on water level not pressure so the flow is not important. 

 

Towel rail won't get warm enough if it's off the UFH mixer circuit. 

 

[VIPMan]

Used 10mm for the hot water supplies to all our taps apart from the bath where we used 15mm. We used a radial system which caused some initial consternation to our plumber but he likes the system. Longest runs were around 17m. No problems with flow rates or pressure. 

[Nickfromwales]

Sorry. I did have a moment where I thought I'd opened this post but was stuffed if I could remember what and when. 

Ebuild had a forum page where unread posts were bold, and opened ones weren't, but here the just disappear after you open them. Still getting used to this forum. . 

Catch this up tomw . 

[TerryE]

You need to do your overall heat calcs and determine the net heating load (that is allowing for occupants and electricity usage ending up as waste heat)  in the winter to sustain your house temperature.  This will probably be around a kW or 2.  You can reckon on 7W/Km² heating from the UFH so if your floor is much more than 3° warmer than your target heating requirement, then you are going to have problems regulating your heating.  JSH's approach was to add a mix-in circuit to the UFH manifold so that the water circulating in the slab was no more than a set point (25°C in his case).   This makes the system far more controllable.

 

What's your mains pressure and flow rate like? Do you need a buffer tank on the mains input side?

 

You will also need double check valves on your mains input and in front of your external tap at a minimum.

 

We also to-and-fro'd about 10 vs 15mm but decided to keep it simple and use 15 throughout because our average pipe run is ~3m.

Edited July 30, 2016 by TerryE

[Nickfromwales]

Ok, just mowed the garden ( another couple of hours I'll never get back ) ?

Couple of things. 

Are the towel rads off the pre blended flow or off the manifold ?

The bath feed can tee off and service the shower I'd have thought. Saves on one run and one less manifold port. 

Only observation beyond that is that the system is solely dependant on the cold mains pressure, and the dhw flow rate of the combi so those are major factors in this design  

[Auchlossen]

Following discussion with plumbers, I think the buffer tank may not be necessary. Modern gas boilers, they say, can modulate down and have anti-cycling controls. WorcesterBosch Greenstar 28CDi Combi is recommended. This will modulate down to 7kW and should deliver 10-11l/min to shower.

Heated towel rails are now out of the frame, and should not be necessary in UFH house.

Radial plumbing with 10mm Hep2O pipes is still the objective, with manifolds close to the boiler, and some shared pipes as suggested [shower/bath in 15mm; sink/dishwasher]. This is still a bit of a challenge to Rod&Billie!

[Nickfromwales]

I disagree with your plumbers. 

The buffer will do little when the house needs heating from cold, but when the house is up to temperature, and that heat is being maintained, it will become quite important indeed. If your boiler is left to short cycle, which there are no measures to mitigate afaik ( and the whole reason a buffer is implemented ), then it will also drop below the point where ideal condensing temperature is achieved, thus reducing the boiler efficiency accordingly. 

If a buffer is used, preferably in the airing cupboard so it kills two birds with one stone, then it can be fitted with a cylinder stat which will dictate the temp that the buffer gets maintained at. The hysteresis of the cyl stat will allow you to pulse heat from the boiler, at it's user defined flow temp, therefore allowing you to set that cycle to happen at the optimum temp for maximum condensing efficiency to be achieved.

Its not a good idea to run Ufh directly off a combi boiler unless you intend to implement a heat loss circuit, such as paralleling the towel rads to heat in unison, as a form of passive buffer. 

 

If you have any reasonable dhw demand then I'd consider a heat store combi tbh, and look twice at the claims from WB about the dhw rates! Their own website had my last 'Worcester insistent' customer cross-examining me as the 30kw combi clearly stated that it was typically suited for a flat or small 1 bedroom house . When I stated that a baxi 28kw gave excellent dhw flow rates, so a 30kw equivalent should be an improvement, said customer made me look at the wording for myself. Barking mad. 

I'm a Baxi or Vaillant man myself, and don't personally rate the WB boilers. 

[Auchlossen]

Thanks Nick, I will take this up again. Please will you advise on thermal buffer store:

• source, since most seem to be larger and designed with multiple coils and immersion heaters [eg Advance Appliances,Mibec]
• should this be in SSteel?
• Is my plan for plumbing it in broadly correct, with input from boiler into the body of the tank and output to UFH from coil?
• controls? valves? pumps?

Edited September 29, 2016 by Auchlossen
misleading term used, buffer store is what I am after not thermal store

[Auchlossen]

And I found this report on the advantages of modulation:

http://www.raypak.com/support/tech_corner/modulation

a bit heavy techie for me...

The extent of modulation appears to vary considerably between boilers,

with Atag and Vokera and Geminox on the hi-modulation end of the scale.

[Trw144]

Can anyone tell me, does a condensing gas boiler just need low return temperatures to be most efficient (in order to condense) or is it also dependent upon having a wide delta t across it?

[Nickfromwales]

Download the MI's for the boiler you wish to fit, and the specs / stats should all be in there

 

[Nickfromwales]

16 hours ago, Auchlossen said:

Thanks Nick, I will take this up again. Please will you advise on thermal store:

• source, since most seem to be larger and designed with multiple coils and immersion heaters [eg Advance Appliances,Mibec]
• should this be in SSteel?
• Is my plan for plumbing it in broadly correct, with input from boiler into the body of the tank and output to UFH from coil?
• controls? valves? pumps?

I'll reply later . 

In a 'high power' business meeting at the mo ??

[Nickfromwales]

When I say to the builder I'm currently subbing to, "I'll be back in an hour with the parts" he asks if that's a builders hour or a plumbers hour...........so when I said later let's assume I meant a day later  

OK

Source : I would recommend Telford. 

S/S : A no brainer for me, deffo yes. 

Plumbing : If there are rads and they are regular steel, then there is the problem of corrosion contamination which you'd ideally want to design out where possible / practicable. I'd probably say run the towel rads from a coil, via a dedicated 2-port manifold, and run the space heating ( ufh ) direct from the body of the TS via a second dedicated manifold. Benefits therein of being able to select the time and temp of each application to suit yourself, eg being able to run the towel rads when the heating isn't necessary but warm towels would be nice. 

C/V/P :

Room stats to Ufh control, ( multiple stats for multiple zones if required ).

Time clocks for towel rads control.

2-port zone valves to achieve both previous. 

Pumps on manifolds will suffice regarding flow to the manifolds from the TS.  

 

With a TS, I assume you'll know you'd be using a system boiler and not a combi as the TS would typically then provide dhw ?

[Auchlossen]

Thanks Nick and other comments above. Lots of good advice here as I had anticipated.

Confusion caused by my use of incorrect terminology, I am actually wanting to use/source a buffer store, following the lead of JSH, for driving the UFH.

Not sure if it is worth putting in heated towel rails at all, or maybe just electric? If house maintains at 23deg, then they will likely dry very quickly. Certainly I take the point that runnning them off the UFH is not very useful, since it will be at same temp as the air to which the towels will have adjusted

I am intending to use the mix-in-circuit mentioned by Terry: I think this is a recognized approach.

[Nickfromwales]

Have you checked @JSHarris blog entry for the supplier of his?

[Auchlossen]

Thanks again for further advice Nick.

Been a busy week or two: kit arrived from Poland on 3 lorries, fully insulated and ducted for wiring, smaller windows [Rationel] fitted, partly plasterboarded, together with various other bits like mega roof window [Fakro], timber and ply. Up and running in 3 days.

No rads, no thermal store, just [poss] buffer to drive UFH.

I re-read the Mill Orchard blog: JSH seems to have sourced his Buffer from Newark.

Gas boiler is Combi:

• I am looking at Vaillant EcotecPro24 as possible gas boiler.
• Geminox seems to have good reviews and very low modulation <1kW.
• Vokera Linea1 or Vision25 have also been suggested.
• Which? recommended WorcesterBosch Greenstar.