Adding Solar and UFH in extension to house with Oil boiler and rads

Tim.Bunce

Hi.

We're about to start building an large extension on our bungalow. (We're knocking a small old extension and building a 110m2 extension onto our 120m3 house.)

I'm looking for a sanity check on our plans for solar DHW and UFH using a combination buffer tank.

I've worked with a plumber to get to the point of having a clear system design and resolve the fine detail of how we'd integrate the old and new, making best use of the solar heat. I've written up the design as a schedule of works (I plan to invite some skilled local plumbers to tender - no unsolicited tenders please!) and pasted some extracts from it below:

* Existing house:

120m3 Bungalow with double glazing plus cavity wall and loft insulation.
4 people plus guests.
Double panel radiators (old-style, no fins between panels)
Fed from external oil boiler (see below) across courtyard into Study.
Copper pipes, mostly in wood/mdf trunking/boxing along the outside walls.
Rad feed runs clockwise in 3/4" piping thru north, east and south of house.
Pipes reduce to 1/2" between "Guest Bedroom" and "Living Room" on plans.

* New Extension

110m3, 3 bedrooms, Ensuite and Shower Room, Utility.
Above standard insulation. South facing roof.
Underfloor heating

* Heat sources for new combination buffer tank heat store:

Existing oil boiler:
Firebird Popular 90, 26kWh/120BTU, 85%eff C-band.
Proposed solar system:
Surface Power. 6 x 1.9m2 collectors = 11.4m2 (Aperture: 6 x 0.95m2 = 5.7m2)
http://www.surfacepower.com/certification.html 783 kWhrs/m2/yr
http://www.seai.ie/Your_Building/BER/BER_Assessors/Technical/Harp_Database/Solar/Details/?ID=44
Heat loss coefficient (a 1 ): 2.074 W/m2K
Zero loss collector efficiency : 0.731
Temperature dependence heat loss coefficient (a2): 0.017 W/m 2 K
Immersion element.
Enable option to add heat from a stove back boiler in future.

* System Controller:

Provide/install/commission system controller which controls:
Underfloor heating, including high temp limits.
Radiators
Oil boiler
Solar panels
Aux heat source, e.g. wood stove back boiler.
Immersion heater

The system controller is to include:
Time control of underfloor heating
Time control of radiators
Weather compensation
Prioritizing of "cheapest" heat source (eg oil vs immersion)
Nighttime setback for underfloor (and ideally the Solo's, described below)
Facilitate heat dump for solar panels to UFH.

* Design of heat store tank:

Combination buffer tank, approximately 750L to 1000L with low heat loss and >=100mm insulation.
Tank should fit through standard doors, i.e., have removable insulation.
Connections:
1. Domestic hot water coil, via TMV, with flow rate sufficient for at least 1 bath and 1 shower.
2. Two solar coils, upper and lower, with thermostatic diverter valve set approx. 55C to send heat from panels to both top and bottom coils if hot enough. (Alternatively, a tank with good stratification behavior like http://www.consolar.co.uk/documents/PI-SOLUS%20II%20UK.pdf or http://www.solvis-partner.de/userfiles/2430_P12-EN_Grossanlagen_Technische_Information.pdf)
3. Immersion element.
4. Boiler flow and return.
5. Aux. heating flow and return.
6. Central heating/UFH flow and return, via TMV.
7. Sufficient sensor pockets for system controller.

* Solo 3 heaters

Some Solo heaters will be used to bring low temperature heating to some areas of the existing house.
The Solo's need a 6-8 meter head pump, with a minimum of 22mm flow and return piping (15mm final connection).
http://www.energyrl.ie/documents/solo/Solo%20VARIANTS.pdf
Solos to run on separate pump (because we may want to add more to that circuit).

I'm happy with where we've got to with this, but I'm also very keen to get a second opinion and other points of view.

Is the overall approach reasonable?
Is the sizing of the panels and tank reasonable?
Any issues I should look out for?

Thanks!

Tim.

Tim.Bunce

No replies. Did I say something wrong?

Poor Uncle Tom

I don't think it was anything you said.....:D

There's a lot of information there and you seem to have your homework done very well, just give it a couple of days to filter in and I'm sure you will get a few replies.

nulabert

Solo 3 heaters
Some Solo heaters will be used to bring low temperature heating to some areas of the existing house.
The Solo's need a 6-8 meter head pump, with a minimum of 22mm flow and return piping (15mm final connection).
http://www.energyrl.ie/documents/sol...20VARIANTS.pdf
Solos to run on separate pump (because we may want to add more to that circuit).

I put 2 of these in an existing house this year. I think they are equivalent to 6KW each. Very handy in big spaces like a hallway. They have 4 settings, and a boost setting. You can set them to be on setting 4 so they throw out a good bit of heat but the real heat is when you manually hit the boost button. I usually hit the boost button when ever i walk past them!


Out of interest, how much is the Solar costing? Just looking at Met.ie, the Solar Radiation for Birr is 913kw/m2 at efficiency of 0.731 that gives 667.6kwh/year. This varies from North to south.

Tim.Bunce

nulabert wrote: »

I put 2 of these in an existing house this year. I think they are equivalent to 6KW each. Very handy in big spaces like a hallway. They have 4 settings, and a boost setting. You can set them to be on setting 4 so they throw out a good bit of heat but the real heat is when you manually hit the boost button. I usually hit the boost button when ever i walk past them!

What temperature water do you use?

How do you find the fan noise at the various levels?

We still haven't quite settled on UFH yet. We have some concerns over the need to leave it on vs the desire to have windows open for ventilation (we like fresh air but can't afford HRV). So installing Solo's (or something similar like Jaga's with DBE) in all the rooms of the extension, instead of UFH, is still a possibility.

Out of interest, how much is the Solar costing?

I have a quote for solar tubes, tank, solar pump, TMV, BS4 controller, and installation, but that's now outdated. (I'm not sure what the etiquette here is about posting costings. You can PM me.)

I've a plumber costing the whole job at the moment and he'll break out the solar costs for comparison. I should have that next week.

Just looking at Met.ie, the Solar Radiation for Birr is 913kw/m2 at efficiency of 0.731 that gives 667.6kwh/year. This varies from North to south.

We're about midway between Birr and Valentia so using that table (thanks!) I make it 936kWh/m2 annual solar radiation for us. That's horizontal of course. I don't know how to adjust that for the panel angle. We'd be mounting the panels at either 40 degrees (direct on roof) or 60 degrees (with mounting bracket) to maximise spring/autumn gain and minimise summer heat dumping and stagnation.