Central heating pump

have a read of this :



(click Technical box at top, then Underfloor Heating, and follow down the page - it goes into various control strategies)

Thanks for that. Although in our case it is old house, new heating therefore radiators, not underfloor! Still useful site though.

Control options are essentially the same, 'though radiators being smaller in area have to be run quite a lot hotter than UFH, so will be rather less efficient ... and don't forget to ensure low-enough return temperatures if you're using a gas or oil condensing boiler (or the condensing won't work), and to avoid short-cycling (too-frequent start-up & shut-down) if you're using any sort of gas or oil boiler, both of which can have quite large effects on efficiency ...

BTW, thanks for the tip-off about the Stratos pump - hadn't heard of its 0-10V option - did you get it at a good price ?

I paid £155 including delivery to New Zealand on ebay for a stratos 30/1-8 which is a good price as long as it works! Minus instructions (available online) and pipe connectors and isolation gate valves - the lack of the latter probably saves more than their cost in postage though. I also have an older grundfos pump but power consumption of the older pump is roughly 3x that of the Stratos so the whole cost of the Wilo pump would be absorbed in 2 or 3 years.

We are installing an ecomax automated coal boiler (http://www.ecomax.co.nz/). The price of high quality coal in my area is so low that the fuel costs are around 0.7p/kWH of power delivered (about 1/4 of the price of wood pellets). May be not the most environmentally friendly of fuels but I am justifying it based on the use of less efficient coal fired power stations to provide peak electricity top-ups. Most of NZ power is hydro (>95%) but peak loads in winter are supplemented with coal fired power that is not efficient (around 50%) compared with 82% conversion efficiency for one of these coal boilers.

It is almost the opposite of a condensing boiler in that for maximum efficiency the return water needs to be hot so that the temperature of the firebox does not drop too much. In fact they recommend putting a mixing valve between flow and return pipes to keep the return water hotter!

The main reason for our Idratek install is to allow better control of the system and part of that is avoiding short cycling - I think that the load building features of Cortex will be just the thing.

interesting about return temperatures for best efficiency ...

coal could be green (!) - ie: unless it's subsidised or employing slave labour, the price will reflect the effort required to extract, and the less effort the less the effect on the environment (direct & indirect) ... plus if it's local, less miles, too !

pump - price looks good, I had a look but couldn't find one with the BMS option, and so the 0-10V connection ... but I'll look again ! Pay-back time - they say 80% savings are possible, so could be, 'though the power would've ended-up as heat, offsetting some of the cost ...

we're trying to weigh the pros & cons of using smart-pump(s) that auto-adjust with load and speed-controllable pumps, with & without manifold, with & without mo-mo or thermo' valves to regulate the zones - clearly stopping gravity circulation could be an issue, and cost, and complexity, but Idratek opens-up the choices & the prospect of greater efficiency ! We had a lively discussion with our (prospective) plumber the other night ...

I have bought a vanilla stratos, not one of the eco options. On looking at the manual again, it looks like an IF module is required for 0-10V control (can be purchased from Mytub and BHL). These seem to come in ?2 flavours and allow either rs485/modbus control or Lonworks system integration.


Just found USA Wilo site with a bit more info (Uk site not much use)


There is also the possibility of IR control the IR module/monitors seem to plug into a pocket or standard PC so an idratek IR transceiver might work if the control codes can be obtained (probably unlikely)






Found a catalogue at last that lists IR interface as standard (see pages 11,12 and 21). Has all the pump curves etc in one place as well.

I'll just have to wait and see what I get - but I don't have IR apart from the DFP in our kitchen!

interesting, thanks - hard info' was proving elusive !

your second link does seem to say a 0-10V interface would be add-able to a Stratos, if your's turns-out not to have one - can't find a price for it, tho' !

Try google shopping for obscure items of plumbing (or the item name + price for a general google search). I have found 3 prices for a if module PLR / ex off all are £93.48 including VAT. Mytub link http://www.mytub.co.uk/product_infor...product=512609 also same price at BHL and in BSS industrial catalogue page 619 http://guide.bssindustrial.co.uk/pdf/red_section.pdf

if you want an eco BMS I have found a 25/1-5 eco Z BMS
http://www.mytub.co.uk/product_infor...product=512609 -£350 including VAT + delivery.


Edit: Found another site with slightly less expensive ECO BMS
http://www.mpcservices.co.uk/wilo-st...ase-i1517.html stratos eco 25/1-5 BMS for £297 incl vat + delivery
http://www.mpcservices.co.uk/wilo-st...ase-i1531.html stratos eco 25/1-5 BMS for £334 incl vat + delivery

many thanks - such prices always seem high, compared with what an ordinary pump costs, until I calculate how much the power saved over a year would save in electricity costs !

Yes. And if you work it out over a few years ... Often the pumps are more powerful too. And of course the potential to connect the pump to your HA system for added exciting data collection and control.

Both the Wilo and Grundfos sites have calculators for the flow rates required. We have a large house and are also siting the boiler in a shed about 10m from the house so the pressure/flow curve of the "standard" domestic pumps is insufficient. Pity really, as my dad bought an unused, boxed grundfos 15/50 pump from a second-hand shop for £6 (really) but it will not be big enough for our system. At that price any difference in power consumption would be less relevant. So he is going to use it to change his solar system from passive flow to pumped.

even so, an extra year or so & even at that price you'd be saving !

we'd in-mind to have a pump per zone (one per floor) & no manifolds, and our plumber is suggesting having manifolds & lots of zones, to allow control per room & part of room ... manifolds are expensive, and with smart pumps & mo-mo control valves connected to Cortex we're not sure they're needed anyone ...

another Wilo pump, smart & with 0-10V on-board :



manual here :



price not too bad (payback ought to be quite short) ,,,

alldone - any news on how your 'Stratos worked-out - we're looking to buy ... so it would be good to know ...

Owing to unforseen delays at local council and plumber of choice going to Zimbabwe to volunteer we are still installing the system. Have 10 of 18 radiators installed and new hot water cylinder but haven't got pump connected up yet! Might be a few weeks still as plumber only coming 2-3 days/week ...