Central heating pump

[alldone]

I have just brought a wilo stratos pump for my new central heating system and have discovered on reading the online instructions that it can take a 0-10V input to proportionately control pump output.

So something clever may be possible based on which rooms are calling for heat and room radiator size, rather than just slaving the pump to the boiler. Has anyone tried this? It may in the end just be easier to set it up as a temperature vs pressure automatic flow change.

[chris_j_hunter]

have a read of this :

http://www.heatweb.com/

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

[alldone]

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

[chris_j_hunter]

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 ?

[alldone]

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.

[chris_j_hunter]

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 ...