Green Building Forum - Hot water in the Winter.... (when its cloudy..)

Hot water in the Winter.... (when its cloudy..)

renewablejohn — Wed, 09 Nov 2011 08:45:49 +0000

Posted By: James NortonTony,

Worst case: 4 showers and one bath - more likley, say 3 showers

9sqm of 42 deg pitch south facing roof available for evac tubes.

No need to go of grid per se and also a desire to avoid within reason the scourge of diminishing returns.

J

Simple really just use thermal oil in a high temp evac tube like the ritter and a variable speed pump with thermostat to control output temperature into the thermal oil accumulator tank. Heat exchanger to DHW tank job done.

Or if you want a biomass solution go for an Otag Bison and get free electric as an added bonus.

Just shows how things have moved on as the microchp unit was not in production back in 2008 and the high reflective ritters came out in 2010.

Hot water in the Winter.... (when its cloudy..)

palebluedot — Fri, 18 Nov 2011 12:28:21 +0000

James - I see you posed this question in 2008. What was the conclusion? Which (if any) system to you install in the end, and did it work?

Cheers!

Hot water in the Winter.... (when its cloudy..)

Justin — Fri, 18 Nov 2011 22:04:43 +0000

Hi James.
Is there any hope in having a tank made with a high-level solar heat exchanger (for winter use)?

This is something I've been thinking. My solar thermal has been stunningly good, providing 100% for us from about the first week in March through to about the third week in October.
(I had to frig the shower pump to make it work at 40C in autumn/spring, but otherwise great)

Since then the poor heat exchanger sat at the bottom of a 230L tank has had a lot to cope with. I'm getting 35C now in mid/late Nov which is OK for washing up, but for showering, is rather like the South of France campsite experience. (Not so much fun when the bathroom is also at 15C).

So would a high level exchanger with only a small volume of water above enable the tubes to get higher temperatures also through the winter? - Albeit at a much reduced volume.

Hot water in the Winter.... (when its cloudy..)

James Norton — Fri, 18 Nov 2011 22:59:40 +0000

In the end the decision was twofold:

1. The actual amount in cost terms of backing up with an immersion is pretty minimal and in a finite world working much harder broke my rule of avoiding the steeper part of the diminishing returns graph when there are still more efficient place to spend the money environmentally

2. I found a stove with a 9:1 boiler to room ratio (woodfire 12i / or Malaga I think in Germany where it is a lot cheaper)

J

Hot water in the Winter.... (when its cloudy..)

James Norton — Fri, 18 Nov 2011 23:01:44 +0000

Justin, with reference to "1." above I would say that unless the whole of the rest of your house, work an lifestyle has been completely greened then you've already cracked it with the solar thermal water.

J

Hot water in the Winter.... (when its cloudy..)

wookey — Sat, 19 Nov 2011 00:03:49 +0000

Justin - it's difficult to get an internal stratifier for solar input without spending a lot of money on fancy german/austrian/italian tanks. You can simply have top and bottom coils relatively inexpensively (from Newark and the like).

One option is to have an external PHE top-loading the tank - this is what I do and it works pretty well in winter (when the sun comes out - e.g 50C today). This option has the advanatge of being very cheap to retrofit to an existing tank as well as providing more useful hot water in winter.

Hot water in the Winter.... (when its cloudy..)

Hairlocks — Tue, 22 Nov 2011 20:20:56 +0000

James,

What is your opinion of the woodfire 12i. I am about to order a woodfire 12F , but can't find out much about them on the internet.

Hot water in the Winter.... (when its cloudy..)

MarkBennett — Wed, 23 Nov 2011 09:33:53 +0000

Posted By: HairlocksJames,

What is your opinion of the woodfire 12i. I am about to order a woodfire 12F , but can't find out much about them on the internet.

I know that the Woodfire 12i was used in the AI PassivHaus/Underhill house. When I last discussed it with Helen they were quite happy with the stove and it was doing a good job at providing the additional heat. They had it teamed with a TiSun Pro-clean stratifying thermal store and a large array of solar and it seemed to be working well. I don't know how it is faring now.

There are a couple of other low heat output stoves on the market, but the WoodFire is probably the cheapest option. We've 95% made the decision to drop the stove from our PassivHaus so I'm not hunting for other options right now.

Hot water in the Winter.... (when its cloudy..)

beelbeebub — Wed, 23 Nov 2011 09:56:42 +0000

we're in the middle of installing a woodfire 12F.

The build quality seems pretty good. the only "black mark" was a small bit of welding to hold the door handle on. It's the same quality as the rest of the stove (i.e. good quality MMA welding, no undercuts, no pitting, no splatter) but whereas the rest of the welding is concealed this is right on the front of the stove, so looks a little out of place as the rest is quite "clean". It's nit-picking really.

I've heard that you have to use dry wood and run it pretty hard to avoid the glass blacking as a consequence of the high water vs room heat ratio, but that shouldn't be a problem as we have a thermal store to absorb the excess for later.

Hot water in the Winter.... (when its cloudy..)

James Norton — Wed, 23 Nov 2011 13:57:14 +0000

Not got ours yet but as I understand the i is basically the F but with basic side panels and legs as being an inset you don't see them, in all other respects the same stove.

There is a German company that sells through ebay and they have them at half the cost of the only UK seller I could find:

http://www.ebay.co.uk/itm/370534743911?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_2015wt_1163

J

Hot water in the Winter.... (when its cloudy..)

Hairlocks — Wed, 23 Nov 2011 15:05:25 +0000

Do they sell the external air kit?

Hot water in the Winter.... (when its cloudy..)

James Norton — Wed, 23 Nov 2011 16:58:26 +0000

I don't think there is a 'kit', you just fix a pipe to the inlet on the back of the stove. They do however also sell the Ladomat load unit.

J