Solid fuel cntral heating HELP with design please

[andrewlato]

Hi
Just got my closed-in stove delivered , it has back boiler 11kw and one in-one out water connections. Ive started to put all new pipework but just wondering where is best to position pump and if i need a gravity feed rad before pump or maybe put a Motorised valve around pump so in case it fails/power cut , system can still take heat off the boiler. this is my proposed design:next to the stove on the ground floor i fitted a 5Mpump with a pipe stat set at 45deg then the pipework is going up (22mm)with one T-off(15mm) to the ground floor (im putting one rad in other room) then on the first floor flow and return are 22mm with all rads(5 together) T'd-off with 15mmpipes .There is also a immersion heater tank with coil which i was going to connect as normal rad(i dont mind that it will take lots of heat as the back boiler is slightly bigger than needed but if thats the problem im happy to hear alternative option).The flow pipe (still 22mm)is then vented going well above all the rads and the return is obviously fed by cold water at first floor level(height difference between water tank and connection to the pipework ~1.7m). my main concern is where to best install pump and what speed should it be set at so it doesnt pump-over the air vent(someone at Jacksons said that as long as it has at least 3 T's between pump and vent it should not pump-over???). then should i fit TRVs on rads with solid fuel boiler or will they cause more bad than good in case they shut when set tempertue is reached?Can i have immersion heater tank connected to single circuit?(it is vented through separate HW pipework and then the main circuit is vented as well).what is the max recommended lenght of 15mm circuit(off 22mm flow pipe) going to a single rad?
many thanks for any advice
AJ

 

[Norcon]

Sorry, my eyes glazed over on the second sentence.
Some schematics here and advice..........
http://www.solidfuel.co.uk/pdfs/link_up.pdf

 

[oilman]

Have you got any guide information from the manufacturers? The fundamental area is the diameter of pipes. I have never seen 22mm recommended as it's too small. There should be NO devices of any sort (pumps, valves, etc) in a heat leak circuit, which should be able to cope with around 2kW at least.

You are on a hazardous mission if you are asking questions like these, and you need to do a LOT of research before doing anything.

If you are intending to burn wood, efficiency drops like a stone when you have a water heater attached.

 

[andrewlato]

im not that much off the track with a design.Thanx for the schemes Norcon, very usefull.
Oilman as per pipe diameter all local plumbers says the same : use 22mm if you put pump or 28mm if it's gonna be heat leak system. i was gonna go for the pump as it distributes heat quicker.
manufacturers books are pretty useless so i have to rely on you , good people.
i have seen system like this working on 22mm pipes with pump but no pipe stat (pump working all the time!!!)and it seemed to be ok, 11kw providing CH and hot water for 3bed semi. any idea of what the maximum working water pressure should be during operation of the stove before i should evacuate neighbours ?

Norcon- the idea with Motorised valve came from people selling stoves Naturalheating.co.uk it seems like the valve when 'on' could be 'closed' and when power fails it would 'open' enabling heat to travel through(around the pump which just stopped), do you think it is not something worth going for?

 

[holty]

you can still go for the vent feed pump arangement if easier,you sound as if your going by the old setup wich does need a bit more consideration.

 

[Norcon]

andrewlato wrote

Norcon- the idea with Motorised valve came from people selling stoves Naturalheating.co.uk it seems like the valve when 'on' could be 'closed' and when power fails it would 'open' enabling heat to travel through(around the pump which just stopped), do you think it is not something worth going for?

A normally opened motorized valve which is energised along with the pump.The pump being fitted on the by-pass around the ZV !.

The danger is pump failure occurence and the ZV shutting. A flow switch detecting flow would be one solution towards making it safer.
With an electrical failure or outage the system should be capable of thermosyphoning to heat leak radiators to dissipate heat.
Strict adherence to venting and a metal F/E container would be important.
I don't think any HETAS approved engineer worth his salt would put his stamp of approval on it.

An injector T set up is the most common method of boosting flow on a gravity (thermosyphon) circuit and is usually only beneficial on a low resistance circuit. (eg. nuetralizer, thermal store or low resistance cylinder coil)