# Gravity flow distance for stove



## PatC (4 Oct 2011)

the distance between my stove and the coil in my cylinder in the hotpress is approx 45 feet. My manual for stove says max 25 feet of 1 inch pipe. Is this distance too far to achieve gravity flow or will it still work only a bit less efficiently due to the increased heat loss. Is there a risk of condinsation on the return. Has anybody got experience over this sort of distance. thank you for any replies


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## Shane007 (4 Oct 2011)

At that distance it will work perfectly fine as long as you have a circulating pump on the system. When there is no power or during a pump failure the flow temperature will be slow to reach the coil because of the distance, the heat will backing and will start to bang.

I would recommend that you re-position either the stove or the dhw cylinder to within 25 feet of each other and install the system to encorporate a natural gravity circuit as per the manufacturer's instructions.

Also if you have another heat source, i.e. oil boiler, ensure that the two circulating pumps can work in unison and not working against each other. Many installations have this simple rule over-looked and when the back boiler and the oil boiler are on together, they either bang or don't heat properly as the pumps are generally installed to pull against each other. Ensure they can be on together and operate in unison.

Are you plumbing it in yourself or is it being done by an experienced plumber?


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## PatC (4 Oct 2011)

Thank you for the time to reply. I will get a plumber to do the installation. I just want to familiarise myself with the installation first so i can make a decision based on my plumbers advice. I will ensure that the oil boiler and the stove circuits are interlocked both mechanically and electrically with the use of a pair of one way valves and electrically knock off the oil boiler when the stove thermostat is up to temperature. By installing a circulating pump do you mean to put it on the gravity circuit through the coil or on the rad circuit? I though it was best to have no restiction on the gravity circuit. My stove cannot be relocated as it is going in the original fireplace in the front room. I could put the cylinder in an upstairs kids bedroom but i don't know if this is ideal. Is it possible to put the cylinder in the attic and pump down to the rads? Is it more efficent to use 4 connections at the back of stove or is it okay to use two. I will eventually put it solar panels so i will have a 3 coil tank to further proof this for me. I hope to end up with an efficent working system that is problem free and safe first and foremost.


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## Shane007 (4 Oct 2011)

A circulating pump will not restrict the gravity flow. It acts as a circulator only. The back boiler on the stove should have a pump on the return pipework wired through a pipe thermostat located as close as possible to the stove itself and located on the flow pipe. The non-return valve should be located on the positive side of the both circulating pumps.

You do not have to "knock off" the oil boiler when then stove reaches temperature as the oil boiler will be thermostatically controlled anyhow. You should however install a room thermostat on the heating & hw zones that will turn off the oil boiler. 

Using the 4 connections is not more efficient but can be advantageous for separating the dhw circuit from the radiator circuit. It is also ok to use 2 and then split.

The circulating pump on your oil boiler should then be on the flow pipe so that it is not pulling against the stove pump. Make sure that the osvp is plumbed behind the boiler pump so that it does not pitch water through the osvp. Ideally pipework should exit flow pipe from boiler, then 3 bar safety valve, then 1st tee is osvp, then no more than 150mm away the f & e pipe, then the circulating pump, then the aav and then tees for heating zone and dhw zone. However, in a situation where there is more than one boiler, all circuits should have a route to the f & e pipe, so it should be placed on the return in a location where this can be achieved.

The cylinder in most cases cannot go into the attic as the cwst needs to be above it and usually there is not enough space. If you are going to install solar at a later date, then it is more cost effect to change to a triple coil cylinder now. Copper is ok for this, but if your budget can stretch to stainless steel it is better. Be wary of some of them. One particular Irish manufacturer only offers a 1 year warranty on their stainless steel ones and they nearly all leak after this time. Joule or Warmflow triple coil cylinders are pretty good. They also have good warranty periods. I think 20 years.


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## PatC (5 Oct 2011)

Thanks for the very informative advice Shane007. I am alot clearer now on what i need to do. I will go with your advice on the stainless 3 coil cylinder. I will discuss all aspects with my plumber and see if we can come up with a good plan. I have a good supply of hardwood already dried in the shed so i look forward to the oil lorry driver forgetting my name. I have a small generator to run heating in the event of a power outage so this would keep me circulating.


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## fmmc (5 Oct 2011)

Patc....have a similar arrangement.  Stove is circa 53 ft from cylinder on same floor in bungalow and have fitted a pump on the return with pipe stat on the flow.  You can adjust the temp on the stat to either pull heat away from the stove earlier (i.e. at lower temps say 60) or allow more heat to the room the stove is located in (i.e. say set temp on pipe stat at 80).  I will change temp on pipe stat to use stove for different reasons (i.e. contributing more to DHW requirements rather than space heating) at different times, but find the space (circa 50ft) not to be a major issue.  Occasionally, when the stat is set high, the stove may have a higher propensity to bang as water temp increases but its not a huge issue for us.  Its probably natural that shorter runs are optimum.


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## PatC (5 Oct 2011)

Hi fmmc- Nice to see somebody has a working system of what i think i will have to end up with. My hotpress dosn't seem a million miles away till i measure it, but there you go. Does this one pump on the return to stove also pump around to rads, or do you have another  thermostat at cylinder coil return and a "mov" on the rad circuit for this. It is nice to know that you can control the heat to the room when you feel you need it at times locally at the stove at the expense of the water.


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## DavyJones (5 Oct 2011)

I have a generally rule of thumb. If it takes more then two lengths of copper to get the flow from the stove to the cylinder it is too far, basically under 40 feet. 

I wouldn't be a big fan of putting pumps on a primary circuit as it should not have valves fitted on it. Depending on where the pump is fitted, a closed valve could be a potential severe hazard.


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## villa 1 (5 Oct 2011)

Make sure that pump isolating valves fitted are 1inch diameter and that they actually measure 1 inch in diameter when in the open position. Many pump isolating valves do not open up to 1inch,  which will seriously affect gravity circulation.
I do not agree with fitting any pump on the 1inch primary gravity circuit((both flow or return) between the boiler/stove and hot water cylinder. This circuit should be completely unrestricted, no valves/pumps etc as these will lead to flow restriction.


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## PatC (6 Oct 2011)

More food for thought now. I guess alot of people in times gone by have their pump down next to the fire/backboiler with a switch there to turn it on when they hear the banging. I understand the possible danger of this but when a person is in the house they seem to be able to manage this system. I think i will have to move the cylinder nearer as i have the option to do it now so i can operate a completely unrestricted primary circuit. I will be adding a new hotpress to the cost of my installation. I think the stove is the cheap part to buy.


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## fmmc (6 Oct 2011)

Hi Patc,  I use stove purely for space heating room in which it is located and for contributing to DHW.  The pump is located in the Hotpress in the utility.  I wouldn't be inclined to alter the layout (i.e. moving your HP) just to accomodate the stove.  There are other effective workable solutions.


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## Shane007 (6 Oct 2011)

I might be missing a point here. Will you be using the stove to heat only dhw or will it also be linked to heating radiators?

I assumed you were and therefore the second flow & return will have to used with non-return valves otherwise oil boiler will heat stove and vice versa. The first flow & return will be gravity only. The second circuit will have to be pumped to avail of non-return valves.

Apologies for my mistake.


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## PatC (6 Oct 2011)

I will be using a Stanley Reginald to heat DHW and run 12 rads.


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