Seperete return an flow for dual heating system?

johneym

hi folks,

need to organize my heating system in a new(old)house I am moving into. There is a stove with back boiler.The hot water cylinder has a flow an return piped to this. There is also an outside oil boiler. There is another seperate flow an return piped to the cylinder for this. So we have 4 pipes, 2 each side on the cylinder. Apart form the pipe at the top of the cylinder etc. My young plumber is a bit of a novice but claims I dont need 2 seperate flow an returns. 1 is enough and more efficient and to use non return valves. Is this corrrect?
Also the cylinder, I wonder if I shoul replace it? Not sure how old it is, but around the connections there is a bit of green hard gunk. It does have however a green aerobord type factory fitted insulation.
Anyone know if I should replace this? How big of a cylinder do I need to run a dual heating system and/or 10 rads?

Thanks a lot for advice,

John

Micky Dolenz

change your plumber now and save yourself a load of heartache down the road.

You need two coils to avoid one heat source heating the other. On a solid fuel primary circuit (flow and return to cylinder) there can not be any valves and this line must be free from obstructions I.E Pumps/non return valves etc.

johneym

thanks Micky,

probllem is at the moment when the oil is on, it heats the water in the stove too!! Even if the stove is not running. What shoud I do to stop this? And should I put the non return valve then on the oil circuit?

Thanks again in advance

John

Sparkpea

I don't have loads of experience with dual link systems but there should definately be two flow and returns and 2 expansions normally. One cold feed
is normally ok but yes u need 2 coils in the hot tank. A non return valve should be fitted beside the oil boiler if possible so it won't heat the oil boiler unless the pump for the oil fired is turned on and normally u should have a non return valve fitted beside the pump for the stove so the stove boiler doesn't heat when the oil is on. This is if 4 pipes r taken off the stove, unrestricted f&r for hw and pumped f&r for ch.

Both systems should not be run at the same time unless u have a baker system
for example installed but this is normally unlikely.

A pipestat should be linked to the tank 2/3 of the way down so when u have lots of hw it brings on the pump to heat the radiators so the hw doesn't get too hot and expand.

Micky Dolenz

johneym wrote: »

thanks Micky,

probllem is at the moment when the oil is on, it heats the water in the stove too!! Even if the stove is not running. What shoud I do to stop this? And should I put the non return valve then on the oil circuit?

Thanks again in advance

John

You would put 2 NRV's on the system. One on the primary from oil as it is pumped and one on the secondary circuit (radiator circuit, which will be pumped) from solid fuel. A competent installer will be able to explain on site.

Carlow52

2 coils essential as the stove system must be permanently vented with NO obstructions on the hot pipe from stove that should go up to and over into the expansion tank

Good advice from Sparkpea, based on the assumption that the are 2 sets of F and R pipes from the stove.

Given the plethora of other plumbing posts by the OP I doubt it.

I suspect the stove is just like a rad:)

Micky Dolenz

Sparkpea wrote: »

A pipestat should be linked to the tank 2/3 of the way down so when u have lots of hw it brings on the pump to heat the radiators so the hw doesn't get too hot and expand.

the only problem with that is when the oil/gas is on and heats cylinder it will activate pump.

johneym

thanks folks for the replies,

you are right Carlow , there is only one flow an return pipe to the stove. The pump is on the return.In this case, is this correct or should there be no pump at all on this circuit?
In any case I am getting a new stove. Wil The stove will have 2 inlets and outlets?
So I presume I should use these?

yoshytoshy

There is a remedy to stop the stove from heating when the cylinder heating ,without using valves.
It involves a bit of pipework ,thats all.

johneym

hi Folks its me again,

my plumber is not as novice as I first thought.He is around 30-35 but tells me he has worked as a plumber in both Germany and Poland. He has already did this system with a few houses here and I called one of his former customers. They purchased a new single coil tank and run a stove and oil boiler.Either one heats the rads and hot water.Its been in and working almost 2 years now.I spoke by phone and I am not a plumber so did not go into detail. So we must be missing something.
I also remember my parents house where they have a range. They installed a few rads and oil boiler about 4 years ago but didnt change the tank. Now both systems can heat the rads but they cannot be working together. Now dont get me wrong, he will insall a dual coil if I want it, but its more time, money, copper etc., which he claims is not really necessary.
Is there anyone out there who has heard or seen this? If not here maybe on the continent?

Thanks

Sparkpea

johneym wrote: »

hi Folks its me again,

my plumber is not as novice as I first thought.He is around 30-35 but tells me he has worked as a plumber in both Germany and Poland. He has already did this system with a few houses here and I called one of his former customers. They purchased a new single coil tank and run a stove and oil boiler.Either one heats the rads and hot water.Its been in and working almost 2 years now.I spoke by phone and I am not a plumber so did not go into detail. So we must be missing something.
I also remember my parents house where they have a range. They installed a few rads and oil boiler about 4 years ago but didnt change the tank. Now both systems can heat the rads but they cannot be working together. Now dont get me wrong, he will insall a dual coil if I want it, but its more time, money, copper etc., which he claims is not really necessary.
Is there anyone out there who has heard or seen this? If not here maybe on the continent?

Thanks

Totally up to you if you get single or dual coil. I'm telling you I wouldn't fit it to a single coil. I wouldn't put my name to a job like that but I have seen it done but to me its not done properly and yes its cheaper to do it the other way so I would not advise it.

Micky Dolenz wrote: »

the only problem with that is when the oil/gas is on and heats cylinder it will activate pump.

Thats true, though I would have an isolation switch on it so when I'm lighting the fire I would flick the switch at the same time though so theres no power to the stat/pump on solid fuel when the oil/gas system is on.