S plan heating system

[Glengormless]

Hi guys. Just a quick question as to the install of this system. If the boiler is fitted downstairs and the cyclinder and valves upstairs does this mean that 4 pipes have to be run upstairs with regards to heating?. Central heating flow, Central heating return, Hot water return( to tee in after all downstairs radiators have been connected ) and another central heating flow to feed downstairs. I realise that if a third valve was fitted downstairs it could be zoned and have no need for the fourth pipe( 2nd ch flow). Is this correct?. Thanks for the help

 

[diamondgas]

Yes! I think!

I've looked at this three times now and am still trying to fathom out what you've said!

Primary F&R will need to go up and heating F&R down somewhere or other.

 

[dontknowitall]

Is it a combi or standard boiler? With a standard just two pipes. With a combi ... errr ... I need to think on that one!

 

[bengasman]

One flow coming out of the boiler, splits in two; one for ch, one for dhw. Returns don't matter as long as the cylinder and every rad have one, and it eventually ends up at the boiler return.
Having said that, if you need to ask this, you should seriously consider leaving it somebody who does this for a living. It will be better, quicker, safer, and probably in the long run cheaper too.

 

[Blackcatgas]

Boiler flow and boiler return to the cylinder cuboard, boiler flow conected into a 3 port valve, A outlet to heating flow pipe, B outlet to the top side tapping of the cylinder, heating return connected into the boiler return pipe, cylinder return (bottom side tapping of cylinder) connected into the boiler return pipe.

 

[Billy Bob Bob]

4 pipes why????????? you only need 2 as said by bcg,diamond and ben have said all you need to remember is the last TEE on the return must go to the cylinder return no rads to come off after this or they will warm up when you put it on hot water only,THE LAST TEE MUST GO TO DOMESTICS

 

[stevetheplumber]

only two from boiler to motorised valves normally in airing cupboard with cylinder but you then need a pair of heating to go to ground floor so in a way yes four pipes
as the cylinder return needs to be last tee on return its normal to run all heating to the airing cupboard but sometimes its possible to run the cylinder return back to boiler if the layout makes this easier

 

[kirkgas]

One flow coming out of the boiler, splits in two; one for ch, one for dhw. Returns don't matter as long as the cylinder and every rad have one, and it eventually ends up at the boiler return.
Having said that, if you need to ask this, you should seriously consider leaving it somebody who does this for a living. It will be better, quicker, safer, and probably in the long run cheaper too.

sorry Ben, school boy error fitting the hot water return tee anywhere "cause it doesnt matter" it certainly does matter and has caused many a plumber many a problem with reverse circulation, the return from the cylinder is always the last connection to the boiler, no matter how much work it adds to the job, i have been at tons of jobs where the "guy" has connected the cylinder and bedroom rad together just outside the airing cupboard and during the summer the bedroom rad heats up when the water is on, us oldies are aware of the old "3 T design" i will wait on someone else stealing the glory of describing what the design is,

 

[kirkgas]

you dont need to run the flow to the airing cupboard for it to come back down again, ok a lot of systems have pump and zone valves taken up to cylinder cupboard and then back down, but it must depend on the actual position between the boiler, cylinder and rads, it is perfectly acceptable to come off the boiler, then pump then tee then the 2 zone valves, one going to cylinder the other for heating with a tee after the valve with 1 pipe going up and 1 going down to each rad circuit, in effect you will then have 2 flows going up or 1 flow going up and 1 flow going back down so pipe length required will prob be similar, the problems arise when people start to mess with a perfectly good design to save tiem and/or money on material and labour by compromising the design, jeezo im old enough to remember when we got 40 (yes 40) man hrs to fit a system, so it allowed us to fit properly and take 3-3.5hrs to flush, inhibit and commission the system when done, not like guys now who only do a hot flush when an upstairs yorkshire fitting leaks cause the flux has melted and they need to drain to fix (not slagging guys here, im slagging those who have cut time and money making a good install and design almost impossible, and that includes the clients as well as the bosses) i talk to guys who get £300-400 to fit a system now, that was the price what 10-12 years ago at least, when £300 was worth something

 

[bengasman]

...the last TEE on the return must go to the cylinder return no rads to come off after this or they will warm up when you put it on hot water only

Am a bit puzzled here.
How can the rads get warm when the ch zonevalve is shut and blocks the flow?


The whole system is parallel ( or at least should be ).
It is like a ladder where the risers ( or whatever they are called ) are the flow and return, with the rungs being the radiators and the cylinder.
There is no real first if the system is properly designed and installed, and the only difference between the cylinder and the rads is that the cylinder has a separate zone valve.

 

[diamondgas]

Hi Chaps,

Sometimes going back to the drawing board proves worthwhile. Upstairs, downstairs and cylinder shown. As bengasman says, you will not get reverse circulation occurring if both upstairs and downstairs are zoned. In theory you will just need 2 pipes to upstairs providing your installing a sealed system. A system boiler or heat only will do the job, the pump will need to be installed before the first tee!

However if it is not zoned up and down then an additional return pipe will be neccessary...

Have I missed anything?

 

[Glengormless]

Thanks for the replies guys. Im outta my time but ive been employed with the same guy and the few times these came up the boss did it. Still not too sure on the answer but ill try and simplify the question as it may have had two questions in one. To prevent reverse circulation and obey the 3 tee rule does the hot water return have to come the whole way downstairs as one of my 4 pipes and tee in AFTER all the downstairs rads returns or is it a case of teeing in after all the upstairs rads returns? Bengasman..im not installing this job. Im just trying to read up on these things and you guys are the ones to ask for answers when i get stumped. And im kinda stumped lol

 

[Glengormless]

Cheers Diamondgas. You answered my question just before i posted! So 2 pipes and if u zone downstairs you will not get reverse circulation. What way would it work if downstairs wasnt zoned?. In a small house for example

 

[diamondgas]

This or a variation of it which means 4 pipes yeh?

If I've missed something out I'm sure a more experienced installer will correct me. It's been a decade or more since I messed around under floorboards!

 

[Glengormless]

Thanks Diamondgas. That answers all questions in one simple diagram. Thats how i pictured the actual install but thought 4 pipes was abit ott so was seeking clarification. Thanks for the help again.

 

[kirkgas]

having zone valve or not doesnt effect or cause reverse circulation, most of the time the problem happens in the following scenario: boiler downstairs cylinder upstairs in bedroom cupboard with bedroom rad further in the room, on hot water only the water comes back down the return, comes out the cupboard and down to the branch of a a tee where the cylinder and rad circuit join together, the water simply goes right and left and up the return into the rad via the lockshield valve, it is easy to connect it this way, but the correct way is to run a return pipe from the rad back to the circuit in the hall, and too run a seperate dedicated return from the cylinder ALL the way back and connect it after the downstairs circuit, some have spilt the difference and connected the hot return half way down, but even then it can cause reverse flow through the nearest downstairs rad

 

[diamondgas]

having zone valve or not doesn't effect or cause reverse circulation, most of the time the problem happens in the following scenario: boiler downstairs cylinder upstairs in bedroom cupboard with bedroom rad further in the room, on hot water only the water comes back down the return, comes out the cupboard and down to the branch of a a tee where the cylinder and rad circuit join together, the water simply goes right and left and up the return into the rad via the lockshield valve, it is easy to connect it this way, but the correct way is to run a return pipe from the rad back to the circuit in the hall, and too run a seperate dedicated return from the cylinder ALL the way back and connect it after the downstairs circuit, some have spilt the difference and connected the hot return half way down, but even then it can cause reverse flow through the nearest downstairs rad

I agree that your scenario is correct kirkgas however I'd have to disagree regards the zone valve. In your scenario, if you turned the radiator off that would stop the circulation yeh? In the same way if you has 20 radiators instead of one teed in as you describe, with a zone valve fitted and closed there would be no completed circuit for the water to 'reverse' through.
If the system is fully zoned, as in my first diagram post, you have in effect 3 separate zones. The cylinder could just as equally be a 3rd heating zone. Each one works independent of each other via zoning... none of the circuits would effect either of the others.

 

[ecowarm]

having zone valve or not doesnt effect or cause reverse circulation, most of the time the problem happens in the following scenario: boiler downstairs cylinder upstairs in bedroom cupboard with bedroom rad further in the room, on hot water only the water comes back down the return, comes out the cupboard and down to the branch of a a tee where the cylinder and rad circuit join together, the water simply goes right and left and up the return into the rad via the lockshield valve, it is easy to connect it this way, but the correct way is to run a return pipe from the rad back to the circuit in the hall, and too run a seperate dedicated return from the cylinder ALL the way back and connect it after the downstairs circuit, some have spilt the difference and connected the hot return half way down, but even then it can cause reverse flow through the nearest downstairs rad

I agree but the easiest way to remember is the hot water return must be the LAST tee to the boiler.
Eco

 

[kirkgas]

I agree but the easiest way to remember is the hot water return must be the LAST tee to the boiler.
Eco

i totally agree and am old enough to have been given the time to do it properly "in the good old days"

 

[kirkgas]

View attachment 2809 This or a variation of it which means 4 pipes yeh?

If I've missed something out I'm sure a more experienced installer will correct me. It's been a decade or more since I messed around under floorboards!

looks good and the way you have drawn it you can see it would have been a lot easier for you to simply join the hot water return into the upstairs circuit before it dropped downstairs, which is exactly what people started to do as they saved a length of 22mm and some time, but in some instances it caused one rad to reverse heat

 

[diamondgas]

looks good and the way you have drawn it you can see it would have been a lot easier for you to simply join the hot water return into the upstairs circuit before it dropped downstairs, which is exactly what people started to do as they saved a length of 22mm and some time, but in some instances it caused one rad to reverse heat

It use to cause whole systems or at least all of upstairs to heat kirkgas. Usually after an extension or additional rad had been added ... Down to differential pressures on the "upstairs" & "downstairs" return pipes causing secondary circulation... Solved with a strategically placed non-return valve, more times than i care to mention to be honest and usually after umpteen diverter valves had been fitted!! lol

 

[Inverness]

I have a problem. I have a s plan fully pumped seal system. I live in a bungalow. When I call for hot water only I get get radiators getting warm. The boiler has two Danfoss motorised valves beside it one for hot water and the other for heating. When I call for hot water The cylinder gets hot and so does the pipe after the heating motorised valve. Could this mean it's letting by?

 

[ShaunCorbs]

I have a problem. I have a s plan fully pumped seal system. I live in a bungalow. When I call for hot water only I get get radiators getting warm. The boiler has two Danfoss motorised valves beside it one for hot water and the other for heating. When I call for hot water The cylinder gets hot and so does the pipe after the heating motorised valve. Could this mean it's letting by?

yes depends on how old the valve is could do with a new one

 

[Inverness]

Nice one. I'm only in my second year of svq3 and I've got a homer I'm doing tomorrow for my friend. I've already purchased new Honeywell motorised valves as there are better quality. And I was thinking I might ask for a professional opinion first. I've done a drawing of the system and worked out the possibilities and this was the only one I could be sure of. Plus was round at the house and I felt the heating pipe after the motorised valve when I called for hot water and it was hot.
Thank you.

 

[ShaunCorbs]

np but next time create your own thread instead of bring one back to life, plz the mods like it that way