Heating system confusion!!

Ok here goes! I'm about to start a heating system for someone, more as a favour than anything else! There are no wiring diagrams as plumbers have designed system themselves. Basically what there is is an external oil boiler, a cylinder & a manifold for underfloor heating. Two motorized valves, one for underfloor heating & one for towel rails. There's also a fire which can be used to do heating instead of boiler. All the info I have from the plumber was a note that basically says "turn hot water on at programmer & this goes through cylinder sat & fires up boiler, pump in boiler then pumps water to cylinder. There will be two pumps, one for pumping water from cylinder to either towel rails or underfloor heating whichever calls for heat. The other pump is fore the fire. Now does this sound about right the way I plan wiring it... from programmer to wiring centre I'll have a permanent feed & neutral & then a 3C & E for HW/UF/TR. Then the brown from the HW will go to cylinder stat & the return from that will switch on boiler. Then the bit I'm a bit confused about... the plumber says it's only the HW that will fire up the boiler so does that mean the black from 3C goes to brown of motorized valve & then the orange does it connect to cylinder pump seen as it's not to fire up boiler? The towel rail the same as UF but with grey to brown of motorized valve. There's also a second stat on cylinder to kick in only if water reaches high temperature so this stat is permanently live. Does that sound about right? The next part of my question is about the manifold. Do I have this right?! The manifold has a supply to it & then 3C & E to each room stat which is straight forward enough, the actuators are all wired in which is easy enough. There's also a manifold pump which I assume just goes into manifold pump connection. There's a connection to boiler then which I assume is just left empty?? When should the pump kick in on the manifold? 101 questions I know but any time I do heating I usually just follow a diagram of which there is none! The plumber did say it's up to the client to make sure they keep the cylinder warm as if not the system will pump cold water.

The pump needs to be running when there is a heat source.
The heat source will fire up when a stat tells it to, with the exception of heating. The heat source should only fire up when a stat calls AND the timer is on.
That's the basics of most heating systems.
Other than making sure the heating pump has over run, that's about my knowledge.
I had a similar issue when I split an old Y plan into a zoned S plan.
It was a pig.
I got a sheet of wallpaper and drew out all the different elements and then worked out how I wanted it to work.
I then ran it passed a,mate of mine who's a heating engineer.
It didn't function as planned initially, but was more to do with a faulty motorised valve.
Good luck dude.

What dictates when the towel rails need heat?

is the fire a back burner?

You have a thermal store due to having multiple sources. The thermal store works in reverse to how you would think it would (like a normal cylinder). The boiler heats the the water in the thermal store, so when the hot water tap is turned on mains pressure cold water (or reduced down to 3bar) passes through the coil/heat exchanger in the cylinder and is heated by the hot water in the cylinder. The towel rail circuit is there so it can get rid of excess heat when the solid fuel is burning (like a heat sink) you are going to need a high and low limit pipe thermostats as close as possible to the solid fuel boiler so the return temperature is kept above 45~to stop corrosion and the high limit set to 90~ so the towel rail pump can kick in a draw some heat away from the thermal store. The gas/oil boiler needs a timer and aqua stat on thermal store wired in series (this is what the plumber has told you that is controlled by the hot water channel on programmer) if the
Boiler doesn't require over run then the pump on the boiler flow will also be wired in with the switch live to boiler. The diagram is the solid fuel/heat sink wiring/towel rail circuit. Obviously the thermal store has to be up to temperature from either the boiler or solid fuel boiler to be able to get hot water and to heat any of the heating circuits.

Leesparkykent said:

You have a thermal store due to having multiple sources. The thermal store works in reverse to how you would think it would (like a normal cylinder). The boiler heats the the water in the thermal store, so when the hot water tap is turned on mains pressure cold water (or reduced down to 3bar) passes through the coil/heat exchanger in the cylinder and is heated by the hot water in the cylinder. The towel rail circuit is there so it can get rid of excess heat when the solid fuel is burning (like a heat sink) you are going to need a high and low limit pipe thermostats as close as possible to the solid fuel boiler so the return temperature is kept above 45~to stop corrosion and the high limit set to 90~ so the towel rail pump can kick in a draw some heat away from the thermal store. The gas/oil boiler needs a timer and aqua stat on thermal store wired in series (this is what the plumber has told you that is controlled by the hot water channel on programmer) if the
Boiler doesn't require over run then the pump on the boiler flow will also be wired in with the switch live to boiler.

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and i thought i was confused by earlier posts.

To be completely honest, if the Plumbers, as you say designed the heating system, it would surely be their responsibility to design / specify the heating system controller, at least that's my way of thinking.

plumbers designed a horse and the result was a camel.

telectrix said:

plumbers designed a horse and the result was a camel.

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I agree to some extent Tel, but if they designed the system they must hsve had some idea how it was going to work and what controls what, or am I hoping for too much?

soz, pete. been car boot. got an interesting item. £2. be giving it a test later.



just clamped tails to CU. 2kW oven pulling 8.5A according to above.

Pete999 said:

I agree to some extent Tel, but if they designed the system they must hsve had some idea how it was going to work and what controls what, or am I hoping for too much?

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They seem just to design for the plumbing only throw what info that has come with parts (well the ones they have not lost/thrown) in the electricians direction to sort.

telectrix said:

soz, pete. been car boot. got an interesting item. £2. be giving it a test later.

View attachment 36634

just clamped tails to CU. 2kW oven pulling 8.5A according to above.

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I remember them, nice find

Andy-1960 said:

What dictates when the towel rails need heat?

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It's a 3 channel programmer, so only thing dictating it is when it's turned on on the programmer.

LankyWill said:

is the fire a back burner?

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Yes.

Pete999 said:

To be completely honest, if the Plumbers, as you say designed the heating system, it would surely be their responsibility to design / specify the heating system controller, at least that's my way of thinking.

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I agree, first time I've been at a heating job that has been designed by plumbers & there's no drawings for electricians.

@Leesparkykent you seem to be pretty clued up on this so a question for you. I have fired the system up & I don't think I'm far away at all now. My question for you is regarding the manifold. Should this be wired totally separate from my wiring centre or wired into my wiring centre so that it only comes on when the UF heating is turned on at programmer?

telectrix said:

soz, pete. been car boot. got an interesting item. £2. be giving it a test later.

View attachment 36634

just clamped tails to CU. 2kW oven pulling 8.5A according to above.

Click to expand...

Nice find tel, I've still got my old Avo analogue clamp somewhere. Have to use the digital for most things nowadays though