Wiring up a relay (PHOTOS enclosed) - please help

The ch room stats operate the zone valves - myself I cannot see why relays are indicated tbqh Billy.

 

Is the pump wired to the boiler, as in the S plan circuit, or does your boiler control the pump to allow for
pump overrun?

 

Correct. Multi-pumps = relays needed.

For UFH systems the manufacturer will quite often incorporate this in their supplied wiring centre, but otherwise use a relays.

 

In the main relays are not required. The zone valve is the relay. Back to basics the thermostat/timer opens valve and the valve energises the boiler. The problem is the pump with an old boiler the pump was energised at the same time as the boiler but with modern condensate the boiler senses the return water temperature as well as the supply water temperature and adjusts the flame hight to keep the return water temperature below the limit to ensure the exhaust gas is below around 80 degs C so latent heat is extracted.

Where two heating circuits come from the same boiler then some control is required so that one system does not close down the boiler when the other one still requires heat. As a result the combi-boiler became popular where the manufacturers software controlled the balance between central heating and domestic water. However with the move to solar panels and the requirement to put excess energy into the domestic water there has been a move back to storage tanks.

However the storage tank is very different and the boiler heats the tank and the tank feeds central heating and domestic water so solid fuel back boiler, solar panels, and boiler all feed into the same system. So the boiler only heats one item the storage tank.

So question one is what boiler are you using as the system you are showing would only work with a pre-condensate type boiler. Since you can't now buy a boiler which has not got the double heat exchanger or the condensate boiler the system will not allow a boiler change in the future.

My son originally wanted to fit the new system and he found only real way is a computer called a controller which has all the thermostats connected to it and all the TRV WiFi heads connected to it and it does all the clever stuff. However the price put him off. So his underfloor heating is from back boiler of solid fuel range cooker and central heating completely independent.

I am sure you can get the old style boiler to work with simple relays but if the old boiler fails what then? Is it really worth setting this all up on an old boiler?

 

Is one pump running for the main heating zone and the HW, the other pump for second heating zone? When the pump for the second heating zone runs, do you want the main pump to run or not?

 

Don't understand myself. No UFH indicated by op. One zone valve controlled by t-stat for one section of heating, the other for the other section, and the third for hot water run via controller/tank stat on the hw primary.

I did once have a problem with backflow on returns on one system fitted a long time ago which caused rads to slightly heat when off and HW engaged, a single check valve on the return sorted it (strategically placed)

 

Back flow of lecky, not water JP.

Two pumps, but they don't both want to come on with boiler, so you can't just common them together, you split with a relay. Sometimes one pump is not enough for large areas. You could go bigger pump, but then it's too big when just one area calling.

 

I had to do that on my system a few years ago JP because the return of the upstairs rad circuit (single pipe system) goes back to the boiler via the cylinder coil return so the rads were getting warm when the water was being heated, a check valve before the tee cured it!

 

When I was a youngen in my first house I did exactly that, teed into the closest pipes for a rad in the toilet backing onto airing cupboard. I thought the electrics must be faulty as rads getting hot when just water on. I think I had teed into the CH flow, but the return was on the cylinders return to the boiler, not the rads. The rads return joined the cylinders right at the boiler.

Plumber mate pointed out the error, and it's stuck in my mind since.

 

If no UFH then no need for the extra pump.
If an extra pump is fitted then you have a plumbing issue.

 

Do you want the new zone to call for heat independently from the original zone and fire the boiler? If so that can be done, let me know

 

I think I have your mind on this;
The HW is irrelevant. But you will need a relay for each heating zone or they will deny each other

 

Dont follow this myself, if an extra zone is added to an S-plan and needs an extra pump then I have always connected the pump to the brown of the new zone valve so if the new thermostat calls for heat the valve and pump operate together. The main system pump is fired by the boiler.

I have seen 1 way manifolds/pumps for UFH, for example a conservatory, that are added on to systems and they have a built in temperature switch so the pump only runs if 1, the stat is calling for heat and 2, the water from the boiler is warm, quite a simple way of doing things.

If you do need to use relays then these are easier to install using a small CU type enclosure.

 

Powering the pump with valves brown is considered bad practice as if valve fails to open, the pump has nowhere to pump. Using a relay, switched by the valves microswitch gives you extra clean contacts to use to power the second pump and the main pump/boiler. The relay keeps the pump lives separate to prevent them influencing each other.

I would generally use a din rail enclosure with fixed lid, relays clipped to din rail, and use din rail terminals for the interconnections. Don't use a traditional wiring centre, have it al in the din rail enclosure. IMO are the most popular around here.

 

If using external input sources then a Buffer Vessel or a Big Low Loss Header is required.

DHW can be kept separate using a 3 port valve

 

Hi Wellesley
I like Peter Palmer's relay better than the ones you have; but as from your post here is my answer:

I was wrong you only need to modify Plan S with one relay

Tx is the block on plan S: Rx is the relays

From plan S the only change you need to make is to give your boiler an isolated and independent feed from T10 so pull the boiler L from T10 and pop it on the unused T9 on the block.

RELAY 1 MODIFY PLAN S
R2+R6 TO T10
R10 TO T2
R7 TO T9

As you can see this only isolates T9 from T10 apart from that Plan S is unchanged

All you need to do now is to take the com (orange) you have to T10 from the new zone and use it as the feed to your new pump and to T9 to fire the boiler

That was fun

Thanks Pal I'm sure there is a more elegant way of doing this

 

Hi again Wellesley

on your new zone you have Normally Open (grey) of your V4043H going to T1 and not T4: You have cut your timer out, and your new zone is on continuous !! You didn't want this right