Help with a relay box rewire

[HRP123]

Hi there thanks for your time to look at this.

I've got a multi pump / circuit system which is connected via a relay box to the boiler and Honeywell timer programmers. Picture attached.

Right now any single circuit can turn the boiler on an off at any time (assuming the programmers allow it). There are central heating (two zones), towel rails (one zone), underfloor heating (two manifolds) and hot water cylinders (2 of them).

I'm trying to rewire the system to make it hot water priority. So basically if the hot water circuit calls for heat, then the other circuits should go off temporarily to allow it to reach temperature as quickly as possible. This should allow me to range rate the boiler down (40kw current) and ensure it doesn't burn crazy amounts of gas trying to satisfy all open circuits at once.

I cannot see any diagrams online for these kinds of relays - I cannot even see the name of the product (generic plastic box). Can anyone help?

Thanks!!

 

[Timmy D]

John will probably be along with the data but I see no real reason for doing this.

Can’t see any big savings to be made. The hot water cylinders need x amount of energy to heat, the house has heat losses and needs y amount of energy to heat.

Hot water priority/range rating aren’t going to change the energy needed.

 

[Chuck]

Looks home made by a DIYer to me. (No strain relief, seems to be using the green/yellow core in mains cable for something other than grounding, etc.) It's what we call a 'death box'.

 

[ShaunCorbs]

Find the hot water relay there should be a normally closed terminal feed the ch zones from this eg remove the common live and install it into the Nc terminal

This means you would have to leave the hot water on permanently and let the stat do the work once satisfied it would allow you to use your heating

They look like finders should have model number on the side of the relay part

A1 is your live switch
A2 neutral
Note this can be flipped

Com is your perm live should be

No should be your call when the stats are calling for heat

Nc should be empty

 

[HRP123]

John will probably be along with the data but I see no real reason for doing this.

Can’t see any big savings to be made. The hot water cylinders need x amount of energy to heat, the house has heat losses and needs y amount of energy to heat.

Hot water priority/range rating aren’t going to change the energy needed.

Actually as this is a heat only boiler I'm trying to use controls and some manipulation to reduce consumption, as for some reason (not sure if it is the LLH or something about the setup) it does not modulate down well enough.

What I have found is that by range rating it down 40% I can get the flow temperature for the underfloor heating and radiators (assuming they call for heat at the same time) down to a level which they don't need to be mixed (making it more efficient, less cycling etc). However if the HW comes on at the same time, it strains the system as the flow cannot meet the required tank temperature.

 

[ShaunCorbs]

Might be worth changing the boiler so you can have two different flow temperature?

 

[HRP123]

Find the hot water relay there should be a normally closed terminal feed the ch zones from this eg remove the common live and install it into the Nc terminal

This means you would have to leave the hot water on permanently and let the stat do the work once satisfied it would allow you to use your heating

They look like finders should have model number on the side of the relay part

A1 is your live switch
A2 neutral
Note this can be flipped

Com is your perm live should be

No should be your call when the stats are calling for heat

Nc should be empty

Thanks for this. What I am going to try first is to use my controls / programmers to try and work out when HW demand is most likely and see if I can prioritise hot water manually. If I cannot, then I will get someone to help me rewire the box with the kind help of your guidance above. Thanks!

 

[HRP123]

Might be worth changing the boiler so you can have two different flow temperature?

Yes this is what I first thought about doing, although this will cost around £4,000-5,000 - so I'm not whether it is worth spending that when the current boiler still works. Ideally I was thinking if I can wait it out 2-3 years then heat pumps / costs may come to a point where they are a better option than currently.

 

[HRP123]

Looks home made by a DIYer to me. (No strain relief, seems to be using the green/yellow core in mains cable for something other than grounding, etc.) It's what we call a 'death box'.

Hence I don't want to call the original plumber back for this!

 

[ShaunCorbs]

Yes this is what I first thought about doing, although this will cost around £4,000-5,000 - so I'm not whether it is worth spending that when the current boiler still works. Ideally I was thinking if I can wait it out 2-3 years then heat pumps / costs may come to a point where they are a better option than currently.

And then inflation rises again so everything is 15% more expensive etc