Adding room and cyclinder stat to an old system with 2 pumps

[readies]

Hi
I have and old Oil fired boiler with two pumps one on the Central Heating circuit and one on the hot water. Currently I have a Honeywell 102E7 mini programmer controlling the system. With this controller you can either have HW (hot water) or HW and CH (Central Heating).
It is currently wired so the HW pump and boiler are always on during the program on time. If the CH is set on then the CH pump is also on during the program on time. If you look at the manual for the 102E7 (apparently made by Danfoss see here <http://www.plumbnation.co.uk/site/danfoss-randall-102e7-7-day-gp-mini-programmer-087n653400/102E7%20Guide.pdf>) this is the first diagram with a few tweaks i.e no room stat and the HW pump is also wired to output 1 (HW on).

Ok - so adding the room stat is just as in this diagram - no problem.
However, cannot seem to find anything that describes how to add a Cylinder stat to control both the HW pump and the boiler.

I think what I need to do is wire the cylinder stat to control the HW pump (insert the cylinder stat between output 1 and the HW pump) and then take the outputs from both stats to a relay of some sort with two inputs to control the boiler.

Is this correct or is there a better (cheaper) way of doing this?
If this is correct what sort of "relay" do I need?
Would it be safe to wire the boiler always on from output 1, even with the HW pump switched by the cylinder stat? Not sure that this would be of any benefit.

The boiler is an Oil fired Camray 5 (basic controls), and does not seem to require any pump overrun - at least as far as I can tell it has not had any for the past 15 or so years.

Thanks in advance

 

[simond]

If you have a two pump system, as you rightly say the only way you can easily separate demands for HW and CH on the boiler is to fit two contactors, or a relay.

In this way the contactor 1 can be energised when the CH timer and stat is on, this will energise the CH pump and the contactor. Or the HW timer can be on, wired thru the cylinder stat to the HW pump, so Contactor 2 will be energised.

Common the outputs from both contactors to the boiler. We often use this configuration where the customer has a two pump system and we're changing the boiler.


Alternatively, you could buy a Grundfos pump plan, which does all this for you with an integrated wiring centre. But the easiest way is the first option, no plumbing required.

 

[CareerChangeChancer]

Sorry to hijack slightly.

What plan is a 2 pump system?

Is this an SMC?

CCC

 

[Terrywookfit]

There is no" Plan" as motorised valves were not used.

Normally known as Fully pumped using two pumps.

 

[readies]

If you have a two pump system, as you rightly say the only way you can easily separate demands for HW and CH on the boiler is to fit two contactors, or a relay.

In this way the contactor 1 can be energised when the CH timer and stat is on, this will energise the CH pump and the contactor. Or the HW timer can be on, wired thru the cylinder stat to the HW pump, so Contactor 2 will be energised.

Common the outputs from both contactors to the boiler. We often use this configuration where the customer has a two pump system and we're changing the boiler.


Alternatively, you could buy a Grundfos pump plan, which does all this for you with an integrated wiring centre. But the easiest way is the first option, no plumbing required.

Any particular type / specification of contactor I should look for?

 

[simond]

D_Hailsham loves this sort of thing.....must be on hols.

Anyway, although you could use Octal relays the neater solution is a couple of these

http://www.tlc-direct.co.uk/Products/WYMESB20.html

and a 4 way box to put them in

http://www.tlc-direct.co.uk/Products/BHCT4.html

You could use a two way box, but some contactor instructions ask for a vacant slot alongside for heat dissipation, so I always use a 4 slot box.

You wire mains to each contactor switch input, and the boiler across both outputs. The HW ON is linked to the coil on one, the CH ON is linked to the coil on the second. This way either or both HW/CH can energize the boiler independently.

 

[matt1e]

as simond has said, you need to use a contactor or relay
you can do what you req using one relay. will do a drawing for you if you need one
(but not now due to it being late and I've been on the voddie)

Matt

 

[matt1e]

did a quick one anyway

View media item 31613
Regards

 

[diytrier60]

Hi Everyone

Having read through readies post and all your replies I now have a good answer to most of my problem that is very similar to readies with one exception. My boiler is in an outbuilding and therefore requires a Frost Stat.

Can anyone advise on how to wire in a frost stat along with the cylinder and room stats, I assume either pump should also run if the boler fires up?

The boiler is a very old Camray 72/95 oil fired pressure jet boiler with a simple Danfoss 4033 timer control. I have now added a wireless programable room stat for more control and the cylinder stat was already fitted.

Originally the boiler was wired in so that it became live anytime the hot water was selected on or timed regardless of any demand from hw or heating and the frost stat was wired to the same terminal making the HW circuit live when the frost stat activated.

So I would like suggestions on how to allow the boiler to come for either HW or Heating or Frost demand individually or can the frost stat link to the HW circuit.

Many thanks in advance for your help.