Heating & Hot Water on together problems

[eddr]

Hi All,

I have recently purchased a house which we have not moved into yet, and first of all discovered that the old programmer which was a Danfoss CP15 would not allow heating + hot water to be on at the same time - the lights would go mental and you'd hear the relays clicking away.

So - Replaced it with a Siemens RWB29 which went straight onto the same backplate - Great, it worked a treat, heating and hot water coming on at the same time, both working fine when the others off also, and the mid-pos valve operating as it should in each situation.

The twist here is I am doing some home automation, and have put 2 remote controlled relay modules inbetween the HW ON and CH ON from the backplate of the programmer. This initially didn't work, then it magically started working - Now it doesn't work again! With the relays in, the programmer is set to constant (Or manual on) for both hot water and central heating. Surely the relays are just doing what the programmer does?

So I took the relays out of the 'loop' and put it back to normal which didn't work until after I played around with turning hot water and heating on and off a few times, it then seem to sort itself out like it was when we first put the programmer in - in other words working normally.

By the way - Hot water works fine through the programmer with the relays in the 'loop' and without, it just seems to be central heating. ALSO I have taken the room thermostat out of the 'loop' as thought maybe this was at fault, which it is not (As heating does come on sometimes after 'playing' around). If you're wondering, the live and call for heat have been bridged.

All the wiring is going through a Honeywell wiring centre.

Any ideas?

 

[mysteryman]

Most control systems such as yours require a 'hot water off' signal from the programmer. You need either to reinstate this, or use changeover contacts on the dhw relay. Why further home automation? What's wrong with the new timer?

 

[picasso]

Your 3 port valve uses a hot water off signal if not from the programmer then from the hot water cylinder stat, as you have found out putting a couple of relays on the programmer wont work, you may have to change to an s plan for your relays to work.

 

[bengasman]

I have recently purchased a house which we have not moved into yet, and first of all discovered that the old programmer which was a Danfoss CP15 would not allow heating + hot water to be on at the same time...
Any ideas?

Yep. By a 21st century timer that allows separate dhw and ch timing. You never want them on at the same time.
Secondly, get a rgi in to service the boiler and check the whole system over whilst the weather is still good.

 

[eddr]

First of all, thanks for all your replies....

Most control systems such as yours require a 'hot water off' signal from the programmer. You need either to reinstate this, or use changeover contacts on the dhw relay. Why further home automation? What's wrong with the new timer?

I wondered what this was for - I have just read about how the mid-position valve works, and it now makes (some) sense why HW OFF is needed. All being said, The HW OFF is still in place.

Why home automation? Take a look at www.idratek.com - you may be drawn in. There are many others, but Idratek is my chosen one. Nothing wrong with the new timer, I just want to be able to control things a bit more!

Your 3 port valve uses a hot water off signal if not from the programmer then from the hot water cylinder stat, as you have found out putting a couple of relays on the programmer wont work, you may have to change to an s plan for your relays to work.

As I said above, I now understand what the HW OFF is for. I shall go off and read about s plan....

I have recently purchased a house which we have not moved into yet, and first of all discovered that the old programmer which was a Danfoss CP15 would not allow heating + hot water to be on at the same time...
Any ideas?

Yep. By a 21st century timer that allows separate dhw and ch timing. You never want them on at the same time.
Secondly, get a rgi in to service the boiler and check the whole system over whilst the weather is still good.

I should hope this timer I got is more than 21st century! It DOES allow seperate, so did the old one - it just wouldnt work. I shall be getting everything serviced well in time for the winter!


I was thinking about putting the relay for central heating on the thermostat live + call for heat, but this is not going to help as I still have the HW OFF problem....

The relays have a common, normally open and normally closed... see http://www.idratek.com/public/docs/datasheets/SRH002_DS.pdf

Any ideas then?

Help muchly appreciated!

 

[bengasman]

I should hope this timer I got is more than 21st century! It DOES allow seperate, so did the old one - it just wouldnt work.

I mentioned independent, not separate.
Which one do you have now?

 

[eddr]

Independant, seperate, means the same to me...
Its a Siemens rwb29, as stated in my first post.

I have now been given some advice to try the following:

Take the hot water away from the timer, and use the relays normaly open and normaly closed for HW ON and HW OFF - I beleive this should work fine, and put the heating back as it was but use relay instead of room thermostat.

 

[bengasman]

Independant, seperate, means the same to me...

Totally different.

Its a Siemens rwb29, as stated in my first post.

Had a quick look at the manual, and it doesn't mention independent; that ususally means it is not.