Vaillant 438 s.53 code only with hot water now

[The831Bunny]

Re-reading my description of current hot water heating it might look as if it is cycling - its not

The heating comes on strong(you can hear a nice roar) until it gets to 85/6 then you can here the heating back off a little but still on until temp drops to 81ish then comes on strong again - it repeats this until it stops but never cycles even at the end.

Given that the hot water is now not cycling with it set to 20 and it seems ot heat up well - would I be right in thinking I can leave alone?

Unfortunately I have no idea where the VR10 has gone or why it was not fitted in the first place or even if there are enough free wires in the cable run from the cylinders back to the boiler!

The boiler is due a service though - how can I find some one around TW19 who is as knowledgeable as you guys?

Thank you both so much for all the help!

I wondered if you meant it was cycling, but good it's not! The 'correct' setting of D.77 is when the boiler modulates (goes quieter) at the end of the reheating cycle as it nears the desired temperature. 20kw sounds about right then, maybe try raising it to 22Kw, it may shave off a couple of minutes. If you find its on/off cycling at anytime, back it off a couple of KW and leave it there.

The quicker you can reheat the cylinders, the sooner the heating comes back on usually you'd expect those cylinders to reheat from cold in approx 30-40 mins. Obviously less for one bath or shower. Sounds like it's in the ballpark now anyway Timing wise on well lagged modern cylinders in a family home, I'd recommend setting the HW to be off 11pm to 5am, on at all other times. That way the HW can be reheated as its used, thus having very little impact on the heating of the house.

 

[Biggles..]

If you pipe the cylinders up as a Christmas tree to all connections , as long as the cylinders are identical then you'll get exactly the same temp in all of them.
Least then if you put the vr10 in a pocket on the outlet you'll have s pretty accurate idea of DHW temp.

Absolutely Lee, but it would only take the coil to be blocked or a balancing valve to be shut on the first cylinder with the VR10, and the second cylinder would reach the primary temperature... VR10 needs to be 1/3rd of the way up a cylinder to sense the drop.

Two cylinders, just bang in the vrc630. lol

One thing we've found is that you could effectively range rate the boiler down to only do the rads, say 20kw tops, and reheat the water during the long heating off period say 11pm-5pm.12-4pm. Modern cylinders loose little heat so will hold heat.
Lots of our hotels do this, get small boilers but utilise the non heating periods to reheat the cylinders.

 

[The831Bunny]

If you pipe the cylinders up as a Christmas tree to all connections , as long as the cylinders are identical then you'll get exactly the same temp in all of them.
Least then if you put the vr10 in a pocket on the outlet you'll have s pretty accurate idea of DHW temp.

Absolutely Lee, but it would only take the coil to be blocked or a balancing valve to be shut on the first cylinder with the VR10, and the second cylinder would reach the primary temperature... VR10 needs to be 1/3rd of the way up a cylinder to sense the drop.

Two cylinders, just bang in the vrc630. lol

One thing we've found is that you could effectively range rate the boiler down to only do the rads, say 20kw tops, and reheat the water during the long heating off period say 11pm-5pm.12-4pm. Modern cylinders loose little heat so will hold heat.
Lots of our hotels do this, get small boilers but utilise the non heating periods to reheat the cylinders.

You and me work to a similar thought train mate lol! Didn't want to over complicate things for the OP, he hasn't atcually found his VR65 yet

Don't see as many commercial set ups as you, and have only come across them with one calorifier too on a 630. Guess you could add it as another zone, just never seen it to play with