Vaillant boiler taking ages to get to target temperature

[Brambles]

With respect to the Header, from the photos posted, that will probably have a high parasitic flow. I would have expected to see a Header with an oversized primary flow and oversized secondary return.

The term often used is Low Loss Header, the configuration posted gives hydraulic separation, but it is unlikely to be low loss

 

[b21playa]

Re install LLH.

Move second filter from primary flow to secondary return in to LLH.

Set secondary pump to constant. You want LLH flow in/out to be the same to prevent return water mixing. Can roughly check with temp probes on all LLH connections.

Set boiler to auto, not limited.

Get a vaillant LLH sensor (ntc) and attach to LLH and boiler.

Set to 65c, ensure return is low enough to condensate.

Forget about it and spend your energy somewhere else .

Hi

There is no filter on the primary flow, it’s a deaerator - spirotec rv2

For the pump speed do you mean constant speed or pressure?

The LLH sensor, is that the vr10 and does it need to go on primary flow on secondary flow?

Also would moving down to a 24kw boiler be ok?

Thanks in advance

 

[b21playa]

With respect to the Header, from the photos posted, that will probably have a high parasitic flow. I would have expected to see a Header with an oversized primary flow and oversized secondary return.

The term often used is Low Loss Header, the configuration posted gives hydraulic separation, but it is unlikely to be low loss

Hi there

The primary and secondary flow & returns are all 28mm up the point where they branch off to the 3 zone valves down to 22mm

 

[John.g]

Hi

There is no filter on the primary flow, it’s a deaerator - spirotec rv2

For the pump speed do you mean constant speed or pressure?

The LLH sensor, is that the vr10 and does it need to go on primary flow on secondary flow?

Also would moving down to a 24kw boiler be ok?

Thanks in advance

NO LLH now?
Can you set d.00 to auto, and put both zones in service until fully heated up, say 30/40 minutes and with the boiler target temp at 75C, then note the flow/return temps, d.40&d.41., that will give useful info, IMO.

 

[b21playa]

NO LLH now?
Can you set d.00 to auto, and put both zones in service until fully heated up, say 30/40 minutes and with the boiler target temp at 75C, then note the flow/return temps, d.40&d.41., that will give useful info, IMO.

Hi john

Haven’t got around to refitting LLH yet, but I’ll set to auto and report back temps

I may wait and get rgi to do it as I need to swap boiler out. The reason for the 624 was I’ve got access to a 3yr old one from a friend who’s removed it for a combi

 

[Chuck]

I may wait and get rgi to do it as I need to swap boiler out. The reason for the 624 was I’ve got access to a 3yr old one from a friend who’s removed it for a combi

Don't assume, without checking, that a Gas Registered engineer will be willing to install a second-hand customer-supplied combi.

 

[John.g]

Hi john

Haven’t got around to refitting LLH yet, but I’ll set to auto and report back temps

I may wait and get rgi to do it as I need to swap boiler out. The reason for the 624 was I’ve got access to a 3yr old one from a friend who’s removed it for a combi

Can you just do those tests now with no LLH connected, you don't require a RGI, just change d.00 to auto, set target temp to 75c and open the two CH zone valves and then check d.40&d.41 say 15/20 minutes after the target temperature has been met.

 

[b21playa]

Can you just do those tests now with no LLH connected, you don't require a RGI, just change d.00 to auto, set target temp to 75c and open the two CH zone valves and then check d.40&d.41 say 15/20 minutes after the target temperature has been met.

Right d.40 is 75 and d.41 is 55

All rads hot apart from loft which saw temps high as 50c flow. Not sure if this is due to height or them being old rads on 8/10mm

The rgi was referred to for changing boiler and getting him to add LLH back in

 

[b21playa]

Don't assume, without checking, that a Gas Registered engineer will be willing to install a second-hand customer-supplied combi.

Don't assume, without checking, that a Gas Registered engineer will be willing to install a second-hand customer-supplied combi

Don't assume, without checking, that a Gas Registered engineer will be willing to install a second-hand customer-supplied comb

Don't assume, without checking, that a Gas Registered engineer will be willing to install a second-hand customer-supplied combi.

Hi

Totally agree, it would be the rgi who decommissioned it and they are happy to install. He said if he didn’t decommission it, wouldn’t install it

 

[John.g]

Right d.40 is 75 and d.41 is 55

All rads hot apart from loft which saw temps high as 50c flow. Not sure if this is due to height or them being old rads on 8/10mm

The rgi was referred to for changing boiler and getting him to add LLH back in

At 75C/55C you are getting 29.3kw rad output or 89.2% of your 33.5kw T50 rating, if you were to run at a flow temperature of 65C then you will get a return temperature of 49.4C with 22.81kw rad output or 68.1% of your 33.5kw T50 rating, so a 24kw boiler may be ok especially as you probably won't be running two zones together for very long periods.