Vaillant boiler taking ages to get to target temperature

[b21playa]

There brilliant and priority hot water and wc heating but you will have cooler rads then stock temp etc

Thanks. Vaillant controls are a bit of a mine field, not sure exactly what I would need? Vr66 wiring centre, weather comp sensor, not sure of which thermostats for both floors and then how to incorporate a vr10 sensor for dhw temp.

Hw priority would be great, can set flow at higher temp for quicker recharge

 

[John.g]

Thanks. Vaillant controls are a bit of a mine field, not sure exactly what I would need? Vr66 wiring centre, weather comp sensor, not sure of which thermostats for both floors and then how to incorporate a vr10 sensor for dhw temp.

Hw priority would be great, can set flow at higher temp for quicker recharge

Are you thinking of not re installing the LLH?.
How are the rads performing now at 65C??, if the return is like the previous 47C then you will be getting reasonable condensing and you may be able to further reduce the target temp. Are you still just running one zone at the time with d.00 set to 20kw or both with d.00 set to 30kw or whatever?.

 

[b21playa]

Are you thinking of not re installing the LLH?.
How are the rads performing now at 65C??, if the return is like the previous 47C then you will be getting reasonable condensing and you may be able to further reduce the target temp. Are you still just running one zone at the time with d.00 set to 20kw or both with d.00 set to 30kw or whatever?.

I’m thinking of leaving it for a bit as it is and see how it goes. Rads seem to be performing fine at 65c, don’t want to reduce anymore as cylinder heat up times will need to be increased hence the thought of changing controls for hw priority on a higher flow temp. Still running d.0 at 20kw and single zone at a time

 

[Chuck]

Given how much is being being built on the assumption, I'd want to check (using a stopwatch) and the gas meter, that the power the boiler claims to be delivering to the system matches the amount of gas being consumed.

 

[Timmy D]

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 .

 

[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.

 

[b21playa]

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.

Many thanks John, your help is much appreciated.

I’ll arrange for boiler to be replaced in the new year along with reinstating the LLH and taking advice from Timmy for addding a filter to the secondary return, a ntc sensor and setting pump speed to constant. Just need to work out how to wire it up and program the boiler

 

[John.g]

Let us know how you get on.

I was looking at those UPS3 PP2 curves the other day for someone else and unless I misunderstood, you said that (with LLH in service) with d.00 set to 20kw and both zones on that you were still getting the boiler target temp of 75C, we now know that the primary flowrate is ~ 22LPM so the secondary flowrate must only have been ~ 7LPM to reduce the rad output to ~20kw. I would be surprised if a secondary head of more than 3M would be required to give a (secondary) flowrate of 22LPM, the UPS3 on PP2 will almost produce that, (it will give 19.5LPM at 2.6M) so looks to me like the pump isn't working as it should (or else some fundamental LLH problem), it might be worth removing the pump head and cleaning out the pump ports and also the impeller vanes, a tie wrap is handy for this, if all clean then the pump may have developed a fault, unfortunately this and a lot of other Grundfoss pumps don't display the power in watts from which the performance can easily be derived from the pump curves, you can allways stick a energy monitor on the end of the pump cable. Anyhow, one way or the other, worth bearing in mind.

 

[b21playa]

Let us know how you get on.

I was looking at those UPS3 PP2 curves the other day for someone else and unless I misunderstood, you said that (with LLH in service) with d.00 set to 20kw and both zones on that you were still getting the boiler target temp of 75C, we now know that the primary flowrate is ~ 22LPM so the secondary flowrate must only have been ~ 7LPM to reduce the rad output to ~20kw. I would be surprised if a secondary head of more than 3M would be required to give a (secondary) flowrate of 22LPM, the UPS3 on PP2 will almost produce that, (it will give 19.5LPM at 2.6M) so looks to me like the pump isn't working as it should (or else some fundamental LLH problem), it might be worth removing the pump head and cleaning out the pump ports and also the impeller vanes, a tie wrap is handy for this, if all clean then the pump may have developed a fault, unfortunately this and a lot of other Grundfoss pumps don't display the power in watts from which the performance can easily be derived from the pump curves, you can allways stick a energy monitor on the end of the pump cable. Anyhow, one way or the other, worth bearing in mind.

I will keep you all posted - just waiting on a date from the rgi, I’m on the cancellation list if anytime comes up.

I’ll take a look at the pump tomorrow and see if it’s blocked and not spinning freely. I wonder if it was the pipework, the flow comes out the pump and then has 2 x 90deg bends to go back on itself. There also wasn’t an air vent on the bend (highest point in that leg)

If the pump is bad, are there any better alternatives?

 

[John.g]

After inspection/cleaning you can then re try it with the re installed LLH, a few temperatures will then establish if its OK or not.
The 6M DAB Evosta3 is a good choice or my own (4 year old) 6M Wilo Yonos Pico with the 3 traditional CC settings plus CP and PP modes which can be incrementally changed in 0.1M steps to give almost any required flowrate. Both of these pumps display the power and the flowrate.

 

[b21playa]

After inspection/cleaning you can then re try it with the re installed LLH, a few temperatures will then establish if its OK or not.
The 6M DAB Evosta3 is a good choice or my own (4 year old) 6M Wilo Yonos Pico with the 3 traditional CC settings plus CP and PP modes which can be incrementally changed in 0.1M steps to give almost any required flowrate. Both of these pumps display the power and the flowrate.

I’ll test it all before buying a new one, could be dirty, could be due to the way it was piped originally. Easy enough to change at a later date anyway

 

[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 Timmy

Should I move the filter from the primary return to secondary return or get another one?

Thanks

 

[b21playa]

Let us know how you get on.

I was looking at those UPS3 PP2 curves the other day for someone else and unless I misunderstood, you said that (with LLH in service) with d.00 set to 20kw and both zones on that you were still getting the boiler target temp of 75C, we now know that the primary flowrate is ~ 22LPM so the secondary flowrate must only have been ~ 7LPM to reduce the rad output to ~20kw. I would be surprised if a secondary head of more than 3M would be required to give a (secondary) flowrate of 22LPM, the UPS3 on PP2 will almost produce that, (it will give 19.5LPM at 2.6M) so looks to me like the pump isn't working as it should (or else some fundamental LLH problem), it might be worth removing the pump head and cleaning out the pump ports and also the impeller vanes, a tie wrap is handy for this, if all clean then the pump may have developed a fault, unfortunately this and a lot of other Grundfoss pumps don't display the power in watts from which the performance can easily be derived from the pump curves, you can allways stick a energy monitor on the end of the pump cable. Anyhow, one way or the other, worth bearing in mind.

Took the head off the pump today; impeller turned fine but there seemed to be some ‘end float’ which I’m not sure if it’s normal

Water colour wasn’t the best so I’ve added some cleaner and connected my twin magnacleanse

 

[John.g]

Took the head off the pump today; impeller turned fine but there seemed to be some ‘end float’ which I’m not sure if it’s normal

Water colour wasn’t the best so I’ve added some cleaner and connected my twin magnacleanse

That looks like excessive wear on the housing where the impeller fits into??, the pump looks quite reasonably clean IMO.
If you have the time/inclination I would suggest to buy a plug in energy monitor like mine below (~ £15ish) and connect a 3 pin plug to the pump cable, connect a mains supply to the pump inlet (as long as its not > say 5bar) stick a bit of pipe on the pump discharge with a gate/lever isolating valve (or a old pump isolating valve with a bit of pipe on the end) on the end, run the pump from a extension lead at say CC1, CC2, CC3 and PP2, and measure the flowrate into a bucket with the valve throttled to give a suitable flowrate (can check that later) and note the power from the energy monitor.