How to set a bypass valve

[BlueLoo]

The pump does seem to be quietThank you BlueLoo and Johntheo5

I am a real novice when it comes to central heating unfortunately so any advice gratefully received. The pump does seem to be quiet powerful to me as some of the TVRs (TRV4s) are noisy with water velocity. I believe from Grundfos data that using PP2 as an option is not a good idea with a ABV. What setting would you suggest for the ABV with the UPS3 on CP1.

Us CS mode.
Speed 1 unless you need to go to speed 2.

With an ABV, PP and CP are useless.

After setting the pump to CS 1, reset the ABV according to the online instructions (really easy).

You'll end up about .4 ish i think.

 

[Graham J W]

Worth me saying how I got to this situation.
Updated old vented system to sealed system. Retained Valiant ecotech plus 424 boiler (24KW) and magnaclean filter. New Grundfos UPS3, Honeywell bypass, motorized valves for downstairs CH, upstairs CH and HW, Honeywell home wireless wall thermostats (one up one down), extended 22mm flow and return with localised 15mm feeding 5 vertical rads downstairs and 4 horisontal Stelrads plus towel rail upstairs. All have Drayton TRV4s. Pressure vessel in airing cupboard.
My loading is approximately 12.5 KW. Upstairs well insulated so that circuit hardly comes on leaving downstairs as the main loading. Flow temp set at 62C and pump on CP1. Bypass set 4.5.
Everything is good when starting from cold (TRVs all open). Velocity noise experienced from downstairs vertical rads (through TRVs). When boiler reaches working temperature at around 60C it maintains it for 20 minutes or so then gradually climbs before going into anti cycle mode ( set at 4 minutes). Pump then stops and starts again, boiler fires up for a few minutes until temp reaches 66C and starts anti cycle again. I have tried balancing the system via the locksheilds and the TRVs ( Draytons balancing key). The latter was worse. If all TRVs are on max the boiler holds the running temperature for much longer. Anti cycle mode is far less frequent. Whatever I try, the flow and return temperatures have no more than 10C difference at best.
Is it feasible that with "extended" 22mm flow and returns plus the new UPS3 the velocity is too high ?.
PS all pipework apart from direct connections to the boiler are plastic. (stabbings to rads are copper).
boiler setup, rad and valve pictures attached.

 

[Johntheo5]

Virtually impossible to set the ABV with a CP setting but I suggest the following as a temporary measure (until you get a manual bypass installed) which should work quite reasonably well even though you will have a constant bypass.
If you have a tower rad ensure both valves fully open, if one is a TRV then open this fully, if you havn't got a towel rad open a TRV fully on your smallest rad or one that wont overheat the room if possible. Put the ABV to setting 0.5.
If this is satisfactory change the UPS3 mode to PP2,

 

[Johntheo5]

Us CS mode.
Speed 1 unless you need to go to speed 2.

With an ABV, PP and CP are useless.

After setting the pump to CS 1, reset the ABV according to the online instructions (really easy).

You'll end up about .4 ish i think.

Unfortunately, CS1 does not behave

Worth me saying how I got to this situation.
Updated old vented system to sealed system. Retained Valiant ecotech plus 424 boiler (24KW) and magnaclean filter. New Grundfos UPS3, Honeywell bypass, motorized valves for downstairs CH, upstairs CH and HW, Honeywell home wireless wall thermostats (one up one down), extended 22mm flow and return with localised 15mm feeding 5 vertical rads downstairs and 4 horisontal Stelrads plus towel rail upstairs. All have Drayton TRV4s. Pressure vessel in airing cupboard.
My loading is approximately 12.5 KW. Upstairs well insulated so that circuit hardly comes on leaving downstairs as the main loading. Flow temp set at 62C and pump on CP1. Bypass set 4.5.
Everything is good when starting from cold (TRVs all open). Velocity noise experienced from downstairs vertical rads (through TRVs). When boiler reaches working temperature at around 60C it maintains it for 20 minutes or so then gradually climbs before going into anti cycle mode ( set at 4 minutes). Pump then stops and starts again, boiler fires up for a few minutes until temp reaches 66C and starts anti cycle again. I have tried balancing the system via the locksheilds and the TRVs ( Draytons balancing key). The latter was worse. If all TRVs are on max the boiler holds the running temperature for much longer. Anti cycle mode is far less frequent. Whatever I try, the flow and return temperatures have no more than 10C difference at best.
Is it feasible that with "extended" 22mm flow and returns plus the new UPS3 the velocity is too high ?.
PS all pipework apart from direct connections to the boiler are plastic. (stabbings to rads are copper).
boiler setup, rad and valve pictures attached.

A anticycle time setting of 4/5 minutes is far too low IMO, it gives a actual recycle time of 2 minutes at 60C, suggest resetting it to a setting of 15 minutes which is a actual recycle time of 5 minutes at 60C.

Also the pump should not stop during recycle., presume you havn't got a roomstat(s).

Can/have you tried UPS set to PP2 with one rad as a bypass?? I see you have a towel rad.

The minimum output of the 424 is 6.2kw.

Edit: I see you have "Honeywell home wireless wall thermostats (one up one down)" so why have TRVs on all? rads, maybe your problem is simply one roomstat shutting off and the remaining load is less than 6.2kw, flowtemp then rises to targettemp+5C, burner trips, recycle?.

 

[BlueLoo]

Worth me saying how I got to this situation.
Updated old vented system to sealed system. Retained Valiant ecotech plus 424 boiler (24KW) and magnaclean filter. New Grundfos UPS3, Honeywell bypass, motorized valves for downstairs CH, upstairs CH and HW, Honeywell home wireless wall thermostats (one up one down), extended 22mm flow and return with localised 15mm feeding 5 vertical rads downstairs and 4 horisontal Stelrads plus towel rail upstairs. All have Drayton TRV4s. Pressure vessel in airing cupboard.
My loading is approximately 12.5 KW. Upstairs well insulated so that circuit hardly comes on leaving downstairs as the main loading. Flow temp set at 62C and pump on CP1. Bypass set 4.5.
Everything is good when starting from cold (TRVs all open). Velocity noise experienced from downstairs vertical rads (through TRVs). When boiler reaches working temperature at around 60C it maintains it for 20 minutes or so then gradually climbs before going into anti cycle mode ( set at 4 minutes). Pump then stops and starts again, boiler fires up for a few minutes until temp reaches 66C and starts anti cycle again. I have tried balancing the system via the locksheilds and the TRVs ( Draytons balancing key). The latter was worse. If all TRVs are on max the boiler holds the running temperature for much longer. Anti cycle mode is far less frequent. Whatever I try, the flow and return temperatures have no more than 10C difference at best.
Is it feasible that with "extended" 22mm flow and returns plus the new UPS3 the velocity is too high ?.
PS all pipework apart from direct connections to the boiler are plastic. (stabbings to rads are copper).
boiler setup, rad and valve pictures attached.

You have a modern, new system.
There should be no need to have the LS valves throttling. This will be counter productive to the boiler when at full demand.

Take note of the settings but open them up full.

Use CS 2(?) speed on the pump, set ABV as per instructions.

 

[Graham J W]

Hi Johntheo5

I,m beginning to think that this is a loading issue. Because I am in the middle of refurbishing the house I do not have all the rads fitted. So the current total loading is 10.59 KW. Split 5.87 KW downstairs and 4.72 KW upstairs.
Boiler is 24 KW.
All rads have TRV4s fitted.

We have just had shed loads of insulation put upstairs so it needs very little heat and with the combination of the wall stat and TRVs all closing quickly the boiler is mainly only heating the downstairs circuit at 5.87 KW.

Now not surprising that the return flow temperature is high and anti cycle mode is coming on so much.

As a trial, I have latched open the upstairs motorised valve by the boiler so the towel rail and upstairs pipework heat up plus I have taken the head off the downstairs hall rad and opened the locksheild.

The anti cycle mode still activates but far less frequently ! So I must be onto something yes ?.

 

[SpecialK]

Can I just ask a silly question? What is the problem with the anti cycle mode activating? Are your rooms not getting up to temp?

If the TRV's close and the return temp goes up the boiler goes in to anti cycle? This is how my system works anyway as the boiler can't modulate down very low. However the circulating pump does continue to run when in anti cycle.

 

[Graham J W]

Hi SpecialK

Rooms are not getting up to temperature.

 

[Graham J W]

Hi Johntheo5

Update. I lowered the partial loading setting to 12KW. This dramatically slowed down the the initial heating up time from cold and seemed far more controlled. With the flow temperature still set at 63, it come up to temperature and modulated for some time. Great I thought.
Then the return temperature started to climb near to the flow temperature. (I think due to the upstairs radiator TVRs closing). The decreasing temperature variance between flow and return then seemed to be the cause of starting the anti cycle mode ?.
So the system issues seem to be 1) load is to low and adjusting the partial load setting looks to have helped that. 2) the return flow temperature is to high. Possible causes could be a) not enough heat loss or b) return flow is to quick. May be both ?.

The 5 downstairs rads are all tower tubular (basically steel tubes I think)

Any thoughts, suggestions please.

 

[Johntheo5]

Initially when TRVs start closing in then the return temperature start falling, resulting in a increasing dT, the rad(s) output starts reducing, the boiler modulates downwards to maintain the target temp at 63C, then when the boiler is at its minimum output (and TRVs continuing to throttle down) the return temp (d.41) will continue to FALL but the flow temp (d.40) will start rising and if the TRVs continue to throttle down then the flow temp (d.40) will reach 68C and the burner will trip, if all the TRVs are closed but other rads are supplying a flowrate then the return temp and the flow temp will start to rise until flow temp reaches 68C and burner trip. but I cant see the return temperature starting to climb nearer the flow temperature, the only logical explaination is that the flow temp (d.40) is reaching 68C and tripping the burner due to the rad demand being below the boiler minimum output. The only flow/return dT that I'm aware of that trips the burner is a high one at ~ 30C.

 

[noddy997]

Initially when TRVs start closing in then the return temperature start falling, resulting in a increasing dT, the rad(s) output starts reducing, the boiler modulates downwards to maintain the target temp at 63C, then when the boiler is at its minimum output (and TRVs continuing to throttle down) the return temp (d.41) will continue to FALL but the flow temp (d.40) will start rising and if the TRVs continue to throttle down then the flow temp (d.40) will reach 68C and the burner will trip, if all the TRVs are closed but other rads are supplying a flowrate then the return temp and the flow temp will start to rise until flow temp reaches 68C and burner trip. but I cant see the return temperature starting to climb nearer the flow temperature, the only logical explaination is that the flow temp (d.40) is reaching 68C and tripping the burner due to the rad demand being below the boiler minimum output. The only flow/return dT that I'm aware of that trips the burner is a high one at ~ 30C.

The burner trip seems to be common on vaillants. I have same issue. A vaillant specialist said this is normal apparently.

 

[Graham J W]

Many thanks Johntheo5, I am very grateful for your help.

I have attached a picture of the heating pipework. As you can see, the plumbers extended the 22 mm flow and return pipes so no more than three radiators could be on 15 mm pipes. Understandable I believe.
My wondering in doing this, is have they made the flow and return too efficient ?. With a less restricted flow and return plus splitting the downstairs and upstairs circuits, I do not think there is sufficient heat loss from system (rads and pipes). Added to this, the upstairs only needs background heat and closes early as we know. The result being dT gets smaller and smaller as d.41 rises. On observing, d 40 does rise up to 68C and consequently tips the boiler (as you say).
By me reducing the partial load to 12KW it seems that I am just delaying the trip / anti cycling mode which occurs when the boiler either reaches 68C flow or when the dT between d.40 and d.41 becomes too small.
I have tried throttling down the lock shields on the downstairs circuit but this increases water noise through the valves.

 

[Johntheo5]

You say the burner trips when the boiler either reaches 68C or the dT between d.40 & d.41 becomes too small, if the latter what are the d40 & d41 readings at the time of tripping?

 

[Graham J W]

d.40 rises to 67 - 68 C and d.41 is about 59 C. The rising of d.40 to 68 C starts the anti cycle. The boiler burner trips followed by the pump several minutes later. d. 41 drops to about 55 C, the pump restarts ( anti cycles looks to be four minutes) followed by the burner, d.40 rises to 68 C and the cycle repeats.

 

[Graham J W]

Sorry, I should have added. When d.40 started rising over the 63 C set point, I quickly opened the TRV on bedroom 1 (largest radiator upstairs) and both flow and return temperature dropped and the boiler stabilised for quite some time modulating at 62 C. Flow and return did eventually rise to anti cycle.