Vaillant 438 with 3 zones, frequent S53

[D_Hailsham]

mmm yes I am using overview but it still gives me a magna 25-80
I don't know if the above link will work for you

No, the link doesn't work

but I am using

flow 1.633
head 6.57
min temp 30
working temp 70
max temp 82
working pressure 1.5
I am using canned rotor only
material cast iron
thread= 1in

I used the overview mode and entered info as above except the "Thread=1in" as I couldn't see where to enter it.

I'm using the UK site http://uk.grundfos.com

 

[matt1e]

The session must have expired for the link not to work or maybe it was only valid for my PC

If you look above the pumps on the right of the webcaps page there is a drop down box for pump material, choose cast iron underneath that there is another drop down box for connection, choose threaded then the system will automatically add another drop down box to enable you to pick a size

Matt

 

[Steelmasons]

Have you seen that there is now a UPS2 range of pumps which have 3 fixed speed and three proportional pressure settings? It replaces the UPS 15/50 and 15/60 It's a simplified version of the Alpha 2L. which was a simplified version of the Alpha 2.

You can even swop just the head on an existing Selectric 15/50 or 15/60.

Have you had the pleasure of wireing one of these? , impellor is exactly the same as a UPS 15/60

Some good info in this thread although the first page indicated it was a circulation issue. , we are now on the 11th page.

 

[fezster]

Some good info in this thread although the first page indicated it was a circulation issue. , we are now on the 11th page.

I dont disagree with any of the advice given re circulation, and a lot of it makes complete sense.

But, Im still not convinced the S53 is due to circulation. Ive said this previously, but I'll add it again here. The d/s circuit has 26KW rads, and has 2 pumps in series. It seems to me it is well within spec of the resistance of the circuit, and there does not seem to be any problems with flow, rads get hot within 15 mins. However, if I range rate the boiler to 30KW or above, I get S53. The flow temp simply rises too rapidly, and the return temp creeps up.

Given this is the exact same problem I have with u/s, i.e. rads are rated at 18KW, and setting d0 to anything above 18 results in an S53. I keep being told this is a circulation problem. At d0=18 however, all rads get hot, and there does not seem to be any flow problems, eg. furthest rads not heating up.

 

[Steelmasons]

Fezster , the time you have allocated to this thread it would of been quicker/easier for you to have purchased/fitted the larger circulator , job done.

It does get tiresome having these type threads about this particular boiler when the issues are purely down to installer error.

 

[fezster]

Fezster , the time you have allocated to this thread it would of been quicker/easier for you to have purchased/fitted the larger circulator , job done.

It does get tiresome having these type threads about this particular boiler when the issues are purely down to installer error.

Perhaps. But having already shelled out a shed load of money trying to resolve this issue because of varying and conflicting advice, Im reluctant to go to the expense of a bigger pump, only to have the same problem.

However, one thing this thread has enlightened me on is the Low Loss Header. It may be the only true solution to having zones of such varying sizes, esp with Vaillant boilers, where S53 seems to crop up a lot.

 

[D_Hailsham]

If you look above the pumps on the right of the webcaps page there is a drop down box for pump material, choose cast iron underneath that there is another drop down box for connection, choose threaded then the system will automatically add another drop down box to enable you to pick a size

Got it.

You don't get the material/connection/size options if you untick the overview box and then select "domestic". That's why it came up with a different result.

 

[Steelmasons]

Size the circulator/s so as to maintain a minimum flow rate through the boiler @ 0.3 l/s (38/(4.2 x 0.3) = 30c temp differential ) , this will allow the boiler to be range rated to max output for all loads.

 

[D_Hailsham]

However, one thing this thread has enlightened me on is the Low Loss Header. It may be the only true solution to having zones of such varying sizes, esp with Vaillant boilers, where S53 seems to crop up a lot.

I've managed to dig up some data on the 26-50R, but not the performance curves. It has a maximum head of 2.7m (at zero flow) and max flow of 3.24m³/hr. At 26kW the flow is approx 1.2m³/hr and the hex resistance about 1.8m. So the 26-50R may just about cope with the boiler feeding a LLH.

However, that is an expensive option; there is a much cheaper one:

Closely Spaced Tees.

It achieves the same objective of isolating the boiler (primary circuit) from the rads and cylinder (secondary circuit).

 

[matt1e]

Size the circulator/s so as to maintain a minimum flow rate through the boiler @ 0.3 l/s (38/(4.2 x 0.3) = 30c temp differential ) , this will allow the boiler to be range rated to max output for all loads.

nope
0.3 l/s is not acceptable at 38Kw neither is a 30c differential

Matt

 

[Steelmasons]

Vaillant header is around 200 quid (40kw) , the 'closely spaced tee' arrangement is a yank thing , by the time pipework is altered along with NRV's then the LLH is a better option.

 

[Steelmasons]

Size the circulator/s so as to maintain a minimum flow rate through the boiler @ 0.3 l/s (38/(4.2 x 0.3) = 30c temp differential ) , this will allow the boiler to be range rated to max output for all loads.

nope
0.3 l/s is not acceptable at 38Kw neither is a 30c differential

Matt

S53 shouldn't rear it's head with a 30c DT , if fitting a LLH then obviously 0.45 l/s would be maintained @ all loads , obviously my point being if OP isn't interested in fitting a LLH then as long as a MINIMUM flow rate is achieved through boiler hex (0.3 l/s) then he shouldn't encounter any issues (s53) , fitted many of these also had to sort many out too!

 

[matt1e]

I've managed to dig up some data on the 26-50R, but not the performance curves. It has a maximum head of 2.7m (at zero flow) and max flow of 3.24m³/hr. At 26kW the flow is approx 1.2m³/hr and the hex resistance about 1.8m. So the 26-50R may just about cope with the boiler feeding a LLH.
.

but this would never allow the boiler to be used at its max capability
any links to the data you found on it Dave?

the performance curve would be good to find!
incidentally webcaps recognises the model no when searching for a replacement and suggests an Alpha2 15-50!

Matt

 

[Steelmasons]

Mattle , plenty of 4xx series boilers out there not fitted on a LLH , 30c differential will not flag up an S53.

 

[matt1e]

S53 shouldn't rear it's head with a 30c DT , if fitting a LLH then obviously 0.45 l/s would be maintained @ all loads , obviously my point being if OP isn't interested in fitting a LLH then as long as a MINIMUM flow rate is achieved through boiler hex (0.3 l/s) then he shouldn't encounter any issues (s53) , fitted many of these also had to sort many out too!

but the minimum flowrate @ full rate though the hex isn't 0.3m/s it is a touch over 0.45m/s
which is going to give you a deltaT of 20c anyway

Matt