Bypass valve

[toneloc]

Hello all,
Does anyone know if the Worcester Greenstar 8000 Life 40Kw have a bypass valve?
If so, does it need a bypass radiator?

Cheers

 

[Madrab]

It'll be in the book of words - Bypass rads are no longer an acceptable method for bypassing boilers and I don't believe the 8000 has an internal bypass.

If there is a possibility of the pump pushing against a closed head - all the valves in the system are shut down - then an auto bypass would be required to ensure min flow through the HEX on overrun.

 

[toneloc]

Brilliant, nice one. Appreciated

 

[GeddyMortgage]

It'll be in the book of words - Bypass rads are no longer an acceptable method for bypassing boilers and I don't believe the 8000 has an internal bypass.

If there is a possibility of the pump pushing against a closed head - all the valves in the system are shut down - then an auto bypass would be required to ensure min flow through the HEX on overrun.

Hey @Madrab Do you know if the Worcester Greenstar Life 36kw System boiler has an Auto bypass valve or not? Couldn't see mention of it in the user manual.

 

[muggles]

No, it'll need an external bypass

 

[Madrab]

^^ Wot he said

 

[GeddyMortgage]

thanks @Madrab and @muggles

Problem on mine has resurfaced again and wondering if its due to an ABV not being fitted.


Im noticing the flow temp on the boiler gets to target way before the radiators get anywhere near. Like it'll get to 75c within 20mins but it takes maybe 40-60mins for the rads to all get hot. In this case it's a 36kw system boiler with an internal pump, which i've set to constant speed.

In this setup all the rads have TRV, bar the towel radiator which as far as I can see has 2 x lock shields which ive not messed about with yet. I dont think it has an ABV either (i'm not hugely technical as you can probably tell!)

So yeah wondering what could be the cause of this and whether I need an ABV or perhaps another external pump to help get the heat away from the boiler?

 

[CountryFan]

If an external bypass is recommended in the mi’s then one should be fitted, and I doubt the reason for what you’re describing.

A bypass is to ensure a constant flow of heated water when the trvs start to close, which may be acceptable if your towel rail does indeed have 2 lock shield valves.

Is the system properly balanced?

 

[GeddyMortgage]

It’s been balanced a bunch of times and does seem quite sensitive honestly.

It’s 11 type 22 rads and 4 triple column designer types.

They do all eventually get hot. So figured it is somewhat balanced correctly. Though it’s like I said above, the boiler flow temp sensor is getting way hotter far sooner than the rads. The boiler then modulates down to 50% and I presume that’s why it’s taking ages to get the rads hot.

I tried it in chimney sweep mode to see if that led to the rads getting hotter sooner and it did.

So yeah I’m wondering if I should try closing the towel rad and testing that… or perhaps fitting a secondary pump as the internal one has been set to max constant speed and wondering if that’s still not enough oomph for the 30 odd kw of rads it’s powering.

It’s CH only btw. This boiler doesn’t do any of the taps / hot water for the property

 

[Johntheo5]

If the flow temperature is up to its target temp and the boiler is running at 50% output then the heat demand is 50% of the boilers output, in your case 40*50%, 20kW, still a fairly hefty heat load,what is the boiler target temp? And any idea of the boiler return temp?

 

[GeddyMortgage]

Target temp is 75c.

It’s 36kw, and when I add up the kw of the rads at T50, the power requirement for them is around 28kw or so.

As far as I can see, it doesn’t have a read out for the return temp. But I guess I could tape one of my fish tank temperature monitors on it and see?

I have been wondering if the boiler heating up so fast is because the pump is either too fast or too slow…I guess either could cause that to happen. But if the return temp is returning very hot would that suggest the pump speed is too high? And if the return temp is low, would suggest the pump speed is too slow?

 

[Madrab]

The boiler then modulates down to 50% and I presume that’s why it’s taking ages to get the rads hot.

No - the boiler modulates down to maintain the output set temps

75deg these days is a bit too hot TBH and If the boiler is overshooting its target temp, then there may be a flow/circulation issue. TBH though it could also be that the system hasn't been balanced properly and that's adding to the slow flow/circulation. What size of pipework is being used? 22mm > 15mm or smaller and is it all the same? Running the boiler in sweep mode just hi fires the boiler for up to 15min or until it overheats

As suggested an ABV wouldn't have anything to do with that.

4 triple column designer types.

Are they vertical column rads or are they vertical tubular designer rads, the former isn't described as a designer rad, the later is and they are quite different, if you see what I mean.

 

[Johntheo5]

Target temp is 75c.

It’s 36kw, and when I add up the kw of the rads at T50, the power requirement for them is around 28kw or so.

As far as I can see, it doesn’t have a read out for the return temp. But I guess I could tape one of my fish tank temperature monitors on it and see?

I have been wondering if the boiler heating up so fast is because the pump is either too fast or too slow…I guess either could cause that to happen. But if the return temp is returning very hot would that suggest the pump speed is too high? And if the return temp is low, would suggest the pump speed is too slow?

A T50 rad, assuming a room temp of 20C with a flow temp of 75C will require a return temp of 65C to give its rated output, it will output ~ 6% more if the return temp is 70C as it is now a T52.5 rad, obviously the lower the return temp, the lower the rad output, just feel the boiler return pipe, you will get some idea of it's return temp by doing so.

 

[GeddyMortgage]

No - the boiler modulates down to maintain the output set temps

75deg these days is a bit too hot TBH and If the boiler is overshooting its target temp, then there may be a flow/circulation issue. TBH though it could also be that the system hasn't been balanced properly and that's adding to the slow flow/circulation. What size of pipework is being used? 22mm > 15mm or smaller and is it all the same? Running the boiler in sweep mode just hi fires the boiler for up to 15min or until it overheats

As suggested an ABV wouldn't have anything to do with that.


Are they vertical column rads or are they vertical tubular designer rads, the former isn't described as a designer rad, the later is and they are quite different, if you see what I mean.

View attachment 397753

Hey Madrab, I'll try dropping to 70 target and see if that helps things at all but from memory it was the same when I used to run 70 last winter.

Pipework is 28mm for the first meter, maybe a meter and a half, then that splits to 2 lots of parallel 22mm runs, one run for the front of the house and one run for the rear, though none of them are zoned. Then it drops down to 15mm for the last meter or so for each rad.


the vertical rads look like the one you attached, they're callled milano Windsor triple column from Bestheating. they do take much longer to heat than the type 22's but ive noticed they do also stay hot longer after the boiler goes off. pic attached.

 

[GeddyMortgage]

A T50 rad, assuming a room temp of 20C with a flow temp of 75C will require a return temp of 65C to give its rated output, it will output ~ 6% more if the return temp is 70C as it is now a T52.5 rad, obviously the lower the return temp, the lower the rad output, just feel the boiler return pipe, you will get some idea of it's return temp by doing so.

Ok so @Johntheo5 @Madrab... I fired it up this evening and monitored it pretty closely myself, I did notice a few things that could help determine the problem?


- The boiler LCD display went from 12 to 40 within the first few minutes
- By 15 minutes in the boiler LCD display was showing 70 odd degrees. (Target is now 70)
- Even though the boiler LCD said 70 in 15 mins, the flow pipe felt no where near as hot to the touch as the LCD display was suggesting.
- By 60mins in or so, the LCD display still showed 70 degrees, but now the flow pipe felt hot to the touch
- The flow pipe felt generally the same-ish temperature to the radiators always
- the return pipe felt luke warm by about an hour in but never hot.



Also worth noting if I haven't already, i've got the pump set to max, constant speed of 400mbar.