Safety Relief Bypass - how to set correctly

[donkeeboy]

Hi, I recently posted about by WB boiler regulary tripping ou ton E9 - 'Safety temperature circuit has tripped'. I reset it and it starts working again, but it happens regularly. I been thinking of airlocks, or a problem with the 3 year old Grundfos 15-60 pump.

Well, ahem, I am now starting to think of the safety relief bypass. I got this short pipe crossing over from after the pump on the flow out of boiler, back onto the return pipe going back into the boiler. It has a valve on it. Im sure you guys are familiar with this.

What is the correct position to set this valve too?

The plumber that installed it told me to close it turning it clockwise all the way, then just turn it back and open it up a little bit. Is this correct?

I was indeed meddling with this sometime ago! When I had airlocks. I think i may have left it perhaps a little bit too closed. Although there was movement on the handle on the valve, it may have still been virtually 100% closed internally. I just opened it up a bit more, and noticed that the boiler tempertaure rose more quickly (yet steadily) to a high temperature, I guess because a higher amount is circulating straight back around back into the boiler. Radiators still got hot all around the house though.

Im thinking if the valve was closed too much, its more possible for hot water to get backed up between boiler and pump, with nowhere to go, thus causing my E9 trip out.

Thanks gents.

 

[doitmyself]

Is is a gate valve or an automatic bypass valve?

 

[donkeeboy]

Gate Valve.

 

[doitmyself]

The problem with a gate valve is that it allows water to pass through all the time; so any setting is a compromise. It would be better to replace it by a auto bypass valve, which only opens when required.

Which make/model boiler do you have?

 

[donkeeboy]

Thanks for that info. Its a Worcester Bosch Greenstar 40CDI conventional boiler. How should I set the gate valve in the mean time? I am trying to determine if this has got anytyhng to do with my E9 fault trips outs or not. Ty.

 

[doitmyself]

It's a Worcester Bosch Greenstar 40CDI conventional boiler.

That's a very big boiler! Not what you would expect to find in the typical 3-bed semi.

How big is your house?
How was the boiler size determined?

You can use the Boiler Size Calculator to find out what size boiler you really need.

 

[donkeeboy]

Yeah its a big house! 8 bedrooms, 19 rads. I thinks its the right size old one was ideal concorde 48.5KW a true beast it was with no PCB to fail! Anyway it was all installed completely new system 3 years ago (old radiators and pipework tho). Its worked fine for 3 years the system is fine in general, but now I am getting these E9 trip outs. Its either the pump (also 3 years old), or airlocks. I am not convinced its either of those, thats why I am now looking at the position of safety releif valve, esp as I have meddled about with it not long before thoses fault codes started appearing. It could also be the boiler sensors/pcb messing up, but for PCB I would expect it to totally fail - not intermittently every few days.

Do you know how I should set this gate valve (until I get it replaced with autobypass) ? I am just trying to rule things out. Cheers.

 

[doitmyself]

Yeah its a big house! 8 bedrooms, 19 rads. I thinks its the right size old one was ideal concorde 48.5KW

Still sounds large! 19 rads would mean each one was approx 2kW average size. Please use the online calc - you may get a surprise!

Its worked fine for 3 years the system is fine in general, but now I am getting these E9 trip outs.

You can read the fault finding for E9 on pages 41-43 of the Greenstar Service Manual.

Do you know how I should set this gate valve (until I get it replaced with autobypass) ? I am just trying to rule things out. Cheers.

How many motorized valves do you have?

 

[donkeeboy]

Hi, I looked at the online calculator but I dont have all the measurements to hand. The boiler is fine - I had lots of pople come around 3 years ago giving my quotes, they all did the measurements and caulclations in detail - including british gas who were very thourough, and all told me to get 40KW boiler. Lots of the rads are big double rads.

It has 1 3-port motorised valve, one port for CH, one for HW, one for CH+HW.

I already know what the E9 means, its the 'Safety temperature circuit has tripped' as mentioned in OP.

The main thing I would like to know is what position should I set the gate position too? Mostly closed, 50/50, mostly open?

Cheers

 

[doitmyself]

It has 1 3-port motorised valve, one port for CH, one for HW, one for CH+HW.

OK, but you are slightly mistaken over what the ports do. The middle port is the input from the pump. One branch goes to the CH and the other branch to the HW. by some clever switching circuitry it is possible to stall the switch in the mid position, so water can go out of both CH and HW ports at the same time.

The design of the valve also means that at least one port is open all the time so there should not be any need of a bypass valve.

I already know what the E9 means, its the 'Safety temperature circuit has tripped' as mentioned in OP.

The link I gave has more info than what the error means. It has the correct fault finding sequence for determining what caused the error.

The main thing I would like to know is what position should I set the gate position too? Mostly closed, 50/50, mostly open?

As I said above, with a 3-port valve there should not be any need for a bypass, so I would try it closed to start with. If this does not work, open half a turn at a time until you get a result.

Do you have thermostatic valves on your radiators? If so have you checked if they are sticking?

PS When does the problem occur - CH only, HW only or HW and CH?

 

[donkeeboy]

Thanks very much thats useful info - your right about the 3port of course what I wrote was wrong. Yes I read the pdf, first thing I did. I phoned Worcester bosch - they reckoned because I am able to remove pump bleed screw, and stop the pump with a screwdriver then it means I have a weak pump. But then on this forum, other disputed that and said that you can stop any pump like that with a screwdriver, good or bad. The pump is Grundfos 15-60 only 3 years old, this is why im trying to rule other things out as I fear replacing it when in actual fact its prob perfectly good.

I will try experimenting with the 3 port valve - its diffucult tho as its not a hard fault, its intermittend. Its done it twice in last 2 days, but then often it will be fine for 2 weeks.

Yes I have TRV's. Not sure if they are sticking, I can check. Certainly they are not sticking in the off position anyway, all rads get hot.

Your prob right about not needing a bypass, no doubt its just the way things are done these days, with all the rules and regulations that exist.

No pattern to the motorsied valve positions it seems - I already went down that avenue when I just thought it was airlock. It seems to be random. I think I will repeat this though just for good measure - in the past on a totally seperate occasion (air lock), it was indeed when the MV moved from one position to another. I'll give it a go once more.

Thanks for your help.

 

[oldplumber]

grunfoss pumps have in the past been prone to clogging up and it was resolved by whipping off he pump head and cleaning up the internals and then refitting. if your system is old and sludged this could be your problem and causing the fault, worth a try before you swap a pump.