Location of bypass valve

[Dannyparty92]

[SUB]dear all with a combination boiler is it required to put a by pass valve anywhere on the flow and return pipes anywhere on the system? Or is there a bypass valve integrated within the combination boiler? Any feedback would be great.[/SUB]

 

[mountainman]

It depends on the boiler, what make and model is it?

 

[Dannyparty92]

Just in general? I take it I would have to read the MI's as a rule of thumb would it be sensible to fit one at the end of the flow to the return?

 

[wheeto]

I take it I would have to read the MI's

Yes!

as a rule of thumb would it be sensible to fit one at the end of the flow to the return?

No, - find out if it's necessary first! And why would you choose to fit it at the end of the run?

 

[Dannyparty92]

Well If it was at the start of a run wouldnt it short circuit?

 

[Mike Jackson]

Not if it's an auto bypass valve as required by the building regs. Most boilers will tell you if one is required and the minimum pipe lengths required. If it's at the end of the runs there will be unnecessary wastage of heat.

 

[Dannyparty92]

Thanks mike . How come if it's an auto bypass at the end of the run how will it waste heat?

 

[kay-jay]

Because the circuit will be bigger

Sent from my GT-I9100 using Tapatalk 2

 

[chris watkins]

There are two reasons for installing a bypass (as Mike say's only auto allowed now).
1. To guarantee the minimum flow rate through the boiler as required by the manufactures, when the heating is on & coming up to temperature the TRV's will be closing down restricting the flow of water around the system. bypass is required at this point to open & allow water to pass from the flow to the return without going through the emitters but as the return pipe will be close to the return temp the boiler will quickly shut down on the thermostat.
2. An auto bypass is also required on a system where the boiler requires an open pathway to dissipate heat from the main heat exchanger when it shuts down. This is most likely when an S Plan (2x2port zone valve) has been installed & the boiler has to control the pump i.e. it has a Pump Live wiring terminal. I this case as previous postings it may need to be some distance away to allow the heat to diapers.
As every read the manufacturers instructions (MI's), something that a lot of people seem incline NOT to do !! at least until things go wrong.

Now you know what they are & how they are used, the next question is how do you set them up so that they work correctly i.e. remain closed in normal operation to keep boiler in condensing mode & only opening when required ? Have a think & let us know.

 

[Dannyparty92]

Sorry about this guys ha I'm just a bit confused as to why if I fitted an auto bypass valve on a heating circuit at the end it would waste heat? As its an auto bypass it would remain closed wouldn't it? Therefore not wasting heat?

 

[chris watkins]

Sorry about this guys ha I'm just a bit confused as to why if I fitted an auto bypass valve on a heating circuit at the end it would waste heat? As its an auto bypass it would remain closed wouldn't it? Therefore not wasting heat?

Danny did you not read 2. ? of my post, I don't know how else to put it ? waste is probably wrong word it will allow heat to be lost from the boiler by opening up & allow hot water to circulate around the system when the zone valves are closed.

 

[Dannyparty92]

Thank you so much guys for your help so where would the ideal

 

[Dannyparty92]

Place to fit an auto bypass valve if the boiler does not incorporate one?

 

[AWheating]

in the a/c before your zone valves. if you are struggling for an a/c then a kitchen cubby or under a bath as long as its accessible for adjustment. the boiler/system type and pump position will effect the positition.

 

[Dannyparty92]

It's on a combination boiler so no zone valves.

 

[mountainman]

It's on a combination boiler so no zone valves.

Could have, I've zoned combi boilers in the past.

 

[Dannyparty92]

I know it is possible but I'm just saying for this instance there is no zone valves.

 

[AWheating]

combi boiler no zone valves would be a min of a 3m circuit from the boiler in an accessible position for maintenance as a general rule.

 

[Dannyparty92]

Thank you very much Awheating an everyone else so how do you know the min circuit from the boiler just 3 meters to allow no short circuiting?

 

[AWheating]

3m is a general rule of thumb but you need to follow both the valves and boilers installation instructions aswell. i dont fully understand your term short circuiting? if set up correctly it will allow the boiler min flow rate through it where ever its fitted (if in a suitable position), the closer the appliance of course the less heat it can remove from the boiler on shut down/over run.

 

[AWheating]

http://www.google.co.uk/url?sa=t&rc...sg=AFQjCNE_7saHbonQzu3F0v4Vukk4BozH0A&cad=rja

[DLMURL]http://www.draytoncontrols.co.uk/AutoByPassValveDatasheet.aspx[/DLMURL]

 

[Dannyparty92]

Ok so rule of thumb 3 meters from the boiler thank you very much for your help .

 

[chris watkins]

Cor that was a bit of luck Dannyparty92 not asking how to set them up otherwise we could have been here all night !!!

 

[Dannyparty92]

Oh yeah sorry about asking questions last place to ask questions on a forum.

 

[Hybrid]

There's rattles flying everywhere lol

 

[chris watkins]

No problem with asking questions Danny it's just how many times, anyway the main thing is you are sorted now so all is OK.

 

[Dannyparty92]

A few times. yes and thank you again.