automatic bye-pass valve

Sparkpea

whats the best way, or proper way to set these? how do you figure out what tension on the spring should be set to?

yoshytoshy

I usually close everything on the system and the bypass ,then open the bypass until I get a flow of water through it.

Buford T Justice

Whats the purpose of a bypass valve, and where does it go , if that isn't too stupid question.....

I know it's to maintain flow rates etc... but what would necessitate having one fitted?
Are they generally for closed or open systems etc......

yoshytoshy

They usually get fitted where there are motorised valves on all circuits ,which close the system completely before the boiler has cooled down.

A lot of newer boilers have their own inbuilt bypass ,so it's not as much a problem.

It's an essential part of any SEAI grant controls installation ,regardless of manufacturers recommendations.

Sparkpea

They are fitted on both open and closed but I don't see the point of them on closed systems personally as theres not going to be pitching.

On an open system with TRVs and cylinder stat when everything closes off the pump has to pump the water somewhere so it pitches and causes all sorts of problems as we know. What happens with the byepass is once its under a certain pressure that you've set it will then pump the water around the byepass (basically a link between the flow & return).

Some people use their own byepass which is a gatevalve or ballofix on the pipe in the loop but then theres always water going through the loop where the automatic one has a spring that will only open once most or all the valves close, hence pumping the water back to the return to the boiler. Of course, if wired correctly a room stat will cause the boiler to lockout but before that happens it should pump around the byepass.

Buford T Justice

I get you now, thanks.

So, where in theory would one fit it?

Sparkpea

they say closer to the boiler the better, but if a boiler is in a garage I prefer to put them in the hot press between the flow&return, that way if there is no boiler lockout the pump will keep pumping hot water from the boiler to the loop thus keeping the pipes into the garage circulating and free from risk of freezing.

DoneDL

These valves were origionally used to allow pump over run on zoned systems with a small heat exchanger, they allow for a more consistent pressure within the system (open or sealed) when different zones or TRVS close down. They also help in maintaining a consistent return temperature so obviously a gate valve is not a proper substitute.
Generally suggested that they are a metre away from the boiler.

Buford T Justice

Right then, that may answer the conundrum of my own heating system

Was up in the attic over the christmas throwing down some insulation and I noticed water from the OSV pipe feeding into the expansion tank. By the looks of the pipe it's been that way for a while. Small steady flow, not enough to reach the overflow, so I don't think its taking in that much fresh water. Only when the heating's on I might add.

All rads bar one have TRV's but at least one of them isn't working properly. There is a balancing valve on the Cylinder circuit. There's also a motorized valve but it was never wired up.

Is it normal for the system to constantly pitch?
I was of the impression that this was more of a safety thing to allow the water expand.

Or, is this a result of valves closing in the system with no Auto bypass valve fitted?

heinbloed

The by-pass valve is usually fitted in the boiler, as yoshytoshy already said.
Only with older boilers they have to be fitted externally.
The 1m distance 'rule' is to allow for a 'safe' installation, no steam should reach them. With modern boilers this isn't a problem, they switch off in such a case.
But with the old 'banger' ( and this is the meaning of the word) steam can enter the heating circuit. And bang what is there.

The reason to install a by-pass valve is to safe on fuel, hence the regulations set down by the subsidising authority.

As soon as there is no more demand on thermal energy (all radiators/heat exchangers closed) the valve will return the produced heat straight back to the boiler. And the boiler switches-off because the high return temperature is demanding it to do so (max. return temperature reached= boiler switches off)

The further away the by-pass valve is fixed the longer it will take the boiler to react, to shut down. And the more fuel/energy/money will be wasted, the pipes in between boiler and by-pass acting as a radiator.
So install it as close as possible to the heat source. As long as there is no steaming risk.

Sparkpea

Pitching is bad. Very bad. Although with you having 1 rad without a TRV and open all the time then perhaps it shouldn't pitch, that should nearly act like the loop, but then again its always pumping heat out so imo makes the system no more efficient having the TRVs. You could try opening the balancing valve on the cylinder more to stop the pitching though first thing I would probably so is increase the size of the expansion pipe or the height of it. So if its 15mm pipe alter it to 22mm or 28mm as much as you can, less chance of it filling and pumping over. Put it as high as poss to the eves so the pump would need to work harder to make it pitch - or install a bye-pass. Or seal the system :-)

Or link the expansion into the cold feed, but I don't like that option.

Outkast_IRE

Sparkpea wrote: »

They are fitted on both open and closed but I don't see the point of them on closed systems personally as theres not going to be pitching.

On an open system with TRVs and cylinder stat when everything closes off the pump has to pump the water somewhere so it pitches and causes all sorts of problems as we know. What happens with the byepass is once its under a certain pressure that you've set it will then pump the water around the byepass (basically a link between the flow & return).

Some people use their own byepass which is a gatevalve or ballofix on the pipe in the loop but then theres always water going through the loop where the automatic one has a spring that will only open once most or all the valves close, hence pumping the water back to the return to the boiler. Of course, if wired correctly a room stat will cause the boiler to lockout but before that happens it should pump around the byepass.

On a closed system dont they help prevent the pump dead heading and thus help increase pump lifespan. Well thats the idea anyway

heinbloed

OutkastIRE wrote:

On a closed system dont they help prevent the pump dead heading and thus help increase pump lifespan. Well thats the idea anyway

That's correct.

Sparkpea

I was out today pricing a new HE boiler to install next week hopefully - should I be fitting a bye-pass then? I sealed the system last year and powerflushed it (that should still cover the warranty for the new boiler - yes?). Also a new pump went on. She needs a new burner but the boiler is 25years old so wants a new efficient boiler - TRVs on all the rads but not on the cylinder. Plenty of room in the boiler house to fit it.


Also on that note, because of the condensing drains freezing on 20mm overflow pipe I was going to install 1 1/4" drain - would that be enough or should I go with 1 1/2"?

Buford T Justice

Sparkpea wrote: »

Pitching is bad. Very bad. Although with you having 1 rad without a TRV and open all the time then perhaps it shouldn't pitch, that should nearly act like the loop, but then again its always pumping heat out so imo makes the system no more efficient having the TRVs. You could try opening the balancing valve on the cylinder more to stop the pitching though first thing I would probably so is increase the size of the expansion pipe or the height of it. So if its 15mm pipe alter it to 22mm or 28mm as much as you can, less chance of it filling and pumping over. Put it as high as poss to the eves so the pump would need to work harder to make it pitch - or install a bye-pass. Or seal the system :-)

Or link the expansion into the cold feed, but I don't like that option.

I've been thinking about sealing the system for a while, but with the aspect of 'its not broke' being in my house, I'm just putting it off.

I didn't think it should be pitching like it was either. afaik the expansion pipe is 3/4" and there's also a rad in the bathroom that doesn't have a TRV at all.

Sorry for slightly hi-jacking the thread, but why would this pitch so much? Seems to be frequent.

Sparkpea

if its pitching its broke, seal it :-)

is it a 5m head pump you have in? whats it set to? could you have the lockshield valves balanced down too much?

slavetothegrind

40mm is the usual recommended methinks!
20 mm inside to 40 for the transition to outside
As for the pitching As spar pea said in last post

heinbloed

Fingers McGee asks:

Sorry for slightly hi-jacking the thread, but why would this pitch so much? Seems to be frequent.

That's because the system is asking for thermal energy suplied to the heat exchangers (radiators).
And the thermal source/boiler delivering more than the distribution can get rid-off.

A possible solution is a boiler with a smaller minimum output. How small or large is the min. output of the existing thermal source/boiler?
You'll find this number in the manual or straight on the boiler. Expressed in kW.

There are other methods to reduce pitching, maybe cheaper ones when compared to an installation of new/better suited boiler.

Buford T Justice

Sparkpea wrote: »

if its pitching its broke, seal it :-)

is it a 5m head pump you have in? whats it set to? could you have the lockshield valves balanced down too much?

Lockshields are at about two turns all round, thought that was fairly ok. Pump is (I think) a 15 50 Grundfos..

heinbloed

s.a.

JohnnieK

Sparkpea wrote: »

I was out today pricing a new HE boiler to install next week hopefully - should I be fitting a bye-pass then? I sealed the system last year and powerflushed it (that should still cover the warranty for the new boiler - yes?). Also a new pump went on. She needs a new burner but the boiler is 25years old so wants a new efficient boiler - TRVs on all the rads but not on the cylinder. Plenty of room in the boiler house to fit it.


Also on that note, because of the condensing drains freezing on 20mm overflow pipe I was going to install 1 1/4" drain - would that be enough or should I go with 1 1/2"?

Go for the 1"1/2. I had an 1"1/2 one freeze on me. It was in a garage and I tee'd into an existing washing machine waste. I should of checked the shore cover though it was full of leaves. They froze and blocked the outlet and it backed up:o. You could say because the cylinder is open there would be no need but I would fit one any way.

JohnnieK

Sparkpea wrote: »

whats the best way, or proper way to set these? how do you figure out what tension on the spring should be set to?

The proper way to set them is to look at the boiler installation manual and it should give the minimum flow rate that the boiler requires. When this is found have a look and the sheet that comes with the by-pass and it will give a chart with flow rates on it and the setting on the valve and you set accordingly. I have noticed though that since the boilers come with an auto by-pass on them they no longer have this information in the manual. Yet the great God SEAI insist that you install them.

JohnnieK

Fingers McGee wrote: »

Lockshields are at about two turns all round, thought that was fairly ok. Pump is (I think) a 15 50 Grundfos..

What speed is the pump running at?

Buford T Justice

JohnnieK wrote: »

What speed is the pump running at?

Not checked in a while, but I think its at full whack.

Buford T Justice

Its a Wilo Circulating pump, like the one

The speeds are 26, 36 & 46 and its in the middle, at 36, if that helps

Its a Grant 50 / 70 Boiler

JohnnieK

Try putting it at 26

Buford T Justice

JohnnieK wrote: »

Try putting it at 26

Will do.

Can you explain the significance of reducing the pumps flow rate? Just so I'd know for myself.

Sparkpea

Well theres 3 speed settings on the pump, say low, med and fast for simplicity rather than speeds. Most houses work on medium by default, if everything isn't heating well on medium you turn the speed up to pump the heat better to the furthest radiators away. If you've a 2 up 2 down house so probably only 4-5 rads then the low setting is ample. If you had it at med on the 4-5 rads and they had trvs on it or on most, then once they start closing down when the room temp is reached the pump doesn't have to pump heat to them but it has to pump the heat somewhere so it then pitches. The standard pumps dont know how to adjust their speed to stop this - whereas a wilo smart pump is said to adjust itself for when trv's close down the pump knows to slow down so it wouldnt pitch. If a system is pitching when all rads are open then its likely the pump is pumping too fast or is too big for the system so turning it to the lowest setting is worth trying to stop the pitching.

yoshytoshy

If theres trouble with pitching and the rads aren't heating properly ,the cold feed is usually in the wrong position.
Remember in tech ,this was part of the apprenticship:(

Took this from a webpage :

"Pumping Over
In some old systems where the circulator is positioned in the return pipe but after the cold feed pipe. The only resistance to the water flow in this setup is the boiler's heat exchanger. This means that if the open safety vent pipe is not high above the feed & expansion cistern/tank 'pumping over' will occur as modern circulators can produce up to 3 times more pressure than older models.

This pumping over of water from the vent pipe back into the feed & expansion cistern/tank will cause excessive oxygenation leading to severe rusting and corrosion of any ferrous components within your heating system.

For domestic installations it is recommended that the circulator be installed on the 'primary flow pipe' after the OSV pipe and the cold feed pipe to provide maximum inlet pressure for the circulator, and to ensure that the circuit is under positive pressure with adequate resistance.

Note: If your old circulator was on the return pipe before the cold feed, which was the common practice years ago, then be aware that the new circulators are more powerful and may cause a massive increase in negative pressure and will without doubt cause air to be drawn into the system causing poor performance and circulator failure.
If the circulator is positioned before the OSV pipe then the water will again pump' over' rather than go around the heating circuit."

Buford T Justice

Thanks guys.

All the rads heat fine, no issues with cold spots etc.....

I didn't install the system, and I'll be getting my fancy new IR thermometer this week so I'll also be able to check that all the lockshields on the rads are on the return and the TRV's are on the feed. I have my doubts.

Stupid question, but is Circulator just a posh word for a pump?

Pump is on the feed out from the boiler and the Cold feed is up in th'attic.

Have you a link to the site you got that from?

JohnnieK

Fingers McGee wrote: »

Stupid question, but is Circulator just a posh word for a pump?

Yeah. It's just Yoshy getting all technical on us

yoshytoshy

Sorry about that ,it was cut and pasted from a website.

Don't know which site it came from ,it was the first one that google threw up:(