unvented secondary return

[fuzzy]

every large commercial installation i have fitted has had a secondary return, dont see how it cools cylinder down as much as you say if the insulation is as much on the pipe as it is the cylinder, in fact some jobs ive done the lagging seems thicker on the pipe. if the water content is calculated as the total amount required heating there is no additional water or heat loss. the only additional efficiency cost is the running of the pump which is outweighed by reduction in loss of expensive water on long runs. I think they are good and many designers agree

 

[Gray0689]

We are talking about domestic here not commercial I've done lots on domestic but can't comment on commercial
But on domestic it's bad practice to have a secondary return pump on all the time it does cool cylinder quite a bit IMHO

 

[fuzzy]

We are talking about domestic here not commercial I've done lots on domestic but can't comment on commercial
But on domestic it's bad practice to have a secondary return pump on all the time it does cool cylinder quite a bit IMHO

which i why i posted that i dont see any real advantage in a domestic property. I didnt realise the conversation was limited t domestic only, the op title is unvented secondary return

 

[Gray0689]

which i why i posted that i dont see any real advantage in a domestic property. I didnt realise the conversation was limited t domestic only, the op title is unvented secondary return

It's not as I said can't comment on commercial I don't do it that's all

 

[SimonG]

Don't know if it's just me but the commercial stuff I did as an apprentice wasn't unvented, hence the swimming pool sized sectional water tanks. I think the cylinders came from IMI Rycroft, but that was a long, long, long time ago.

 

[tamz]

As far as i'm concerned, a secondary return on a domestic is a total waste of energy especially in these energy efficient green times.
From my experience, most who ask about it carefully seperate their rubbish, burn condensing boilers and energy saving light bulbs, and generally do their bit for the planet but they can't wait 10 seconds or so to step into a shower.Save the planet my rse!

 

[Megaflo-Experts]

There are benefits of a secondary return in certain domestic properties. Quite often large bungalows with long pipe runs in 22mm pipe - that's potentially a lot of water to draw off before getting hot water. Also remember the hot water left in the pipe will cool down and need to be drawn off when the next person uses the hot water; that's wasting water and heat! The return pipework should be in 15mm (or even smaller!) and I normally wire the pump to come on when the hot water is on, which generally works for the customer. However, it will be more efficient if the pump had some sort of temperature sensor (if such thing exists) to determine if it needs to come on or not.

I don't think a flow switch will work as the the user will still need to draw off the cold water before getting hot water!

 

[fuzzy]

if plumbed in correctly with sufficient lagging etc the only disadvantage i see is power to the pump and noise. If its in a cupboard or separate room the noise issue can be reduced. What is the amount of power the pump uses? if you want it based on temp would a pipe stat work ?

 

[quality]

if you want it based on temp would a pipe stat work ?

I have used this method before nice and simple and works a treat

 

[quality]

if you want it based on temp would a pipe stat work ?

<br>I have used this method before nice and simple and works a treat although I used a capillary stat

Stange edit ??????

 

[SimonG]

Would you use the pipe stat in conjunction with a timer? and would you use the pipe stat to turn the pump on or turn it off?

 

[quality]

Depends on demand for hot water

 

[stevetheplumber]

As far as i'm concerned, a secondary return on a domestic is a total waste of energy especially in these energy efficient green times.
From my experience, most who ask about it carefully seperate their rubbish, burn condensing boilers and energy saving light bulbs, and generally do their bit for the planet but they can't wait 10 seconds or so to step into a shower.Save the planet my rse!

everytime you open a hot tap on a lengthy draw of your wasting water that has been heated so secondary is saving in that sense
one house i look after is six floors high and cylinder is in base ment

 

[mike_s]

As the original poster I'm really happy with the discussion here, cheers.
It has got me thinking, especially the cooling effect on the hot water store with the pump running from morning til night like they plan to but they actually havn't been using the secondary return pump as they wern't sure about having it on all day.
It is a large 5 bedroom property and they say you can go for a *** before the hot water comes through so the wait is an issue as it is more like minutes rather than seconds at times.

A pipe stat certainly sounds more useful, combined with the timer. Their secondary return pipework is actually all in 22mm I think and lagged most of the way, I mentioned that 15mm would've been more efficient. The cylinder and pump is in a loft room that could become a bedroom, I tried it out and the noise wasn't a major issue after all.

I would like to find out more on the cooling effects of having the pump running all day which they may try out, I see if the pipe is 15mm or less and lagged properly it shouldn't be majorly inefficient.

Seeing as they are coping without the secondary return pump running and if the heat losses from it are that great then probably not worth installing in most domestic situations.

 

[quality]

On / in / with any system that is not the normal 3 bed semi, most systems require a bit of trial and error.
Equipment has to be installed correctly to start with and that goes without saying. But the user is one of the biggest factors which determine how a system should be controlled.

I have had some nightmares, but to combat those I have had plenty of sweet dreams

Let them run for four weeks and then decide what needs to be done thats what I normaly do

 

[fuzzy]

As the original poster I'm really happy with the discussion here, cheers.
It has got me thinking, especially the cooling effect on the hot water store with the pump running from morning til night like they plan to but they actually havn't been using the secondary return pump as they wern't sure about having it on all day.
It is a large 5 bedroom property and they say you can go for a *** before the hot water comes through so the wait is an issue as it is more like minutes rather than seconds at times.

A pipe stat certainly sounds more useful, combined with the timer. Their secondary return pipework is actually all in 22mm I think and lagged most of the way, I mentioned that 15mm would've been more efficient. The cylinder and pump is in a loft room that could become a bedroom, I tried it out and the noise wasn't a major issue after all.

I would like to find out more on the cooling effects of having the pump running all day which they may try out, I see if the pipe is 15mm or less and lagged properly it shouldn't be majorly inefficient.

Seeing as they are coping without the secondary return pump running and if the heat losses from it are that great then probably not worth installing in most domestic situations.

no cooling affect if lagged as much as the cylinder

 

[Gray0689]

Yes it will cool if pump running all time won't be lagged like cylinder
As said before fuzzy this is domestic won't be lagged like commercial

 

[fuzzy]

Yes it will cool if pump running all time

if the lagging is at least the same as the cylinder how does it cool anymore than it would in the cylinder?

 

[Gray0689]

if the lagging is at least the same as the cylinder how does it cool anymore than it would in the cylinder?

Because it won't be lagged the same as the cylinder the cylinder will be 50mm lagging

 

[SimonG]

Scientifically speaking............It will cool, even the cylinders have a heat loss of about 2.5 kw in 24hr period (approx) with the 2" foam they have applied. Doesn't matter how well insulated the flow and return are on the hot water side you will have heat loss of some description.

 

[fuzzy]

Scientifically speaking............It will cool, even the cylinders have a heat loss of about 2.5 kw in 24hr period (approx) with the 2" foam they have applied. Doesn't matter how well insulated the flow and return are on the hot water side you will have heat loss of some description.

never said you wont get heat loss, im pointing out that there is no reason why the heat loss will be anymore if it is lagged the same.

commercially this is alwasy the case, from some posts here i get the feeling people are undervaluing returns based onheat loss which doesnt need to be so

 

[Gray0689]

Fuzzy your talking about commercial not domestic it does cool cylinder and it won't be lagged with 50mm insulation
I've fitted approx 50 secondary returns on large domestic property's and seen it done a few different ways the only one that works well is on a timed pump if on 24/7 cools cylinder considerably
As been stated before secondary returns are only good if there is very Long pipe runs this can be done away with if the likes or architects /designers could position cylinders boilers in more central positions in houses but as we all know this don't happen

 

[fuzzy]

Fuzzy your talking about commercial not domestic it does cool cylinder and it won't be lagged with 50mm insulation
I've fitted approx 50 secondary returns on large domestic property's and seen it done a few different ways the only one that works well is on a timed pump if on 24/7 cools cylinder considerably
As been stated before secondary returns are only good if there is very Long pipe runs this can be done away with if the likes or architects /designers could position cylinders boilers in more central positions in houses but as we all know this don't happen

ive also done it on large domestic, same theory applies, just lag it properly, i dont see the problem

 

[Gray0689]

ive also done it on large domestic, same theory applies, just lag it properly, i dont see the problem

Tell you what fuzzy we will agree to disagree then lol

 

[fuzzy]

Tell you what fuzzy we will agree to disagree then lol

lol, ok mate, well agree that i am always right, a bit like the missus in out house:49: