Is a Low loss header essential

[harrygashull]

I am fitting two Worcester 18Ri's and an unvented HW tank in a few weeks and have got the spec more or less nailed down.

Im just debating wether we actually need to use a LLH or if that would be a waste of time.

I have seen boilers connected to the same primary flow and return before and they work absolutely fine.

Any advice would be appreciated.

 

[stevetheplumber]

you dont need a low loss header provided the pipework is sized right also depends on what your running of it ?

 

[ShaunCorbs]

why you putting in two 18s and why not just one 40kw?

 

[harrygashull]

Customer wants in built fail safe so if one fails then the other is still there working, and they also can turn one off in summer.

Theres not a gread deal of difference in price between buying two smaller boilers.

 

[ShaunCorbs]

Customer wants in built fail safe so if one fails then the other is still there working, and they also can turn one off in summer.

Theres not a gread deal of difference in price between buying two smaller boilers.

no but could 18kw handle the total system heat loss?

 

[harrygashull]

Will be running the two boilers into 3 zones Upstairs CH, Downstairs CH and hw

Was planning on using 28mm primaries from boilers with the addition of an automatic bypass.

I could also put a radiator in the circuit and use it as a sort of thermal store to guarantee no overheats?

 

[ShaunCorbs]

how many rads on each of the two zones ?

 

[harrygashull]

I would assume that when the system is put into 'summer' setting that one boiler would be turned off and the pipework would be capable of dispersing heat. If not a radiator may help with this?

 

[kozak1968]

I would speak to worcester bosch. I know the vaillant can come up with fault codes due to the pressure differential.

 

[harrygashull]

There are around 10 rads per zone (all quite large)

Im also allowing for if the customer wants underfloor heating in the future.

So in reality the boilers are going to be throttled back to about 3/4 of their total output.

 

[ShaunCorbs]

There are around 10 rads per zone (all quite large)

Im also allowing for if the customer wants underfloor heating in the future.

So in reality the boilers are going to be throttled back to about 3/4 of their total output.

yea but think about what your saying if one breaks there going to be running 20 rads + maybe underfloor and hot water off one 18kw boiler my opinion bad system design

 

[Norcs]

I've never heard off a system being badly designed because one boiler has broken down and the other still operates providing heat to parts of the home depending on which zone is opened.

 

[ShaunCorbs]

I've never heard off a system being badly designed because one boiler has broken down and the other still operates providing heat to parts of the home depending on which zone is opened.

but not design to take total load (one boiler) if the customers are happy with that your game make sure you get it in writing tho

 

[Norcs]

Both boilers supply the total load.

 

[Kev the gas]

What is the heat requirement of the unvented hot water cylinder ?

 

[kozak1968]

There's no point in doing half a job. If it cost more to do it the right way so be it. You're the engineer so do it the right way, otherwise you will get call backs and you will lose out in the end.

 

[ShaunCorbs]

Both boilers supply the total load.

yes but as he said the reason they want two boilers is one for back up (so they still have heating and ho****er) incase one goes down so design the system right

so size up the system for one boiler and then add a back up boiler

so if one goes down the other one will be able to heat the system (totally)

and then you wont get a phone call in the middle of winter my heating isnt warm (when running off one)

 

[Norcs]

By "designed right" you mean one large boiler to cover the load?

What happens when it breaks down?
The customer has no back up.

 

[ShaunCorbs]

By "designed right" you mean one large boiler to cover the load?

What happens when it breaks down?
The customer has no back up.

no calc the total heat load + (10 -15%) buffer

then pic the boiler size with your heat load

and get two boilers of that size, so they always have one back up / one to spread the heat loading

 

[Norcs]

Not many customers would opt for a system like that I would have thought. Have you installed many like that?

 

[Nostrum]

yes but as he said the reason they want two boilers is one for back up (so they still have heating and ho****er) incase one goes down so design the system right

so size up the system for one boiler and then add a back up boiler

so if one goes down the other one will be able to heat the system (totally)

and then you wont get a phone call in the middle of winter my heating isnt warm (when running off one)

And you can reply, 'that's because your boiler is broken'.

You'll get a better modulation range from two smaller boilers, which judging by the set up, the demand could vary considerably.

OP, I'd use a LLH.

 

[ShaunCorbs]

And you can reply, 'that's because your boiler is broken'.

You'll get a better modulation range from two smaller boilers, which judging by the set up, the demand could vary considerably.

OP, I'd use a LLH.

yes but when the cus has asked for on boiler to be used incase one goes down + with general heating etc

 

[Nostrum]

Customer wants in built fail safe so if one fails then the other is still there working, and they also can turn one off in summer.

Customer sounds like he's using common sense, you sound you're just suggesting installing a boiler which will be sat doing :nono: all for 99.9% of its life.

I think it's safe to assume that if the boiler fails in deepest darkest winter, one will not do the job of both. It will still be able to do something.

 

[ShaunCorbs]

Customer sounds like he's using common sense, you sound you're just suggesting installing a boiler which will be sat doing :nono: all for 99.9% of its life.

I think it's safe to assume that if the boiler fails in deepest darkest winter, one will not do the job of both. It will still be able to do something.

do you think the cus will accept that stating that he wants a back up boiler and you saying he can only run 1-2 systems off it not the full heating/ hot water

thats why i said either do it right or get the cus to sign to say the back up boiler/ system is there for the essentials eg hot water or heating zones and not both

your call op but think either the cus will complain if not done right

and depending on system size i would use a llh or use bigger than 28mm f+r

 

[Unregistered]

Yes, we have fitted several like this. The most recent being two floor standing worcester 40cdi classics. However the pipework involved in this system was much larger(2"+) and I wasnt worried about the boilers turning off prematurely.

 

[ShaunCorbs]

Yes, we have fitted several like this. The most recent being two floor standing worcester 40cdi classics. However the pipework involved in this system was much larger(2"+) and I wasnt worried about the boilers turning off prematurely.

any reason you didnt go for a couple of worcsters 162?

 

[Unregistered]

The tank is 210l unvented and MI's say that it requires around 18kw... In order to achieve the stated 30min reheat time.

has anybody included a rad in the primary circuit before to increase its water capacity? or is it a stupid idea in my head lol

 

[ShaunCorbs]

The tank is 210l unvented and MI's say that it requires around 18kw... In order to achieve the stated 30min reheat time.

has anybody included a rad in the primary circuit before to increase its water capacity? or is it a stupid idea in my head lol

log back in else a mod might close this

 

[harrygashull]

Sorry mr moderator lol

 

[harrygashull]

The 162 would be over sized for this app

 

[ShaunCorbs]

The 162 would be over sized for this app

the other one with two 40s in

 

[harrygashull]

There was no wall space available in the plant room of the old folks home lol

 

[harrygashull]

View attachment 23972

 

[ShaunCorbs]

View attachment 23972

doesnt work

 

[harrygashull]

https://www.************/MCSHeating....1448828964./1036871043052742/?type=3&theater