Central heating not circulating after New Navien Combi fitted to Santon Premier system.

[SJB060685]

£2400 to supply, fit and commission a boiler is really quite low, let alone not sign the necessary paperwork. I can tell you right here and right now that £1300 on new trv's will not solve your issue and had you agreed to that you would still be where you are now. These guys who undertook the work really don't know what they're on about and I genuinely feel your pain.
We've given you all the information you need to move forward. Make sure the new technician that attends is fully aware of the problem and everything we have discussed and hopefully they get you sorted.
Note for the future, an installer/engineer who charges pennies for a job should not be trusted.

 

[JohnHuson]

Than you.

£2400 to supply, fit and commission a boiler is really quite low, let alone not sign the necessary paperwork. I can tell you right here and right now that £1300 on new trv's will not solve your issue and had you agreed to that you would still be where you are now. These guys who undertook the work really don't know what they're on about and I genuinely feel your pain.
We've given you all the information you need to move forward. Make sure the new technician that attends is fully aware of the problem and everything we have discussed and hopefully they get you sorted.
Note for the future, an installer/engineer who charges pennies for a job should not be trusted.

 

[ShaunCorbs]

Any update?

 

[JohnHuson]

I have spoken to an extremely efficient Navien technical advisor and it seems the boiler is capable of providing
the output as needed.
The next step is to balance the system yet again.
I think the system requires a shunt pump to provide the heat to rads 10 metres away. It needs a low loss header?
And hydrallicly balanced? (cant spell that)
My logic is that now the boiler is capable the heat needs moving around the system.
It may even require two pumps around the two levels?

 

[SJB060685]

By the sounds of it the residual pump head after pumping through the boiler heat exchanger is not enough to overcome your index circuit resistance which is why you're experiencing the problems you are. You could either add a LLH and additional correctly sized pump or CCT's and pump. If the secondary side is the same flow rate as the boiler either will work, you just need additional pressure to circulate around the system. Adding pumps in series is not a good idea.

 

[JohnHuson]

I would add that so far my dealings with Navien UK have been superb. Helpful staff and a good
well built product.

 

[ShaunCorbs]

What did the heating engineer say ?

 

[JohnHuson]

By the sounds of it the residual pump head after pumping through the boiler heat exchanger is not enough to overcome your index circuit resistance which is why you're experiencing the problems you are. You could either add a LLH and additional correctly sized pump or CCT's and pump. If the secondary side is the same flow rate as the boiler either will work, you just need additional pressure to circulate around the system. Adding pumps in series is not a good idea.

Thanks for that, it makes sense. May I ask what is the reference LLH and CCt's please. I had a local central
heating engineer around to asses the system to add extra whoomph to the system but after an initial visit he is not returning
my calls. They are a good working family, even the young children are doing their bit for the pub/restaurant and I would
like to see them sorted. Cheers, John.

 

[SJB060685]

LLH is a low loss header, or alternatively know as a low velocity header. Both a LLH and CCT's (close coupled tee's) are a means of hydronically/hydraulically separating the systems. This means the two pumps will not affect each others operation. The boiler pump will circulate at its rate and the secondary side pump will draw what it needs to. As your system is just rads the flow rates either side of separation should be the same. The secondary pump is just supplying the pressure needed to overcome your index circuit (the circuit with most resistance).

 

[JohnHuson]

Thanks for that, it makes sense. May I ask what is the reference LLH and CCt's please. I had a local central
heating engineer around to asses the system to add extra whoomph to the system but after an initial visit he is not returning
my calls. They are a good working family, even the young children are doing their bit for the pub/restaurant and I would
like to see them sorted. Cheers, John.

He said that the boiler was capable at 4okw output for the need. he did agree that the output of the inbuilt
pump was not going to provide circulation on two levels at a distance of 10 metres to the extremes.
He suggests a pump for each zone on a low loss header and hydrallicly balanced.