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

[JohnHuson]

I enjoy a pint at my local pub/restaurant owned by a hardworking Chinese family. I have had many years experience on property maintenance and they asked for my help.
He had an old LPG gas boiler feeding a Santon Premier unvented cylinder feeding 23 radiators and hot water for the kitchen. New boiler is a Navien combi and the pipework is a work of art!
The installers came out again and said boiler works as it should so problems is not of their making.
The upstairs living accommodation has a separate combi system.
When the fitters arrived he was given an option to retain the unvented cylinder, so he did.

The central heating no longer circulates around the building and about six radiators get warm.
I have bled and done everything to get it going but no improvement. It worked fine before the boiler change. The system was not drained. It was flushed four years ago. All TG's are working fine.
I notice that the original central heating Granfoss pump sucks the flow downwards to the cold feed of the cylinder at the bottom as a secondary feed. I found that the water temperature between 2 feet from the pump to the cylinder went from warm to cool indicating lack of flow?
I cracked open the drain cock and the temp from the pump to the cold supply into the cylinder is now even.
The expansion vessel is at 3 bar pressure.

I changed the pump to a nearly new pump which is working as it should. Still no improvement.
The problem is either; the installation of the new combi boiler? The routing of pipework not being correct? Or me not seeing the obvious?
Your help appreciated please. They are really nice people and I might get a couple of freebie beers.

 

[ShaunCorbs]

Pictures?

 

[snowhead]

Confused,
The system worked before the new boiler was fitted I assume.
Someone has fitted a replacement and now the system doesn't work and it's not of their making.

A couple of things,
To be able to say it's not of their making they'd need to know exactly what the issue is, so should be offering to fix it even if it means charging more than originally quoted.
They're the best positioned to fix it, they know how the old boiler was piped and how they've piped in the new boiler.

But they clearly don't know what the issue is, otherwise they'd have said as defence of why it wasn't of their making.

It would be the same as driving a car to a garage for a new engine, the garage fitting it and it starts but the car won't drive and the garage saying take it away the problem is not of their making.

My guess is that they maybe good boiler fitters, or even excellent, but have no understanding of heating systems and faults.

 

[JohnHuson]

System worked fine with the old LPG boiler, now does not since they adapted the new combi boiler to
work with the Santon Cylinder. It was the customers decision to retain the cylinder and now the heating
will not circulate. The boiler is producing heated water OK.
I agree with you regarding the installers.

 

[JohnHuson]

System worked fine with the old LPG boiler, now does not since they adapted the new combi boiler to
work with the Santon Cylinder. It was the customers decision to retain the cylinder and now the heating
will not circulate. The boiler is producing heated water OK.
I agree with you regarding the installers.

My Chinese friend has a pub and restaurant for past five years. They work hard and the UK is their future home.
The old Ideal Concord LPG boiler was knackered. They needed a quick solution so found an installer who could provide
a solution within days.
The Ideal Concord system was working well before the boiler expired. It was servicing the kitchen domestic outlets and four toilet
hand basins plus 23 radiators at various levels. The system is mainly 15mm to the rads and a lot of 22mm in the loft
and supply flow.
They installed a Navien 40kw domestic boiler in a commercial kitchen. They were assured that it would do the job.
The customer was most aware that if the Combi boiler failed to operate; the Concord cylinder storage with immersion was a back up and
would be a good idea.
New boiler is now installed. The central heating is not working. The first few rads will heat. If we balance the system we can get warm rads.
We asked the installers to come and solve the problem and the boiler was leaking water from the casing. They did attend very quickly and replaced
a seal on the cold supply to the heat exchanger. They charged £200 under guarantee for 35 minutes work.

We now have a system which provides good domestic output but no radiator heating to most of the area where it worked well before the boiler
change.
The installer says the 23 TRV's need to be changed at an extra cost of £1300 to solve the problem.

 

[ShaunCorbs]

Do you know the old size of the concord eg kw and the new one ?

 

[JohnHuson]

Do you know the old size of the concord eg kw and the new one ?

Hi, It was a floor standing CX LPG about 25 years old. Will check output this evening and reply.
Thanks.

 

[ShaunCorbs]

So probably 60kw

 

[SJB060685]

If Shauns guess is correct and the original boiler output was around 60kw, then a new boiler with a maximum output of 40kw is not man enough.

 

[JohnHuson]

So probably 60kw

Hi, it was a 40 CX so I assume 40kw same as new one?

 

[ShaunCorbs]

Yes so that in theory is good

Did they remove the external pumps ?

 

[JohnHuson]

No changes were made to the radiator system apart from adapting the 40KW combi to the system and the non vented
cylinder remained as it was. My concern is that is a combi 40KW combi capable to feed a system with 22 to 54mm
feed around two zones? This is a Pub so the 23 rads need a supply which can be quick and efficient. We have now got
heat in around nine of the 23 rads. That has taken two days of the boiler running.
The system has been purged of air, rads bled, drain feeds on each point to at least 10 gallons drained.
I would add that the system worked well prior to the installation of the new combi boiler.
The installer has suggested the TRV's are stuck. They are not, and the flow of water within the circuits are free of problems.

 

[ShaunCorbs]

And the old pump was it removed or left in ?

 

[JohnHuson]

And the old pump was it removed or left in ?

The secondary pump was changed but was working fine on all three speeds so original pump was refitted.

 

[ShaunCorbs]

Any chance of a few pictures of how they have pipes it ?

 

[JohnHuson]

The secondary pump was changed but was working fine on all three speeds so original pump was refitted.

The original pump in the old boiler was scrapped when the boiler was removed. The Combi internal pump
I hope is doing its job. The secondary pump on the cylinder cold supply is working as it should.
This is driving me nuts!
Either there is a circulation problem caused by lack of pump pressure from the ne combi or a restriction that
has suddenly appeared on the change over?

 

[ShaunCorbs]

There you go the internal pump of the new boiler is not man enough for the system it needs the old pump back on / one sized correctly

 

[JohnHuson]

There you go the internal pump of the new boiler is not man enough for the system it needs the old pump back on / one sized correctly

I guess you are right. If it needs an additional push pump where in the system should it be located to move things around?

 

[ShaunCorbs]

Should be after the llh

I hope there’s additional expansion tank / tanks ?

 

[SJB060685]

Sounds like you need to separate the system. Also is the old boiler a non condenser @ShaunCorbs and the rads possibly ∆T 60?

 

[JohnHuson]

Should be after the llh

I hope there’s additional expansion tank / tanks ?

Thanks Shaun but I did not get the last word meaning? iid?

 

[ShaunCorbs]

Sounds like you need to separate the system. Also is the old boiler a non condenser @ShaunCorbs and the rads possibly ∆T 60?

Yep

Low loss header as condensing boilers don’t like older systems tbh I would fit a plate heat exchanger to save the new boiler as I doubt they cleaned the system

 

[JohnHuson]

Sounds like you need to separate the system. Also is the old boiler a non condenser @ShaunCorbs and the rads possibly ∆T 60?

No, the old boiler was a 20 year old Ideal Concord CX40 floor standing unvented.

 

[JohnHuson]

Are you in travelling distance of Chester?

 

[ShaunCorbs]

About 10 miles away 🙂 but I booked up sorry

 

[SJB060685]

Yep

Low loss header

Then if the old boiler was running at ∆T 11°c the pump would of been capable of the higher flow rate and pressure required to overcome index circuit.
Sounds like this needs a low loss header and suitably sized secondary pump. The secondary side pipework will be ok in size but the new boiler internal pump isn't capable.
Alarming really as the installer really should have considered this 🤔

 

[ShaunCorbs]

Then if the old boiler was running at ∆T 11°c the pump would of been capable of the higher flow rate and pressure required to overcome index circuit.
Sounds like this needs a low loss header and suitably sized secondary pump. The secondary side pipework will be ok in size but the new boiler internal pump isn't capable.
Alarming really as the installer really should have considered this 🤔

Makes you laugh tho they thought a 15-70 would do 2” pipework it’s the state of the industry atm either people don’t care or they don’t know chances are it was a 25-80 or 32-80

Was he even commercially qualified to work on the install

 

[JohnHuson]

Then if the old boiler was running at ∆T 11°c the pump would of been capable of the higher flow rate and pressure required to overcome index circuit.
Sounds like this needs a low loss header and suitably sized secondary pump. The secondary side pipework will be ok in size but the new boiler internal pump isn't capable.
Alarming really as the installer really should have considered this 🤔

I agree. The boiler developed a leak from the heat exchanger seal 9 weeks in and charged 200 quid to do a 35
minute job under guarantee. Now they do not want to know.

 

[ShaunCorbs]

I agree. The boiler developed a leak from the heat exchanger seal 9 weeks in and charged 200 quid to do a 35
minute job under guarantee. Now they do not want to know.

Didn’t they call the manufacturer out ?

 

[JohnHuson]

No and the customer got a gas certificate but the commissioning report was not completed.

 

[SJB060685]

I agree. The boiler developed a leak from the heat exchanger seal 9 weeks in and charged 200 quid to do a 35
minute job under guarantee. Now they do not want to know.

That would of been a warranty job and the manufacturer liable for payment, not you!
Unfortunately to rectify this is going to cost more and the situation clearly demonstrates the installer doesn't understand the principles.

 

[ShaunCorbs]

Time to get a solicitor involved

 

[JohnHuson]

That would of been a warranty job and the manufacturer liable for payment, not you!
Unfortunately to rectify this is going to cost more and the situation clearly demonstrates the installer doesn't understand the principles.

This customer is prepared to spend money in excess of what was paid for what should have been paid under
warranty in a small claims court.

 

[JohnHuson]

So where in the system should the extra push pump be located please?

 

[ShaunCorbs]

Where the old boiler pump was

 

[SJB060685]

I think between us we have arrived at the problem. My concern now though is as I mentioned above are the existing rads at ∆T 60°c, if so the flow temperature will need to be around 90°c to give a rad MWT temperature of 80°c and full out put.

 

[JohnHuson]

I think between us we have arrived at the problem. My concern now though is as I mentioned above are the existing rads at ∆T 60°c, if so the flow temperature will need to be around 90°c to give a rad MWT temperature of 80°c and full out put.

yes hat makes sense but I have to get the water around the system in the first place.

 

[JohnHuson]

The boiler is capable enough so where do I install a secondary pump?

 

[SJB060685]

yes hat makes sense but I have to get the water around the system in the first place.

Yes I agree completely. However I suggest separation, pumps in series is not always going to work.

 

[ShaunCorbs]

Post 35

 

[JohnHuson]

Yes I agree completely. However I suggest separation, pumps in series is not always going to work.

You are magic and clever so thank you.

 

[JohnHuson]

So where should we install the extra pump please?

 

[ShaunCorbs]

After the external heating plate heat exchanger which will need to be added

 

[SJB060685]

You're going to need to separate the system and as Shaun says a plate heat exchanger is your best bet as it will protect the boiler circuit from your decades old and no doubt fouled system. once you separated then a suitable pump will be installed on the flow out of secondary side of the plate heat exchanger.
At this point I strongly urge you to find a firm/engineer who understands the principles of hydronic system design.

 

[JohnHuson]

After the external heating plate heat exchanger which will need to be added

That is also my logic and I thank you for your help. If the boiler produces hot water and the circulatory system
is free to flow then all that is required is to pump it around?

 

[ShaunCorbs]

Close enough

 

[JohnHuson]

I have a qualified engineer arriving tomorrow afternoon. Thank you for your input! John.

 

[SJB060685]

A pump is required to supply the pressure required and the flow rate required. It's actually the system that creates the pressure but the pump has to be able to meet demand. As it stands the boiler integral pump just can't do this.

 

[ShaunCorbs]

I have a qualified engineer arriving tomorrow afternoon. Thank you for your input! John.

Do they do commercial heating systems ?

 

[SJB060685]

Close enough

As you said close enough mate but I must add if the secondary side is staying open vented then pump in that image is not situated ideally. One would need it to be V,C,P on the flow out on secondary side.

 

[JohnHuson]

What nice giving people you all are. Thank you. You really can effect peoples lives by your contribution.

 

[ShaunCorbs]

As you said close enough mate but I must add if the secondary side is staying open vented then pump in that image is not situated ideally. One would need it to be V,C,P on the flow out on secondary side.

If it’s a combi it’s sealed or they’ve linked the pressure switch out as navs can’t be run ov

 

[SJB060685]

We do this because we are passionate about our industry, unfortunately for your friend he employed the services of someone who quite frankly doesn't know the basics and as Shaun mentioned before that's damaging.

 

[JohnHuson]

Do they do commercial heating systems ?

Not sure but will check out. There appears to be a vast misunderstanding what the roles are between plumbers, heating engineers,
central heating specialists.

 

[SJB060685]

If it’s a combi it’s sealed or they’ve linked the pressure switch out as navs can’t be run ov

Yes. So in that case if secondary side is sealed as well then a vessel of suitable size is required.

 

[ShaunCorbs]

Not sure but will check out. There appears to be a vast misunderstanding what the roles are between plumbers, heating engineers,
central heating specialists.

When your there tomorrow grab a couple of pictures of the set up

 

[JohnHuson]

We do this because we are passionate about our industry, unfortunately for your friend he employed the services of someone who quite frankly doesn't know the basics and as Shaun mentioned before that's damaging.

Yes, life is full of givers and takers. I find it easier to be a giver as I sleep soundly.
Well done for sorting out my problem.

 

[JohnHuson]

Will take photo's tomorrow.

 

[SJB060685]

Yes, life is full of givers and takers. I find it easier to be a giver as I sleep soundly.
Well done for sorting out my problem.

We've arrived at the problem and can advise on the possible solutions but ultimately it's down to you to find a suitable engineer. Unfortunately knowledge and experience comes at a price, something you and your friend have now discovered.
Can I ask, you said your friend was charged just over 2k, was that supply and fit?

 

[JohnHuson]

We've arrived at the problem and can advise on the possible solutions but ultimately it's down to you to find a suitable engineer. Unfortunately knowledge and experience comes at a price, something you and your friend have now discovered.
Can I ask, you said your friend was charged just over 2k, was that supply and fit?

£2400 supply and fit but did not supply commission document or make the system work. They said that the lack
of circulation was due to knackered TRV's and said we would need to pay an extra £1300 to replace the 23 valves
and make the system work as it should.
I agree to the logic that we need to ensure the hot water is pumped around to reach the extremities of the 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.

 

[SJB060685]

Are the radiators on the secondary side all expected to be running at the same time?

 

[JohnHuson]

I think you just sorted it! Well done and thank you. I now have to find an engineer who can do all that.

 

[JohnHuson]

Are the radiators on the secondary side all expected to be running at the same time?

yes on two separate levels

 

[JohnHuson]

yes on two separate levels

What a great job you do! I do a similar role with car problems. Its good to help!.

 

[JohnHuson]

I have balanced the system but still the extremities are cold. We are going to take up your suggestions as soon as we can
find a plumber/ heating engineer in striking distance of Runcorn/Widnes/Frodsham.

Your help has been most appreciated. Thank you.

 

[gmartine]

Look for a plumber with a commercial ticket as they'll be more familiar with CCT's and LLH.

 

[JohnHuson]

Thanks.