7 head pump upgrade on an Intergas boiler

[evets51]

I've got quite a longstanding problem with a 1.5 year old 18kw Intergas system boiler which takes over an hour to get all radiators hot - and even then they aren't scalding hot to the touch even though the water temp is set to 80 on the boiler.

Potted history - it was a replacement boiler we had put in when we moved in, to replace a 17kw Ideal boiler. Its a 5 bedroom / 17 radiator house, approx 2200 sq ft - most people seem to think the boiler is too small, however having put my details into the boiler size calculator at idhee.org (double-glazed, 270mm loft insulation, cavity wall insulation) it came up with 13.6kw. Also the previous owners, who I trust, assured me the previous lower capacity Ideal boiler coped adequately.

Its a microbore system - originally sludged up badly and heating performance was awful (rooms wouldn't heat up at all), but we had 2 power flushes done plus a load of Fernox sludge remover. The three worst radiators for getting hot are in the living room and hallway - I've taken these radiators off and run a hose through them and no sludge, so I'm reasonably sure the system is clean.

The boiler shortcycles all the time - so fires for the first 2 or 3 minutes, then backs off for another 2 minutes or so before firing again etc. If it was firing constantly and took an hour or more to heat up I'd believe it was undersized - but it can't be right for it to be shortcycling constantly like this? So yesterday I closed off all radiators other than the three which are the worst performers, and fired up the heating. All 3 radiators got red hot within 20 minutes (hotter than I've ever felt them) - hot at the top and bottom (even though the boiler still shortcycled).

Its been suggested that the problem is the pump not being able to move the water around the system adequately. I've no idea what the pump system on the Ideal was. I've spoken to Intergas and they tell me the pump on the current boiler is a "5 head" pump, but you can get a "7 head" pump as an upgrade - £140 for the part. Just looking for opinions on whether or not that is likely to be a big help and worth trying? We've spent quite a lot of money on powerflushes / having people in to add Fernox and drain the system etc, and one of the options on the table at the moment is ripping the whole system out and adding all new radiators plumbed in 15mm copper with a new, bigger boiler. Obviously that's going to cost a small fortune though so would like to avoid if possible!

 

[happyflyer]

You need someone to come and look at the whole system, where do you live?

Boiler does appear on the low side, I would work out the heat losses for each room properly

 

[johnnyplumb]

was the heating working ok after the new boiler was installed

 

[evets51]

You need someone to come and look at the whole system, where do you live?

Boiler does appear on the low side, I would work out the heat losses for each room properly

I'm near Cambridge, we've had several people come to look at the whole system and provide estimates etc but opinion has been divided so far between getting another powerflush done, getting a new bigger boiler, getting the whole system repiped etc. So just trying to canvas as wide an opinion base as possible really.

No the heating never worked when the new boiler was put in - the powerflush that was done as part of the boiler install was done off one of the radiators. This is why we later had a second flush done from the flow / return pipe on the boiler - which was much more effective. That (and the Fernox stuff we'd had put in in the meantime) really improved the performance a lot as originally it took 3 / 4 hours to get the house up to temp. These days if its 1/2 degrees outside it takes approx 1.5 / 2 hours to get 19.5 inside - much better but still could do with improvement.

 

[happyflyer]

You will get all sorts of people guessing, there may be a number of problems not just one, that's why they guess, you need one man who knows what he is doing
and your problems are over, trying to fixed with such deep routed problems will be difficult, if you don't get someone to physically come and look at it you will go round
in circles, sorry I am not nearer maybe there is a member near you, these people don't usually fail because they come back and tells us all how they fixed it.

See if some does pop their head above the parapet for you.

Good Luck

 

[galaxy_plumbing]

sound like poor circulation. does furthest radiator get hot? as said, its hard to help over internet in this case.

 

[Killy Bing]

Get an engineer off this forum, that pump should be more than capable.

I suspect that the issue would be more due to system layout.

the previous owners said the old boiler was capable but as you also said the system was sludged up badly.

Has there been any extensions in the past?
has the boiler been moved?
what had the ideal boiler replaced or was the the original?

 

[evets51]

Get an engineer off this forum, that pump should be more than capable.

I suspect that the issue would be more due to system layout.

the previous owners said the old boiler was capable but as you also said the system was sludged up badly.

Has there been any extensions in the past?
has the boiler been moved?
what had the ideal boiler replaced or was the the original?

Yes 2 extensions in past - a big bedroom / en-suite / wardrobe over the double garage (1 large, 1 small radiator in there plus heated towel rail which is the bypass circuit) and conservatory (2 radiators plumbed in series so only 1 ever gets hot! - doesn't matter as we don't use conservatory in winter). Extensions were 5 years old for bedroom and 10 for conservatory when we moved in - so they'd lived with them for a while.

Ideal was the original house boiler - been there since 1993 when it was built. There is another house of exact same build in our street (including extensions) which had the same boiler and same microbore etc and they said it worked fine for them too.

Boiler is in the same place as it always was. The big bedroom is the longest throw from the boiler - approx 8.5 metres from the airing cupboard to the radiator. Its the worst performing of the lot but I don't really care as don't like a warm bedroom. Funnily the small radiator in the wardrobe (same distance) performs well.

The lounge and hallway are the ones I really care about - they haven't been altered since the house was built.

 

[oz-plumber]

Hi evets,

What the problem could be is that the radiator valves are not opening enough.
If you have the original radiator valves, particularly the thermostatic types, the valve can get stuck in the closed, or near closed position.
Before you go ahead and replace the boiler or pump, remove the thermostatic heads and pull the metal pin up with a pair of pliers.
I would say - from the information you have provided - that this could be the issue.
Or the lockshield valves are not opened up enough - valve on returns side of heater.
If the boiler was too small there would be no way it should be short cycling, it would be going flat out all the time.

Oz-Plumber

 

[Gas]

You size boilers for the hot water demand, not heating. I would get this system balanced properly using the two thermometer method, getting the correct temps on the flow and return and sorting out the bypass in the process.

I would put money on this sorting it.

 

[Ermintrude]

Do the pipes come out of the wall or floor for your rads ? Are they kinked or impinged in any way?

I would suggest u fit a wilo pico pump and a magnetic filter. As powerflushing on a microbore system isn't ever going to get it completely clean .

Do u have a valve which is on a 15mm copper pipe and connects the pipes either side of the pump? If so is this red hot when heating only is on? If so turn it off completely then open it 1/4 of a turn. Also there may be a valve on the outlet of your hot water cylinder, turn it down until when your heating and hot water are running the pipes coming from either side if the 3 port valve are the same temp . Measure temp and adjust at. 3 min intervals.

Sounds to me like the bypass ( pipe bridging pump is open too much)?

 

[Leo21]

The boiler size is not the issue, its circulation. Ermintrudes solution sounds good, have you been in touch with Intergas. They may have a way of programming the boiler to work better with your system, they have an anti cycling devise. This will stop the boiler coming on as fast when the temperature drops below the boiler thermostat requirements . Slowing down the heating up process. It's not the perfect answer, but I may over come some of the issues.

an upgraded pump wouldn't hurt either.

 

[dancinplumba]

Hi evets,

What the problem could be is that the radiator valves are not opening enough.
If you have the original radiator valves, particularly the thermostatic types, the valve can get stuck in the closed, or near closed position.
Before you go ahead and replace the boiler or pump, remove the thermostatic heads and pull the metal pin up with a pair of pliers.
I would say - from the information you have provided - that this could be the issue.
Or the lockshield valves are not opened up enough - valve on returns side of heater.
If the boiler was too small there would be no way it should be short cycling, it would be going flat out all the time.

Oz-Plumber

Be careful pulling pins, they come out if pulled too hard and you have a leak

 

[dancinplumba]

Has the power setting been increased ? The 7 head pump is good idea

 

[dancinplumba]

What speed is the pump in boiler set to ?

 

[happyflyer]

I have spoken to the guy and he has more balancing problems than I care to mention, he needs to put them right first before he can move on with all the bells and whistles,
he has been badly advised with the boiler and pump combined, internal pumps will always have a limit and the pressure drop on the Intergas alone is rather high to start with.

When people re-retrofit a modern boiler onto and old (minibore)system they need to be very careful what boiler set-up they use your are in theory back engineering the boiler onto the system, its not all about sludge, power flushing, magfilter etc is about will the boiler hydraulic cope with the old system, it may also have been added to and the original index circuit is no longer the index circuit.

This plumber has just stuck a new boiler on and not look at the big picture.

BTW the plumber has done a runner, now fancy that.

 

[Killy Bing]

I have spoken to the guy and he has more balancing problems than I care to mention, he needs to put them right first before he can move on with all the bells and whistles,
he has been badly advised with the boiler and pump combined, internal pumps will always have a limit and the pressure drop on the Intergas alone is rather high to start with.

When people re-retrofit a modern boiler onto and old (minibore)system they need to be very careful what boiler set-up they use your are in theory back engineering the boiler onto the system, its not all about sludge, power flushing, magfilter etc is about will the boiler hydraulic cope with the old system, it may also have been added to and the original index circuit is no longer the index circuit.

This plumber has just stuck a new boiler on and not look at the big picture.

BTW the plumber has done a runner, now fancy that.

A small low loss header and another pump it is then.
take the intergas out of the equation completely.

 

[happyflyer]

A small low loss header and another pump it is then.
take the intergas out of the equation completely.

100% with you on that one 1king, look a bit of a bugger in the kitchen wouldn't it, ship boilers house springs to mind, could go in the CC but this one is full anyway
but you are right, its not got to that yet get the balancing sort first because his system is un-balance-able at the moment.

 

[dancinplumba]

Bet previous owner had it banged in to make house more saleable

 

[happyflyer]

Bet previous owner had it banged in to make house more saleable

Wrong, this chap had it fitted, original boiler failed in first week they moved in.

 

[Killy Bing]

I would love to be able to get my teeth into this job/headache!
shame tbh

 

[happyflyer]

I would love to be able to get my teeth into this job/headache!
shame tbh

How far is Cambridge from you.

 

[Killy Bing]

About 90 miles. It wouldn't be worth my while
safe gas install is far closer

 

[Simon F]

You size boilers for the hot water demand, not heating. I would get this system balanced properly using the two thermometer method, getting the correct temps on the flow and return and sorting out the bypass in the process. I would put money on this sorting it.

not when its a system boiler.
so the boiler is short cycling, turning itself off because it is up to temperature, so what temperature is the return pipe??
is there one or two radiators that get piping hot quickly? = balancing issue.
have the parameters been properly set?
ch power to max 85 percent??
is installation type set to position 3- heat only!??

 

[Gas]

... have you been in touch with Intergas...

:lol: (installer for them)

 

[happyflyer]

This is interesting, the statement below in red is from the Intergas IM, can any of you experts tell me why Valliant put the ABV inside the boiler
and not suggest it be 20 ft away, if you guys ever put an Intergas in a terraced house and you can't fit the bypass 20ft away, you will fall
foul of Intergas IM, whatever will you do. What they appear to be suggesting is that some heat loss is set into the equation not just minimum water flow
through the boiler, if all the 20 ft of pipe was lagged, what then, I would be interested on your take on this.8.1.2 Thermostatic radiator valves


If all radiators are equipped with thermostatic or radiator valves, an auto bypass must
be fitted in order to guarantee minimum water circulation. The auto bypass must be at
a distance of at least 20 ft from the appliance in order to prevent overheating of the
appliance. A radiator without thermostatic valves is not a suitable by-pass.

 

[Mike Jackson]

It's there to comply with the building regs. The bypass inside a boiler is there to protect the pump and not to comply with the building regs.

 

[happyflyer]

Mike are you saying that if you fit a Valliant you need to also fit another ABV 20 ft away from the boiler ???


Mike PS you are right, IM for Valliant, wonder if plumbos are fitting one, two of my friends have Valliant with no external BP, if one bypass can give a plumber a headache setting up two what will that do, if someone has a flow problem we should be saying, " have you set both ABV "

3.13 Bypass


A system bypass will be required fitted at least 1.5
metres away from the boiler, refer to the current issue
of central heating system specifications (CHeSS).

 

[evets51]

Just an update to say thanks very much for all the advice. I had a very educational chat with happyflyer yesterday who was very generous with his time. It turns out one of my major problems is the towel radiator fitted as a bypass. The valves were wide open and its plumbed in larger bore plastic pipe - so all the hot water was screaming around there and back to the return pipe rather than going around the radiators. Last night I closed both valves and then opened them one turn only - this morning the system was much much faster to heat up, far less boiler cycling. I still have problems as more than half my radiators have a TRV on each end and no lockshield valves so impossible to balance - going to get those replaced and attempt balancing, and fiddle some more with the valves on the towel rail bypass to try to get it perfect. But certainly seem to be on the right path.

 

[happyflyer]

Steve,

When you have the items done I have suggested, I will help you balance the system, it will be a little more demanding than a newly installed system since the different bore diameters, I will be sending you another email today about the towel rail bypass and the proper alternative.

BTW you forgot to mention there is no balancing valve on the primary return on the cylinder coil too and the water is screaming around there when the HWS valve is open.

Tony

 

[Leo21]

Here goes! Why do you need a bypass on a "y" plan? There's always a port open to either the cylinder or a bypass radiator! Both long enough runs and usually longer than where the bypass would be fitted.

 

[evets51]

Here goes! Why do you need a bypass on a "y" plan? There's always a port open to either the cylinder or a bypass radiator! Both long enough runs and usually longer than where the bypass would be fitted.

Its an S plan I believe - 2 separate motorised valves, one for hot water and one for heating.

 

[evets51]

not when its a system boiler.
so the boiler is short cycling, turning itself off because it is up to temperature, so what temperature is the return pipe??
is there one or two radiators that get piping hot quickly? = balancing issue.
have the parameters been properly set?
ch power to max 85 percent??
is installation type set to position 3- heat only!??

Yup it appears to be balancing as said above. The ch is on max 85% though yes, pump speed is turned up to max and installation type is 3.

 

[doitmyself]

the pressure drop on the Intergas alone is rather high to start with.

Why do you say that? The 18SB (OP's boiler) drop is only 0.75m at full output, which leaves 3.5m for the heating circuit.

Don't forget that the boiler is designed to work with a 20C differential, so a lower flow rate and consequently much lower pressure loss.