Ideal classic Boiler overheat

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bigrinks

Hi all, first posting so please be gentle!

I've got a ideal classic boiler and a megaflow tank sealed / unvented system. approximatley 10 years old and serviced regularly.

Even from new the system has been very poor at heating my livingroom radiators which struggle to get above 33 degrees C with system on. On radiator( the furthest doesnt heat up at all). Flow in hot, flow return cold and in some radiators - stone cold.

General view is that i have a blockage in downstairs loop (unlikely) or that system incorrectly installed (likely). Having investigated the latter, i now know the system is 22mm arterial copper feed with flow and return being15mm branches to each radiator. However, my downstatirs circuit consists of very short 22mm feed and return and majority being 15mm and feeding multiple radiators - and very long lengths!

I've since drained and piped in 22mm connection from exisitng 22mm direct into the rooms with poorly operating radiators. This reduces length of 15mm branches and provides a feed for multiple radiators.

Now systems running, i can report very little change in rad temps (still 33 deg C) although the cold ones all now get to 33 DC quickly. With air temp set high, boiler cuts out repeatadly due to overheating before restarting a few mintues later. Balancing therefore usless as it seems to make a constrained system worse.

Any ideas what to look at next? How to track down the problem.

This problem seems to be of little interst to professionals and i've been given the run around since October - presumably due to difficulty?

Sorry for length of the post!!!

Mark
 
:welcome: to the forum bigrinks :)

What temps are you getting on your main flow and returns at the boiler? Check for around 11 Deg C Difference between the two ... If a lot more than 11 DegC then suspect a blockage on the primary flow or return ... Or a dodgy pump!

You need to trace the blockage and best place to start is by checking the primaries before you start on the heating or hot water supplies IMHO
 
diamondgas said:
:welcome: to the forum bigrinks :)

What temps are you getting on your main flow and returns at the boiler? Check for around 11 Deg C Difference between the two ... If a lot more than 11 DegC then suspect a blockage on the primary flow or return ... Or a dodgy pump!

You need to trace the blockage and best place to start is by checking the primaries before you start on the heating or hot water supplies IMHO
Click to expand...

hi thanks for this advice and warm welcome!

I will check tonight and report back with temp readings. When you say primaries i assume you refer to the main 22mm feed and return between the boiler (kitchen) to the heating cupboard (first floor) which contains the tank,pump and various valves. It is from this cupboard that the flow and return then serve the upper and lower floors.

Temp difference between 22mm flow and return downstairs is definatley more than 11Dc.

Pump was on my list to question but last heating engineer has confirmed that it correctly rated (verbal with no test undertaken) FYI - its running in position 3 (highest) which another engineer says is incorrect. How is the pump tested? no noise or vibration from it.
 
Primaries are as you've said the two from the boiler to the cupboard!

Was your system originaly an open system converted to sealed? It's unusual for a sealed system to block up unless you've been topping it up over and over again in the time since it was installed :)

Are you in a hard water area? Another thought is it may be scale!

Lots of possible resons for poor circulation to be honest .... :)
 
Thanks for the suggestions guys.

Some more info.

1, pump is working it just does not have any abnormal sounds from it. Quiet but definately functioning.
2, Air - possibly. Long standing issue and system drained down and refilled at weekend so i guess air lock would have moved or something. Could be in the boiler? is this possible?
3, System never really needed topped up. Ran at fairly constant 1.5 bar.
4, No its a new system fitted ten years a go to a new build property. No conversion or messing.
5, Right pipe temps. At current bolier setting (3 out of 7). Feed fluctuates between 44.8 and 48.8 DC. Return 37-40. Boiler is currently operting for a bout 2 ninutes, shutting down for 4 and then restarting for 2. This cycle varies but it is on most occcasions this frequent. If its relevant i think there is abalabcing pipe with valve in heating cupboard????? assume this bridges between feed and return?
6, Not hard water area. Scotland! When system emptyied it seemed free flowing with only minute steel particles in bucket. Nothing that would suggest sludge and colour of fluid was a light grey.

Help!

Mark
 
Id go for a new pump to at least rule if out. If I had an overheating ideal classic my first port of call would be pump change at speed 2 if open sys and speed 3 if sealed
 
Mbear said:
Id go for a new pump to at least rule if out. If I had an overheating ideal classic my first port of call would be pump change at speed 2 if open sys and speed 3 if sealed
Click to expand...

Thanks, i've got a heating engineer (another) visiting tonight to have a look. If he shows up that will be a bonus. He reckons he can check the pump (hand over it?) and is convinved it shouldnt be aspeed setting 3 - should be 2. Hes fully aware that its a sealed pressureized system. Will see what he thinks and report back later

Thanks again for the advice.
 
1st thoughts are your F&R temps are pretty low ... I'd have expected closer to the 80C but then as you say it's on no 3 so probably okay :) Circulation sounds okay though which moves my thoughts away from the pump and more towards ballance! On off frequency indicates he water could be wizzing through the hot water circuit and/or by-pass missing the heating.

2nd: if you can, check the f&r temp diff on heating only. If okay then it's most likely a ballancing issue ... suspect the ballancing valve, turn it off if you can, or heating system circulation problem .... getting to a point where a visit would be beneficial tbh :) Hopefully the guy this evening will help you...!
 
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diamondgas said:
1st thoughts are your F&R temps are pretty low ... I'd have expected closer to the 80C but then as you say it's on no 3 so probably okay :) Circulation sounds okay though which moves my thoughts away from the pump and more towards ballance! On off frequency indicates he water could be wizzing through the hot water circuit and/or by-pass missing the heating.

2nd: if you can, check the f&r temp diff on heating only. If okay then it's most likely a ballancing issue ... suspect the ballancing valve, turn it off if you can, or heating system circulation problem .... getting to a point where a visit would be beneficial tbh :) Hopefully the guy this evening will help you...!
Click to expand...

Thanks, will check f&r on heating circuit tonight and get back to you. Assume taking temp differential in cupboard will be fine or does the proximity to balancing pipe make this a stupid place to take reading? Note i do not think there is any other balancing pipe in the downstairs system. I assume if the circualtion is overly good, reducing pump speed might also help?
 
Get the engineer to check the gas working pressure @ the boiler, and @ the meter.

Ideal Classics are normally bullet proof.
 
Sounds to me like the flow and return are either crossed or have been tee'd in together at some point. Causing the flow to bypass and just go round the boiler mainly, with a little going to the rads. You might find a random gate valve in the airing cupboard, see if it's on the primaries and trying tinkering with it. The installers for the company I work for decided it would be a good idea to add some on the y-plans they were putting in.

If that's not the case, you could follow the flow and return under the boards up to the airing cupboard and see if they cross or have anything coming off them before the diverter valve.
 
bigrinks said:
Thanks, will check f&r on heating circuit tonight and get back to you. Assume taking temp differential in cupboard will be fine or does the proximity to balancing pipe make this a stupid place to take reading? Note i do not think there is any other balancing pipe in the downstairs system. I assume if the circulation is overly good, reducing pump speed might also help?
Click to expand...

Sorry I wasn't that clear regards heating f&r temps .... You're still wanting to check at the main boiler f&r just with heating only on! This'll give you some indication as to how the water is circulating. If still as before 8-10 degC diff then the water is circulating fine somewhere! The question will then be where, and how do I reduce where it is currently circulating to increase it to where it isn't going? However if the temp diff increases a great deal then that'll indicate a reduced flow to heating circuit ... :)

Do you know if the system design is 's'plan or'y'plan? Maybe even a few pictures of the set up in the cupboard could help us understand a bit more :)
 
I would agree with diamond gas .What you refer to as a balancing pipe should have a gate valve across it. Try shutting it down and running the system. We had a job recently with symptoms similar to yours where one of the pump flange valves had been shut down at some point and then opened but had sheared in the partly open position and was restricting the flow.
 
Hi alot of good ideas coming through. Thanks.

Some updates....

1, F&Fr temps quoted at boiler are for central heating only. Hot water was off.
2, I've tried running the system with gate valve on balancing link both full open and full close. Its definately screwing the valve but makes no difference to boiler cutting in/out.
3, Tepid water comment. Noted. But turning boiler water temp up makes boiler cutting out worse and puts extra strain on boiler and pump. Without a propoer fix i;m reluctant to run the boiler harder. Problem i think is more about boiler cutting out frequently than rad temps. Solve one - fix the other?
4, Heating engineer did not inspire me with confidence. Reduced pump speed to 2 a he initially was confident that water is wizzing around system. Within 5mins he now wants to re pipe the return direct to the boiler from kitchen (were i have added my 22mm extensions). This would bypass the exisitng return that goes via the cupboard / tank etc. - Doesnt seem plausible to me - Thoughts? Checked valves etc all working fine-apparently!
5, Yes ideal classic is older design - not the most efficent but relaible - other than fan. Mines recently oiled, working smooth and quiet.
6, Didnt get check on gas pressure etc but would suggest its ok.
7, Y / S plans - No idea what the difference is. No heating layout drawings either. I'll try get a photo. Bf in through valve 1, pump, valve 2, T branch to balance pipe, diverter valve(silver box)? then another(white box) then hf. return branches to water system, balance pipe.
8, Hr/Hf crossed - Yes a real possibility but cant be checked without floor / roof removal - Major job.
9, I meaured hr/hf in cupboard. Variations are up to 18degrees. Difficult to identify the range but roughly 43degrees with hf being the more stable of the two.

Other points to note.
8, Temp difference on hr/hf under floor is massive until heating been on for a bit. Even with rads warm, Hr can be piping and Hf barely luke warm
9, there is one other gate valve linking heating system to hot water system. Im assuming its some sort of balance also controlling how much hot water from heating circuit goes through exchanger to hot water circuit.

I'll truy get some photos.

Mark
 
Interesting pump change.

Those pics might suggest why the engineers who have visited havent seemed too keen :crazy:
 
Still suspect that pump is at fault. just because you can feel it vibraiting dos not mean its not faulty, think I would change pump , but how do you get at it ?? my find motor running but impeller not , can you tell if pump speed alters when you switch over,:shocked:
 
Something to try, see if you can get any better flow to your radiators .... picture 5, the 22mm gate valve is the balancing valve for the hot water. The 15mm one at the top going up and over the pump, that looks like the bypass valve.... Turn them both off, fully clockwise, AND put the boiler on heating only. This will guarantee that the pump is only circulating water around the heating system... If you've still got 8-10 DegC on the primary F&R then there are some radiators that are heating fine and allowing th water to circulate freely. They maybe compromising the flow to the others... 8-10 DegC says that you have a good pump and good circulation ... The cutting out sounds like maybe another issue!

I think you need someone up on system design who can cast an eye over your installation. .. All I can say without seeing it personally is that you have a circulation problem.. :)
 
Again thanks all.

1, Pump can be accessed although you need long arms! i'll look into replacing and report back. No obvious effect of reducing pump speed but it must be working as the furthest rad from pump heats from cold in about 5mins.
2, Will try closing off balancing valves (heating and water) then assessing temp variation.

So far the consecious of thought is that its either a circulation problem (suspected) or doggy pump (which i can replace to remove from equation).

Further update. Having had a fiddle with my neighbours system (same system but different installation) they also seem to have a boiler that cuts in and out when trying to get to temp. Perhaps not as frequent as mine though! I'm suspoicious of the TRV valves on my livingroom rads so i've drained and flushed (using filling loop) system again and fitted high flow manually adjustable valves to replace trvs (Look like lockshields but with white thumb knob). Even with these full open - no change to system operation or temp of livingroom rads. Therefore i think the heating return hr is the problem and somewhere close to the cupboard as im nearly certain its all free flow 22m to the livingrooms.

How to track it down though! thats the problem!
 
Hi bigrinks .... soz about the few replies been walking in the Lake District across the weekend :)

Regards the circulation issue please do not rule out the primaries but from the info you've given they are less likely! If the boiler is cutting out then the heat build up is enough to trip the overheat usually around 90C+ ... That points to circulation if you know the flow is getting that high at some time. The conclusion would be; heat not being removed quickly enough or a dodgy o-heat!

Regards the fault being in the return, you just do not know? If it's effecting ALL radiators then it's either the heating primary flow or return. Either one will cause grief :)

Here's a question I haven't asked as yet; Does the boiler cut out on hot water only at all? Coz if it's cutting out on both hot water and heating circuits then it'll deffo point toward the boiler/pump/or primary circulation pipework! :)
 
diamondgas said:
Hi bigrinks .... soz about the few replies been walking in the Lake District across the weekend :)

Regards the circulation issue please do not rule out the primaries but from the info you've given they are less likely! If the boiler is cutting out then the heat build up is enough to trip the overheat usually around 90C+ ... That points to circulation if you know the flow is getting that high at some time. The conclusion would be; heat not being removed quickly enough or a dodgy o-heat!

Regards the fault being in the return, you just do not know? If it's effecting ALL radiators then it's either the heating primary flow or return. Either one will cause grief :)

Here's a question I haven't asked as yet; Does the boiler cut out on hot water only at all? Coz if it's cutting out on both hot water and heating circuits then it'll deffo point toward the boiler/pump/or primary circulation pipework! :)
Click to expand...

I think your on to something here!...

Right normal operation water and heating on. boiler set to position 3 (43DC water out), system will heat rads from cold until hot then start this 2m cutting in / out cycle.

With heating off and only water on the boiler didnt start (presumably cause its at temp). turning up the boiler temp control to full resultign in boiler starting, running for 2 mins then starting this 2 min cycle.

both balancing valves are part open/shut.

So i guess we are now saying its the pump, primary circuit or boiler temp gauge. Can the later be easily sourced/replaced?
 
e/bourneplumber said:
what happens if you turn off all the upstairs rads and have heating on only? does the downstairs circuit heat up properly?
Click to expand...

Heats up but never hot. Boiler starts the 2mins trip cycle. Given the choice it seems to prefer to heat upstairs. Think the issue is now definatley the boiler tripping which prevents the heat being pumped around.
 
did you say you replaced the downstairs heating circuit in 22mm? could it be that the pipe work is crushed or blocked? if not i would have to go with above suggestions and thinks failing pump, partially blocked heat exchanger, maybe faulty auto bypass.
 
e/bourneplumber said:
did you say you replaced the downstairs heating circuit in 22mm? could it be that the pipe work is crushed or blocked? if not i would have to go with above suggestions and thinks failing pump, partially blocked heat exchanger, maybe faulty auto bypass.
Click to expand...

Patial replacment with 22mm as nearly all downstairs was running of 15mm with 4 rads taking a feed from a single 15mm in one instance. 100% guaranteed that new piping not crushed or bent. I used plastic pipe which is fitted nearly perfectly straight, capped ends whilst threading. Nearly full 22mm from cupboard to rads in livingroom now (except short 15mm tails).

How do i check heat exchanger and autobypass? - Doubt that any sludge build up as system relatively new and clean when drained down. Really doubt its sludge etc.
 
when you first put on heating or hot water, ie when system is cold, feel the pipe work after the auto bypass, it should stay cold, it should only open when there is a pressure against it, like when a valve has closed and then the bypass should open to let the heat from the boiler cycle to cool down a bit. they are usually adjustable.

if you've got no blockage in the downstairs circuit, and no crushed pipes, and when you shut everything other than the d/s circuit the rads only get warm rather than hot, and the pipe work is all in 22mm other than the feeds to the tails of the radiators, then i would change the pump maybe to a 15.60, 6m head. heat exchanger is not something you can do yourself, and if it comes to taking out yours, i would think about getting a price for a new boiler. imo. does the boiler make a kettling noise as it heats up, like when you first put kettle on from cold, this would indicate scale in the heat exchanger, and you could have it descaled or add a descaler into the system yourself via a radiator.

also just a thought, you seem to know the layout of the pipe work pretty well, do you know where the return pipe from the down stairs circuit tees into. it could be that it is teed in the wrong place and instead of going straight back to the boiler it is going elsewhere. you may need to get some one in to have a proper look.

but i would start with the pump.
 
Thanks. not sure were the autobypass would be located!!!

I'm now thinking the limited heat in downstairs rad is because the boiler wont stay on long enough to do the business! Obviously previous thoughts was blocked or restricted system causing this.

Boiler does make a faint bubbling noise before switching off. Mind also that hf and hr at boiler dont exceed 47dc on current setting 3.

hf and hr in downstair system run in parallel around the house. If hr tees into something it shouldn't it would need to be in first floor. It must go back to tank before boiler else rads would heat when only hot water on?
 
bigrinks said:
So i guess we are now saying its the pump, primary circuit or boiler temp gauge. Can the later be easily sourced/replaced?
Click to expand...

It certainly sounds like it is :)

What sort of flow temp are you getting with the boiler stat on full and/or when the "2min cycling" comences? How hot is your hot water getting by-the-way? You should be heating your cylinder to 60C!
 
apologies, ive just looked at the pics and you dont have an auto bypass only a gate valve!
the scale noise is usually heard when cold as it hisses and pops when it expands with the heat, from the pics the pipe work looks ok, obviously cant see whats going on under the floor, i would start with changing the pump.
you may have to get some one in to give you better advice as they would be able to get their hands on. if you know what i mean!
 
as above...sounds v low f+r temperatures...possible bypass stealing heat or bp on blr not correct??inlet pressures? meter governor?got to prove boiler operating correctly before going for system issues:)
 
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