central heating only comes on with h water, stumped engineer

[UpgradeME]

Why is everyone forgetting the heating works perfectly when on with the hot water.

I agree with Matt1e on this one. I don't think it does "work perfectly", the rads may get some heat when a limited amount of water passes through the rad circuit, however, if the 3-port valve is manually turned to CH (with the actuator/head off and the programmer set to CH&HW), the boiler kettles and turns off.

That to me is not an electrical fault, it sounds more like a flow restriction of some sort.

 

[bonkersbill]

Hi all, i am following this post but its all been back and forth wether its electrical or flow which until i get some tests to do to rule out one or the other i'm stuck, some of your abreviations are not clear to me, some answers to the latest questions,
Other side of back boiler is outside
it is 2 x 22mm pipes with 15mm tees
the pipe from the bottom of 3pv which i assume is the hot feed to the rads is bent, runs along side the 2x28mm pipes then drops through the floor, the copper end pipe you can see is just a spacer, this then 1st tees of to the bathroom rad, then the 22mm goes to rest of upstairs rads, the 2nd tee is one of the 15mm pipes which goes down the conduit which passes the side of the boiler, i thought these 15mm were supplying the down stairs rads?
The 22to 28mm pipes go from boiler to bottom of hw tank and to the grundfoss to feed the 3pv
the gate valve opens and closes.

 

[bonkersbill]

1&2,Picture 1 22to28 to boiler i have labled wrong, this is the 22 which goes under the floor to the rads from the bottom of the 3pv
3, spacer
4, correct
a, this pipe tees, 22mm to rads, 15mm to rad in bathroom
b&c, wronly labled, this is to rads and the pipe from the bottom of the tank is the 22 to 28mm to boiler
5, pic 3 is above floor between tank and the top of the conduit to the boiler, also shows 22mm dropping below floor to rads
6, all correct if DHW is HW tank

 

[bonkersbill]

i have turned the gate valves on and off many times and have heard water rush through but i will check this, as for the pump this has been metioned before but i have been unable to order a seal kit from grundfoss.
not sure what the de-air eject unit is, the little barrel perhaps, if so and is advisable, i have no problem doing the plumbing if some one tells me what goes where.
i have had the CH on all winter with the HW on at the same time, i dont think the down stairs rads are as hot as the upstairs but it has been working ok, ocasionally the heating comes on but no heat to any rads, if i restart it, it works ok

 

[bonkersbill]

The wire in the room thermostat to L3 is yellow not green my missis tells me, i am a bit colour blind, this i remeber the engineers saying is wired into the programmer

 

[doitall]

I'll leave you too it.

let me know when you want to sort it.

Where are you located by the way.

 

[bonkersbill]

Wakefield and i want it sorting, flow or electrical, which is it, what tests does any one have to prove or dis prove either, theres been some talk of wires missing or in wrong place, 3 engineers have checked that everything is being called for and when it should be.
Why does the boiler turn off after 30 secs and if i turn the heat up on the boiler why does it kettle, if this is a wiring problem surely there must be a test or i could bypass some thing at the wiring box to keep the boiler going, same thing if its pipes blocked. the problem is every one has different oppinions and no one is telling me where to start, the engineers that came did not know where to start, so they did nothing which left me replacing parts that did not need changing to rule them out, so where do i go from here, what tests would you do to find the problem or would you all just start replacing parts in the hope of accidently finding the problem?

 

[UpgradeME]

Why does the boiler turn off after 30 secs and if i turn the heat up on the boiler why does it kettle

Both of these statements indicate there is a lack of flow through the boiler. When the flow is restricted, a kettling sound is heard, followed by the boiler stat switching off the boiler.

Are there any indicators (LED/LCD) on the boiler after it cuts off?

what tests would you do to find the problem or would you all just start replacing parts in the hope of accidently finding the problem?

Logically.

1) Has it always been like this since you moved into the house?
1b) if not, what changed?

2) I would attempt to draw/map out the piping as much as possible (see the one I did for my house below) to help identify where there may be an issue with the pipe work / system which someone may spot.

Untitled

• UpgradeME
• 14 Mar 2011
• 2

3) Once I could see the detail in 2) I would then look to see if I could bypass parts of the circuit to help identify where the restriction may be.

 

[dave18]

bonkersbill

There are several things that do not make sense to me,

!, The title of this thread implies that you are a heating engineer. but several things that you say makes me wonder if you are the home owner,

2, There seem to be too many mistakes in your posts as to which pipe is what how can we help if we have incorrect info.

3, further to my earlier post: The pipe in photo 1 marked "22to28 to boiler"
this pipe has 2 ends
end 1 is connected to?
end 2 is connected to?

4, pipe from bottom of 3port valve goes to?

a, is it joined to pipe marked "22to28 to boiler"?

b, does it go through floorboard DIRECTLY below 3pv

c, if none of the above where does it go?

d, is photo of the under floor pipework DIRECTLY under the 3pv.

e, in above photo does the pipe go DIRECTLY to the 3pv

f, in the picture of the 3pv the pipe leaving the bottom of the 3pv showes it going into a fitting of some sort, what is this fitting?

g, if a Tee where do the other two pipes go to?

More photos would probably help so pipes can be followed from picture to picture.

David

 

[bonkersbill]

The LED light goes out when the boiler shuts down, the rads have never been right since i moved in, rads down staiars never got too hot and came onslightly in summer when turned off, things changed when i moved and replaced the HW tank and altered all the times on the programmer to try and save money which meant HW and CH came on at different times, which we now know CH wont come on with out HW. i will post tommorow a diagram i did.
Dave i am the home owner with some reasonable DIY plumbing ability but not engineering skills. i have answered most if not all of your questions from yesterday further up the page, the 22to28mm caption is over the wrong pipe, it should be over the one further to the right that comes out of the bottom of the tank, the one out of the bottom of the 3pv is the one that goes under the floor boards to the rads, you can see it goes to a tee which feeds 1 rad in bathroom and the other 2 upstairs rads, there is a tee off this to a 15mm which goes down past the boiler, i assume to feed the downstairs rads, the other 15mm is of the return of the upstairs rads and follows the othe towards the boiler.

 

[matt1e]

Why is everyone forgetting the heating works perfectly when on with the hot water.

and why are you forgetting that electrically, everything works as it should

The heating does not work perfectly when the how water is also on,
the boiler shuts down via its stat (with symptoms of poor flowrate through it) everytime the hotwater is satisfied and closes off the port feeding the cylinder coil

the only electrical fault that would do that on a y-plan is one that would stop the pump while the boiler is firing, and that isn't happening according to the op

Matt

 

[dave18]

bonkersbill

If you do not want help just say and we will all give up and go down the pub.

Yes you did give answers to my first lot of questions

Please reread your answer.

You have a pipe going hot water tank in one sentence, and then the same pipe doing a totally different job in the next sentence.

THAT IS WHY I HAD TO ASK THE SAME QUESTIONS AGAIN.

I MADE THE QUESTIONS VERY SIMPLE SO YOU COULD ANSWER THEM WITH ONE OR TWO WORDS NOT A PARAGRAPH OF RAMBLINGS SAYING THAT YOU HAD ANSWERED THE QUESTIONS.

Just remember I am in Kent you are north of Watford I cannot see your pipes from here.

Correct and sensible answers may have cut down on the 9 pages of the forum.

So do you want help or not up to you

David

 

[UpgradeME]

I thought I'd have a look at the installation manual for the OP's boiler (Baxi Bermuda Inset 2, exact model unknown). The interesting thing is this paragraph:

3.6 Overheat Kit & Sealed Systems

1. An overheat thermostat kit is available to facilitate the installation of a Bermuda Inset 2 boiler to systems incorporating a combined feed and vent and to flats and dwellings where the building design prevents the boiler vent pipe rising continuously to the feed and expansion tank. (This must not be used on gravity systems.) Baxi Part No 234885.

2. The boiler can be applied to a sealed system with the use of the overheat kit.

3. Information regarding the application of the overheat thermostat is included with the kit.

Looking though the manual, I cant see any other overheat circuit, if the OP's boiler is turning off, has someone incorrectly installed the above kit!? - I have googled Part Num 234885 and can find a picture but can't find the instructions online.

Does anyone know how/if the OP can check if a "Overheat kit" has been installed? Where should he be looking? Does anyone have a link to the instructions? (OP, if no-one can help, perhaps email Baxi and ask for a copy!)

 

[4xpaws]

Bonkersbill,

On the 3 programmer settings you get the following results:

1.CH & HW. All appears to work fine (ie. HW in cylinder & rads warm up to temperature), until cylinder stat is satisfied. Then, the 3PV moves across to CH only and ~ 30secs later boiler overheats and the boiler stat cuts in. - I don't think you've got an 'overheat' stat fitted otherwise the boiler would trip out and would then need manually resetting. Its just the normally thermostat kicking in.

2.HW only. All works fine. Boiler fires, you get HW

3.CH only ~ 30secs later boiler overheats and the boiler stat cuts in.

You’ve confirmed its not a wiring issue when you set the programmer to CH&HW with cylinder stat calling for heat. It was all fine (ie. HW in cylinder & rads warm up to temperature). When you then removed the actuator head off the 3 Port Valve body and manually turned the spindle to CH only position ~ 30secs later the boiler overheats and the boiler stat cuts in. You haven’t changed the state of the circuit yet the fault's occurred. Turn the spindle back to mid position ie. HW&CH, and the boiler fires up assuming either the room stat, or cylinder stat, is still calling for heat (However, the boiler won't fire up instantly mind you, only once the heats pumped out of the boil and the boiler thermostat clicks for heat)

You could with the actuator on call for CH only on the programmer with the room stat calling for heat. (~ 30secs later the boiler will overheat causing the boiler stat to cut in and turn off the boiler). Then remove the head off the actuator and turn the spindle to the mid position. The boiler will fire up and you get heat in the rads (& HW in cylinder will also rise in temp).

Its not a flow restriction. As when you set the programmer to CH&HW with cylinder stat calling for heat, the HW and rads are all fine (ie. HW in cylinder & rads warm up to temperature).

If it was a flow restriction, then the restriction is always there until you physically clear it. However you’re miraculously ‘clearing’ it when you set the programmer to CH&HW with cylinder stat calling for heat. (ie. HW in cylinder & rads warm up to temperature).

You do mention the downstairs rads are possibly not as warm as upstairs. I would balance all the rads first to see if this alters their performance for the better.

The two 15mm down the conduit pipes could very well be supplying some, or all of the downstairs circuit. If its some, look for other boxing. If its a suspended ground floor, the 15mm pipes running down in the boxing next to the boiler could just continue right down and under the floor before going on to the ground floor rads. Or if its a concrete base, the pipes are set in the concrete.

If at some place you can feel these 15mm pipes, switch off all the downstairs rads and with the heating in the CH&HW setting, get someone on command to turn on and off one rad downstairs at a time and feel if any heat travels down one of the 15mm’s and also returns up the other. You’ll then know which rads these 15mm’s are feeding. The pipes run in 15mm could well be undersized (and explain your observation the rads ‘could possibly be hotter’ downstairs), it depends on the combined KW/btu size of the radiators the pipework supplies and the ‘length’ of pipework to them. However, balance all the rads first and see what improvement this makes to the ground floor ones.

It is a piping issue. You are getting reverse circulation. Its possible someone's tee'd the central heating return pipe into the primary flow from the boiler (ie. The 28mm pipe you’ve identified as running from the boiler to the Grundfos to feed the 3PV.) mistaking it for the return. You will get hot rads as long as the 3PV is in the mid-position. It would also explain why, when the rads are 'working' (ie, only in HW&CH mode), you mentioned the CH circuit feed pipe (the one exiting vertically down from the bottom of the 3PV) isn’t that warm (it should be cooking), as its actually become the CH return from all the rads and the water is flowing up the pipe in reverse into the 3PV and exiting through the HW side to get back to the boiler. Shut the HW exit on the 3PV and there's now no effective circuit to get the heat out the boiler. So it overheats. The boiler thermostat kicks in but it will take a long time for the heat to get out of the boiler and the boiler re-fire as there is no circulation through it. The pump is now circulating water in a loop the correct way through the CH feed, through the rads, through the CH return, into the primary flow... and back to the pump. You may notice a rise in temperature of the CH feed pipe where it leaves the 3PV when this has happened. The boiler is now effectively a dead end off the pump circuit... until the 3PV opens the HW circuit and the water's then pumped through the boiler and immediately reverses direction around the CH circuit.

You need to trace where the CH return is teed into the 28mm pipework. So follow the pair of 28mm pipes back to the boiler. eg remove the boxing cover running down the side of the boiler. Look for previously lifted floorboards running close to the 28mm route prior to it going down the conduit. Try lifting the floorboards right above the conduit. Look into the builder's opening to the sides of the back boiler with a torch. Or get someone Gas Safe registered to remove the fire front to the back boiler to be able to see into the builder's opening more easily (book an early service on the back boiler if it isn't yet due and have a look then). You've got to think they would tee it in prior to the conduit to save materials and time. Also, they're more likely to guess the wrong pipe as the boiler return.

Once you've found the CH 'return' check which 28mm pipe its tee'd on, the hotter (boiler flow) or colder (boiler return). These will be easier to distinguish when the boiler fires from cold. Ideally go right back to the back boiler - the top exiting pipe is the flow (it could be set up flowing the wrong way through the boiler!) Assuming direction of pumped flow through boiler correct, then shift over the CH 'return' run to the boiler return and throttle back the HW gate valve in the middle of pic 1. Then balance your rads. Have a read up about the tee rule on return pipework first. ie. on the return back to the boiler, tee in all rad returns first, then finally tee in the cylinder return.

Must admit I was confused with your title, I thought it was about hydrogen powered central heating and cricket.

 

[matt1e]

that was a pretty long way of saying "the pipework needs sorting!as the poor circulation in the rad circuit restricts the flow(rate) though the boiler too much",
if thats what you mean 4expaws

at a guess sludge build up over the years causing problems not helped by the 15mm suspect return and the fact its an old open vented system.......probably
Matt