Halstead ACE HE 30 DHW strange problem

[John Plumber]

Hi All,

This is my first posting as I’m new to this forum.

I wonder if there is someone out there who can help with a very strange fault on a Halstead Ace HE 30 combi boiler ?

The boiler is about 5 years old but being in a holiday home has only had limited use, probably equivalent to less than a year of a normal full time boiler.

The problem is that the DHW doesn’t gets hot but not hot enough, certainly not enough to give a good shower or to provide really hot water for washing up.

Symptoms are:-

Central heating is fine.

After a bit of experimenting I have found the following strange behaviour:

If I run a HW tap near the boiler (within six feet) the boiler fires up, the water runs hottish, more than warm but not really hot, i.e. you can still hold your hand under the flow. The actual flow is fine, very similar to the cold. It will stay at this hottish temperature for as long as the tap is run.

Now, and this is the interesting bit, if I open a second nearby HW tap, just a bit then the flow from the first tap goes up in temperature to that you would expect, i.e too hot to keep a hand in it. Again it will stay like this for as long as both taps are run.

Turn off the second tap and the first tap goes back to hottish, (but not hot enough to give a good hot shower).

My first thought was the flow switch but I have measured the contact closure and it closes as soon there is any flow and stays on solid until the flow is stopped.

The only clue I have is that you can hear the boiler going from one burner noise level with the one tap flowing to a louder noise when the second tap is opened, I guess this is the burner being modulated.

Somehow the boiler is seeing a marginal increase in flow and deciding to go into a higher heat mode.

The second tap doesn’t produce any hot water but I wouldn’t expect it too, the boiler has only ever been able to keep one tap flow hot, yells from the shower when the kitchen tap is run…but I guess that’s normal.

As the flow switch is on, and it’s a simple on/off control, I can't see what is causing the boiler to go into ‘hotter’ mode when two taps are open but not when just one tap even when the flow is strong?

Incidentally things used to be fine so it is definitely some sort of fault.

I am reluctant to start buying thermistors, hydroblocks, circuit boards etc. until I can work out just where the fault is.

Any ideas would be more than welcome.

Many thanks

John B

 

[Barry98]

welcome to the forums john the plumber whats the heat exchangers condition

 

[ManchesterGas]

Check the diaphragm, I bet it has a small hole.

 

[John Plumber]

Hi bod, thank you such a swift reply, heat exchanger not been removed or checked, it's not a hard water area and having had so little use I had assumed that it should still be fine.

 

[John Plumber]

Hi Manchestergas, thank you for such a prompt reply.

It is interesting you should suggest the diaphragm as this is often a solution posted on forums about other halstead models but for the life of me I can't see where there would be a diaphragm in this particular model unless it's buried in the hydroblock assembly.

any advice as to its exact location would be very welcome.

Thanks again

 

[ManchesterGas]

Ahh, just seen the MI's. Have you checked all the filters? is the flow regulator still fitted? Is the flow switch variable? do all the thermistors read as they should? There's not much to them so can't be too hard to go through everything, failing that, phone Halstead.

 

[John Plumber]

Hi Manchestergas

Thank you again for your helpful response. I will do as you suggest although I doubt it is a flow issue as there is plenty of water being delivered at the hot tap, it's just not very hot. It has a simple on/off flow switch which seems to be working fine.

Thermistor would seem a good candidate as it it is giving wrong values on temperature change it might confuse the logic, but that is just a guess.

I know I might be pushing my luck but do you happen to have the hot/cold values for the DHW thermistor ? I have a feeling it has been quoted elsewhere at about 500 ohms but I could well be mistaken. That would be much appreciated if you can help.

Thank you

 

[ManchesterGas]

Hi John,

Sorry, I don't have the values, you will need to speak to Halstead.

Adam.

 

[bigad100]

I have had this problem before where a mixer tap/shower was passing. This allows cold water to mix with the hot water bypassing the boiler. When u open the other hot tap it allows the cold out here and u get proper hw again. To prove I would feel the he draw off from the boiler when running just the one tap if this is hot and water only luke warm at tap then the boiler is fine!

 

[DirksPlumbing]

What kind of flow rate do you get on the hot water? Could the flow switch be twisted?
But on the other hand it sounds more like the heat exchanger circuit does not get rid of the heat so the flow temperature sensor throttles.
Check the temperatures near the flow temp sensor. That could tell you more.
And of course check if the flow switch does contact properly.

 

[John Plumber]

Thank you both bigad100 and Dirksplumbing for your helpful responses.

To pick up on the points:-

1. the flow from the hot tap is fine, pretty well at rising main pressure.
2. When say the bathroom sink tap is running, the boiler sees demand, the flow switch closes and there is flame and fan. The water gets hotish but not really hot, just about hot enough for say a shower.
3. Now if I turn on another hot water tap, say the bidet, just a little bit, the sink tap now gives really hot (too hot to keep a hand in) water at the same rate. Close the bidet tap and the sink goes back to hottish.
4. I really don't think it's a flow issue as the flow switch closes and stay closed and the boiler fires up and stays fired up.

I like bigad100's idea but I can see no evidence of this being the fault.

Looks like I'll have to dismantle and clean the plate exchanger but I am struggling to see how that would cause the symptoms.

Again thanks to all, and keep the ideas coming.

 

[DirksPlumbing]

I think without multimeter, flow cup, gas gauge and thermometer this will remain guesswork.

 

[bigad100]

Before you go taking the plate out I would just run the tap measure the temp of the hw draw off. If this is hotter than the water temp out of the tap then it is definatly mixi g with the cold somewhere else. Try isolating any mixer taps/showers one at a time if this fixes the problem then you know which one is at fault. Easy test to do before taking it apart.
If the plate was blocked I would expect the water to fluctuate going hot then cold. If the boiler is staying on when you are drawing hw then the flow switch is fine. Also check its not dumping heat down the ch side!

 

[acecharly]

Im not the greatest repairman but could this not be associated to gas working pressure being too low?

 

[John Plumber]

Before you go taking the plate out I would just run the tap measure the temp of the hw draw off. If this is hotter than the water temp out of the tap then it is definatly mixi g with the cold somewhere else. Try isolating any mixer taps/showers one at a time if this fixes the problem then you know which one is at fault. Easy test to do before taking it apart.
If the plate was blocked I would expect the water to fluctuate going hot then cold. If the boiler is staying on when you are drawing hw then the flow switch is fine. Also check its not dumping heat down the ch side!

Thank you again bigad100. I haven't been able to spend much time on the problem in the last few days due to other work.

I did find this though. The DHW draw comes out of the boiler and straight into a T one way goes to the sink the other to the bath then on to other sinks and a shower.

If I run the sink nearest the boiler and feel the draw it's hottish. As soon as I open the bath (i.e. the other leg of the T) just a small amount the boiler draw gets really hot as does the leg going to the first sink, and its tap.

It is so consistent I just have the feeling that it is something like a strange airlock or there is something else in the boiler other than the flow switch that is telling it to deliver more heat.

If it was something like say sludge build up I just can't see how such a small change in draw would cause the boiler to change temperature each and every time I do this test.

Anyway I agree with others that I need to do more calculated analysis and stop trying to theorize the problem.

The CH stays cold throughout, but when turned on is fine with all rads getting hot with flow getting too hot to hold.

Gas flow is fine, it is fed by 22mm, and the pressure to a large hob with wok burner is excellent. (No the hob isn't on when the boiler is on, thought of that one ;-)

Again thanks to all who are pondering for me.