Warmflow 70/90 KabinPak hot water tepid

[fre2709]

Hi All,

tried to add this information to a thread that seemed to be 3-years old. Obviously that didn't work because I had no answers yet.

My boiler had a service and since then has been playing up. Tripping the H/L stat and hot water starts out hot then by the time the bath is half-full is tepid. It never used to do this. Could get a full bath and be nice and hot.

Had the engineer back and apart from suggesting changing a few parts seemed stumped. Since then following his advice I have changed...

Pressure Vessel.
Control Stat.
H/L Stat
Both Auto Vents.

Seemed to reduce the incidence of tripping for a while but now it is back.

Any ideas?

Thanks in advance.

 

[MarkOil]

Is the DHW tank in the boiler up to temp?
When you open the hot tap, does the DHW pump start and burner fire?
Could be the flow switch. Could be so many things really.
Do you have problems with limescale? could be the heat exchanger clogged, turn the water off and remove the DHW out, and see if it looks clogged up.
If your not convinced that guy knows what he is doing, get another engineer off Oftecs website.

 

[MarkOil]

Although, some of them things wouldn't cause stat's to trip.
Need to find out what temp's the HW tank etc are reaching really.

 

[fre2709]

Hi, had a word with the guy who fitted it. He seems to think it may be the pumps not dissipating stored heat in the boiler fast enough. The build-up's causing the H/L stat to trip.

It's done it four times tonight seems to be getting worse. As long as it hasn't tripped out boiler fires fine on opening tap. Water starts off hot (from the heatstore) then gets cooler as you leave the tap to run. We have the blending valve on max at the moment to try to improve the temperaure but doesn't help much.

I think all the control circuitry is fine, just something causing it to overheat.

 

[SimonG]

Id be keener on seeing what the pressure gauge is reading whilst all this is going on.

 

[fre2709]

When it has gone completely cold. Pressure sits at 1.3 bar. When running at about 2.1 bar.

I Used to lose pressure until I changed the auto-vents and pressure vessel. Since then not...

 

[SimonG]

You have changed?

 

[kimbo]

Is this the one with the flexible pipes if so they have a habit of getting blocked also there are check valves in the pump outlets as they are plastic they sometimes distort if the boiler overheats and it could be that they are stuck shut.
Difficult to say without being there.

 

[fre2709]

Thanks Kimbo,

so having someone change the pump heads alone would probably not fix it? Are these check valves available separately or do you have to buy the whole dual head pump assembly to get them? They don't seem to be on the boiler parts list in the manual...

I have noticed that the boiler seems to take a long time to warm up the water store. For instance this morning it had tripped again. So I reset it and turned off CH until it had finished warming the store. Turned on CH and that came on OK although there seemed to be an long delay before boiler fired even though CH pump light was lit. I opened the tap to draw water for a hand basin and the water store kicked back in but took about 15 minutes to get it up to temp. I am sure it never used to take that long - but then I never used to sit there watching it either.

 

[kimbo]

Difficult to diagnose without being there. Check valves are plastic and fit in pump outlets hwos sell them part no w2219. Buy one and remove pump assembly and check them. I am afraid it is trial and error unless you get someone in who knows the boiler.

 

[fre2709]

Hi All,

Just an update. Had another engineer out today. Seemed to think that Grundfos pumps rarely went wron and it was more likely to be a blockage in the heat exchanger or a malfunction in the mixing valve.

Bought the parts from Abgo Western. A suggestion by Kimbo regards the check valves has prompted me to contact HWOS regards supply of these.

Can anyone tell me how many I need? There are gate valves on all connections to the dual head pump assy. Are there check valves in each one? i.e. do I need three?

 

[kimbo]

Two one for hot wster and one for heating. As I said if you have the flexible pipes from the boiler that would be my firdt port of call

 

[fre2709]

Hi All,

managed to get two non-return valves from HWOS arrived today. Got my plumber coming round tomorrow, will inspect the flexible pipe when we take it off the pump assembly. As it's almost Christmas I hope that it isn't obviously that or I will have to put it back together as is with new valves, heat exchanger and mixer valve and hopes that fixes it.

If I change pumps and pipes in the new year, I'll nearly have a new boiler... :smug2:

 

[kimbo]

My bet would be the flexis they either block up with debris they collapse from the inside