Heating intermittent

[charlieno]

Hi all,

I hope you can help! I had my boiler and pump replaced a week ago - new ones are Ideal Logic Max Heat2 H24 and Grunfos UPS4 GO. All seemed OK when it was installed (in place of an old, still working boiler and pump). However, each day the heating refuses to work. Often when it comes on the radiators are stone cold, or tepid at best. I have had the plumber back several times and he seems baffled. Every so often it starts to work normally for no apparent reason and without touching anything (after maybe 6 hours of running and not distributing heat to the radiators). But then when the room thermostat cuts out, when it turn back on the radiators don't warm up and the room temperature slowly drops.

We have tried various settings on the pump with no reliable success. Often a change makes it start to work but the next day we are back to stone cold. One strange thing is the power at the pump, even when on setting 3, can vary from 5-10W to over 40W when the system isn't working properly.

Boiler is set at 65C which seems to be plenty high enough when the system works.

House is a large bungalow (extended) with 11 radiators, mostly double ones. The control valves are Honeywell V4043H for the hot water and radiators. Expansion tank in loft. The TRVs were changed at the same time - most were over 20 years old and some starting to leak where the control pin is. Other than that, all other pipework is the same, except for some shuffling of pipes to the boiler so they were in the right place for the feed/return.

Any suggestions as to what the problem could be or things to try? I though maybe an air lock somewhere but the plumber thinks not.

TIA.

 

[Harry Bloomfield]

new ones are Ideal Logic Max Heat2 H24

That's a heat only boiler, and I assume you have a 3-port valve, directing the heated water, to the radiators, and or to heat up water in your cylinder?

It sounds as if that 3-port valve actuator, is probably misbehaving, sticking, jamming. Next time it fails to heat the radiators, try giving the actuator a good clout with your hand. You will likely find it, in your airing cupboard, next to your HW cylinder, with 3 pipes entering the valve.

 

[charlieno]

Thanks for the reply. It doesn't have a 3 port valve, it has two 2 port valves like this

https://i1.wp.com/s1.manualzz.com/store/data/014547444_1-4f6a612d90096bed9e1eb528865f3fac.png?strip=all

Honeywell V4043H. They have a manual over-ride lever so you can easily tell that they have opened as the lever is connected to the acuator. Also, you can feel the temperature of the water on either side of the valve to check it's open.

They weren't changed and were working fine and still seem to be. -Just the boiler and pump were changed.

 

[Harry Bloomfield]

Honeywell V4043H. They have a manual over-ride lever so you can easily tell that they have opened as the lever is connected to the acuator. Also, you can feel the temperature of the water on either side of the valve to check it's open.

Similar fault, to the 3-port...

That valve for the heating, may have a faulty microswitch. If it is opening, but not then passing a signal to the boiler to fire, you will not get any heating.

When the heating valve is open, try giving it a good tap.

 

[charlieno]

The 2 port valve doesn't have a microswitch. Also, the boiler is definitely firing and pumping hot water - it just doesn't make it to the radiators.

 

[Harry Bloomfield]

The 2 port valve doesn't have a microswitch. Also, the boiler is definitely firing and pumping hot water - it just doesn't make it to the radiators.

Are you absolutely sure about the microswitch?

If the boiler is firing, and pumping hot water, either the water is not being circulated, or you have a blockage. As work has just been done on the system, I would suspect an air-lock, your system has not been properly refilled, or bled properly.

Try turning off, all but one radiator, run the system, until that one radiator is hot, then repeat with each of the other radiators, bleeding them between.

 

[charlieno]

Sorry, you are right it does have a microswitch. What I was confusing it with was the fact that the microswitch doesn't turn off the motor in the valve so it just sits there stalled while the valve is on.

However, the microswitch definitely tripes, the pump runs and the boiler is on, and hot water is circulating, just not in the radiators.

I will discuss the airlock theory again with the plumber when I contact him again tomorrow. The system filled fine and was fully bled at every radiator. I also went round every radiator again yesterday to see if there was significant air, but there wasn't.

Any idea why the pump power varies so much? Sometimes <10W, other times around 40W.

 

[Harry Bloomfield]

The system filled fine and was fully bled at every radiator. I also went round every radiator again yesterday to see if there was significant air, but there wasn't.

Likely the airlock, is in the pipes.

Any idea why the pump power varies so much? Sometimes <10W, other times around 40W.

It should be a steady wattage, it suggests to me, the pump has air in it.

 

[CountryFan]

I though maybe an air lock somewhere but the plumber thinks not.

That should be the first thing to look at imo, especially given it’s been a week.