Ideal classic ff380 - cycling

[oldskoo1]

Anyone very familiar with this range of boiler?

It's an old one, fitted around 12 years ago. I am trying to determine if I have a flow / blockage issue or if it's normal to cycle so soon and often.

After it comes in it last around 15mins before stopping. Finger touch the flow seems to have reached its stat set peak. Return however is still quite cool, perhaps half as hot. It then cycles 2mins on 1min off roughly, until it's met its demand.

The boiler is serving a 3 storey with 21 rads, all but the ground floor and landings have trvs. I've opened the valves fully on most on the ground floor to try and alleviate the issue. No luck.

Pump has been removed and inspected, it's turning fine, a little black cleaned and installed back on speed 2. It's a grundfos 15-60. On 3 it created cavitation.

Boiler has had a new pcb, fan and air tubes changed, electrode done too.

Do you think return is slowed down by a blockage or is this typical behaviour of this un modulating boiler?

Thanks

 

[oldskoo1]

I should add

The stupid cretin who installed this system put the pump on the return and it ran like this for 10 years.

I'm not sure if the pump potentially could be tired even more so from this error.

Also I have not had the stat changed.

 

[Agile]

It was quite normal to put the pump on the return then.

Running on cooler return water, the pump itself runs cooler which is better for it.

I cannot comment usefully without knowing the temperatures on your boiler as measured on the flow and return using a contact probe when the boiler has been firing for say 10 min.

Has the pump impeller been inspected for dirt blocking it?

Tony

 

[oldskoo1]

Now I'm wondering if the system still isn't set up right

I noticed that the return pipe according to the manual was the one getting hot first. So I thought the pump was drawing heat away from the wrong pipe. The pump is upstairs and the arrow is pointing upwards.

Now the simple fix sounds like when i called the heating engineer to fix this he should have reversed the pump direction to push was through the boiler and back up?

Instead he swapped the pipes over and now the correct one according to the manual is getting warm first and presumably pulling water up and away.

But maybe the intended operation was indeed to push water back into the boiler but they just got the pump the wrong way round?

The limit stat was an issue as it was on the return until he swapped the pipes the correct way.

Unfortunately I don't have clip thermometers to check the temps.

I did remove and inspect the pump myself as the gates held and I saw no obstruction and the impeller moves freely, just the odd small bit of grit on the blades.

 

[Agile]

The only way to know if the flow is adequate is by measuring the temperatures of the flow and return.

Whether pipes or pump direction should have been corrected depends on where the fault was.

Tony

 

[oldskoo1]

Picked my dads infrared thermometer up after work tonight and had a shot at getting a reading.

Put a black piece of PVC taper over the pipe to get a more consistent reading.

I got 52c on the flow and 39c on the return. The boiler stat is set to 3 which i think equates to roughly 65-67c, thats so the kiddies don't burn themselves immediately.

Whilst i was at it i had a got at the radiators and they were pretty much the same at the flow and the pump casing was 57-60c.

Every stage of the warm up the return measured between 10 and 13c less than the flow.

Obviously the reading seems lower than the stat setting, i'm not sure why this is, it obviously isn't the perfect tool for the job.

Curious why the pump was higher, i assume this is normal. Pump still makes a trickling noise.

Also wondered if you had any advice for me about the possible flow of water from the boiler.

I just want to check, looking at that picture i'm saying the water from the boiler enters the bottom of the pump going upwards in the pipe nearest in the picture. That is certainly the one that gets hot first, but the pipe with the grey valve controller on it also gets hot and i'm assuming this is the exit to the CH circuit. I just want to be sure the pump is going in the right direction considering it makes that trickling noise which to me sounds like cavitation and its only on speed 2!

For some reason the forum isn't showing my image : https://farm4.staticflickr.com/3927/15311204180_590967cf01_b.jpg

Boiler output is 23.4 kW
Flow required 30.3 l/min
Pump grundfos 15-60 on speed 2.

 

[Agile]

Your boiler is designed for a temperature differential of 11 C.

In your case the flow rate seems spot on!

As long as the hottest pipe is the one on the boiler designated as the flow then everything seems pretty much spot on!

The accuracy of IR thermometers is pretty variable but will be useful for comparative measure like flow and return temperatures where the inaccuracies cancel out.

The only type to be used for proper scientific measurement are the contact type. But I am confident that your methods are adequate for the scope of determining the flow rate as worked back from the flow and return temperatures.

Nothing to worry about !

Tony

 

[picasso]

Your boiler is not designed to be run at the temps you want, the return should be minimum 60c to prevent the boiler condensing, if you want the rads to run at 55c you will have to change your boiler and does the hot water cylinder ever get up to temp ?

 

[oldskoo1]

Great thanks guys

Hot water cylinder does get to temp and boiler stat at 3 seems the lowest I can go to avoid scalding fingers but allow hot water to work.

But I see what you mean now, return water will be 52-55, not designed for this boiler.

Should I be running it at max?

Just wondered if you could give your opinion on why the pump is making that trickling running water type noise (like rapid clicking), I get this at the boiler pipes where it's more like sloshing water. In that pic I posted is the pump going in the right direction?

Thanks

 

[oldskoo1]

Ps it's an unvented system, pressure is sitting at 1.8bar (a little high) and rises to 2.3 bar with heating on.

Can't find any air in system. Bled the top radiator after months with ch not being on and then again recently after it had been on a few times and nothing came out. We have an auto air vent which does work as it sprang into action when I took the pump off.

I just wonder wether the pump on 2 is not powerful enough to get water around 3 floors and 20 rads or I still have a blockage or the pump is a bit tired after 12 years especially as it was fitter pulling water away on the return pipe anti gravity for 10 years running against the Gravity. Pump is on 2 and noisy and csvitation on 3 and whistling trvs is not a good way to wake up. When I drained the system last year water was surprisingly clear and s refill with x100/x200 and bleeding a rad all looks ok. didn't think there was any sludge in there. Pump a touch black on the outlet and centre screw.

I've got some silicone grease and local stock of the same model and the gates hold but I'd rather not put down 120 quid if I don't have to.

I'm not looking for an excuse to fix it but I want to make sure the family is warm this winter. What with incorrectly install flow and return and a dodgy pcb the last 2 winters have been a frustration.

 

[Agile]

I would not recommend that you take any actions based on an assumed measurement with an IR thermomenter. It could be considerably higher.

Better to get a contact thermocouple sensor and test meter.

Tony

 

[oldskoo1]

I think we've got some success guys

I put the thermostat on max on boiler. As its non modulating I'm assuming it makes no difference to gas consumption, maybe even reduce it as it gets to temp quicker and less cycling wastage.

It stayed on for 28mins which is a record. It raised 2c in 40mins, also a record. Boiler maintained a 10-14c difference in pipes.

Pump measured 80c on the casing. Rad pipes showing up some balancing issues.

I should have tried the boiler stat up earlier. I was thrown off because a faulty relay on the pcb and incorrect piping caused terrible cycling in the past.

Plus I don't know why the pump and boiler is making a water trickling noise and the pump sounds gritty too.

Should I bleed off some pressure its 1.8 cold, 2.3 hot.

 

[Agile]

You have not mentioned the flow and return temp now.

Running the heating at a higher temperature is likely to use more gas.

The pump bearings may well be quite worn and so noisy.

Tony

 

[oldskoo1]

I think the infrared thermometer doesn't play well with the pipes even with tape on.

They measured 65c flow and 51c return. As the pump measured 80c which is several meatres away I can only assume the true flow is the same.

 

[Agile]

The temperature of the pump is higher than the heating water because the electrical power consumed increases it.

Pumps are usually about 20 C higher than the heating water which actually cools the pump!

Tony