Problem with megaflo hot water cylinder?

ComicGeek

dharm999 said:

A;so, if the boiler is set up for ‘holiday mode’, how do I switch that off, as I want to make sure that everything is set up for normal running to get a base line that I can compare against.

Normally that would be a programme setting on the heating programmer, rather than on the boiler itself. You would just need to turn off the holiday mode on the programmer. Normally holiday mode would just reduce the target temperature for the house (ie reduce from 21 degrees to 16/18 degrees), but you mentioned earlier that you don't have a separate thermostat for the radiator circuit so might not actually be doing anything at the moment.

ComicGeek

dharm999 said:

I’m not now sure what my next steps are.  I need to find out what pump is in the loft, but once I know that, what next?  Get my plumber to turn down the pressure the pump,is set for, and see if that makes a difference to how often the pump comes on at night?  How to track down what is causing the pressure to drop that is causing the pump to kick in?  Where do I start with that? 

As you have a sealed heating system and Megaflo, the tanks in the loft are either redundant from a previous heating system, OR form part of your cold water storage/booster system.

The pump you hear could be lifting cold water up to a tank, be pumping down from a tank, or be unconnected to any tank and just pumping from the main. Grundfos do a rubbish UPA 15-90N home booster pump, which can pump up to 16 litres per minute directly from the main without needing any storage tanks.

Next step is to get the pump details and see whether if/how it is connected to any loft tanks. The pumps have pressure and flow sensors which can go wrong, tanks can have stuck ball valves and be overflowing through drains etc - something is wrong with the system, now a case of eliminating things one by one. If it is an inline booster pump, then potentially you could replace with a coffin tank and pump set in the loft. 

Albermarle

Grundfos do a rubbish UPA 15-90N home booster pump, which can pump up to 16 litres per minute directly from the main without needing any storage tanks.

I thought you were not allowed to pump directly from the mains?

ComicGeek

Albermarle said:

Grundfos do a rubbish UPA 15-90N home booster pump, which can pump up to 16 litres per minute directly from the main without needing any storage tanks.

I thought you were not allowed to pump directly from the mains?

You are allowed to, but only up to 16 litres per minute. Above this you need to use a break/storage tank first, and then pump from the tank.

dharm999

ComicGeek said:

dharm999 said:

A;so, if the boiler is set up for ‘holiday mode’, how do I switch that off, as I want to make sure that everything is set up for normal running to get a base line that I can compare against.

Normally that would be a programme setting on the heating programmer, rather than on the boiler itself. You would just need to turn off the holiday mode on the programmer. Normally holiday mode would just reduce the target temperature for the house (ie reduce from 21 degrees to 16/18 degrees), but you mentioned earlier that you don't have a separate thermostat for the radiator circuit so might not actually be doing anything at the moment.

I can’t see anything on the programmer for holiday mode.  I’ve attached two pictures, one of the boiler, showing the icon lit up in Green that looks like a holiday mode symbol and the other for the two controllers.  Only the hot water program is switched on, the heating is off on both programmer, and we control the heating in individual rooms by using the UFH controllers in the rooms.

dharm999

ComicGeek said:

dharm999 said:

I’m not now sure what my next steps are.  I need to find out what pump is in the loft, but once I know that, what next?  Get my plumber to turn down the pressure the pump,is set for, and see if that makes a difference to how often the pump comes on at night?  How to track down what is causing the pressure to drop that is causing the pump to kick in?  Where do I start with that? 

As you have a sealed heating system and Megaflo, the tanks in the loft are either redundant from a previous heating system, OR form part of your cold water storage/booster system.

The pump you hear could be lifting cold water up to a tank, be pumping down from a tank, or be unconnected to any tank and just pumping from the main. Grundfos do a rubbish UPA 15-90N home booster pump, which can pump up to 16 litres per minute directly from the main without needing any storage tanks.

Next step is to get the pump details and see whether if/how it is connected to any loft tanks. The pumps have pressure and flow sensors which can go wrong, tanks can have stuck ball valves and be overflowing through drains etc - something is wrong with the system, now a case of eliminating things one by one. If it is an inline booster pump, then potentially you could replace with a coffin tank and pump set in the loft. 

Thanks, I will get the pump details and try to get pictures of the set up in the loft

ComicGeek

According to the boiler manual (see below), that button is supposedly 'not used'. It looks like a button, so personally I would just press it and see if the light turns off. 

dharm999

I also saw that in the manual and thought, ‘well it’s in use’!  Have pressed the button and the number display goes to a horizontal line, I think it wants me to set a temperature for holiday mode, but as to how I do that, when the manual says the button shouldn’t be in use, is anybody’s guess!!

dharm999

Managed to get in to the loft and taken some pictures and made a note of the pump make and model

Grundfos 
Mq345 Aoabvbp

Model

96440345 p7 0236

@ComicGeek Does this help to work out what might be going on?

Thanks

ComicGeek

That is a pretty large domestic booster pump - the inlet is the horizontal pipe on the 3rd photo. That should be connected to the cold water tank if you trace it back, as it's too large a pump to be connected directly to the main. So the tank should slowly fill up from the main, and then this pump pushes the water back down the house to create higher flow rates and higher water pressure.

The pumped outlet is from the top of the pump. It has an integral pressure and flow sensor to stop it constantly stopping/starting, and definitely shouldn't be running when there is no water usage at night time. There also seems to be a pressure reducing valve on the outlet, which might be because the pump doesn't have any variable speed control, just on/off. 



The night time operation could be a failure of the integral pressure or flow sensors, which normally means replacing the whole pump unit. That model isn't manufactured anymore, but easy to get an intelligent variable speed pump set now.