mains hot water tank fault

[david4924]

i am new to this forum and looking for any advice, i am a gas engineer.

i am having problems with a mains hot water thermal unit this is an albion, its a direct mainsflow twin pump system one pump to circulate primary hot water circuit and one to pump ch. there seems to be 2 problems one is that the heating is not reaching correct tempreture the radiators get warm but not the way they should be. also as soon as i put hot water pump on water then comes out of the vent pipe into the f and e tank. could this be due to a burst coil in the hot water tank? andif so how would i confirm this?
both pumps have been changed not even a year ago and i have checked them and they are running fine. here is a pic just to give u a better idea, i would be grateful for any advice?

 

[ecowarm]

Hi David and welcome to the forum, which pump causes the pumping over? What is the stat at the bottom of the store set at? What is the boiler stat set at?
I would have boiler stat set to MAX and thermal store stat set at 80C.
The pump on the left is the primary pump ie from/ to boiler, and the other one is the secondary heating pump ie to/ from radiator circuit. These can both be direct to store so unlikely to be causing pumping over. It is proberbly settings that are wrong

 

[david4924]

hi there, thanks for the reply. boiler is set at max and the cylinder stat was set at 70C, the pump on the left is the hot water pump and is the one that is causing the overflow from vent pipe. as soon as pump starts the water overflows but if i put speed setting on pump to minimum it stops. what do you mean the both pumps can be direct to store?

 

[GQuigley67]

the hot water is not pumped in thermal stores, it goes through a heat exhcanger inside the cylinder and is heated up that way and is mains pressure, the 2 pumps are for the heating circuit and the boiler. I don't have much experience with Thermal Stores other than replacing a boiler which was connected to one and it had me scratching my head for a while lol

If the pump is not pumping over on lower setting then I would leave it at that, the Cylinder stat should be controlling the boiler, maybe the Boiler is switching itself off before the Cylinder has reached temp ??

 

[david4924]

i know im the same dont have much experience with thermal stores. boiler runs until stat has reached temp i have tested the stat so that when i turn stat down it cuts off power to boiler and hot water pump (the one on the left) i have left setting on minimum so this seems to have solved the overflow problem but was just wondering why it suddenly started as the pump wasnt originally on this setting. just dont know why heating pipes are only getting warm. it is a strange system it is wired up so that the boiler only fires up when u switch hot water on therefor you must have hot water on to get heating cant just put heating on.

 

[ecowarm]

The pump on the left is primary pump and when the stat on the store calls for heat it comes on. this will happen for either h/w or heating. I would turn up the store stat and make sure the boiler is set to maximum. How it works is you have to have a full store of very hot water, you open a tap and mains water goes through a coil and is heated (like a combi) if the hot water in the store drops the boiler and pump will fire. It is better to have this side on constant and the heating side timed. If you turn on the heating pump you have to have a store of hot water and the boiler needs to be ready to fire as soon as the store temp drops. If you have the heating on and the primary side not on you will very soon have not very warm rads.
It is better to think not as h/w and heating pumps but that they are both heating pumps.

 

[GQuigley67]

yes that is the way the one i was working on was set up, seems like it uses alot of gas to me having to keep the store up to temp 24/7

 

[Best]

Maybe not 24/7, but thermal store would need to stay at heat when large amounts of hot water is used. Think store temp should be 65 degrees.
The " heat exchanger " on Mainsflows is just a lot of microbore pipes (giving large surface area) with the cold mains passing through & becoming hot. If PRV fails, so does coil. To check coil, if exp tank is overflowing, just look in exp tank with a torch & you will see hot water coming up from feed if coil gone.