Boiler firing constantly for hot watere

[pwater]

Hi

First time poster, apologies if I miss any details. I have just moved into a house with a pressurised hot water tank and a bronze pump to keep hot water flowing around the outlets.

I have noticed that the tank constantly fires the boiler for a few mins every 20/30 mins to keep it at temperature. My main question is, is this efficient..as even at 3am it fires to keep the water hot in the tank. There is no timer on this, just a timer for the bronze pump which I have set to not pump around while we are asleep.

The boiler is a greenstar and while it has seperate temperatures for the radiators (house is underfloor) and hot water, everything seems to be fed off the radiator temp meaning I can’t run the underfloor at a lower temp as the hot water won’t come up to min temp.

Hopefully this makes sense, any advice on this would be appreciated as a few plumbers don’t seem to have much of an answer on if this is the right setup and if it makes any sense..

Many thanks

P

 

[CBW]

I don’t know about the bronze pump (think it’s called secondary return), but could be a failed motorised valve.

 

[ianmcd]

pics of everything you have would be best as your description doesnt sound right

 

[Iddy]

There should be timer for your hot water as well!

The boiler is likely a system boiler - the hot water control knob on the boiler is redundant - Worcester just use the same fascia as they do on their combis.

The temperature of the water going into your floor will be reduced at the ufh manifold, but yes, you'll need to keep your boiler thermostat at around 68-70°C so the cylinder can be heated up to 60°C.

 

[jeff the gasman]

Fit a timer to the secondary pump.
Time the hot water and get motorised valve checked. It’ll cost you a fortune the way it’s being used.
Secondary circulation only at peak times of usage.

 

[pwater]

Many thanks for all the previous replies on this. I turned off the secondary pump, which has definitely reduced the boiler firing to top up the tank. However I have become a little more scientific, and am monitoring when the boiler is firing as the attached shows.

I have noticed it’s still firing from cold once every hour to top up the tank, even during the night when there is no usage. I assume this is pretty inefficient from a gas usage POV as I am firing the boiler to 100% to get it to temp, then it’s only running for a few mins before shutting off again, rather than running for longer and modulating down as it does with the UFH.

The tank is a santon pp300b, stat set to 4 (which I think is around 60 degrees), in normal conditions (I.e i don’t have a slow leak of hot water somewhere) should I expect to lose enough heat to cause this every hour?

I will have to do the math, but my gut says putting a timer on this to run in the morning and afternoon for an hour or so will likely end up being more efficient and also stop it raising my return temps when the UFH is on and stopping the boiler condensing as well for periods..?

Any thoughts appreciated.

Thanks

Paul

 

[pwater]

I have tested this today, by turning off the hot water from the tank, since I have done that it hasnt fired at all, which would say to me:


1. There is something leaking a small amount of hot water
2. Even with the pump off, the pressure of the cold into the tank, is pushing hot water around the secondary circulation circuit slowly, leading to the drop in temp

Can I/is it even possible to isolate the secondary circuit?

Ta

Paul

 

[MNW67]

EDIT: Deleted to avoid confusion. Made logical error!!

 

[jeff the gasman]

I have tested this today, by turning off the hot water from the tank, since I have done that it hasnt fired at all, which would say to me:


1. There is something leaking a small amount of hot water
2. Even with the pump off, the pressure of the cold into the tank, is pushing hot water around the secondary circulation circuit slowly, leading to the drop in temp

Can I/is it even possible to isolate the secondary circuit?

Ta

Paul

Wouldn’t stop the leak

 

[pwater]

Wouldn’t stop the leak

Yea, was more an either or, so wanted to narrow it down. I isolated the secondary pump using the valves either side and killed the power to it, so will see how that is tonight!

 

[jeff the gasman]

It still won’t make any difference to the leak!

 

[jeff the gasman]

You could have gravity circulation occurring.
Single check valve sorts that!

 

[pwater]

You could have gravity circulation occurring.
Single check valve sorts that!

Thanks, would that be a check valve on the hot water flow side?

 

[jeff the gasman]

If the pump is on the flow, just fter it.

 

[pwater]

I think that’s what I have, I actually seem to have 3 non returns, have attached a pic if that is helpful…

I have currently closed the valve after the recirculating pump and turned it off to rule out any issues with that.