If a heating boiler is run all night and the thermostatic radiator valves are turned down, then there might be very little flow through the pipes when the valves start to shut off.
This is assuming no bypass circuit to maintain flow has been fitted, or it too has been almost closed.
Would this cause damage or undue wear to the heating pump?
(I am asking about a regular combi boiler, such as a Baxi 630.)
If no bypass has been fitted there is usually a radiator on the system that shouldn't be shut off, maybe a towel rail or a bathroom radiator without a TVR.
If a room stat is being used the radiator in that room should not have a TVR. The TVR may close down the radiator before the thermostat temperature is reached and the boiler will be continuously be getting the demand for heat.
While there may not be a dedicated bypass circuit the system may have a radiator or two working as a bypass.
The pump in a modern combi boiler may/will be working in proportional pressure control mode and adjust to TVRs shutting down.
Much more likely that the flow becomes too low and the boiler shuts down and flags up a fault.
TVR is a sports car.
restricted flow tends to lead to short cycling on the boiler, or an overheat condition within it
There's a bypass in the form of a heated towel radiator in the bathroom but it has to be almost left closed or the room gets unbearably hot. (The radiator goes from floor to ceiling and all the walls are isolated to allow tiles to lie squarely.)
My old boiler would stop and show a fault when the TRVs shut down. I was wondering if the pump in a modern boiler will slow down to almost no rotation when presented with very low flow.
Perhaps the safest thing to do is lower the heating thermostat on the boiler so the rooms don't get too warm overnight and shut the TRVs.
I used to get a boiler fault on my previous boiler (an old Ideal Isar from decades ago) when the TRVs shut off. It seems the pipework isn't a large loop with the radiators spurring off it.
Well to quote from the manual:
"5.2.4 Bypass The boiler utilises the primary side of the DHW plate heat exchanger as an automatic integral bypass."
However as a general rule, you will not damage a boiler with short term use like that... it will either short cycle on it's internal stat, or if flow is completely occluded, trip out with a fault code.
In a more general sense, long term use will increase the wear rate on the parts since there is far more stopping and starting.
There should also be some form of interlock that prevents the boiler running when the house is already up to temperature. This is typically a room stat in a room with a fixed output radiator.
Possibly the worst thing you could do is lower the flow temperature at the boiler (boiler thermostat??) as this could/will cause short cycling. Short cycling is not good for the longevity of the boiler.
I don't know how sophisticated your controls are but a programmable room thermostat may be a solution. A programmable room thermostat allows different temperatures for different periods of the days to be set. For instance with mine I set a low target temperature during the period 11pm to 6:30am then a couple of day/evening temperatures depending on the time of day.
That's rather slack. A heated towel rail might be turned off. It can't be assumed that the user knows that something has to be left on.
Better for economy as condensation is more efficient. That's what I do as the TRVs are fiddly and noisy.
It only better if the boiler can modulate down far enough to keep the flow dialled in (lower) temperature. If the boiler cannot not modulate down far enough you just get short cycling. Many UK boilers are oversized for the (CH) system and cannot sustain a efficient burn.
It may be "slack" but it is/was a common practice.
It's no longer accepted practice. A system must now be fitted with a bypass valve.
Operated by rising system pressure? One was fitted by my plumbers. Sadly the circuit arrangement is such that the pressure then drops below the hysteresis point and the valve re-closes leading to system hammer. On the *to do* list when I next do a drain down and have discovered a solution! Yes. I do have a suitable, charged, pressure vessel.
No, with no flow load on pump reduces.
Which is why you install that radiator without user adjustable valves on it.
However many modern boilers include an internal bypass these days.
It is a loop of sorts, but with the radiators (in parallel) forming a part of it. So if you interrupt the flow on all rads you no longer have a loop :-)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.