Optimal use of a Combi in Winter?

stiofan85

Lots of threads about combi boilers this week. I'm a bit concerned that I am using mine incorrectly, as it seems to be on quite a lot and it's the first winter we have it.

Timer is set to come on in the morning between 5 and 8 (up at 6am) then again between 5pm and 10pm (home at 6pm). This guarantees house is warm and hot water available.

Stat in upstairs landing, with no rad nearby - there's a small rad at the bottom of the stairs without a TRV and it's fairly useless since the hallway is not insulated, we've no porch and is just cold. All other rads have TRVs. Stat is set to about 18 degrees and the rest of the house is cosy. I tweak the TRV in the kitchen here and there, but that's about it.

The small rad in the hall is always on and quite hot. I'm wondering if this is going to cost me a lot of money over winter. The small rad seems to be doing little for the hallway since it's the coldest part of the house. Does it need to be on for water to flow? Would it be better to have a wireless stat in the living areas to prevent the boiler being constantly called for heating? Or can I close off the rad in the hallway?

Any advice would be appreciated!

Dardania

Your usage / setup of stats seems quite reasonable, and the times setup also. I would tend to keep your current configuration.

Having the rad in the hallway on isn't really an issue...

One possible optimisation you could make is to see if the boiler is cycling on / off e.g. every 15 minutes. That could suggest your heating flow temperature is a touch high, and you could reduce the boiler flow temperature a bit, to encourage the boiler to run more consistently. If the flow temp is reduced, the temperature of water returning to the boiler is reduced, and that enables you to use the heat of the exhaust flue to pre-heat the flow water (the whole condensing boiler unique selling point...)

Wearb

Having the stat in a place that can't be properly heated is what's causing most of your problem. I presume that your house has just one heating zone. Reason the rest of the house is cosy with stat set to 18 is that it takes a lot of heat to bring that area to 18. I would expect that the cosy areas are higher than 18, as the heating struggles to bring the hall area up to temperature.

Solution is to move your stat to living area and turn the TRV in that area up to full and let the room stat control that temperature. You could then over a period of time (days or a week) adjust remaining trv's to compensate for new position of stat. Wouldn't worry too much about a TRV on the hall rad as it seems undersized anyway.

Easiest solution would be a wireless stat. Put receiver where the existing stat is and thermostat in living area.

rolion

Also,is much more efficient to keep a house warm than to make it hot / cold / hot cycles.

stiofan85

Wearb wrote: »

Having the stat in a place that can't be properly heated is what's causing most of your problem. I presume that your house has just one heating zone. Reason the rest of the house is cosy with stat set to 18 is that it takes a lot of heat to bring that area to 18. I would expect that the cosy areas are higher than 18, as the heating struggles to bring the hall area up to temperature.

Exactly, the hall is cold and I set the temp much lower than I would expect the rest of the house to be at.

Wearb wrote: »

Wouldn't worry too much about a TRV on the hall rad as it seems undersized anyway.

It's 400mm wide, single panel. I was planning to fit a 500mm (600mm if i swap a double socket to a single) double panel just to make the hall a bit less cold, despite it being poorly insulated. Would a 500mm/600mm double make much of a difference?

Wearb wrote: »

Easiest solution would be a wireless stat. Put receiver where the existing stat is and thermostat in living area.

For the sake of €40 for a simple wireless stat & receiver I think it's worth a punt. I love the ease of instant hot water and the TRVs seem to do their job well elsewhere, so the system is almost perfect - sorting this last bit would nail it I think. This seems to be what I'm after:

https://www.amazon.co.uk/gp/product/B003EQ8FMC/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

@dardania, I had already done as you suggested and lowered the temp. IIRC I dropped the temp from 70 degrees to 60 degrees, which helped fine tune the TRVs and the temperature in the house smoothened out.

Thanks lads

stiofan85

rolion wrote: »

Also,is much more efficient to keep a house warm than to make it hot / cold / hot cycles.

Makes total sense. The place is consistently cosy and the rads don't come on much, although we're still only in October. It's just the one in the hall that I'm concerned about. The boiler seems to fire up the main rads for a short period, then the TRVs kick in and they go cold but the heat remains thanks to the insulation.

I insulated the exterior walls in the living room and kitchen with loads of insulation in the attic. Upstairs barely has the rads on in the evening so by the time I go up to bed the heat that has risen seems to be sitting in the bedrooms but blocked by the attic insulation. Again, just cosy with what seems to be little effort from the rads.

Despite this though, as I said the boiler seems to be firing the whole time and that small rad in the hall is hot but not doing much due to the lack of insulation there (job for next year).

stiofan85

I've been keeping an eye on the gas meter and it has been flying up. Seems the boiler is constantly on and costing me money. Got the wireless stat so gonna install it this weekend and see how I get on. Situation hasn't changed much - rads in main rooms rarely come on as the house holds the heat nicely. The rad in the hall is always on though

Boiler is a glowworm 25c. Manual says it has an inbuilt bypass - if I turned off the hallway rad would the boiler be okay? It is doing feck all except spending money!

stiofan85

stiofan85 wrote: »

I've been keeping an eye on the gas meter and it has been flying up. Seems the boiler is constantly on and costing me money. Got the wireless stat so gonna install it this weekend and see how I get on. Situation hasn't changed much - rads in main rooms rarely come on as the house holds the heat nicely. The rad in the hall is always on though

Boiler is a glowworm 25c. Manual says it has an inbuilt bypass - if I turned off the hallway rad would the boiler be okay? It is doing feck all except spending money!

A “GAS” boiler bypass can’t be used as a system bypass although a lot of boiler manufacturers will say otherwise.

If you’re system needs a rad to be used as a bypass(which seems so) then look to using the bathroom rad as it’s the only room we should ever be wet and naked and a bit of extra heat doesn’t go a miss and it’s handy to dry towels you can then fit a TRV to the hall rad which if it doesn’t work you can then happily turn it off leaving the bathroom rad to do it’s thing.

Fitting a room stat in the hall although usually a good idea may not give you the results your looking for as the insulation you’ve fitted may have changed the heat characteristics between the hall and your rooms also as mentioned your hall rad maybe undersized.

stiofan85

Wireless thermostat is working really well and rooms are warm but boiler only running when it needs to.

Happy with the result, will see how my gas bills go!