British Gas 330 Heat only boiler costing me a fortune!

[Chris009]

Hi,
I have a Glow Worm 330 heat-only boiler installed in an outhouse that has a frost protection system that kicks in to stop the pipes from freezing. It has been using between £6-£7 of gas a day when I have been away with work.

It's currently -4 degrees so I don't think I can turn the boiler off as the pipes may freeze. It's insane how much the bills are considering I'm not even home and the heating is switched off.

I know there is a frost protection thermostat in the boiler that is meant to fire if the temperature drops below 8 degrees. I also have a pipe thermostat on the return that is meant to turn the boiler off when the water in the system hits 10 degrees. The issue is that the temperature in the house is 15 degrees and the heating is coming on and the radiators are warming up.

Is there a fault? Any guidance on how to reduce gas usage would be greatly appreciated as it costs me a fortune to not have the heating switched on.

Many thanks!

 

[stem]

Generally that's how frost protection systems work. They circulate water through the system but when the return temperature water to the boiler reaches 10C it goes off. So the radiators shouldn't really get that hot before the return flow temperature hits 10C, and if they do not for very long, although the radiator inlet pipes may get hot briefly. If you think the system is warmer than necessary to provide the necessary protection against freezing, then you could lower the froststat to 5C and the pipe stat to Min. But I would monitor it for a while to make sure it is still working to provide a sufficient level of frost protection to the parts that are outside of the ambient house temperature.

Are you sure that the heating isn't being switched on at any point by the normal controls?

 

[Chris009]

Hi, thanks for your help. The hive frost protection is set at 7 degrees and the pipe thermostat to 10 degrees. Is it safe to turn the pipe thermostat down to minimum?

Thanks again

 

[stem]

The Hive will be measuring the ambient indoor temperature so if that's at 15C, the Hive's frost protection at 7C shouldn't kick in (unless the area the Hive is located in does drop below 7C). I just wondered if you had the heating set to be 'on' for an hour or two as well and were not just relying on the external frost protection system.

Whether it's safe to turn it down is really up to you to determine. Hence....

I would monitor it for a while to make sure it is still working to provide a sufficient level of frost protection to the parts that are outside of the ambient house temperature.

From your post you obviously feel your house is being heated more than necessary now, so if you want to save gas turning it down is really your only option, other than switching some radiators off that you don't feel would be at risk of freezing. You would have to be at home to manually turn them back on when you wanted full heat again though.

In the past, I've set pipestats to more than 10C (Mr Cautious) and the radiators do start to heat up as the boiler will supply them with hot water as if they were on normally. However, it only usually takes a few minutes for the return pipe to reach 10C and they go off again. Pipe stats aren't that accurate, so maybe that's some of the problem with yours and it's letting the return pipe get above 10C. If you have a thermometer you could check it. A replacement pipestat costs about £30-40

I notice that the pipestat cable isn't secured under the cable clamp properly so you might want to attend to that, although that's a safety issue, it won't effect its operation.

Also, If the hot water cylinder is still being heated while you are away, that shouldn't consume much gas. Provided of course that the cylinder and its connected pipes are well insulated and not loosing heat. Obviously you can ignore this if you're not heating the hot water.

 

[Chris009]

Yes, I was thinking the same thing about the pipe thermostat, I think this is where the issue may be. I put my hand on the pipe under the insulation and it was red hot. I would say well above 10 degrees with the heating switched off. Is it a simple job to replace the thermostat?

 

[stem]

They are held on the pipe with a spring that clips it on, and there are a couple of wires to remove and re-attach. [Note the use of the cable clamp in the pic below ] Make sure that you get a pipestat with the same temperature range as yours. There is a cylinder thermostat that looks identical but has a different operating temperature range.

Just a thought; a recent thread has just discussed a problem with a pipestat that was wired up incorrectly. Surely, it's too coincidental that it's the same in your case isn't it? You can read it here.

 

[Chris009]

 

[Chris009]

I found the frost thermostat behind the boiler. I guess the boiler kicks in if the outhouse is less than 5 degrees which is all the time at the moment. The water in the system is at 35 degrees and the boiler is still firing. Surely the water in the pipe doesn't need to be 35 degrees for the pipe thermostat to register the temperature as 10 degrees?

 

[Harry Bloomfield]

I found the frost thermostat behind the boiler. I guess the boiler kicks in if the outhouse is less than 5 degrees which is all the time at the moment. The water in the system is at 35 degrees and the boiler is still firing. Surely the water in the pipe doesn't need to be 35 degrees for the pipe thermostat to register the temperature as 10 degrees?

A simple test of a mechanical thermostat, is the 'click test'. Sweep the setting knob back and forth, it should produce a distinct click going each way, one the on temperature, the other the off temperature, which will be around 5C apart, plus somewhere in the middle should be the actual temperature the stat is measuring.

I found the frost thermostat behind the boiler. I guess the boiler kicks in if the outhouse is less than 5 degrees which is all the time at the moment. The water in the system is at 35 degrees and the boiler is still firing. Surely the water in the pipe doesn't need to be 35 degrees for the pipe thermostat to register the temperature as 10 degrees?

Unless there is some heating in the space, other than the boiler, that stat will never be satisfied. Probably best to set that to minimum, off and maybe add a pipe stat in it's place - but attached to the boiler.

Alternatively, you could try experimenting by somehow attaching that existing stat, to the boiler casing.

 

[GoferBlue1947]

If you want a really accurate temperature controller then I suggest the Elitech STC1000. Fantastic piece of kit at less than £20. I bought one to prevent the pump on my wood pellet boiler starting up before the boiler contents reached 60C.

 

[Chris009]

If you want a really accurate temperature controller then I suggest the Elitech STC1000. Fantastic piece of kit at less than £20. I bought one to prevent the pump on my wood pellet boiler starting up before the boiler contents reached 60C.

So would you attach the thermostat to the boiler?

 

[stem]

Surely the water in the pipe doesn't need to be 35 degrees for the pipe thermostat to register the temperature as 10 degrees?

In theory, the pipe shouldn't be 35 degrees, it should be no more than 10. But there are possibilities that may make it so:

1) The boiler has a pump overrun that even when the pipestat turns the boiler off. The pump continues to run for a few minutes to dissipate residual heat in the system. Depending on the design of your system it may be possible for some hot water to get back to the boiler without loosing a lot of its heat. For example, my boiler has a by-pass between the boiler flow and return and when the motorised valves closes, this effectively creates a short return circuit in and out of the boiler, so that would raise the temperature above 10C (there are other scenarios as well). The acid test is that even if it did hit 35C, the boiler should be off at this point and should not come back on until the pipe falls below 10C.

2) Something else is demanding heat from the boiler, or has been recently. Are both CH and HW off at the programmer and have been so for some time?

 

[GoferBlue1947]

So would you attach the thermostat to the boiler?

I assume the STC1000 unit can be used to replace a thermostat in any equipment that needs heating (or cooling) but it certainly has greater accuracy and a lesser hysteresis effect than a conventional thermostat. See:

https://www.elitecheu.com/collectio...mperature-probe-sensor?variant=43090166382851

Have a chat with the Elitech guys.

I think I would be wary of tinkering with any components inside a gas boiler but replacement for a pipe thermostat would be ok. It worked very reliably with my wood pellet boiler.

 

[Londoner2]

I had the same setup from 2004 to 2019 as boiler was in an outback building, the honeywell frost stat was set to 5c and pipestst to 20c, i lowered to frost stat to lowest as possible, in that time the pipes never froze.

Im based in London and so we had odd winters which were really cold and teh boiler used to fire every night every hour, i fine tuned it so it did not come on for long, my energy bills were ok but then again the energy prices were much lower then.