glow worm

[toptinker]

hi had my new boiler for approx 2 months now and works well?
all i ask is we only use the boiler (glowworm flexicom 18 hx ) when we need it. turn it on when we feel cold, we put the hot water on for 2 hours in the morning and maybe 2 hours at tea time. thats all we need ? when we turn it on (hot water) in the morning the dig temp on the boiler approx reads 14 deg. once its been on for say 5 mins it shoots up to 70 deg (set at this) then cuts out goes down to say 50 deg then kick in and out around about the 60/70 deg mark. should the water heat up this quick ?

 

[mogget]

Sounds like normal behaviour to me. Are your hot water and radiators getting hot when you ask them to, and only when you ask them to?

 

[ianmcd]

The temperatures on the display are the temperature readings of the primary water in your boiler and not the temp of the water in your HW cylinder, your boiler however shouldnt cut in and out as you describe, if you think of it like an accelerator in a car it should run at full power then as the water heats up it should slow down and only use the required amount of energy as the heat transfer demands, contact your installer as your appliance is still under warranty, if the installer cant sort the problem he/she can call Glow worm out free of charge as long as it is not an installation fault

 

[toptinker]

when i say cuts in and out, it sort of runs the burner then sort of slows down then kicks up. the installer did say it was normal. so i think then it is normal the way its running. the c/heating is ok hot as it should be. the hot water is also ok . the issue i had was setting the thermostat on the cylinder. its set at about 65 deg at the mo.

 

[dcawkwell]

You have the classic symptom of a new boiler hooked up to an old hot water tank. Or there is a problem with the water getting around the coil in the cylinder.
The tank has a lazy coil and heats up the cylinder slowly.
The boiler can't modulate down enough to handle the little heat that the coil is actually taking out into the hot water tank.
Hence the boiler shoots up to 70 degrees fairly quickly and then cuts off waiting for the water to cool cycling.
By contrast my boiler will belt away using a lot of power to heat the cylinder it for about 20 minutes. It then cycles a couple of times and the cylinder is then hot and the boiler cuts off with its work finished.
When you had the boiler replaced you should have had the tank replaced.
Also a vented boiler is old fashioned and has no place in a modern heating system you should have gone for a sealed system boiler at the same time.

 

[TCCHeating]

It sounds like your boiler is not actually completly cutting off, but just modulating. I suspect there is a gate valve on the flow or return to the cylinder coil. This is used to balance the system (restricts the flow to hot water, so as not to starve the central heating when both the ch and hw are on at the same time)

Maybe opening this up a bit more may help you stop the excessive temp fluctuations. And modulating up and down all the time when you are heating hot water only.

 

[toptinker]

your correct it does have a gate value. this is shut, how much should i open it ? when i have opened it in the past there is a rush of water. is this a cold feed ? i am happy with the boiler so not sure what to do now with all your input ?

 

[TCCHeating]

Sorry, i think all I have done is confused you there will probably be many gate valves on your system, If you are happy with the boiler then as said previously, just Relax

 

[toptinker]

thanks. the pump for the boiler has 2 gate valves near it 22mm pipe, these are either side of the 3 way valve. the 15 mm gate valve is just to one side of these, over the years though i think has always been closed or maybe a touch open ? if i opened it a tad what would i expect the system to differ ?

 

[swbjackson]

Sounds like the 15mm gate valve is being used as a bypass. I wouldn't fiddle with it as your boiler doesn't normally need a bypass.

As others have said the coil in your cylinder doesn't transfer the heat into the water as quickly as a modern one which is why the boiler is behaving like this.

 

[toptinker]

cheers mike. so would you agree and leave as it is, i get heating and hot water. i just wanted to see if the boiler is working as it should ?