Boiler and Megalow mistery

[RenzoPan]

Boiler and Megalow mistery

Hi,
Just moved into a house from a flat and I have a couple of queries.

We have a Worcester gas fired boiler - Greenstar Ri (in the kitchen on ground floor) and a megaflow (on the first floor) plus a small red tank that I do not know what it does.

Heating is set to off on the boiler, while water is set to on (not on a timer, always on).

1) issue/question
I noticed that often the gas fired boiler is turned on, and it would seem to happen when using the hot water eg to do the dishes.
Does it mean as soon as I use some water, the megaflow gets the boiler fired up to replace the water used? Is that efficient from an energy perspective? I.e. I might use the hot water only many hours later..
1) possible solution
I assume a way to deal with that is that I could just set a timer for the water on the boiler (eg only in the am or at night when the Energy is cheaper), though that would mean we might use the whole hot water in the tank and run out. Would that mean no hot water, or hot water but through boiler (so less pressure)?

2) issue/question
even if the heating is off, I noticed that both the radiator (tower rail) in the bathroom and the radiator in the main entrance (possibly on the way up to the megaflow from the boiler) get warm. Is it just that they are both in the way, so rather than having a pipe run directly from to the boiler to the megaflow, it runs through these 2 radiators?

2) possible solution
Is the solution to just turn off these two radiators with their valve when not hot enough? So that even if the water flows to the megaflow, it still doesn’t go through them?

Thanks for your help!

 

[gmartine]

Hello

You're mostly right on all your queries...

Much depends on your pattern of use and the size of cylinder but a common solution to your HW issue is to have it timed to come on twice in 24hrs say. Once overnight/very early morning and the other late afternoon/very early evening to cover evening use. It isn't efficient to have the boiler firing to recharge the cylinder everytime HW is used, better it has one long uninterupted burn.

The HW and CH circuits are usually seperate but it's not unusual for the bathroom heating to also be piped into the HW circuit so you have warmer towels and bathroom without actually having the CH on.

The fact that another rad heats up too indicates you may have some reverse circulation issues, not really a huge problem and requires investigation and as you say you can always turn off one of the radiator valves until your CH is on more permanently. Also if you switched to HW timed a couple of times a day/night it becomes much less of an issue.

The red tank is an (ev) expansion vessel, when you heat up water it increases in volume so it needs something to expand into. Hope that helps.

 

[fowlerboi]

1) I think its just co-incidence or that your cylinder stat is badly placed. Once the cylinder loses hot water as you draw it off, its then replaced with cold water from the bottom. Once the cold water cools the cylinder below a certain point the thermostat will fire the boiler up. I bet you if you played around the boiler wouldn't fire all the time.
1) Gas isn't cheaper at certain points in the day, its a flat rate.
2) The towel rail might be piped up on purpose to come on with the hot water to ensure you don't get damp towels, though this would be better suited to timing your hot water rather than leaving it permanantly on. Your entrance hall might be the same if its a bit of a coat/boot room or something. Is it part of an extension? It could be they just piped it up badly. (see reverse circulation)
2) Leave the bathroom one and move to timed hot water. Turn the hall one off in the summer

 

[RenzoPan]

Many thanks to everyone.
I’ve turned off the hall one and set the timer to come on 2 a day. Initially it was only 1 hr each time and I realised that left us with cold water (2 people took long showers) so I bumped it up to 2.5 hours each time. I’ll do a bit of trial and error.

Question: when the megaflow had run out of hot water I expected the hot water to come straight from the boiler “on demand”, allowing me to take a hot shower. Instead only cold water came through. Is it because the “new” new water from the boiler was going into the tank? Is that normal?

 

[fowlerboi]

The boiler is a closed loop. It heats up water and pumps it to the cylinder where it goes through a coil which heats up the cold water inside the cylinder. The two different waters never touch

 

[gmartine]

Just to add your boiler isn't a combi so will now only come on to charge the HW store during the two timed periods you've set irrespective of how much HW you have left.

If say everybody showers in the morning which leaves your HW store cold til the next recharge you could just increase your heating period to cover the morning use say between 4 til 8am.

 

[RenzoPan]

Just to add your boiler isn't a combi so will now only come on to charge the HW store during the two timed periods you've set irrespective of how much HW you have left.

If say everybody showers in the morning which leaves your HW store cold til the next recharge you could just increase your heating period to cover the morning use say between 4 til 8am.

Thanks…
It I replace my boiler with a combi boiler, would that allow me to still get how water on demand right away, when the cylinder is empty?
Ie if no hot water in the cylinder, first provide hot water to the shower/kitchen, and if not, re-fill the cylinder with hot water.
Thanks

 

[fowlerboi]

A combi would remove the cylinder. Everytime you need hot water it would heat it up on demand.

A combi isn't always better, location/ amount of water being used/how many bathrooms are things to weigh up and you will need to speak to an engineer to have a look.

It sounds like you're having schedule issues. Please could you list below:

• Hot water programmer times
• cylinder size
• what times family members use hot water for baths/showers
• how many family members

 

[RenzoPan]

A combi would remove the cylinder. Everytime you need hot water it would heat it up on demand.

A combi isn't always better, location/ amount of water being used/how many bathrooms are things to weigh up and you will need to speak to an engineer to have a look.

It sounds like you're having schedule issues. Please could you list below:

• Hot water programmer times
• cylinder size
• what times family members use hot water for baths/showers
• how many family members

I’ve now changed it to 2.5 hrs in the early hours of the morning and 2.5 in the early afternoon, before the kids come back from school.

Cylinder is 170liters

• generally wife and u shower in the morning and kids late in the afternoon
• 2 adults and 2 children

 

[Chuck]

A combi would remove the cylinder.

It's possible to have a combi and a DHW cylinder on a heating zone. E.g. combi provides HW to kitchen and one part of the house, cylinder provides HW to rest. This arrangement can work nicely for medium-sized houses as long as the zones's flow temperature is 65°C.

 

[EvilDrPorkChop]

It's possible to have a combi and a DHW cylinder on a heating zone. E.g. combi provides HW to kitchen and one part of the house, cylinder provides HW to rest. This arrangement can work nicely for medium-sized houses as long as the zones's flow temperature is 65°C.

What's the point though? Just seems a daft arrangement to overcomplicate things. Also if anything you want the kitchen tap off the combi, as that's the tap most people open and shut for 10 seconds.

 

[Chuck]

What's the point though?

Post #8 opened with "A combi would remove the cylinder." My point was that this that this doesn't always have to be the case.

Just seems a daft arrangement to overcomplicate things.

There are circumstances where such a setup solves problems. For instance, if the boiler is in the kitchen but there is a long run to the cylinder. Or, when the household wants to be able to run two showers at the same time. There are other ways to solve these problems, of course, e.g. electric showers and undersink heaters but, in my opinion, combi+cylinder can be an option worth considering.

Also if anything you want the kitchen tap off the combi, as that's the tap most people open and shut for 10 seconds.

Sentence 2 of my post started "E.g. combi provides HW to kitchen...".

 

[RenzoPan]

With the situation below, this morning we had 4 showers, and the forth person had cold water.. I turned on an extra hour on the boiler at that point, but the water was still cold… (I really wish the system was smart enough to send water to the shower first.. and then fill the cylinder).

i guess 170liters is just not enough to take 4 showers one after the other….?



Cylinder is 170liters

• generally wife and u shower in the morning and kids late in the afternoon
• 2 adults and 2 children

 

[ShaunCorbs]

Set the boiler to come on before you go for a shower or set the time for heat hw from 0060-2200 you can take 15 showers then

 

[RenzoPan]

Set the boiler to come on before you go for a shower or set the time for heat hw from 0060-2200 you can take 15 showers then

I’d be interesting to know what turning it on between 6 and 2200 means in terms of electric bill…

 

[Ben-gee]

Look, if you want hot water you have to pay for it- the more you want the more you pay.

If you press boost for an hour when the first person showers, the boiler will replace the water they use and you can all have nice hot showers.

 

[ShaunCorbs]

I’d be interesting to know what turning it on between 6 and 2200 means in terms of electric bill…

It’s heated via gas isn’t it hence the boiler

Also won’t use any more energy than normally as your using the hot water so your using energy that has to be replaced

Also gas is 1/3 cheaper than electric

 

[EvilDrPorkChop]

170L is barely enough for 2 showers for us, never mind 4. Unless you're in for like 2 minutes