heating cools when domestic HW is on

[jasonuk11]

I have an open vented system with 2 2port motorised valves. When both CH and HW are on the whole house rads cool down significantly.If i turn off HW then CH returns to hot pretty quickley.
Is there a way to limit the HW through the hot water tank?

 

[Agile]

Yes, a professional installer would have installed a gate valve on the supply to the cyl heating coil so you can balance that against the heating.

Not many installers are that professional though. Most like to do the minimum possible and as quick as possible!

If you have a valve then close it and open by 1 1/2 turns as a starting point.

Tony Glazier

 

[OwainDIYer]

it's quite normal to give priority to the hot water, with modern fast recovery cylinders they should heat up well before the house starts getting cold.

If the house starts getting cold as soon as the radiators cool down you need more insulation.

 

[Agile]

He has an open vented system!

That means its old and will not be fitted with a modern fast recovery cylinder!

Tony

 

[jasonuk11]

thanks for info, im also wondering whether the stat on the hot water cyclinder could be faulty because the water gets very hot and turning the stat i cant hear it clicking in and out hence would the valve to the cyclinder never close hence my problem?

 

[JohnD]

you didn't tell us what your boiler is.

I used to have an old, iron, 15kW boiler, which struggled to heat the house in very cold weather, and you could feel the house cool down when the cylinder (having been refilled with very cold winter water) was being reheated after a bath. The cylinder was balanced down to restrict flow, but the boiler was not powerful enough.

When I had the cavity walls insulated, the heat loss from the house dropped, and it no longer cooled down when reheating the cylinder.

My new boiler is 24kW which has ample power. Now, when the cylinder is beng reheated from cold, all that happens is that the Flow temperature drops for a few minutes, while the (modulating) boiler turns up its fan speed and flame size to build the temperature back up. Within a few minutes it is back up to temperature, and able to start turning its power lower again.

Some people set their programmer so that the HW comes on half an hour before the CH, to reduce contention and simultaneous demand.

Yes, your Cylinder stat might be faulty.

Does it look like this?
http://www.screwfix.com/p/drayton-hts3-cylinder-stat/95630

It runs at mains voltage so you must turn off the power and test for dead before tinkering

What colour is your HW cylinder?

 

[Mark Br]

He has an open vented system!

That means its old and will not be fitted with a modern fast recovery cylinder!

Tony

That's quite an assumption being that you don't know if it's the original cylinder, etc.

Correct me if I'm wrong, but aren't OV boilers still fitted nowadays, I'm sure I fitted one only last year.

 

[jasonuk11]

the boilker is a glowworrm 18hxi 18kw, think irts around 6 yrts old. The cylinder looks old. Its copper with just lagging wrapped around it, and the stat is similar to the one you have shown.

 

[jasonuk11]

One of my 2 port valves got wet while i was changing the pump. There are 4 wires and the grey one seems now to be shorting to earth. I disconnected it and everything still seems to work, i presume all 4 wirs have afunctin, orange ones are the motor, what are the other 2

 

[Agile]

That's quite an assumption being that you don't know if it's the original cylinder, etc.

Correct me if I'm wrong, but aren't OV boilers still fitted nowadays, I'm sure I fitted one only last year.

A copper cyl with seperate lagging certainly sounds old!

I agree that many OV boilers are still installed but the energy efficiency advise is that they systems should be converted to pressurised because they are about three percenbt more efficient.

Tony

 

[jasonuk11]

One of my 2 port valves got wet while i was changing the pump. There are 4 wires and the grey one seems now to be shorting to earth. I disconnected it and everything still seems to work, i presume all 4 wirs have afunctin, orange ones are the motor, what are the other 2