Sealed room boiler heats some rads in summer!

[dubman]

I have a sealed room boiler and in summer I use it to heat water. There is a switch on the boiler which I have in the "summer" position. But when the boiler is set only to heat water, a couple of rads get very warm and others slightly warm, Do you think it would be ok, in the summer, to turn off a valve at the boiler manifold to stop water circulating around the rads? Thank you.

 

[migoplumber]

depends where the valve is, sounds like you need to find your motorized valve ( sometimes next to the hot water cylinder) and check its shut and not passing.
good luck

 

[diesel_ltd]

if your cylinder return is not the last tee back to the boiler the rads can back heat on hw only if this is the case it would need repiped, when was the system installed??

 

[Billy Bob Bob]

as above poster tee in wrong place last tee must always go to domestics

 

[dubman]

Ok, I must check the pipework and see if I can figure out what you mean about the "last tee" situation. The boiler was installed about 2 or 3 years ago, and I think some rads have always heated slightly, though maybe not every time, when I had it set for hot water only. Thanks.

 

[ferret]

Ok, I must check the pipework and see if I can figure out what you mean about the "last tee" situation. The boiler was installed about 2 or 3 years ago, and I think some rads have always heated slightly, though maybe not every time, when I had it set for hot water only. Thanks.

You must first check that the motorised valve is not letting hot water pass (either a 3 port valve port marked 'A' or a2 port valve with an arrow) when you have hot water only on on the programmer , if it does change it ! if not it is piped wrong and will need altering. The last 'T' is the bottom pipe from the hw cylinder (known as return) this must be the last joint/junction before going back to the boiler. Also sometimes a bathroom radiator is piped to be on all the time , this can also be wrong causing back circulation. If you can,t solve it and don,t want to pay a plumber fit Thermostatic valves to the rads they will turn themselves off.

 

[dubman]

ok, I will have a detailed look at the piping and try to identify the valve you mention with the arrow. I might post a drawing of the pipework. Thanks.

 

[dubman]

I have been reading the installation notes. This boiler is installed in a garage, one floor lower than the rads, In the notes I read that if the boiler is installed in a place lower than the radiators, it is recommended to install a siphon at the exit of the boiler, with a view to preventing the "heating of the installation by natural convection, when there is not a demand for heating". I actually did install a siphon originally, but at the HW flow, as in diagram. The notes just say to install the siphon at the "exit" of the boiler. Maybe I should have installed it at the other "exit" - the "flow to rads"?

The only Tees I see next to the boiler (in the pipework I installed) are the two, as in diagram (flow to rads and return from rads).

I wonder if the location of the boiler might explain the back heating problem?

My drawing is not exactly to scale, and the upstairs and downstairs flows to rads may be mixed up in the drawing, but I think it doesn't matter. Thanks.

 

[ferret]

Dubman what boiler is it??

 

[dubman]

It's a Spanish boiler: Domusa MCF-DXV 40 (Sealed Room). Am I allowed to post a link to the installation manual in English here?

 

[ferret]

It's a Spanish boiler: Domusa MCF-DXV 40 (Sealed Room). Am I allowed to post a link to the installation manual in English here?

Right now i see, ok its not anything we suggested earlier as its all in together so forget it all , the only way the rads can get warm is if the pump on the hydraulic pack is running! or the non return valve is letting by , I think it best you get someone in to look at it who is ofay with these boilers , not necessarily Domusa but something like it similar to istor or powermax. see if the pump runs though first it may be a simple control fault.

 

[dubman]

yea, actually I'm a bit suspicious about the programmer. I might try changing it for a more well-known one, and see if it makes a difference. Thanks.

I notice that when I turn on the DHW, the radiator return pipe (at the manifold) gets hot more or less immediately. I think one possible solution might be to install a 1 inch anti-return valve on the manifold as near as possible to the bolier. But I also posted a question in the Domusa forum, so we'll see what they say. Hopefully if I get it solved soon, I will let you know the solution. Thanks.

 

[dubman]

I got it solved. In the Domusa forum they told me initially it could be a problem of the retention valve ( a valve near the heating pump), Another option which I suggested was to install a non-return valve on the Heating return, which the person in Domusa agreed would be a solution, but I understood from Domusa that changing the retention valve would also be a solution, Anyway I opted to install the non-return valve on the heating return pipe, just next to the boiler. So now no heat gets to any rads or heating pipes in the house when I only want DHW. Thank you.