Hot water problems

[greenslime30]

Hi all,

Had an extension built over the summer and as part of that we had a new boiler fitted. Have got evohome controlling everything, which was installed and working fine a year before the new boiler. Have noticed since the new boiler the hot water struggles to get hot, evohome shows it’s been on for 3hrs and is struggling to get above 36 degrees. Central heating works fine.

Never had an issue with the hot water with the old boiler. We used the immersion over the summer whilst the work was being completed.

We have a cold water tank in the loft and a cylinder in the airing cupboard.

Any ideas?

I can’t see how it’s a problem with the boiler as the heating is fine. But I’m just guessing.

Is this a problem with the hot water cylinder? If so why was it working fine before and with the immersion and not now??

Just trying to have a bit of an idea before I call the plumbers back.....trying not to look like a complete fool and don’t want to be having work done if it’s not necessary.

Thanks

[Andehh]

What boiler is it? Any dials or knobs on the front?

[bazjude2998]

Could be cylinder stat or motorised valve, Plumb ( excuse pun ) for stat

[greenslime30]

Boiler is a baxi 400.....only one dial on the front with a picture of a radiator, that’s turned up to 90.

[clockworks]

Dodgy 2 port valve on the hot water circuit (partially closed, not allowing enough water to flow through the hot water coil), or maybe the radiators need balancing to restrict the flow (water taking the path of least resistance, so hot water cylinder not getting full flow).

Does the hot water get up to temperature if you switch off the heating for an hour while hot water is on?

Is the pump speed set too low?

[greenslime30]

Thanks for the replies.

As for the stat, I think evohome controls this with an external stat on the outside of the tank, it’s reading correct as far as I can see!

Stupid fecking technology......evohome has been nothing but an expensive pain in the arse!!!

[essayer]

Does the boiler have some output range rating or ‘automatic’ setting?

[greenslime30]

I’ve just turned all the heating off and will see if the hot water gets hotter.

I’ll report back later, thanks for the tips.

As for the boiler, my level of technical knowledge is as follows - it’s white and is bolted to the wall with two green lights on the front.

[clockworks]

Do you have 2 Evohome relays (BDR91, small whit boxes with a grey pushbutton and 2 LEDs) screwed to the wall near the boiler?
If so, do the green lights come on on both of them when the heating and hot water are supposed to be on?

Edited by clockworks on Wednesday 15th November 19:30

[greenslime30]

Yes I’ve got those two white boxes, one is labelled heating and one hot water and yes the green light comes on each of the boxes when the heating and hot water are on.

[greenslime30]

So after just running the hot water and not heating the temp has increased 1 degree but nothing significant.

The copper pipe that feeds into the side of the cylinder is hot but not ‘hot hot’ - I can hold onto the pipe....should this not be hotter??

Plumber who fitted the boiler should hopefully be out to have a look at some point over the next week.

[fastbikes76]

What hot water cylinder is it? There should be a cylinder stat on it somewhere below halfway down, make sure that is between 55-60 degrees. Recently did a call out for the same thing, turned out someone had bumped the stat dial when chucking crap in the cupboard and turned the stat down to minimum!

Do you have 2 zone valves (ie one for hw and one for ch) or is it just one mid position valve that does both ? It will be a silver square box on the copper pipe work somewhere . Any pics would help us work out what you have there.

[greenslime30]

[greenslime30]

Bloody sideways photos!

There are three metal boxes....one for hot water, one for the UFH and one for the radiators.

There is no traditional thermostat for the cylinder...the white box strapped to the cylinder is the evohome thermostat and that is controlled by my control box which is currently set at 60 degrees with a tolerance of 10 degrees.

It’s like copper Spagetti junction!

[CorradoTDI]

Was wondering if there is an air lock in the heating pipes to the cylinder but I can't see any vents that you could open to bleed..

[anonymous-user]

In your photo:

there are two valves which may not have been set correctly.

The red gate valve 'A' in the return from the cylinder coil is sometimes fitted to 'balance' the cylinder flow relative to the heating when both are operating. Mark the position of the handwheel, then count the required number of turns anticlockwise to fully open the valve (so you can re-set it later). Don't force things - the valve may already be fully open! Leave the valve fully open.

The bypass valve 'B' looks like a simple 1/4-turn 'ballofix' type. Again, note the position of the screwdriver slot, then fully close the valve (slot at right-angles to the pipe direction).

Fire up the hot water with the heating off, and see if things improve.

Was the pump replaced at the same time as the boiler? It looks like a 'smart' pump, which may not be appropriate for your system.

Put the valves back to their original state when you've finished playing!

Edited by anonymous-user on Wednesday 15th November 23:15

[clockworks]

greenslime30 said:

Yes I’ve got those two white boxes, one is labelled heating and one hot water and yes the green light comes on each of the boxes when the heating and hot water are on.

Green lights on and a water temp reading on the controller means that the Evohome system is all working.
That leaves a water circulation problem (closed or faulty valve) or a wiring fault between the BDR91 and the boiler/2 port valve.

I wonder if the new boiler has been wired incorrectly, or the 2 port valve has siezed up during the summer while the boiler was switched off.

When you tested it with just the hot water running, did the boiler actually fire?

[Pheo]

Check the two port valve is working - turn the hot water on with your hand on it and you should feel it move.

[greenslime30]

When I tested it with just the hot water on the boiler fired and seemed to be working fine.

I’ll have another look tonight when I get in. Thanks for the suggestions, the battle continues!

[greenslime30]

Well the plumber came over and has changed the pump, I’m not sure this was the issue. He turned all he electrics off to do this and then turned it all back on and hey presto it all worked fine. Plumber then leaves and 20min later it’s back to its old tricks. I press the reset button on the boiler and it works again for 20min.....then stops again.

Plumber has been told and is coming out again.....

I hate central heating systems!!!!! Aaaaarrrgggghhhhh!