HELP! Advice needed on unusual system in our new home! Potterton Suprima HE (70) Boiler

[Davedon]

Hi there,
thanks for taking the time to read this, and hopefully help.
i moved into a new (old) house last year, and we have a central heating system which appears to have been fitted in 2008. It comprises...


Potterton Suprima HE (70) Boiler
Green wilo gold 60 pump
honeywell motorised valve
Potterton EP2002 time switch
Gravity fed indirect HW tank with thermostat
10 radiators with old-ish TRVs


there is no room thermostat. So from my limited knowledge, we have an unvented system with indirect gravity fed hot water? is this not unusual? I have just been hit with a hefty bill for winter usage. I know that the house is draughty etc and i am upgrading insulation and windows at the moment but I would like some advice about a more efficient way to operate the system.


1) as we have no room thermostat, the heating is either On or OFF. The TRVs are useless for accurate temp control. Do you think a wireless room stat would be a sensible addition to our system? How easy is this to install? We have a boiler interlock that switches the demand on and off with the timer.


2) it seems that we can only get CH when the HW switch is on as well. Is this a fault or just the way our system is installed? Just a bit annoying when you need an hour of heat at night but no need for hot water.


3) the boiler has a separate thermostat. I know this will not have a great effect on the radiator temp, but is there a sensible setting to get efficient use from a condensing boiler?


4) I have to top up the water in the system every week or so. I just noticed a small leak on the joint between the HW thermostat and the HW tank. It looks small, but could this cause the boiler to lose say 0.75-1 PSI per week?


I would appreciate any advice you can pass on,


many thanks,
dave

 

[MrMeek]

no, you have a indirect gravity system no unvented, get a plumber to look at installing a thermostat/ look at how your heating is controlled, and yes a leak will cause it to loose pressure.

 

[tamz]

Sounds like you have a sealed heating system and an open vented cylinder. Not at all unusual.

1. Any type of roomstat will save you money. Programmable ones just offer more options.
2. How many motorised valves do you have? and do they have 2 pipe or 3 pipes? Do you have a cylinder stat?
3. The boiler thermostat controls the water temperature leaving the boiler. The higher it is set the hotter the water circulating through the system and the bigger your gas bills. How you set it may be governed by the output of the radiators you have fitted and how the system has been balanced but you should try to keep it set to about 60. Your boiler should be condensing most at that setting keeping your bills down.
4. You have a bigger leak than that one. You may need someone to check this

 

[Reg Man]

Get a qualified person in who has Unvented HW certificate and energy efficiency qualification for CH. Gravity HTG to unvented? no room Stat? No zone valves? Non compliant.

 

[tamz]

Everybody missuses the word gravity these days Steve. Just no educating them :lol:

 

[Davedon]

Hi guys,
thank you all for taking the time to reply. Some great info.
i don't think I described the system very well, it is as tamz describes...a sealed heating system (with expansion vessel) and a vented HW cylinder heated by a coil. I have one motorised valve downstream of the pump which is 2-port (V4043H). I have a cylinder stat. I will definitely look into a room stat though as the timer is a very crude way of controlling the heating.
The leak I described is actually worse than I thought, a drip every 10 seconds or so. I took off the foam insulation around the pipe and it seems to have been like this for a while. I have now tightened up the joint between cylinder stat and cylinder, and it seems to be dry....however now my boiler is not firing?! ARGH! With demand from both CH and HW it shows demand at boiler but no firing, and after a minute or so lockout light. I have tried a reset a couple of times but no luck. Oh well, best call out an expert!
thanks again guys

 

[Reg Man]

Everybody missuses the word gravity these days Steve. Just no educating them :lol:

Gravitating towards an early night one thinks.

 

[tamz]

When you say cylinder stat do you mean a ravi valve or similar. Like a trv head with a wire and probe stuck on the side of the cylinder? and the motorised valve would be on the heating pipe.
These were common in the 80's. That would be why you only have one 4043 and why your programmer is set to 10 program. You don't have an interlock as the water side keeps running. When the thermostat shuts the water flows through the bypass and the boiler will still fire. A very inefficient and expensive way to work your heating system from a time when gas was cheap.
That means you would have to upgrade your system with another motorised valve and an electric cylinder stat fitted to the hw side. You can make your ep2002 into 16 program by moving a switch on the back.
This would give you independent control of water and heating then fit a room stat too.

Sods law with the boiler :smile:

 

[Davedon]

You are spot on tamz,
the cylinder stat is as you described, a TRV head with a wire and probe on the cylinder. And further inspection would reveal the motorized valve is on the heating pipe, with a branch upstream leading to the HW cylinder I think. It is a strange setup as the boiler is in an outhouse connected to the garage, the pump and valve in the garage, and the timer in the kitchen, with the cylinder under the kitchen floor!! Whereabouts in Scotland are you tamz? Anywhere near Renfrewshire?!

So despite the boiler being relatively new (2008), the heating of both water and CH are very inefficient due to my lack of interlock? And the only thing controlling the ON/OFF to the boiler is the timer? No wonder the bills are so high. Is this easily remedied?
cheers :willy_nilly:

 

[tamz]

You are spot on tamz,

Thats because i'm psychic :lol:

Whoever fitted your boiler should have upgraded it but that is water under the Erskine bridge.

I'm near the M8 services so about 25 miles away. PM me (click my name) if you want a price for upgrading it.

 

[tamz]

Dave i can't reply to your PM as your inbox is full. Email me on my address i gave you.
Thanks

 

[kay-jay]

Thats because i'm psychic :lol:

Whoever fitted your boiler should have upgraded it but that is water under the Erskine bridge.

I'm near the M8 services so about 25 miles away. PM me (click my name) if you want a price for upgrading it.

Davedon you couldn't find a better more knowledgeable plumber than tamz pretty much anywhere in the UK. That he is relatively local to you is a stroke of luck.
If he lived near me i would get him to do my plumbing......and im a plumber🙂

 

[tamz]

:speechless::teeth_smile:

 

[kay-jay]

Ach its true tho tamz. You're more knowledgeable than any other plumber i know and this is why you are so respected on the forum.

 

[Dotty]

Seconded.

But then you did start out when god was a boy........

 

[Davedon]

This is good to hear, as Tamz has come up with a great solution for my system. He lives close to me, and it's great to hear your recommendations. Thanks to all who give their time on this forum

 

[lame plumber]

Seconded.

But then you did start out when god was a boy........

bit harsh coming from the devils spawn🙂

 

[tamz]

Yer embarrassing me now :smile: