Issues with <10yr old heating system installation

MrThrifty

Where to start... Okay, well this is both a query and an unavoidable rant about issues with a central heating system that came with a newish-enough house built less than 10 years ago. I showed the setup recently to a boiler service guy who said it was a typical system and was well-installed (in terms of controls and plumbing near the boiler). If this is the case, then I would think other people out there have the same issues listed below and so have included some which I have now sorted myself.

In a nutshell, the system consists of the following:
- Firebird Heatpac oil boiler (non-condensing)
- 1 controller, wired to zone valves
- 3 zone valves (2 heating and 1 hot water), with microswitches wired to boiler and circulating pump
- No room thermostat
- No TRVs on any rads


And the issues from day 1 are as follows:

1) The safety thermostat for the boiler trips when the boiler turns off after the rads have heated up.
- I used to overcome this by reducing the boiler control thermostat to something quite low like 50degC. But I learnt recently that the issue is caused by the way the boiler and pump are always switched together and so I resorted instead to integrating the timer delay circuit from a bathroom extractor fan into the system and adding a bypass valve. The result of this is that the circulating pump keeps going for about a minute after the boiler is turned off. I've since learnt that I can get an off-the-shelf pipe thermostat to facilitate the overrun would be the more conventional solution!

2) The pressure relief yoke inside the boiler housing is continuously leaking (drip, drip kind of rate).
- I suspect this problem is related to issue 1 above and therefore was caused in the first place by the lack of a pump overrun and bypass valve.

3) When the rads are hot, but the rooms are still heating up, the boiler starts cycling on and off every minute or so. This to me is not good from a boiler efficiency point of view.
- I was thinking the issue here is the circulating pump. I've played briefly around with it but didn't really notice a difference. I was originally thinking the pump had to be run at a faster speed to get the heat away from the boiler but then I was thinking it had to go slower to allow more time for the heat to dissipate from the rads?! Is this on-off thing an issue at all?

4) There is no room thermostat in the system - i.e. the zones and boiler are simply controlled by a timer-type controller.
- Given that the controller is located in a very cold garage at the opposite end of the house to the living room, this means frequent unpleasant trips there to boost the heat if necessary. I'm telling you, this is the most annoying thing ever. However, I am planning to get over it by using a wireless programmable thermostat and relay box from the likes of Honeywell or Heatmiser. I presume this isn’t a crazy idea?

5) The hot water cylinder always gets quite warm when the other heating zones are on.
- Is this normal? I’m starting to think that the hot water zone valve (Danfoss type) might not be closing properly. Has anyone come across this before? I'm guessing that I'm going to have to drain the system to investigate properly...

6) There’s no thermostat on the hot water cylinder.
- I’ve read that there should be given that it has its own zone control valve but I wonder if this is really necessary. Any takers?


With all due respect to any heating system installers out there, but having a central heating system installed in the 21st century without any control thermostats seems just plain stupid to me. And the same goes for not having any pump overrun. Maybe I'm missing something.

Anyway, any feedback on the queries mixed in all of this rant would be appreciated!! And apologies for the shockingly long length of it!

Plombier

1. If the high limit is tripping frequently then get it replaced.
2. Could be caused be faulty boiler stat as in No. 1.
3 Points to a faulty boiler stat as in No. 1 & 2
4 Thats a good idea, luckily the system as described seems to be installed to facilitate this upgrade.
5. Turn on just the hot water circuit, remove the actuator from the valve turn the spindle at 90deg from pipe if it stops heating valve is OK, replace actuator turn off the heating circuit, turn on a radiator circuit if water heats actuator is faulty.
6. Thats part of the upgrade you mentioned in No. 4.

Buford T Justice

With regards to the pump, are you telling us that the pump is powered via the boiler stat?

As in, when the boiler switches off because of the temp reached, does the pump continue to pump as normal, whilst the timer is switched on?

MrThrifty

Fingers McGee wrote: »

With regards to the pump, are you telling us that the pump is powered via the boiler stat?

As in, when the boiler switches off because of the temp reached, does the pump continue to pump as normal, whilst the timer is switched on?

No, the timer switches the zone valves which then switch the pump and boiler on together when open if you follow me. The boiler control stat then switches the boiler if it reaches the set water temp but the circulating pump keeps going. Issue used to be when timer closed the zone valve which then switched off boiler and pump together. The residual heat in the boiler would cause the boiler safety stat to trip coz there was no water flow (pump off and valves closed!).

MrThrifty

Thanks for your response Plombier. Note that I sorted issue 1 with the home-made pump overrun and bypass valve fix. I assumed issue 3 was caused by the water temperature rising to reach the boiler control stat temperature, thus temporarily turning off the boiler, then the water temperature dropping over a minute to a few degrees less, and then the stat resetting and triggering the boiler on again. I'm not sure if these stats normally have some kind of hysteresis or something where they trip at say 60degC but don't reset till the temperature drops to say 50degC? From what you're suggesting, it sounds like they should?

As for issue 5 (dodgy valve), I twigged myself afterwards that the actuator can be detached from the mechanical valve and will test as you suggested tomorrow.

Plombier

Some boiler stats can have a switching hysteresis of up to 15 deg. and you say your boiler cycles every minute that why I think its a faulty stat.

Iderown

Mr Thrifty,

I'm just a wee bit suspicious of the original wiring of your system. Not just because of the lack of cylinder and space thermostats.

By the way, it is a pretty easy job (for an electrician) to install thermostats. He would need to know exactly how to connect them between the timer and the motorised valves. The OR logic function, which switches the burner, is arranged by the microswitches in the motorised valves.

There should be a "permanent live" connection to the burner/boiler circuitry. This live energises the pump during the pump overrun periods. This is when the system is no longer calling for heat but just after the burner has stopped. For the pump overrun facility to be effective, the pump must have a water circuit to pump through. At this time all the "house" motorised valves will be closed. Some installations arrange for one radiator to be open all the time (sometimes a heated towel rail). It is connected directly to flow and return water circuits - not in a motorised valve path.

JohnnieK

Iderown wrote: »

Mr Thrifty,

I'm just a wee bit suspicious of the original wiring of your system. Not just because of the lack of cylinder and space thermostats.

By the way, it is a pretty easy job (for an electrician) to install thermostats. He would need to know exactly how to connect them between the timer and the motorised valves. The OR logic function, which switches the burner, is arranged by the microswitches in the motorised valves.

There should be a "permanent live" connection to the burner/boiler circuitry. This live energises the pump during the pump overrun periods. This is when the system is no longer calling for heat but just after the burner has stopped. For the pump overrun facility to be effective, the pump must have a water circuit to pump through. At this time all the "house" motorised valves will be closed. Some installations arrange for one radiator to be open all the time (sometimes a heated towel rail). It is connected directly to flow and return water circuits - not in a motorised valve path.

Heatpacks dont have a permanent live unless a frost stat is fitted.

MrThrifty

Yup, there's no frost thermostat fitted... Okay, back to basics here, clearly I should put in a pipe stat to 'properly' facilitate the pump overrun. Should I also then put in a frost stat too? Maybe a stupid question here but do all these stats work independently, i.e. with their own pipe temperature probes? You'd think you could get an all-in-one control/frost/pump-overrun stat with one probe that fits within the boiler housing?

This thing is starting to crack me up now - it seems the more you look the more you realise that standard controls were not included in the system.

As for the faulty control stat Plombier, I still need to look at this. But I did have a look at the hot water valve... and the actuator is working grand. It would seem that when the mechanical valve is in the off position, there's still a flow of water through the valve. I'm saying this based on how quickly the pipe on the other side of the valve got hot. Are these things known to go? Or could it have been caused by a pressure build up on day one coz of the lack of a pump overrun. Note though that there is a pressure/air release yoke between the pump and the valves.