underfloor heating Eco Hometec hs boiler.

[mark]

We have been installing a system supplied by Eco hometec. (ec31hs) Its a mixture of under floor heating and thermostatic valve controlled radiators. The underfloor heating (all one zone) is on the ground floor of a new well insulated extension whilst the rads are in the older stone built farmhouse and the top floor of the same extension.

The boiler has a programmer built in but we have been supplied with a cm67 programmable thermostat. I am a little disappointed with the information we have been supplied with. Originally the system was to have radiators only with an outside temp' sensor allowing the boiler to control the heating. It seems that including under floor heating means the outside sensor is not much use.

It seems we are supposed to install the cm67 in the room that is to be used most in the UFH area. There are no zone valves at all. The manifold is an 'invisible heating' compact. According to the wiring diagrams it seems the cm67 should be wired back to the 240v rail on the boiler

Will the cm67 not switch off the boiler once the UFH area is warm enough? If the older part of the house has a rad with an open TRV how will the boiler switch on without sending more warm water through the UFH manifold. There is a thermostatic regulating valve on the UFH manifold flow with a probe to measure the water temperature in the manifold.

TIA

[Andy Hall]

I have one of this range of MAN boilers although not this specific model.

You should be able to use the outside sensor *and* the programmer.

If you use what is basically a "standard" thermostat like this - in the sense that it is an on/off control then there are terminals to deal with that.

It depends on how you connect up and the function number that you set.

MAN also supply a modulating room thermostat/controller the RE2132 which is actually made by Siemens. This one, together with the boiler controller does all that the CM67 does and more and without having to turn the boiler on and off. You can adjust the relative sensitivity to the inside and outside temperature measurements and the ratio between the two. Eco Hometec can supply these as well.

There is a better translation of the manual with more information from the other MAN distributor, MHS boilers.

are for the higher power versions of the boiler but a lot of the information is the same.

There are two versions (possibly more) of the boiler controller - one has DIP switches and is described in the links above to set the function number, the other has the setting on the panel menu in the installer section. It looks like MHS have removed the PDF of the non-DIP switch version, so if that is what you have, send me a mail and I'll forward you a copy. It does give a better explanation for each.

You should be able to achieve zoning as well by the use of motorised valves

.andy

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[fred]

I too wondered what the problem was with using the proportional (modulating) control, either outside or inside, but I think it's the use of the thermostatic blending valve to lower the u/f heating temperature. To me it looks like the blending valve will reduce the u/f flow temp to a constant 40 or 50, or whatever the required setting is, which will override the modulating action on the boiler.

In a rad system it will mod down from 80 or 70 to 50 or 40 so you can get proportional control over the boiler & rad heat output. I think this action is clipped if you use a (flow) thermostatic blender, which of course you must do to protect the installation.

So, I think I understand the problem, just can't think of the solution yet.

[Christian McArdle]

It can't. That's what zone valves are for. Perhaps you should install some.

Christian.

[Andy Hall]

I am not sure that that is completely true, although I see what you are saying. The boiler is using outside temperature sensing and indoor temperature sensor if available. More directly it senses the flow and return temperatures of the water. The controller controls the fan (and burn rate) and also modulates the pump to between 30 and

100%.

THe effect of the blending valve, as seen by the boiler is to affect the heat load (expressed as flow rate and temperature drop. In that sense it is not a lot different to a set of radiators.

It will be influenced but not prevented, because in effect the blender is an attempt to match the temperature requirements of the UFH to what the boiler might want to do at the top end.

If several circuits are combined in parallel - e.g. the UFH and the TRV controlled radiators, the boiler will see a mix of heating loads and respond to the total. In a zoned system, one may have to balance one load against another anyway.

For example, I have my house zones as normal TRV controlled radiators (at present) and then a separate circuit to heat my workshop. The two circuits are connected using a stainless steel plate heat exchanger. The primary side of the heat exchanger is connected as though it is another heating zone. The flow resistance through this is probably lower than the heating zones and I have fitted a balancing valve to reduce the flow if needed.

In fact if I monitor the boiler behaviour using the PC software, I can get graphs of temperatures, pump level and fan speed (burn rate). The workshop circuit has its own thermostat/controller driving a separate pump. A flow switch next to the heat exchanger senses the flow and opens a zone valve on the primary side. If the workshop circuit is cold, I notice a brief temperature drop at the boiler return and it modulates up the burn rate and the pump a little to compensate that.

Hence I think that for this kind of purpose, the exercise can be looked at in total load terms.

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[timegoesby]

I read on their web site that there is a two temperature model boiler, so UFH can be at one temperature and radiators at another. I read it that it was all done inside the boiler and pipes are just connected to it? This sounds very handy. How does this work?

[mark]

In message , Andy Hall writes

Something to do with the low temperature of the UFH apparently. Something specific to IH's manifold?

Again it seems that choosing UFH in addition to the rads scuppers its use.

This boiler does not have DIP switches :(

I spoke with IH and ECO today and they have suggested using CM67's linked to a honeywell 2 port valve to control the rads and the UFH. This makes sense to me but it looks as though we will lose some of the boilers features.

The UFH zone valve will be controlled for temperature and time by the CM67, the manifold pump and boiler will be switched on via the grey and orange wires of the zone valve (I think!)

The rads will have a separate cm67 to provide a different time programme which will open and close a 2 port valve which will allow the TRV's to control the room temperatures. (The cm67 will be set for a temperature of 30 degrees.)

The boiler will have no on-off time programmed in.

Does this make sense? Will the radiator circuit need another system pump?

Please excuse the questions but we'd like to get it right....

[mark]

In message , Christian McArdle writes

Thanks.

[mark]

In message , timegoesby writes

On ours there is one circuit for the DHW and another for the CH.

The UFH and the CH are both on the low temperature circuit. The higher temperature circuit is for the DHW

[Andy Hall]

I don't see why. As a minimum you should be able to arrive at having the outside temperature sensor as one of the terms in setting the output level of the boiler even if you are switching the heat demand on and off from another source.

I don't think that you can use the RE2132 controller at the same time as another room thermostat, but you could have it as the controller in one of the areas if you like. However, even without that, the boiler will giave an appropriate modulated power level when you have a set of simple switched zones connected.

OK, that's like mine. If you would like to send me an email, I will send you a PDF of MHS's manual for that. It explains the function numbers quite well.

It will still modulate very well to match the total load.

I don't see why it should, unless I have missed something

.andy

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[mark]

In message , Andy Hall writes

I do have an external sensor and the cable for it is installed in the building fabric; I'll connect it up.

:))

Thanks for the input; I feel as if I've had to work quite hard at getting the detail out of Ecohometec and I'm not exactly happy about it.

As usual I've had more sense in here!

Have you had your boiler long? How is your experience of it?

Thanks again.

[Andy Hall]

I didn't have quite the complexity of different systems that you have (although my workshop arrangement which is certainly different thermally to the rest of the system); but what I did was to produce a set of questions and sent it to them before buying. Only when the answers were satisfactory did they get the order.

I found it necessary to play with the various adjustments for the control slope to provide a good match between that and the thermal behaviour of the house. I did this a little over a few weeks. It would be pretty difficult to work it out ahead of time.

Since spring 2002 and it has performed really well. Gas savings compared with the previous 65% efficient boiler have been the predicted 25-30%.

.andy

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